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Transcript
Medical Imaging
Technique and Procedures
Medical Imaging
Technique and Procedures
Alfonce Mang’oka Nyalla
Acrodile Publishing Ltd
Medical Imaging Technique and Procedures
Copyright © Acrodile Publishing Limited, 2015
All rights reserved. No part of this book may be used or reproduced by
any means, graphic, electronic, or mechanical, including photocopying,
recording, taping or by any information storage retrieval system without
the written permission of the publisher except in the case of brief
quotations embodied in critical articles and reviews.
Acrodile Publishing Limited
P.O.Box 15298-00509,
Lang’ata-Nairobi, Kenya
Email: [email protected]
Website: www.acrodile.co.ke
ISBN 978-9966-007-34-6
Typeset by Medlar Publishing Solutions Pvt Ltd, India
Contents
Forward
xi
Chapter 1
Medical Imaging Techniques and Procedures
Objectives
Medical Imaging
Medical Imaging Modalities
Branches in Imaging
Considerations in Imaging
Ethics
Effects of Ionizing Radiation
Somatic effects
Genetic effects
Radiation Protection
Upper Limbs
Shoulder girdle
Imaging Technique
Hand
PA and oblique
Oblique
Ball catching PA oblique
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3
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4
4
5
Hand Oblique Projection
Fingers
5
5
v
Thumb
Index and middle finger
Ring and 5th fingers
Wrist joint
Scaphoid views
Carpal Tunnel
Forearm
Elbow joint
Ulnar groove
Transthoracic
Humerus
Lower Limb
Foot
Toes
Ankle joint
Tibia and fibula
Knee
Patella
Femur
Shoulder Girdle
Shoulder joint
Scapula
Acromio-clavicular joints and clavicle
Clavicle
Pelvic girdle
Pelvis
Hip joint
Vertebral Column
Cervical
Thoracic vertebrae
Lumbar vertebrae
Sacro – Iliac Joints
Chest
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vi
Acute Abdomen
17
AP supine
Dorsal decubitus
17
18
Chapter 2
Medical Imaging Techniques and Procedures
of Skull, Teeth, FBs and High Kilovoltage Technique
Objectives
Skull Imaging
Radiographic base line (RBL)
Anthropological line
Coronal
Interpupilary line
Equipment
Patient preparation
Indications
Cranium
Basic views
Supplementary views
Base of skull
Pituitary fossa
Jugular foramina
Facial bones
Occipito-mental (OM)
Mandible
Dental Imaging
WHO dental formulae
Types of dentistry imaging
Orthopantomography (OPG)
Land marks
Equipment
Patient preparation and indications
Centring points
Occlusal views
Bite wing views
Orthopantomography (OPG)
Radiation protection
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24
24
25
25
25
25
25
26
26
26
27
27
v
High Kilovoltage (KV) Imaging
Objectives
Advantages
Disadvantages
Applications
Foreign bodies-FBs
Types of FBs
Imaging procedure
Sinuses and Fistulae
Sinus
Fistula
Fistulography
Faecal fistula
Pediatric Imaging
28
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31
Chapter 3
Medical Imaging Techniques and Procedures Using
Contrast Media and Mobile Examinations or Portable
Contrast Examinations
Alimentary Tract Examinations
Barium studies
Examinations of GIT
Responsibilities and duties of radiographer
Barium swallow
Barium meal
Barium follow through
Barium enema
Contrast medium
Small bowel enema
Urinary System
Patient preparation
Indications for IVU
Equipment and accessories
Retrograde pyelography or ascending pyelography
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48
Reproductive System
Nervous System
Myelography
49
50
50
Circulatory System
Interventional radiology
51
51
Chapter 4
Medical Imaging Techniques and Procedures – Modern Modalities
Objectives
Ultrasound
Transducer
Ultrasound Terms
Production of ultrasound
Transducers
Display Modes
Types of transducers
Knobology
Major Examinations
Abdomen
Small parts
Indications
Gynaecological
Obstetric indications
Computerized Tomography – CT
Objectives
Computerized tomography
CT terms
CT equipment
CT generations
Scanning procedure
Display/archive
CT image formation
Image quality
Advantages
Computed Radiography (CR)
Principles of computed radiography
53
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56
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57
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58
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62
Advantages of CR
Disadvantages of CR
Digital Radiography (DR)
63
63
63
v
CR verses DR
Benefits of CR and DR
Medical applications of CR and DR
Industrial applications
Photostimulable phosphor (PSP)
Image contrast
Nuclear Medicine
Objectives
Definition
Classification
Radiotherapy
Objectives
Definition
Reasons for therapy
Branch therapy
Teletherapy
Applications
Magnetic Resonance Imaging (MRI)
Objectives
Definition
Equipment
Applications
Operation
Images
Contrast media
MRI coils
Hardware
Magnets for MRI
Quench
Advantages of superconducting magnets
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References
73
Forward
This book is intended to fill a gap in the lack of books and more so local
ones for the training and reading in Medical Imaging Sciences especially in
medical imaging techniques and procedures. The subject in medical imaging
called Imaging and Therapeutic Modalities (ITM) is more deserving. This is
a core subject in which students and radiographers gain knowledge, skills
and attitude in imaging and therapeutic procedures to assist them carry out
diagnostic and therapeutic procedures for patients needing these examinations in the hospitals.
The book will be of more value to all students undertaking training in
Medical Imaging, Radiographers and any other medical professional with an
interest in medical imaging.
This book covers the wealth of experience of the author; who has been
teaching in the department of Medical Imaging Sciences (MIS) in Kenya Medical Training College (KMTC) for the last thirty one years with ITM as one of
the main subjects. Notes have been compiled for a long time but the last two
years have been dedicated to the writing of this very vital book to assist the
users.
1
1
Chapter 1
Medical Imaging
Techniques and Procedures
 Objectives
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Topical outline
Imaging
Modalities
Branches
Considerations
Ethics
Radiation protection
Image quality
Upper limbs
Lower limbs
Shoulder girdle
Pelvic girdle
Spine
Chest
Abdomen.
 Medical Imaging
The science of taking images for diagnostic purposes – The old name is Radiography which does not embrace all the imaging modalities. This meant
that X-rays were used to produce images on the film which was finally called
radiograph
1
Medical Imaging Technique and Procedures
and no other energies like Ultrasound, Magnetism (MRI) and radioisotopes
could be used.
 Medical Imaging Modalities
The modalities are six, namely:
1.
2.
3.
4.
5.
6.
Conventional imaging using X-rays
Ultrasonography using sound waves
Computerized Tomography uses X-rays
Magnetic Resonance Imaging using magnetism
Nuclear Medicine using radio nuclides and
Radiotherapy using gamma rays and X-rays which is a therapeutic
procedure.
 Branches in Imaging
1. Medical
2. Veterinary and
3. Industrial Imaging.
 Considerations in Imaging
•
•
•
•
•
•
•
•
•
•
Patient identity
Waiting time
Preparation: Psychologically, physically and physiologically
Privacy
Comfort, Hygiene
Immobilization
Care – before, during and after the exam
Consent
Procedure explanation
Equipment – sound.
 Ethics
The dos’ and don’ts’ when dealing with a patient are:
•
•
•
No request form no imaging
No consent when needed no imaging
No imaging under intoxication
2
Medical Imaging Techniques and Procedures
•
•
•
•
•
•
•
•
No abuse or confrontation with patient
Radiation protection
Privacy of patient
Prior patient preparation
Records kept
Integrity
Prevent cross infection
Explain procedure.
 Effects of Ionizing Radiation
Ionizing radiation has harmful effects. The only modalities without ionizing radiation effects are MRI and ultrasound although the latter may
have thermal effects on an un born child. These effects are Somatic and
Genetic.
Somatic effects
These affect the person who is irradiated and include: hair loss, eye
cataract, erythema, still birth, abortion, nausea, vomiting, cell death and
leukemia among others.
Genetic effects
They manifest in the offspring and entail body deformities due to gonad cells
damage of the parent. The deformities and mutations may involve loss of
body parts like limbs.
 Radiation Protection
This is done by practicing the following:
•
•
•
•
•
•
•
•
Beam collimation
Fast screens and films-high speed
Meticulous technique
Proper instructions
Patient identification
Short exposures
Inverse square law
Doors closed
3
Medical Imaging Technique and Procedures
•
•
•
•
•
Few people in the room
Do not use faulty equipment
Use of protective materials
Minimize use of ionizing radiation
All this is for self, staff, patient and the public at large.
 Upper Limbs
The upper limb:
Shoulder girdle
Consists of Scapula, clavicle and the arm consisting of humerus, forearm
(radius and ulna), 8 carpal bones, 5 metacarpals and 14 phalanges. The
joints are shoulder, elbow, wrist, carpo-metacarpal, metacarpo-phalangeal
and inter-phalangeal.
 Imaging Technique
There are mandatory views or projections thus:
•
•
•
Basic views antero-posterior and lateral
Supplementary or additional views
Alternative views when the basic projections are impossible example the
chest AP instead of PA for very sick patients, children or in theatre or
the ward.
 Hand
PA and oblique
Hand is for grasping and formed by phalanges and carpals. On a 24×18 cm,
hand in pronation. Fingers extended. Centre to the head of 3rd metacarpal.
Collimate beam and FFD is 100 cm.
Oblique
Hand 45 degrees from pronation, fingers curved and supported on foam pad.
Centre to the head of 3rd metacarpal and FFD 100 cm. Lateral may be done
for bone displacement and same film used.
4
Medical Imaging Techniques and Procedures
Ball catching PA oblique
Figure 1.1
This demonstrates rheumatoid arthritis.
 Hand Oblique Projection
Fingers
Are formed by the 14 phalanges each digit with three phalanges except the
thumb which has two and the projections are PA and Lateral.
Postero-anterior (PA)
The hand lies on a cassette with extended fingers and hand in pronation.
24×18 cm cassette/film used. Focus Film Distance FFD is 100 cm. Centre
over the head of proximal phalanx of 3rd finger and collimate beam to the
area of interest.
Lateral
Hand and forearm rotated 90 degrees, thumb rests on a foam pad. Centre
over the head of 1st phalanx or proximal of index finger. FFD is 100 cm, film
24×18 cm and beam collimated. To show bone displacement if fracture
present.
5
Medical Imaging Technique and Procedures
Thumb
Postero-Anterior: Hand in lateral 90 degrees from pronation, thumb rests
on a foam pad. 24×18 cm cassette used FFD 100 cm. Centre to the metacarpo-phalangeal joint.
Lateral
Hand in pronation, palm slightly raised on foam pad. Centre to the metacarpo-phalangeal joint.
Alternative
Latero-medial thumb perpendicular to film for lateral and AP inward and
outward posterior part on film.
Index and middle finger
Lateral
Hand rotated inward until lateral of index in contact with the film, the rest
of fingers flexed. Centre over the head of 1st phalanx of index finger. Film
24×18 cm and FFD 100 cm. The other portion of film used for the PA which
is same as hand with restriction to the two digits.
Ring and 5th fingers
Latero – Medial aspect of the fingers in contact with 24×18 cm cassette, rest
flexed and thumb on foam pads. Centre to the head of 1st phalanx of ring finger. PA as of hand with beam restricted to the fingers and same film.
Wrist joint
Formed by scaphoid, lunate, triquetral, radius and ulna. Ulna isolated by a
fibro-cartilage. Wrist bones medio-lateral are Pisiform, Triquetral, Lunate
and scaphoid proximally. Distally latero-medial is Trapezium, Trapezoid,
Capitate and Hamate. Capitate is the largest and first to ossify, lunate half
moon and likely to be dislocated. Scaphoid is the most frequently fractured.
