Download Mid-coronal

Mid Term Revision
Imaging Procedure 1
Dr Mohamed El Safwany, MD.
Creating the Image
• Scatter
–Creates fog
–Lowers contrast (more grays)
• Increases as
–kV increases
–Field size increases
–Thickness of part increases
Effects of collimation on scatter
• Collimate to area
of interest reduces scatter
and radiation
dose to the
patient
Grids
• A device with lead strips that is placed
between the patient and the cassette
• Used on larger body parts to reduce the
number of scattering photons from
reaching the image
Grid is placed
between patient (behind table or upright
bucky) & cassette
If placed BACWARDS CAN CAUSE
GRID ERRORS
Factors that affect the detail of
an image
SID
Source to Image Distance
• The greater the distance between the
source of the x-ray (tube) and the image
receptor (cassette), the greater the image
sharpness.
• Standard distance = 40 in. most exams
• Exception = Chest radiography 72 in.
*See page 74