Views are PA and Lateral.
Postero-anterior
Wrist on a 24×18 cm cassette in pronation, patient besides the X-ray couch,
elbow flexed. Centre between the styloid processes of radius and ulna.
6
Medical Imaging Techniques and Procedures
Lateral
Elbow flexed and wrist at 90 degrees. Centre to lateral styloid process. For
Colles fracture and displaced epiphyses-ulnar deviation. Colles fracture is a
fracture of the distal radius which may be difficult to heal hence calling for
fixation of metal plates or nailing.
Scaphoid views
Four views used:
•
•
•
•
PA as normal wrist
Lateral as wrist
PA ulnar deviation as PA but hand rotated outward or laterally
PA or AP oblique.
 Carpal Tunnel
Formed by depression of carpal bones. Nerves, vessels and ligaments pass
here and carpal tunnel syndrome occurs which is neurological. An axial view
is done with patient sitting backwards fingers on the film.
Figure 1.2
Wrist joint showing Colles fracture PA and Lateral.
7
Medical Imaging Technique and Procedures
Forearm
Antero-posterior
Forearm on supination and elbow extended. 24×30 cm cassette used. Centre
to middle of forearm. FFD 100 cm and beam collimated.
Lateral
From supination 90 degrees rotation. Elbow is flexed. Centre to the middle
of forearm.
Elbow joint
Formed by Trochlea and Capitellum of humerus linking with Trochlear notch
of ulna and head of radius.
Antero-posterior
Forearm and arm supinated, joints extended-Centre 2.5 cm below midpoint
of epicondyles using FFD 100 cm and 24×30 cm cassette.
Lateral
Elbow 90 degrees flexion, arm and forearm same plane. Joint 90 degrees
from supination. Centre to the lateral epicondyle.
Ulnar groove
This is a groove to medial humeral epicondyle. Passage of ulnar nerve. Ulnar
called funny bone because of the sensations from the nerve.
Patient sits backwards, elbow 45 degree flexion. Centre to lateral
part of medial epicondyle. FFD 100 cm, 24×18 cm cassette and beam
collimated.
Transthoracic
Elbow strapped on chest – Centre through the chest. Avoided b e c a u s e
of high radiation dose to the patient.
Humerus
Antero-posterior
Patient lies on the X-ray couch. Arm abducted and elbow extended. 40×15 cm
cassette used. FFD 100 cm, beam collimated. Centre between the joints or
8
Medical Imaging Techniques and Procedures
middle of cassette. Both joints included or one near the injury not to miss
a fracture or dislocation. The upper arm is the humerus and lower is the
forearm or radius and ulna.
Lateral
From supination, the humerus is rotated 90 degrees with flexed elbow.
Centre as for AP.
 Lower Limb
Has lower and upper part. Consists of femur, patella, tibia, fibula, tarsals (7), metatarsals (5) and 14 phalanges. Called leg with upper and
lower leg.
Foot
Made of tarsals, metatarsals and phalanges.
Dorsi-plantar oblique
Patient steps on a 30×24 cassette, foot rotated 45 degrees medially. Centre
through cuboid-navicular area. FFD 100 cm and beam collimated to area of
interest.
Dorsi-plantar
Patient sits on the couch, foot on cassette, knee medial rotation. Centre
through cuboid – navicular region. Lateral can be done for foreign body (FB),
Flat foot weight bearing. This condition is called Pes Planus. Calcaneal spur
is a bone growth on the calcaneus which is very painful – lateral view in
weight bearing done for both calcani for comparison.
Toes
Dorsi-plantar, dorsi plantar oblique and lateral as for the foot but centering
to the toe of interest. Sub-talar joints also the same. March fracture may
occur along the metatarsals common with marching soldiers.
Ankle joint
Hinge synovial joint formed by talus and distal tibia and fibula.
9
Medical Imaging Technique and Procedures
Antero-posterior (AP)
Patient sits on the X-ray couch; leg extended and foot medial rotation to
make malleoli equidistant from the cassette. FFD 100 cm, 24×30 cm cassette
used. Foot is vertical. Centre between the malleoli.
Lateral
Patient is rotated to injured side. Ankle joint and knee in contact with cassette. Malleoli superimposed. Centre to medial malleolus. Stress views could
be done. This is applied by the surgeon. Potts fracture may occur along distal
tibia.
Tibia and fibula
Normally called lower leg. AP and lateral done. AP – Patient sits on the couch,
knee extended, malleoli equidistant, 30×40 cassette used. Centre to middle
of leg and include joint near point of injury if not all joints.
Lateral
Patient (Pt) is rotated to injured side, knee flexed, malleoli superimposed.
Centre to middle leg. Horizontal beam used on patients on traction. FFD
100 cm and same cassette used as in AP projection.
Knee
Synovial hinge joint formed by femoral condyles, tibia and posterior aspect
of patella.
Antero-posterior
Patient sits on the X-ray couch, knee extended, foot vertical and condyles
equidistant from cassette, 24×18 cassette used, FFD 100 cm. Centre through
the joint or 1 cm below apex of patella.
Lateral
Patient rotated to injured side, Condyles superimposed, heel supported.
Centre to medial condyle and collimate beam to area of interest. FFD 100 cm
and cassette 24×18 cm.
10
Medical Imaging Techniques and Procedures
Patella
A sesamoid bone from ligaments.
Skyline view or infero-superior view done and lateral. Patient lies prone
and knee at 90 degrees. Centre to inferior surface, tube angled 15 degrees
cephalad that is beam towards the head.
Tibial tubercle in Os Good Schlatters disease a lateral is done. This is
degeneration of tibial tubercle. PA done prone. Intercondylar view for loose
bodies in knee joint.
Femur
Longest and strongest bone of the leg to bear the body weight.
Antero-posterior
Patient lies supine, knee and hip extended, foot vertical and medial rotation
to avoid neck foreshortening. FFD 100 cm, 15×40 cm cassette. Centre to
middle of cassette and include all joints if not one near point of injury.
Lateral
Patient is rotated to the affected side, condyles superimposed, centre to middle of femur or cassette. Sometimes horizontal beam is used when patient
on traction or on weights.
 Shoulder Girdle
Formed by 2 scapulae and 2 clavicles.
Shoulder joint
Freely movable joint formed by glenoid cavity and humeral head. AP – Pt lies
supine on the X-ray couch, elbow extended and scapula parallel to film,
24×30 cm cassette used FFD 100 cm. Centre to coracoid process or through
the joint.
Axial view (Supero-Inferior)
Patient sits beside X-ray couch, joint flat as possible. Curved cassette used
if available (24×30 cm). Centre through the joint. Muscle calcifications AP
done in external and internal rotation of arm.
11
Medical Imaging Technique and Procedures
Stryker’s view
This projection is to demonstrate recurrent subluxation of the shoulder
joint. The hand is over the head. Centre through the coracoid process or
the joint.
Scapula
AP-Pt lies supine and rotated until scapula parallel to 24×30 cm cassette.
Centre to humeral head. FFD 100 cm.
Lateral
Pt prone and rotated 60–75 degrees. Centre to medial border of the scapula.
Acromio-clavicular joints and clavicle
For children both joints done for comparison. Centre between the joints.
Cassete 24×18 cm.
Clavicle
AP done centring to middle of clavicle. FFD 100 cm and cassette 24×18 cm.
Pelvic girdle
Attachment for lower limbs. Has 2 innominate bones. 3 bones Ischium, Ilium
and Pubic bones to form acetabulum which receives head of femur to form
hip joint.
Pelvis
Formed by innominate bones. Posterior is coccyx and sacrum. AP done.
Pt supine and pelvis symmentical A.S.I.S (Anterior Superior Iliac Spine) equidistant from the cassette. FFD 100 cm and 35×43 cm cassette used. Centre to
midline 5 cm below A.S.I.S or 5 cm above upper border of symphysis pubis.
Erect for weight bearing in subluxation weight on each leg. Symphysis pubis
small aperture AP.
Hip joint
Synovial joint of lower limb formed by head of femur and acetabulum of the
pelvic bones.
12
Medical Imaging Techniques and Procedures
AP
Pt supine, legs medial rotation. Pelvis symetrical. Centre to midline 2.5 cm
above symphysis pubis. One hip centre to femoral pulse. FFD 100 cm and
cassette 24×30 cm for one hip.
Lateral
Pt is rotated to injured side knee and hip flexed. FFD 100 cm, cassette
24×30 cm, beam collimated. Centre to femoral pulse. Femoral neck true
lateral is done using a horizontal beam.
Figure 1.3
Hip joint AP showing fractured neck of femur.
Von Rosen view
This is for congenital hip dislocation or dysplasia. Hips rotated 45 degrees
each. Centre to the midline at the level of femoral pulse. Occurs mostly in
children. FFD 100 cm and cassette 24×30 cm.
13
Medical Imaging Technique and Procedures
Frog position
Pelvis symmetrical, hips, knees flexed and rotated externally. Centre as for
Von Rosen view. This shows epiphyses. FFD 100 cm and cassette 24×30 cm.
 Vertebral Column
Consists of 33 irregular bones as follows:
Cervical 7, Thoracic 12, Lumbar 5, Sacral 5 and Coccygeal 4.
Cervical
Difficult to demonstrate because of mandible and shoulders which obscure
the vertebrae. AP – chin raised. Centre to sternal notch. Open mouth for
1–3. Lateral FFD 150 cm. Centre 2.5 cm below angle of mandible. Obligues
for intervertebral foramina. Posterior show opposite side. Swimmers view
for cervico-thoracic junction.
Thoracic vertebrae
AP and Lateral. AP-Pt supine and pelvis symmetrical, knees and hips flexed.
FFd 100 cm, cassette 15×43 cm. Centre to middle of cassette with beam
collimation.
Lateral
Pt rotated 90 degrees from supine, legs and hips flexed, foam pad under the
spine to reduce lordosis. Centre to middle of cassette. Scoliosis (lateral spine
curvature) and kyphosis (antero-lateral curvature) a larger film is used.
Lumbar vertebrae
AP
Patient supine, knees and hips extended, pelvis symmetrical, FFD 100 cm,
film 24×30 cm. Centre to the midline at the level of lower costal margin.
Lateral
Patient rotated 90 degrees from supine, joints flexed, Centre 2.5 cm anterior
to the body of lumbar vertebra (L 3). FFD 100 cm, cassette 24×30 cm,
foam pad under spine to reduce lumbar lodosis and beam collimated.
14
Medical Imaging Techniques and Procedures
Figure 1.4
AP and lateral lumbar spine.
Figure 1.5 Lumbar
vertebrae lateral
projection.
Coned view
For L5 S1. This is as lateral lumbar but centre to joint and cassette
size 18×24 cm. It should be noted that lumbar vertebrae there are
three basic views as described. Coccyx and Sacrum as for pelvis and beam
collimated.
 Sacro – Iliac Joints
S – Shaped joints difficult to demonstrate. Prone projection done and that is
enough. Sometimes obliques are done for both sides. Ankylosing spondilitis
is arthritis of the joints which fuse and cause a lot of pain. These views done
for various traumatic and pathological reasons.
Chest
This is the area from root of the neck to the diaphragm. AP and Lateral done
for various infections.
15
Medical Imaging Technique and Procedures
PA
The patient stands facing a pedestal bucky, Chin raised, palms on the hips
and shoulders down ward. FFD 150 cm, 43×35 cm cassette or 35×35 cm
for women and other men. Centre to the midline at the level of midpoint
of medial borders of scapulae-T4level of sternal angle. Exposure made on
arrested inspiration. Lateral – Pt rotated 90 degrees from PA. Spine paral
lel to cassette. FFD 150 cm, cassete 40×30 cm. Chin raised and arms over
the head. Centre through the axilla at the level of T4 or to middle of cassette. Exposure is made on arrested inspiration. AP done as alternative and
oblique additional. Posterior oblique shows ribs near cassette and anterior
opposite ribs. Post Nasal Space (PNS) lateral neck cassette level of pinna.
Valsalva manoevre used. Thoracic inlet for goitre also done. Trachea and
larynx with “E” phonation.
Lordotic view done for interlober effusion or collapse of right middle
lobe. PA – Pt faces cassette and leans backwards 45 degrees. Centre to the
middle of the cassette.
Apical view
For apices-Tube 30 degrees cephalad, – reverse Lordotic or leans backwards.
Figure 1.6
16
PA chest.
Medical Imaging Techniques and Procedures
Bronchography
An imaging investigation of the bronchial tree. Water soluble contrast
medium is used but presently it is not common for it has been replaced by
the other medical imaging modalities. The bronchi and their branches in the
lungs are visualized to detect any lesions in the airway. Mostly done to check
for bronchiectasis which is dilatation of the bronchi and masses of the lungs.
It is done under aseptic procedure and local anaesthetics. A sterile trolley is
necessary. It is quite an invasive procedure.
Figure 1.7
Bronchography images.
 Acute Abdomen
Severe sudden abdominal pain or colic which calls for immediate attention.
The indications are:
Renal calculi, Biliary calculi, Trauma, Bleeding DU, Peritonitis, Food poisoning, Chest infection, Typhoid, Intestinal obstruction, Ruptured viscera,
Tension pneumonia and internal bleeding.
The basic views are AP abdomen supine, AP erect and chest. Supplementary – Dorsal decubitus and Lateral decubitus using horizontal beam to
show fluid levels.
AP supine
Patient lies supine, spine straight and pelvis symmetrical. Centre to the midline at the level of lower costal margin. Exposure is made on arrested expiration to avoid motional blur – Shows distension and gas distribution. AP erect
as for AP supine but patient is standing. This shows fluid levels. FFD 100 cm
and cassette 43×35 cm.
17
Medical Imaging Technique and Procedures
Dorsal decubitus
Pt lies supine; one arm over the head and the other supports the cassette by
the side. FFD 100 cm, cassette size 30×40 cm, beam horizontal and exposure
on arrested expiration. Centre to middle of cassette. For fluid levels when
erect impossible.
Lateral decubitus AP or PA as for supine but horizontal beam used – for
fluid levels.
Kidney, Ureters and Bladder-KUB. This will show the abdomen and
more so the urinary system for stones or pathology.
AP supine done making sure the upper poles of kidneys are shown and
no folding of clothes or skin. FFD 100 cm, cassette 43×35 cm and exposure
on arrested expiration.
Figure 1.8
AP abdomen.
18
19
Medical Imaging Technique and Procedures
Chapter 2
Medical Imaging Techniques and
Procedures of Skull, Teeth, FBs
and High Kilovoltage Technique
 Objectives
•
•
•
•
•
•
Describe the imaging technique for cranial and facial bones
Explain the WHO dental formula
Discuss the imaging technique for the teeth
Explain pediatric imaging
State High kilovoltage and soft tissue imaging
Discuss foreign body imaging.
 Skull Imaging
Skull has 14 facial and 8 cranial bones.
Cranial bones make the cranium with the vault and base. Facial bones
make the face. Skull is very difficult to image because of the shape and bone
position. The land marks include:
Radiographic base line (RBL)
A line from E.A.M to the outer canthus of the eye.
20
Medical Imaging Techniques and Procedures of Skull, Teeth, FBs
Anthropological line
From EAM to the infra orbital line.
Median sagittal plane through middle of the head and body (AP).
Coronal
Anterior to posterior plane
Interpupilary line
Between eyes (pupils).
Equipment
General X-ray machine, H.T generator, Cassettes of various sizes and positioning pads.
Patient preparation
Remove all radio-opacities and reassure the patient.
Indications
Brain pathology, Trauma leading to fractures, dislocations and displacement
of bones. Grids are used when necessary for the thick body parts.
 Cranium
Basic views
•
•
•
Postero-anterior or Occipito-frontal
Townes view – 30 degrees fronto-occipital
Lateral view.
Supplementary views
•
•
•
•
SMV – Submento – Vertical view for skull base.
SMV under tilted for jugular foramina.
Coned lateral view for pituitary fossa with horizontal beam as for lateral
skull.
Tangential view for lesions.
21
Medical Imaging Technique and Procedures
Occipito-frontal
Patient lies prone on the X-ray couch, hands clasped under the chest, the
body straight, median sagittal plane and RBL perpendicular to the film.
Interpupilary line parallel to film. Centre in the midline 5 cm below RBL,
FFD 100 cm, cassette 24×30 cm. This view shows petrous portion of
temporal bones within the orbits. To throw the bones from orbits angle the
tube 20 degrees caudad and 5–10 degrees petrous in infraorbital line
centering at the glabella.
Fronto-occipital
This can be done when the injury is posterior, for children and severe injuries.
AP patient lies supine, RBL and median sagittal plane perpendicular to the
film, 24×30 cm cassette used, FFD 100 cm. Centre 2.5 cm above the Glabella.
Townes view 30 degrees
Fronto-occipital. Positioning same as fronto-occipital with tube angled
30 degrees caudad.
Lateral
Patient lies prone, head rotated
with injured side in contact
with couch, interpupilary line
perpendicular to film and
median sagittal plane parallel
to film. The arm of injured side
along the trunk and the other
arm folded hand in front of face.
FFD 100 cm, cassette 24×30 cm
and grid used. Centre between
glabella and EAM or 2.5 cm
above EAM. In all cases of
trauma, horizontal beam used
to show ventricular air, aerocoele in frontal bone and free
air in the sphenoid bone.
Figure 2.1
22
Lateral skull projection
of a child.
Medical Imaging Techniques and Procedures of Skull, Teeth, FBs
Base of skull
Sub mento-vertical view (SMV)
Patient seated or supine is maneuvered such that the RBL is parallel to the
film and angles of the mandible equidistant from the film with neck extended.
FFD 100 cm, cassette 24×30 cm. Centre between angles of the mandible with
tube angled 5 degrees cephalad-to face. Pillows used.
Pituitary fossa
Coned lateral view done with horizontal beam. Centre 2.5 cm above and
in front of EAM. PA and Townes are also recommended when necessary.
24×18 cm cassette, FFD 100 cm and grid applied.
Jugular foramina
Lie along petro-occipital suture and transmit internal jugular veins, accessory and glossopharyngeal nerves. SMV is done with tube angulation of
20 degrees caudad. Shown between transverse processes of atlas. FFD
100 cm, 24×18 cm cassette and grid used. For localized lesions and depressed
fractures, tangential views done. Centre to the lesion in profile (aligned).
Facial bones
Fourteen facial bones and very difficult to image because of the bone
arrangement. Indications and requirements basically the same as those of
cranial bones. The basic views are: Occipito-Mental, 30 degrees Occipito –
Mental and Lateral. Supplementary views are Fronto-Occipital for zygoma,
Lateral coned for nasal bones or Occipito-Mental and Supero-Inferior.
Orbits – 20 degrees Occipito – Frontal, Occipito-Mental and lateral. Optic
foramina – Obliques 35/35 degrees both sides.
Occipito-mental (OM)
Referred to as Walters view. Patient is seated or lying prone on the couch
with hands under the chest. Median sagittal plane perpendicular to the film,
orbito-meatal line 45 degrees to the film, FFD 100 cm, grid, 24×30 cm cassette, chin on couch. Centre to the nasion with central ray passing through
superior orbital margin. 30 degrees Occipito-Mental (OM). As for OM but centre to the midline at the level of lower orbital margins with the tube angled
30 degrees caudad. Shows more of zygoma and maxillae and if over tilted
23
Medical Imaging Technique and Procedures
can show Odontoid peg of the Axis which is the second servical vertebra.
Severe injuries supine done as Mento-Occipital with 45 degrees tube angulation and horizontal beam seated or erect for fluid in maxillary antrium.
Lateral
As for cranium with patient prone, interpupilary line perpendicular to film
and median sagittal parallel, arm near injured side along trunk and the other
in front of face, 24×30 cm cassette, FFD 100 cm centre to the zygoma. For
black eye erect or supine done to show orbital empysema which is associated with air in the ethmoidal sinus. These cthree projections for facial
bones are also used for para nasal sinuses in times of sinusitis and in sitting
position to show fluid levels.
Mandible
This is the only movable bone of the skull. In PA obscured by the cervical and
lateral superimposed. Fractures common and dislocations. Orthopantomography (OPG) can be done to show the whole of the bone. Basic views are PA
and lateral oblique.
PA
The patient lies prone, chin tucked in RBL and median sagittal plane perpendicular to the film, hands under the chest. FFD 100 cm, film 18×24 cm and
centre in the midline at the level of angle of mandible.
Figure 2.2
Mandible PA with fracture right body.
24
Medical Imaging Techniques and Procedures of Skull, Teeth, FBs
Lateral oblique
Patient half prone with shoulder remote from injured side supported on pillows or foam pads and hand in front of face. FFD 100 cm, cassette 18×24 cm,
RBL and sagittal plane parallel to film. Centre 5 cm below the angle of the
mandible remote from the film with the tube angled 20 degrees cephalad to
separate the two sides of the mandible.
Temporo – mandibular joint (TMJ)
A sliding synovial joint demonstrated by 35 degrees Fronto-occipital and lateral obliques 25 degrees both sides. TMJ – Both sides as in mandible and in
closed and open mouth to see the extend of movements of the joints.
Para nasal sinuses (PNS)
Frontal, Maxillary, Sphenoidal, Ethemoidal and mastoid air cells. OM, OF
15 degrees caudad and patient steady. Lateral with beam collimation done.
FFD 100 cm, Grid and cassette 24×18 cm.
 Dental Imaging
Adult human being has 32 teeth. Two types of teeth-temporary or deciduous
and permanent. These are Incisors, Canines, Premolars and Molars. A child
has 20 teeth referred as milky teeth. Erupt at 6 months to 2 years. The child
has 4 incisors, 2 canines and 4 molars in each jaw. The teeth are attached to
the socket by cement and periodontal. Adult 4, 2, 4 and 6 each jaw. Have
crown, neck and root.
WHO dental formulae
In adult
18 17 16 15 14 13 12 11//21 22 23 24 25 26 27 28 – Upper jaw right to left
each two digits a tooth by name.
48 47 46 45 44 43 42 41//31 32 33 34 35 36 37 38 – Lower jaw right to
left each two digits a tooth by name.
Child formula
55 54 53 52 51//61 62 63 64 65 – Upper jaw right to left each two digits a
tooth by name.
25
Medical Imaging Technique and Procedures
85 84 83 82 81//71 72 73 74 75 – Lower jaw right to left each two digits
a tooth by name.
Mesial are the arches anterior towards incisors, distal posterior towards
molars, labial or buccal cheek side of the jaw and lingual or palatal inner
jaw side.
Types of dentistry imaging
Two types thus Intra oral and extra oral. Films occlusal denoting upper and
lower jaws. Panoramic tube operates from inside the mouth.
Orthopantomography (OPG)
Specialized equipment to show both dental arches and good for fractures
and rami of the mandible.
Land marks
a) Upper positioning line
Extends from tragus of the ear to the ala of the nose – 3–7.5 cm above
upper occlusal plane.
b) Lower positioning line
Line from tragus of the ear to the angle of the mouth. 2 cm above lower
occlusal plane with open mouth.
Equipment
Include a special dental machine, dental chair, hangers, films 1.1/4×1.5/8
adults and children smaller 1×1.1/4 inches. Occlusal larger with lead foil to
absorb scatter. Film Identification is quite difficult. The hanger should show
upper and lower teeth locations which represent the various teeth. Embossment should face the operator and biting surfaces. Flip to check tightness
so that they do not fall. Clip should not coincide with the embossment and
inscribe name on a tabloid or tang on the hanger.
Patient preparation and indications
Win patient confidence, identify with form, remove dentures and FBS from
face. Infections like dental caries, un erupted teeth, embedded teeth, edentulous patients and retained roots. Patient is usually in sitting or lying on a
26
Medical Imaging Techniques and Procedures of Skull, Teeth, FBs
dental chair or stool. Always the occlusal planes are horizontal and median
sagittal plane vertical. This is achieved by moving the head and tucking the
chin in. Patient should relax and made comfortable. Head moved and foam
pads used for supporting the patient. For canines and incisors, the film is
placed vertically and premolars and molars it is placed transversely in the
mouth. Tube is directed at right angle to the film. This may not be possible
due to the curves but a compromise is reached.
Scissors, finger or any other improvisation is used to support the film
and the patient must be at rest. The average tube angulations are as follows:
Upper jaw
Incisors + 55 degrees, Canines and Premolars + 45, Molars + 35 and Occlusal + 85.
Lower jaw
Incisors – 20, Canines and Premolars – 10, Molars – 50, Occlusal – 90.
Centring points
Upper jaw
Incisors – Tip of the nose, Canines – Ala of the nose, Premolars – just below
midpoint of the orbit and Molars – outer canthus of the eye.
Lower jaw
Incisors – Symphysis menti, Premolars – In line with midpoint of orbit on the
body and Molars – In line with outer canthus of the eye on the body.
Occlusal views
Taken using occlusal films to demonstrate cysts, alveolar pathology and get
plan view of the mouth. The occlusal film is placed between the teeth and
for upper incisors; the tube is directed at Nose Bridge at 65 degrees. Plan
view tube at vertex at 90 degrees to the film. Lower incisors SMV tube at
40 degrees and plan view centre to menti.
Bite wing views
These demonstrate upper and lower crowns for dental caries. Film is placed
horizontally and one bites on a bite block. Tube is centred at the occlusal
plane at right angles to the film. Edentulus patients i.e. patients with no teeth,
27
Medical Imaging Technique and Procedures
increase angulation for root and gum, decrease exposure gum less dense and
include the whole root.
Orthopantomography (OPG)
Technique used to obtain the whole of the dental arches tomograms using a
special machine called OPG – Orthopantomogram. This is used for:
Check jaws at first orthodontic visit, mandibular fractures, TMJs, show
changes in gross pathology of maxilla, nose and ear. The machine has
X-ray tube, slit diaphragm linked to a curved cassette, film holder and
control desk. The tube and film move in opposite direction, patient is
stationary. Due to the curves, the change of direction is twice to remain at
right angles with the arches. The slit beam transverses the whole arches
making exposure. In patient positioning, the head is adjusted and held in
a Cranio-Stat. Upper and lower arches are at focus.
Radiation protection
High dose imaging procedure because of the low exposures and difficult
due to:
a)
b)
c)
d)
e)
f)
Only low Kv is used in most dental units 55–60 kv
Short FFD used
No additional filtration
Multiple exposures needed
No lead lined cones
General equipment can be used but hard to move.
Pt should wear a lead rubber gown, beam away from body, hold film by
finger not staff or radiographer and use meticulous technique.
Exposure factors
Dental unit: FFD 23 cm, Time 0.25–1 second, MA 10 and Kv 45–60.
General unit: FFD 50–62 cm, MA 50, Time 0.25–1 second and Kv 75.
Fine focus is used for details.
Films are processed in a special dental processing unit. Make sure films
are not mixed even with the general ones. Good temperature 68 degrees,
4 minutes, proper mixing of chemicals and washing.
28
Medical Imaging Techniques and Procedures of Skull, Teeth, FBs
 High Kilovoltage (KV) Imaging
Objectives
•
•
•
•
Explain high Kv imaging
Name high Kv applications
Explain the advantages of this technique
State the disadvantages of high Kv imaging.
In imaging, high Kv means carrying out examinations using high range
kilovoltage – range 100–150 kv. At 50 kv low energy high contrast – photon
electric absorption (attenuation) i.e. 50% Compton scatter. At 100 kv high
penetration, less scatter and absorption hence leveled densities. Scatter is
reduced by use of cones, grids, light beam diaphragm (LBD) and compression
of the region-less volume – less kv high skin dose high kv equal densities.
High kilovoltage is not common now because of the many modalities in use
and automated programmed machines with no exposure selection manually.
Advantages
1.
2.
3.
4.
5.
6.
A wide range of tissue density can be visualized in a single film
Reduced MAS – reduced chance of motional blur on the film
High anode heating reduced – less time
Greater range of exposure latitude
Low MAS fine focus fine details
Radiation dose to patient reduced.
Disadvantages
1.
2.
3.
4.
5.
Special equipment with high Kv needed
Loss of details and poor contrast in the soft tissues
High grid ratio due to scatter
Gonad dose high in chest imaging
Risk of over penetration unless using APR (Automatic Programmed
Radiography)
6. Poor detail in skeletal work and poor contrast in tomography.
Applications
1. Hysterosalphigogaphy (HSG) – reduced gonadal dose
2. Barium examinations – rapid serials hence less heating
3. Pelvis – iliac regions
29
Medical Imaging Technique and Procedures
4. Cervical and thoracic spine
5. Lateral views of lumbo-sacral region.
Foreign bodies-FBs
These are strange objects or materials in the body which are not supposed to
be in the body. They are introduced through natural orifices or penetrating
wound. The aim is to:
1.
2.
3.
4.
Establish presence and identity of the FB
Show the position in relation to other body structures
Locate position if required
Assess secondary or associated damage to the body.
Ensure no artifacts to confuse with FB, clean cassettes, bucky and remove
clothes. Two views at right angles and no movement. Follow up to be sure
and do tangential views to establish whether tissue embedded. Cover large
area not to miss and localize before incision or removal.
Types of FBs
Four types for both adults and children thus:
1. Ingested through mouth by swallowing e.g. fish bones, meat bones,
dentures, teeth, coins, pins, screws and toys and can be in the pharynx,
oesophagus downward.
2. In haled FBs – go to the lungs and can cause lung collapse – dentures,
corns, peanuts, beans and clips.
3. Inserted FBs – to the orifices thus mouth, urethra, rectum, EAM and
vagina.
4. Embedded FBs – lodged in the tissues – glass, lead shots, bullet shrapnels (bullet pellets), arrows, scissors and knives – immediate attention.
Equipment depends on the type and patient preparation is assurance,
procedure, cloth removal and ask for how long FB in situ.
Imaging procedure
1. Ingested FBs for children AP alimentary tract cover lower neck and symphysis pubis. Short exposure factors, cassette 43×30 cm. Adult films in
order – lateral neck, chest posterior oblique and AP abdomen. Positioning as in conventional imaging.
30
Medical Imaging Techniques and Procedures of Skull, Teeth, FBs
2. Inhaled FBs – PA chest as for routine imaging. Lateral or oblique may be
done.
3. Inserted FBs: Nose-Routine Occipito-Mental and a lateral. Ear–basic
views of the skull and tangential views may be necessary. Contrast may be
used to coat the FB if radiolucent. Urethra, vagina and rectum – AP pelvis
and endoscopy may be done.
4. Embedded FBs – Can be in the limbs, abdomen, skull and chest – AP done.
5. Eye FBs – Intra – Ocular – OM and lateral – Another may be taken, 2 exposures looking straight up and down.
 Sinuses and Fistulae
Sinus
Its a cavity within the tissues. This can involve muscles and bones. It leads
from surface to inside or vice versa from abscess or drainage tube. Sinography may be done using contrast. This will show source, extend and ramifications or channels. Patient reassured and dressed. Pressure is applied on the
sinus if bleeding occurs.
Fistula
Abnormal passage connecting a cavity to another or surface to body e.g.: Fistula in Ano – Ischial rectal from to skin, Biliary fistula – there is bile leakage
from gall bladder or ducts after surgery. Blind fistula opens at one end only.
Fistulography
Radiographic examination of a fistula using contrast medium. Done using
contrast medium. If in colon, water soluble contrast used. Patients with
radioactive implants attended in minimal time.
Faecal fistula
Follows intestinal operation and there is sepsis.
Vesco-vaginal fistula (VVF)
An opening from urinary bladder to vagina. This can be due to surgical error,
delivery or ulceration due to carcinoma.
31
Medical Imaging Technique and Procedures
Recto-vaginal fistula
Due to peritoneal tear or in delivery. Faecal matter in vagina.
Macroradiography
Can also be done which involves magnified images of the body part in
question.
 Pediatric Imaging
This is very difficult because of the nature of the patients. It needs a lot of caution and patience to avoid repeats which add more ionizing radiation to the
patient. Projections may change hence one will be doing alternative views
e.g. AP of chest. Proper identification of patients and films is very important.
Use meticulous technique to eliminate repeats which will add more ionizing
radiation to the child hence more danger of radiation hazards.
32
Medical Imaging Techniques and Procedures of Skull, Teeth, FBs
33
Chapter 3
Medical Imaging Techniques
and Procedures Using
Contrast Media and Mobile
Examinations or Portable
1. This will include contrast media examinations of body systems.
2. Mobile and Portable examinations. These are – Ward Imaging, Operating
theatre Imaging, Home based Imaging and Forensic Imaging.
3. Most of the contrast examinations have been replaced by the modern
technology thus CT, MRI and Ultrasound.
 Contrast Examinations
These will include: Alimentary tract, Biliary tract, Urinary system,
Reproduc- tive system, Central nervous system, Circulatory system and
Interventional radiology. The sequence is as follows:
1.
2.
3.
4.
5.
6.
Definition of the examination
Patient preparation
Contrast medium used and dosage
Indications and contra-indications
Role of the radiographer
Equipment and projections or technique.
33
Medical Imaging Technique and Procedures
 Alimentary Tract Examinations
Barium studies
Organs of the gastro intestinal tract (GIT)
These organs are the mouth, pharynx, oesophagus, stomach, small intestines
and large intestines or colon. Accessory organs are pancreas, biliary tract or
tree, salivary glands, liver, tongue and teeth.
Examinations of GIT
The following examinations are carried out in the investigation of GIT thus:
Barium swallow, Barium meal, Barium follow through and Barium enema.
Contrast media
Barium sulphate in form of suspension or paste. This opacifies the organ
in question such that the soft tissues can be seen. Gastrografin with iodine
where barium sulphate is contra-indicated e.g. in partial or complete stenosis, bleeding DU, acute illness or fistula. Air in double contrast barium
enema.
Equipment
X-ray set with fluoroscopic facilities. Preferably with image intensifier and
television monitor, Tilting couch with floating table top, Foot rest, Adequate
output preferably 300 MA, under couch and over couch X-ray tubes.
Accessories
Loaded cassettes (all sizes), 43×35 cm, 40×30 cm, 24×30 cm, 18×24 cm,
barium cups, feeding cups and mixers, Pillow, lead rubber aprons, gloves,
clean no-opaque gowns, swabs for wiping mouth (vomitus), bowl and receptacle for solid materials.
Responsibilities and duties of radiographer
Before examination
1. Clean or tidy the equipment.
2. Switch on the equipment and make sure it is in good working condition.
3. Place the table in the required position, ascertain required lighting as
necessary.
4. Have adequate clean cassettes of appropriate sizes.
34
Medical Imaging Techniques and Procedures Using Contrast Media
5. Place the cassettes appropriately; they should not be mixed up-the
exposed and unexposed.
6. Select the required type speed, fast or slow screen cassettes or films.
7. Check for tight closure of cassettes to avoid film fogging and
8. Prepare the barium sulphate suspension.
Care to patient
1.
2.
3.
4.
Receive and identify the patient
Change the patient and explain the procedure
Check for instructions if followed
Escort patient to examination room.
During examination
a)
b)
c)
d)
e)
f)
g)
Administer barium sulphate to the patient
Help radiologist communicate with the pt
observe the pt and report any incident
Ascertain pt’s comfort
Change the films after exposure
Adjust exposure factors (new equipment does not need this)
Protection from radiation to all people in the room.
After examination
a)
b)
c)
d)
e)
f)
g)
h)
Help the patient from the couch
Have the pt clean the mouth
Ask patient to change back into his clothes
Escort the pt to waiting area
Inform of any follow-up films
Clean the room and prepare for next examination
Process the exposed films
Remind pt of next appointment and discharge pt if fit, from the department and
i) Inform of any change of colour of faeces.
Barium swallow
This is a radiological examination of the pharynx and the oesophagus by use
of contrast medium. Contrast medium used is barium sulphate in paste form
35
Medical Imaging Technique and Procedures
and is best done under screen control. Radiographers can also do it without
screening.
Indications for barium swallow
Foreign body, carcinoma, oesophageal varices, strictures, stenosis and fistulae. Investigation of heart diseases and gastroesophageal reflux disease
(GERD).
Patient preparation
a) Patient is given a written appointment indicating clearly date, day and
time of examination, not to eat or smoke after midnight before the exam.
b) Wear a hospital gown and remove all jewellery including body jewellery such as nipple and belly-button rings, dentures, hair clips, or other
objects that might show up on an X-ray film.
c) Patient is put on the couch mostly in vertical position, given thick paste
of barium sulphate which serves as a bolus.
d) Position the patient behind the image intensifier and instruct the patient
to swallow.
e) Then follow the bolus image on the screen and take the films periodically
as required.
f) Posterior-anterior and lateral views taken of the chest are done with
obliques. Exposure on arrested expiration and beam collimated. In
absence of screening facilities, blind radiography is employed.
Barium meal
This is an examination of the stomach and duodenum with the aid of barium
sulphate suspension as the contrast medium. The lower portion of oesophagus is also examined.
Indications
Peptic Ulcers (PU), neoplasm, pyloric stenosis, foreign bodies and hiatus
hernia.
Technique
1. Patient is initially in erect position.
2. Patient is put in the right anterior oblique position.
36
Medical Imaging Techniques and Procedures Using Contrast Media
3. Small glass of barium is given to the patient to drink. This is observed
closely on the screen as it passes down the oesophagus to the stomach.
4. The patient rolls on the table twice for even coating of the stomach walls.
Take posterio-anterior and right anterior oblique views.
5. Patient is given more barium suspension to drink if necessary. Right
and left anterior oblique views are taken to show posterior and anterior
aspect of lesser curvature.
6. Patient placed in supine position to demonstrate the fundus of the
stomach.
7. Patient is examined in Trendelenberg position to demonstrate any hiatus
hernia.
8. Serial of films are taken to demonstrate the duodenum. Split films are
taken to demonstrate part of the duodenum (caps) which may be taken
at short interval speed.
Any technique employed should produce radiographs with all the phases
of movement of the cap. When there is a delay at the pylorus of the stomach,
the duodenal cap does not fill immediately; the patient is made to lie prone
with the left side raised and a pillow placed beneath the ribs of the left side.
Barium follow through
Radiological examination of the whole small bowel from duodenum, jejunum
to ileo-caecal valve following introduction of contrast medium. Combination
of fluoroscopy and overcouch is usually employed. This is performed when a
lesion at the distal end of the ileum, appendix, caecum or the proximal part
of the ascending colon is suspected. After giving barium meal fluoroscopic
examination of stomach and duodenum is performed. Then films are taken
after 2, 3 and 4 hrs.
This is helpful in diagnosis of the appendicitis, ileo-caecal tuberculosis, Crohn’s disease and carcinoma of caecum. Patient preparation as for
barium meal.
Technique
1. After contrast introduction, patient lies prone or on the right side until
barium has left the stomach.
2. Over couch radiographs taken in prone till contrast reaches the terminal
ileum at 15 mins interval, then half-hourly.
37
Medical Imaging Technique and Procedures
3. Once stomach is empty, pt can take food to accelerate transit of barium
through the small bowel.
High kv (120 kv) with short exposure time used.
Prone view
a) Pt lies in the mid-line of the x-ray table. 35×35 cm cassette used, centre
to the mid-line of cassette.
b) When stomach is full, lower boarder of cassette placed at the level of
posterior iliac spine.
c) When empty, lower boarder is placed at the lower margin of symphysis
pubis.
Erect view
Shows fluid levels in presence of jejunal diverticulosis.
a) Lower border of 35×35 cm placed at the level of symphysis pubis.
b) Centre to the midline at the level of lower costal margin.
Use high KV technique.
Barium enema
This is a radiological examination of the colon by retrograde infusion of
contrast medium. Double contrast used because it involves radio paque and
radio luscent contrast media, (air and barium sulphate). Consider possibility
of pregnancy in women of reproductive age.
Indications
Bowel polyps, Ulcerative colitis, Acute appendicitis, Twisted bowel loops,
Cancer, Colitis, persistent diarrhoea, megacolon, Intussusception,
Hirschsprungs disease, Congenital abnormality and Diverticuli.
Patient preparation
•
•
•
Low residue diet 4 days prior to exam.
Empty the colon before examination, either by use of aperients 2–3 days
or colonic washout before examination.
Nil by mouth 4–6 hours before examination.
38
Medical Imaging Techniques and Procedures Using Contrast Media
•
•
•
•
•
Pt undresses completely and wears an open – back gown.
No pre-medication required. In some cases, buscopan is given to relax
the smooth muscle and reduce bowel peristalsis.
Patient to take 2 tablets of dulcolax at least 2 days prior to examination.
Light meals a day before exam.
Patient to place dulcolax suppository in the rectum half an hour before exam.
Contrast medium
Barium sulphate about 500-600 mls introduced rectally. More required in
case of megacolon. Luke warm water for burium suspension.
Trolley set up
•
•
•
•
•
•
Enema container with suitable tubing length.
Enema drip which is adjustable in height … 100 cm.
Polythene connection between tubing and catheter.
Catheters, disposable enema set preferred.
Barium sulphate suspension at correct temp. 38 degrees.
Gause swabs, lubricating jelly, Dressing towels, bowl receivers, Bed-pan
readily available and cover and shringes.
Equipment
As for barium meal.
Technique
1. Explain exactly what will be done to the patient.
2. Position the patient on his side with knees flexed.
3. Lubricated catheter inserted approximately 10 cm into the rectum and
secured in place by tape.
4. Balloon is then inflated by means of disposable syringe. Height of enema
bag about 100 cm above the table.
5. With patient prone, the table is tilted 10 degrees head downwards.
6. Little barium is run through the tube to confirm no blockage.
7. Patient asked to turn over on his back.
8. Barium is run slowly until it reaches the splenic flexure.
9. Air is gently pumped forcing the column of barium along the colon creating double contrast.
39
Medical Imaging Technique and Procedures
10. When the filling is right, undercouch films are taken. These are PA oblique
and Lateral.
• Over couch films include AP. Patient rotated on the left side and then
into the right anterior oblique to coat the internal mucosa.
• Under couch views are taken with the patient in lateral, oblique and
erect positions.
Antero-posterior
Patient lies; supine lower border of cassette is placed at the level of the symphysis pubis. Centre in the midline at the level of lower costal margin.
Figure 3.1
Postero anterior (PA) Enema projection.
Left lateral decubitus
•
•
Patient lies on the left with his arms on the pillow above the head.
Grid cassette supported vertically or posterior to the patient.
40
Medical Imaging Techniques and Procedures Using Contrast Media
•
•
Horizontal beam used and centre at mid-line at the level of lower costal
margin.
Right lateral decubitus patient lies on the right side and procedure as for
left lateral decubitus.
Post evacuation projection
AP abdomen done when immediate examination is complete and after evacuation positioning as for AP abdomen.
Ileostomy and colostomy patients
Examination of the colon distal to the site of colostomy is usually performed
by infusing barium via the rectum until it reaches the site of colostomy. Contrast medium e.g. urografin 150 or hypaque 25% may be used instead of
barium. This is to avoid barium leaking from the anastomosis site and pooling outside the lumen of the bowel.
Intussusception
This is a condition in which one part of the alimentary tract becomes pushed
or invaginated into another part below. Common with the terminal ileum
being pushed into the first part of the colon. Mostly common in infants
between 4 months and 2 yrs. If diagnosis is uncertain, barium enema may be
used to confirm producing a typical cup-like appearance at the head of the
enema (where it is entering).
Hirschsprungs disease
Condition in which the rectum is normal, narrowed section of the sigmoid
colon and grossly enlarged colon above this. Occurs due to congenital anomalies and is idiopathic (unknown origin). Ba-enema may be used to confirm
this condition.
Colonic washout used and enama wash-out enema recommended after
exam.
Patient after care
•
•
•
Patient leaves the department when fine.
Warn the patient of colour change in the faecal matter.
Take plenty of water to minimize faecal impaction.
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Medical Imaging Technique and Procedures
Complications of barium enema
Barium impaction is a blockage of the colon caused by the barium. This is a
rare event. Dehydration due to taking enemas and laxatives before the procedure. Puncture of the colon. Small risk of cancer due to radiation exposure.
Double contrast
•
•
•
•
•
•
•
Double contrast technique is done after infusion of barium sulphate has
been completed and colon has been partially evacuated.
Colon is distended with air.
Small defects that may have been previously obscured by barium may
become visible with double contrast. Also demonstrates polyps.
Air is pumped in gently by means of a syringe.
Rotate the patient to manoeuvre the air round the colon.
Under-couch radiographs are taken using KV 10 less than for filled colon.
At the end of exam, remove the catheter and direct the patient to lavatory
to get rid of air.
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Medical Imaging Techniques and Procedures Using Contrast Media
Figure 3.2
Barium enema showing CA colon
43
Medical Imaging Technique and Procedures
Small bowel enema
•
•
•
This is an examination of the small bowel.
Contrast injected via a catheter to the area of interest.
In barium enema, catheter is put through the rectum. Catheter to stomach and duodenal area then followed to the end.
Diabetic pts for colon examination
Diabetic pts present special problems as it is essential to starve before examination. Diabetic pts rely on properly controlled diet. Patients who receive
insulin are asked to omit the morning dose and carry them with their normal
breakfast to the dept; alternatively a meal can be arranged with the hospital.
Given 1st priority in the hospital and department.
Biliary examinations
Oral cholecystography, Intravenous choledochography, Endoscopic retrograde choledocho-pancreatography (ERCP), percutaneous transhepatic choledochography and Operative choledochography.
Post operative T-tube choledochography radiographic examination of
the biliary tracts is usually required to assess the function and demonstrate
anatomical abnormalities.
Contrast medium is therefore needed to demonstrate the biliary tract.
Contrast medium may be given orally, intravenously or by retrograde cannulation of the ampulla of vater, percutaneously into the hepatic ducts, direct
injection at operation and through a drainage tube after operation.
Biliary tract may also be examined by CT and ultrasound. Oral contrast
medium is excreted by the liver and enters the gall-bladder where it is
concentrated.
Oral cholecystography
An iodine-based oral contrast medium is ingested the evening before the
examination. Films of the right upper quadrant the following day demonstrate an opacified gallbladder. It does not opacify if there is cystic duct
obstruction or the patient is jaundiced. Calculi are seen as filling defects.
A film after a fatty meal shows the extent of gall-bladder contraction.
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Medical Imaging Techniques and Procedures Using Contrast Media
Figure 3.3
Ap abdomen showing full gall bladder.
Operative cholangiogram
This investigation is performed at cholecystectomy when the cystic duct is
cannulated and contrast injected to outline the common bile duct.
T-tube chlangiogram
This examination may be carried out approximately 10 days after surgery to
identify any remaining calculi in the common bile duct. Contrast is injected
into the T-tube under fluoroscopic control to exclude residual calculi.
Figure 3.4
A normal T-Tube cholangiogram.
45
Medical Imaging Technique and Procedures
Transhepatic cholangiogram
A fine needle is inserted directly into a bile duct in the liver under local
anaesthetic.
Contrast is injected to visualize the entire biliary system and thus try and
elucidate a cause for obstructive jaundice.
Endoscopic retrograde choledocho-pancreatography (ERCP)
After the patient is sedated and the pharynx anaesthetized, an endoscope is
introduced and advanced through the mouth into the duodenum. Contrast
injection is directed into the ampulla of Vater, to demonstrate both the bile
ducts and the pancreatic duct. Common bile duct stones can be removed
through the endoscope by insertion of a catheter with a balloon. Malignant
common bile duct strictures can also be stented.
Figure 3.5
ERCP Examination.
Ultrasound is the initial investigation of choice in a patient with jaundice.
This may demonstrate a dilated common bile duct down to the level of the
stricture. ERCP will show abnormalities of the upper gastrointestinal tract
and the pancreas, in addition to the common bile duct stricture. Transhepatic cholangiography may be required if ERCP is unsuccessful.
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Medical Imaging Techniques and Procedures Using Contrast Media
Percuteneous transhepatic choledochography (PTHC)
This is the radiographic examination of the biliary tree following direct injection of contrast medium into the liver tissue. Indications Jaundice, thought
to be of obstructive origin, differential diagnosis between intrahepatic and
extrahepatic obstruction (Cholecystitis), demonstration of dilated intrahepatic ducts (dilated intrahepatic ducts are usually confirmed by ultrasound
before this examination is done).
Technique
1. The bile ducts are dilated; bile is aspirated before contrast medium injection and send for microbiological examination.
2. If a bile duct has not been entered during the first withdrawal, this may
be attempted up to 10 times.
3. After which the examination is abandoned with assumption that bile
ducts are not dilated.
4. If the examination reveals obstruction or dilated intra hepatic ducts, the
patient goes to theatre for laparatomy. Postero-Anterior (P.A), 45 degrees
Right Posterior Oblique, Right Lateral, Trendelenburg Position (Supine
Postero-Anterior P.A).
Figure 3.6
Ultrasound image showing GB calculus.
47
Medical Imaging Technique and Procedures
 Urinary System
Excretion system of the body consisting of two kidneys, two ureters, urinary bladder and urethra. Examinations of this system are plain abdomen,
Intravenous urography (IVU), retrograde pylography, cystography, cystourethrography, renal puncture and renal arteriography.
Patient preparation
•
•
•
•
•
Abdominal preparation for removal of gas and faecal matter as for barium meal
Laxatives can be given for two days before examination or a day depending on the departmental routine.
A series of films are taken for intravenous urography. One AP abdomen
as a control or scout to check preparation, positioning, exposures and
reveal any renal culculi. This examination (IVU) demonstrates the whole
urinary system thus kidneys, ureters and urinary bladder.
After injection of contrast medium conray 280 or urografin 60% 20–
40 mls films are taken thus nephrogram immediately, 5 minutes, 15
and 25 mins full length. The rest are focused on the renal area.
Post micturation film is taken of the pelvic region to show bladder empting capacity. This examination is being replaced by other modalities like
CT and ultrasound although in ultrasound there is limitation when one is
looking for the physiology of the kidneys.
Indications for IVU
Renal failure, hydronephrosis, renal mass, hypertension, ectopic kidneys,
pyelonephritis, ruptured kidneys, renal calculi and renal TB.
Equipment and accessories
•
•
•
•
•
•
General X-ray unit with adequate output,
Potter bucky
Films
protective devices
Gowns and compression bands.
After AP abdomen, supplementary films may be taken thus erect AP
abdomen for gall calculi differentiation, prone also calculi movement and
obligues.
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Medical Imaging Techniques and Procedures Using Contrast Media
•
Delayed films can be taken for delayed excretion. A surgical trolley will
be prepared with the following: Upper shelf 20 or 50 ml syringes, 2 ml
syringe, IV needles, kidney dish, drawing up cannula, dressing bawl,
a pair of dissecting forceps, towels and swabs. Lower shelf will hold
ampoules of contrast medium in warm water, file, sphygmomanometer
or tourniquet, skin cleanser, vomit bowel, sand bag, oxygen cylinder and
resuscitation drugs.
Figure 3.7
IVU image.
Retrograde pyelography or ascending pyelography
Not an examination of choice and not common presently. It demonstrates
the pelvicalyceal area and the ureters. Catheters inserted in theatre. Equipment and technique as for IVU. Other modalities have replaced this examination. Cystography and urethography involve passage of a catheter through
the urethra to fill the bladder with contrast medium then films taken of the
bladder and urethra. Urethra as one is passing urine to outline the urethra
with contrast medium. Renal puncture or taking of biopsy is currently done
with aid of ultrasound, CT or II.
49
Medical Imaging Technique and Procedures
 Reproductive System
Male and female reproduction system for life continuity in terms of future
generation. The female has internal and external organs. The examinations
are grouped into two parts:
1. Obstetrics for gravid uterus and
2. Gynaecological for non gravid uterus.
Gynaecological examinations are two:
a) Plain pelvic examination to show uterine lesions or masses and
b) Contrast media examinations.
The most common contrast medium examination is hystero salpingography (HSG) to show cause of infertility. Ultrasound has taken over
the female examinations to avoid irradiating the foetus and the mother.
HSG is being carried out at the moment. Hysterosalpingography demonstrates the uterine cavity and uterine tubes to determine patency of the
tubes.
• This examination may be done using general equipment or by fluoroscopy or screening. Equipment for general work and screening equipment
needed.
• A trolley with upper sterile part and lower unsterile is needed. Contrast
medium can be conray or urografin 60% or non ionic contrast medium
in the market.
• Patient preparation is needed to avoid gas and appointment given a day
or so.
• Privacy paramount for it is a very embarrassing examination. A series
of projections of pelvis done AP during and after the injection of
the 20 mls contrast medium. Patient is reassured and when stable
discharged.
• Trolley items will include: Upper shelf vulsellum forceps, vaginal speculum, uterine sound, uterine cannula, sponge holding forceps, tissue
forceps, 10–20 mls syringe, lotion bowl, gallipots, towels, gauze swabs
and gloves, gowns and masks. Lower shelf – cleansing lotion bradosol
or other but not spirit, contrast medium, file, receiver, pad and bandage,
emergency try and small mackintosh towel.
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Medical Imaging Techniques and Procedures Using Contrast Media
Figure 3.8
HSG AP pelvis showing peritoneal spill.
 Nervous System
This comprises of central and autonomic nervous system. Central has spinal
cord and the brain which has cerebellum, cerebrum, mind brain, Pons varolii
and medulla oblongata. Inside is the vetricular system of the brain.
The examinations are: Plain radiography, Ultrasound-cranials, CT, MRI,
Myelography, and Ventriculography, air encephalography, cerebral angiography, discography and radiculography.
Myelography
A contrast examination of the spinal cord and nerve roots by use of contrast
medium injected through the subarachnoid space. The injection is given via
a lumbar puncture at L2 L3 and L4 L5 levels to avoid injuring the spinal cord.
This is done to check for blockage of spinal cord by tumours or enchroachment into the canal by prolapsed intervertebral discs. An invasive examination now replaced my other imaging modalities especially CT where CT
myelography is carried out. A sterile trolley is required for this procedure
and equipment with screening facilities and high output generator.
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Medical Imaging Technique and Procedures
Figure 3.9
Myelography images.
 Circulatory System
Consists of heart, blood vessels and blood. Examinations are – plain radiography, barium swallow, arteriography, venography, CT, MRI and ultrasound.
Digital subtraction angiography obsolete. Indications – CCF, stenosis, aneurism, strictures, varices and clots. Sterile trolley used with upper and lower
shelves. Angio limited to area of interest e.g. femoral
Sailography
Contrast examination of the salivary glands by use of a water soluble contrast
medium. Salivary glands are three pairs situated along the mandible with
sublingual being under the tongue behind symphysis menti, submandibular
below and medial to the body of mandible and parotid the largest from
zygoma to the angle of the mandible.
After introduction of contrast medium, the technique is lateral and inferosuperior, for the first two pairs and AP and lateral oblique for the parotid
glands. Contras is injected in aseptic technique. This examination is no longer
done.
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Medical Imaging Techniques and Procedures Using Contrast Media
Angiography
This examination is for the arteries after injection of contrast medium
through direct puncture or catheterization. This done in several way and
referred according to the area being investigated. Can include carotid
angiography, femoral arteriography, brachial, aortography and four vessel
among others. The indications are aneurysms, clots, angiomas and stenosis
of the arteries.
Venography
A contrast examination of the veins using contrast medium. It will depend on
the region being examined. It is done under aseptic technique. Indications are
clots, strictures, varicoses and space occupying lesions.
Ventirculography
This is a contrast examination of the ventricular system of the brain done
after injection of contrast medium. Brain ventricles are four thus lateral two,
3rd and 4th ventricles. These are examined to check for blockage, masses and
stricture.
Interventional radiology
This is done as need arises and to specific areas. Some examples include
renal cyst drainage, abscess, peritoneal drainage, specimen and many others. Remember patients are booked and starved accordingly in most of the
contrast examinations for physiological preparation.
53
Chapter 4
Medical Imaging Techniques and
Procedures – Modern Modalities
This module consists of:
Ultrasonography – US, Computerized Tomography – CT, Nuclear
Medicine – N/M, Radiotherapy and Magnetic Resonance Imaging – MRI.
 Objectives
•
•
•
•
•
Define ultrasound
Explain Ultrasound physics and key terms
State the modes used in ultrasound
State the types of transducers
Explain the applications of ultrasound.
 Ultrasound
Sound beyond hearing. This is caused by mechanical vibrations. Ranges from
2 megahertzs to 15 Mhtzs. Hearing range 20 htzs to 20 Khtzs. Hertz is one
cycle per second and it is the unit of measurement for ultrasound energy.
Ultrasonography is the technique of producing images using a transducer.
Transducer is an instrument capable of transforming one form of energy to
another.
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Medical Imaging Technique and Procedures
Transducer
Produces and receives or detect energy. Mechanical energy converted to
electrical. Air and fat reflect back almost all the energy in wave form. Sonic
energy used to detect approaching marines. Also bats use this energy –
sonus – sound and Graphic – write. Higher frequencies have shorter
wavelength and demonstrate superficial structures with good resolution – 7 mhtz, 8–15. Lower frequencies long wavelength and penetrate
deep structures and resolution is lower – 3 mhts – 5. Propagation speed
depends on the medium. This is faster in solids, tissue and fluid. Artefacts
also occur as scanning is taking place and they may be shadowing, reverberation, mirror and ghost.
 Ultrasound Terms
Frequency
Number of vibrations per second. Measured in hertz – one cycle.
Amplitude
Distance moved by the vibrating molecules from the neutral position. This is
loudness in the audible range.
Wavelength
Distance between two peaks of the cycles.
Velocity
Rate of wave movement, rigidity or compressibility.
Production of ultrasound
Sound is produced by thin crystals/ceramic activated by electromagnetic
waves of a specific frequency. The crystals are called Piezo electric crystals. Signal/wave is send and received back after a short while. Back wave
carry information about the structure and can be displayed on an oscilloscope as an image. Cathode ray tube displays the images. Medium can
be compressed or stretched releasing energy – Transducer has ability to
send and receive energy – pressure electricity. Sound waves returned as
echoes.
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Medical Imaging Techniques and Procedures – Modern Modalities
Transducers
These are the devices capable of producing and receiving sound waves. Contain piezo electric crystals. They are of higher and lower frequencies 2.5 mhtz–
15 mhtz. The higher the frequency the shorter the wavelength and demonstrate
superficial structures and good resolution and vice versa. Transducer has a
plastic housing, acoustic insulator to damp the oscillations, crystal elements,
insulating cover, electrodes and a cable for power supply. Transducer surface
must be smooth. Aquesonic gel applied for good skin contact, lubrication and
air removal. Air is a bad reflector for it will reflect back almost all the waves.
 Display Modes
This is what is seen as image but due to the speed; one may not see the form
of display like dots. The major display modes are:
1) A-mode – this is amplitude mode. Displayed in form of spikes, linear,
straight and one dimension.
2) B-mode or brightness mode displayed as dots and in two dimensions
thus horizontal and depth in form of dots.
3) Motion mode – display in form of dots. For moving parts like fluid, blood
and heart. Mixture of A and B.
Doppler Effect by Andrea Doppler a German mathematician is also
motion. Car approaching, moving away.
Types of transducers
These can be linear or sector. Linear can be curved or curvilinear. Sector
rectangular. Special type for intercostal spaces and cavities – TVS, TRUS and
for orbits. Sector has one crystal which swings and are 2 broad types thus
mechanical and electrical.
Knobology
The radiographer has to understand the machine very well in terms of how
it functions. The major knobs/keys are:
TGC – Time Gain Compensation – to compensate for the time lost in the deep
structures for the echo to come back.
Gains – different gain through all structures.
Depth – How far a reflector is.
55
Medical Imaging Technique and Procedures
Focus – level of organ – capture.
Freeze – stop the image from moving on the screen.
Markers and print buttons.
 Major Examinations
•
•
•
•
•
Abdomen
Obstetrics
Gynaecology
Small parts and
Interventional.
Abdomen
Extends from the diaphragm to the lower border of symphysis pubis. The
organs are liver, kidneys, pancreas, spleen, peritoneum, uterus, urinary bladder, gall bladder, ovaries, intestines and vessels. Any organ which sends echoes
is echoic if not anechoic or echo free. Some cast posterior enhancement or
shadowing. Urinary bladder is bright thus enhancement and stones dark
thus shadow. Spleen echoes brighter than kidneys. Kidney cortex hypo echoic
compared to medulla which is hyper echoic due to the tubules, fat, vessels
and calyces. Pancreas on top of three vessels SMA bright, Aorta below SMA
and splenic vein. Pregnant mother explore and state foetal well being thus
cardiac activity, liquor, head, limbs, spine, placenta and take measurements.
Measurements
1. BPD – Bi parietal Diameter – along the parietal bones. Inner to outer.
Masai shield with an arrow.
2. FL – Femoral Length – single bone end to end.
3. AC – Abdominal Circumference – check spine, stomach and umbilical vein.
4. CRL – Crown Rump Length.
5. HC – Head circumference.
Trimesters
These are three stages in foetal growth:
•
•
•
1st trimester 1–12 weeks,
2nd 13–26 and
3rd 27–36 or term.
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Medical Imaging Techniques and Procedures – Modern Modalities
All the stages have their own abnormalities – Full bladder. Gynaecological ultrasound for non gravid uterus to check for masses or other abnormalities. The bladder should be full of urine.
Small parts
These are the organs which are superficial and include:
Mammary glands, Testes, Thyroid gland, Prostate gland and eyes.
Breast has 6 parts: Areola, Axillary, UIQ, LIQ, OUQ and OLQ.
Examine seated slowly sagittal, coronal and transverse planes.
Indications
Abdomen
Reasons for U/S are: Hydatid cyst, splenomegally, portal hypertension,
hepatomegally, jaundice, abdominal masses, peritonitis, ascites, gall stones,
renal stones, intestinal obstruction, renal failure, hydronephrosis, nephritis,
abcesses, FB, ruptured viscera and hernia Moghania and Bodalek. Sliding
when fundus up gastro-oesophagus and rolling.
Gynaecological
Gynaecological indications
are fibroids, masses, haemorrhage, IUCD, bi-cornate
uterus, retained products,
PID and cystitis.
Obstetric indications
These are gestational sac,
blighted ovum, implantation, placental site, hydatidiform
mole, ectopic
pregnancy, multiple pregnancy, maturity, abnormality, dermoid cyst, threatened
abortion, incomplete abortion, spoting and dating.
Figure 4.1
57
Gravid uterus.
Medical Imaging Technique and Procedures
Cranials for kids for trauma, coma, biopsy and defects. Made easy by anterior
and posterior fontanelles.
Patient preparation
•
•
•
•
•
These include 6–8 hours starvation for abdominal organ.
Physical, sociological and physiologically.
Full bladder.
All scanning protocols to be observed as departmental routine and this
are done in coronal, sagittal and transverse.
Identify caudad and cephalad.
 Computerized Tomography – CT
Objectives
•
•
•
•
•
•
Explain the concept of CT
Explain the key terms used in CT
List the equipment for CT
Describe the scanning procedure
Explain image quality in CT
Explain radiation protection in CT.
Computerized tomography
This is a diagnostic modality which uses the principle of tomography to produce body images. A series of images are produced in form of slices while in
tomography the layers lie on each other. X-ray machine, detectors and computer used.
(Developed by Hounsfield and his team in 1967–1972.) Medical use commenced in 1972 and thin layers obtained with no overlap to pick tiny lesions.
CT terms
Hounsfield (N)
The unit of measurement of attenuation. This measurement determines the
attenuation of X-rays through the body, water 0, bone + 3500 ad air – 1000.
Voxels
Volume elements are small blocks of tissue calculated by a data processor in
the gantry.
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Medical Imaging Techniques and Procedures – Modern Modalities
Pixels
Picture elements thus final image.
Matrix
Number of volume elements per slice. Final image 320×320, 512×512,
1024×1024.
Window level/width
Grayness of displayed image and differ in bone, chest soft tissue, head and
mediastinum.
CT equipment
Gantry
Houses tube, detectors, coolers, circuit breakers and interlocks.
Patient couch
Offers vertical and horizontal movements and has a cradle to move the
patient.
Computer system
Collects data and records it in form of images – Operator console, viewing
system – Screen, data storage and print
•
•
BMD – bone mineral densitometry
PDU – power distribution unit.
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Medical Imaging Technique and Procedures
Figure 4.2 CT machine setup.
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Medical Imaging Techniques and Procedures – Modern Modalities
CT generations
1st generation
Was too massive and used long exposure time – 5 minutes, translate rotate
configuration, pencil beam and single detector – head only.
2nd generation
Translate rotate, fan beam, detector array and short time – 30 secs. Could
scan head and body.
3rd generation
Rotate, fan beam, shorter time – 1 second and detector array. Could produce
ring artefacts.
4th generation
Rotate stationary configuration, fan beam, detector array, shorter time 1 sec.
5th generation
Rotate mutate scanners with electron beam. Have brushes and multislice 4,
16, 32, 64…
Scanning procedure
Consists of three stages thus: Measurement, Reconstruction and Archiving/
display.
Measurement
Determines attenuation of X-rays along multiple narrow paths or columns of
tissue. Measured in Hounsfields and gantry height determines this measurement. Voxel is the volume and pixel is the picture element while matrix is the
final image. Numbers according to attenuation. Water 0, air –1 and bone +1.
Image reconstruction. Process of creating images from scan data. This involves:
a) Pre-processing of data including re-ordering of the data and is done by
programmable array processor – Prospective reconstruction.
b) Retrospective construction in which after the re-ordering, the images
can further be cut into small slices like from 5 to 2.5 as in joints and in
helical and spiral mode. This is done after examination is over.
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Medical Imaging Technique and Procedures
Display/archive
This is the displaying of images on the monitor. The images are also stored
in discs, files and can also be printed to have hard copies. The hardware for
this is in the operator’s console. There are other interesting abilities of the
console like field of view.
CT image formation
X-ray source is collimated to fan beam which transverses the patient and
coupled to radiation detector made of gas-Xenon. A reading is made each
time tube moves per degree to 360 degrees and at the end the several readings are recorded for computer processing. Small blocks of tissue (Voxels)
absorb radiation and this determines the final image (Pixel) and the number
of voxels per slice is called matrix and the larger the better the resolution
320×320, 512×512, 1024×1024.
Figure 4.3
CT image showing subdural heamorrhage with midline shift
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Medical Imaging Techniques and Procedures – Modern Modalities
Image quality
The final image quality depends on:
• The technical excellence of the radiographer.
• Machine reliability and efficiency-resolution and sensitivity – ability to
differentiate small densities.
• Patient co-operation.
• Processing of the films.
• Radiation protection should be upheld by observing all the necessary
measures like ALARA principal and inverse square law.
Advantages
•
•
•
•
•
•
•
Thin slices with detailed images
Small lesions picked up
eliminates the need for invasive procedures
No superimposition of structures
Very fast/quick
Archiving in several ways
Applied in the whole body.
 Computed Radiography (CR)
Principles of computed radiography
Computed radiography (CR) can use same equipment as the conventional
imaging except there is no film instead is a plate called photo stimulable
phosphor (PSP). This is a cassette with screen like material. There is no need
of a processing machine either manual or automatic. Laser scanner or reader
used – CR reader.
The plate carries the latent image which is digitized and can be read
after feeding into a computer. The digital image can be viewed and enhanced
using software that has functions similar to other digital image processing
software as in digital imaging (DR).
CR and DR can produce an image in a matter of seconds hence shortens
patient stay in the hospital.
Imaging plate
CR imaging plate (IP) contains a photostimulable storage layer 0.1–0.3 mm
thick and it stores the radiation dose as a latent image within the layer as
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Medical Imaging Technique and Procedures
electron energy. The reader reads this latent image using photomultiplier
tube.
Imaging plates can be used several times unlike X-ray films and also are
reusable.
Advantages of CR
•
•
•
•
•
•
•
•
CR can be incorporated into the existing imaging department without a
lot of financial implications.
High resolution giving more detailed images.
No need for processing laboratory manual or automatic hence no chemical handling.
Filmless hence no need for intensifying screen and films.
Saves time for it is very fast and not much radiation dose to the
patients.
Images can be shared with other institutions for knowledge sharing
information.
No extra room as a processing laboratory is not needed.
Repeats avoided with less time in the department, less fatigue to the
equipment and the radiographer manning the department.
Disadvantages of CR
•
•
•
•
•
Cassette handling that is imaging plate (IP) which is not the case
with DR.
Manipulation of image causes geometric unsharpness and low resolution.
Imaging plates are more expensive and can be damaged causing image
artifacts and eventually have to be replaced.
Images acquired are subjective because of the ease of manipulation by
the radiographer.
Possibility of damaging the PSP.
 Digital Radiography (DR)
Digital radiography involves entry of data into the computer as patient identification. The cassette is inserted in the DR reader and image shows on the
screen. Image manipulated, marked on the side left or right, density checked
and can print or archive in the computer or send to Picture Archiving Communication System (PACS).
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Medical Imaging Techniques and Procedures – Modern Modalities
 CR verses DR
1. CR uses a plate while DR uses a detector or flat panel which changes
X-ray to electrical energy in form of image which can be manipulated and
fed into a screen for viewing and archiving.
2. DR faster and resolution high.
3. DR is expensive than CR. It is important to note that CR uses a laser reader
and DR a detector.
Benefits of CR and DR
•
•
•
•
•
•
•
•
•
•
•
•
•
No wet processing required.
No darkroom hence saves space.
No consumables like chemicals for processing.
No chemical disposal reduces costs and protects the environment.
No film or chemical store, saves space.
No rooms full of films stored.
Reduction of artifacts, improves image quality.
Higher image quality for one is able to manipulate the image.
Share images via email or CD, quicker referral.
Multiple plates of various sizes, flexibility of image capture and saves lots
of time.
Reduced repeats which reduces radiation dose to the patient, staff and
the radiographer.
Resolution and detail improved hence getting images of good diagnostic
value.
No need to repeat images due to loss of films for it is a filmless technique.
Medical applications of CR and DR
1. Mostly used because they have proven reliability.
2. Flexibility to address a variety of clinical use and lower costs.
3. Can convert an existing X-ray room to computed radiography (CR) as
what is needed is a laser reader and a photo stimulable plate (PSP) and
DR will need a flat panel.
Industrial applications
1. Corrosion surveys on pipes often through installations
2. Examination of valves for erosion
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Medical Imaging Technique and Procedures
3.
4.
5.
6.
7.
Checking for patency in pipes and valves
Checking for cracks in pipes and valves
Examination of boiler water walls
Automotive casting inspection
Code work for nuclear installations on all size piping.
Photostimulable phosphor (PSP)
Material or photo stimulable phosphor is a material which when exposed to
external stimuli or energy like X-radiation emits light or fluorescence and is
called a phosphor. It has layers which play different roles just like the film
and intensifying screens. These layers are the base, reflective layer, phosphor and overcoat protective layer. Lead backing for scatter absorbing is also
present in the PSP.
Image contrast
Contrast is the difference between black on a white surface. Densities can be
differentiated quite well and this is called good contrast. There is high, low
and poor contrast. The clear object will be of good contrast and poor is when
the object is not clearly viewed.
Exposing a film to produce higher densities increases the radiographic
contrast. Contrast in radiography makes the image on an X-ray or other scan
visible.
Contrast is the difference in image density between two areas. For
instance, one area of a scan may be very dark and another very light. Radiographers need contrast in order to spot broken bones or defects on organs.
Images can have a high level of contrast or a low level. The difference in
the density of two parts of an image is greater in high-contrast images. The
higher the contrast, the easier it is to spot problems and abnormalities in
a scan. If areas of the subject vary in thickness, the contrast will be greater
between those two thicknesses. Additionally, taking an X-ray using low voltage will create an image with high contrast.
 Nuclear Medicine
Objectives
•
•
Definition
Principle
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Medical Imaging Techniques and Procedures – Modern Modalities
•
•
•
Classification
Equipment
Applications.
Definition
Radio nuclides or radioisotopes are used in medical field to diagnose and
treat. It works on the principle that the injected radionuclide has a tracer
which takes it to a target organ. The organ absorbs the substance and radiation is released which can be recorded with organ facts. These details are
captured in an image and will give information about the organ.
Figure 4.4
Bone scan in N/M.
Classification
Nuclear Medicine is divided into two divisions:
1. SPECT
2. PET.
SPECT stands for Single Photon Emission Computerized Tomography.
A gamma camera is used and has a sensitive detector able to detect gamma
rays during NM investigations. Thallium activated Sodium Iodine is used
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Medical Imaging Technique and Procedures
due to its high sensitivity to gamma radiation. A gamma camera has a head,
collimators, detector crystal and an array of photomultiplier tubes, Computer interface, Image display system and printing system or archiving/
display system.
The gamma rays carrying patient information are fed to the detectors
which produce light which is fed to the photomultiplier for enhancement
then computer system for image processing and display on the monitor/
print. The energy used is 120–350 kev and the radio isotope is inside the
patient’s body or organ.
Positron emission tomography (PET)
The radionuclide used decays by emitting positrons which are negatively
charged electrons. Very short lived and travel short distances before being
stopped. These combine with electron to form two photons with energy of
511 kev and travel perpendicular to each other.
SPECT and PET radionuclide inside the patient. Energy ranges differ with
SPECT at 120–350 kev and PET 511 kev and the equipment differ slightly in
structure and principle. In PET, the part under examination is inside the gantry and surrounded by detectors for image acquisition and archiving. Radio
nuclides prepared under aseptic technique in a HOT lab.
Radionuclide
SPECT uses Technician 99, Iodine 123 – 3 hours, Iodine 131 8 days, Xenon
133 kev 8 days, Thallium and Indium 111 2–8 days.
In PET nuclides are Fluorine 18–110 mins, Oxygen 15–21 mins, Gallium
68 mins, Nitrogen 10 mins, Potassium 38 mins and Copper 62. In the hot
laboratory, these are mixed with a molecule or tracer to be specific to the
target organ.
NM applications
The whole body and in particular the body organs. These are kidneys, liver,
thyroid gland, heart, pancreas and lungs. Some nuclides can be taken orally.
Radiation protection – very crucial to the public, patients, radiation
workers and other patients. Recommendations to be followed like ALARA
principle, ICRP and IAEA.
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Medical Imaging Techniques and Procedures – Modern Modalities
 Radiotherapy
Objectives
•
•
•
•
•
Define radiotherapy
State the types of radiotherapy
Explain the reasons for doing radiotherapy
Identify radiotherapy applications
Explain radiation protection and quality control in radiotherapy.
Definition
This is radiation therapy by use of gamma radiation to treat cancer and
tumours. Soft radiation also used. Seen as shortening life but it prolongs life
and relieves pain and stress. There are two types of treatment apart from
chemotherapy and surgery namely:
1. Branch therapy
2. Teletherapy.
Reasons for therapy
•
•
•
•
•
To alleviate pain
To stop haemorrhage
Prolong life for a while
Give patient hope
Arrest tumour growth.
Branch therapy
The source of radiation is the patient. Radionuclide inserted using aseptic
technique and the lesion is the source of radiation. Energies used are to the
tune of mega electron volts.
Teletherapy
Source is from outside but not within the patient. Linear accelerators used to
produce energy of MEV. Simulation is the first step in this kind of treatment.
A simulator consists of an X-ray source like CT, MRI or conventional imaging. In simulation, the field size is determined and the target area identified
precisely. Dose calculated.
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Medical Imaging Technique and Procedures
Two main concepts used:
•
•
Tissue Maximum Ratio (TMR) and
Depth dose.
Applications
Radiotherapy is a treatment of choice when surgery and chemotherapy
are impossible. It is applied in all body regions like: Head, Neck, Pelvis,
Chest, Abdomen and its organs to treat masses of various types. Radiation
protection is as for NM. Be aware of disposal procedure for radio nuclide
wastes.
 Magnetic Resonance Imaging (MRI)
Objectives
•
•
•
•
•
•
Define Magnetic Resonance Imaging
Explain principle of operation in MRI
Define the terms used in MRI
Explain the equipment used
State the coils used in MRI
Explain the types of magnets used in MRI.
Definition
This is an imaging modality which uses magnetic field to create images.
The body has hydrogen which acts as magnets in the body interacting with external radio waves. Longitudinal magnetization occurs when
there is equilibrium. Medical use began in 1972. Cooling is done by liquid
Helium gas. There is relaxation after excitement. Proton movement called
precession or spin.
Equipment
The equipment for MRI is similar to CT and includes: Gantry with coolers,
detectors, magnet, Magnetic shields for different body parts, Patient table
and cradle, Operator console and computer and printer.
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Medical Imaging Techniques and Procedures – Modern Modalities
Applications
All body parts as in CT and more sensitive to neurological procedures. These
are the spine, brain, chest and abdomen and other body parts.
Tesla is the unit of measurement and is equal to 10 kgs. Guess is the
smallest unit of measurement. Ranges are 0.3 tesla to 3 tesla hence have 0.3,
0.5, 1, 1.5 and 3.
Operation
The higher the magnetic field the higher the precession. Radio frequency
make the protons precess in synch (in phase) and opposite ones cancel.
RF switched off longitudinal magnetization increase again and this is called
longitudinal relaxation (back to normal state) and is defined by a time constant T1. Transversal magnetization decreases and disappear and is called
time constant T2. Liquids long relaxation time, T1 long. T1 darker fluids in
image and T2 bright – World War 2 – water white.
Images
•
•
•
•
T1 darker images
T2 white images of fluid
Proton density between T1 and T2
Time to repeat a pulse at 90 and 180 degrees then tissues have relaxed
and at the same state.
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Medical Imaging Technique and Procedures
Figure 4.5
A normal MRI myelography lateral projection
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Medical Imaging Techniques and Procedures – Modern Modalities
Contrast media
This increases lesion detection and diagnostic accuracy. Gadolinium
and magnevist used and blood appear white when no contrast and dark
with contrast. Suppression helps to damp fat and other intervening
substances within the body which obscure the needed slices hindering
diagnosis.
MRI coils
These help in different ways some of which are:
•
•
•
•
•
Shim coils – for magnetic field homogeneity
Encoding coils – for the slice thickness
Gradient coils – for slice selection (Noise due to anchorage. Part of
machine couch)
Surface coils – for signal reception
Volume coils – surround body part-Send and receive the signals.
Hardware
The most important part of MRI machine is the magnet. Earth field is one
Gauss and this was a German mathematician who measured geomagnetic
field and won a Nobel Prize. Electrical and mechanical adjustment to get
field homogeneity is called Shiming.
Magnets for MRI
They are three:
1. Permanent magnet – Always ready and no need to magnetize. Has low
field strength (0.3 T), environmental interference, thermal instability
and too much weight about 100 tones.
2. Resistive magnet – Hybrid and uses current. Low energy (0.3 T), electromagnetic, gets too hot, resist current, cooling needed and environmental interference.
3. Superconducting magnet – Mostly used. Special high current. Electricity and gas cooling thus helium and nitrogen (liquid –4 to –296 degrees
centigrade). At this point the conductor loses its resistance. The liquid
gases for cooling are called Cryogens.
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Medical Imaging Technique and Procedures
Quench
This is loss of superconductivity of the magnet. It becomes resistant due to
high temperatures. Cryogens boil and pass thro quench lines. If switched off,
will be rumped (heat high) and quenched to restore the magnetism.
Advantages of superconducting magnets
•
•
•
•
High magnetic field 0.5 to 3 tesla
No environmental interference
Homogeneous magnetic field
Good images and high resolution.
MRI machine installed away from magnetic objects like computers, metals, cars and Farady cage used for shielding the machine from other magnetic fields.
74
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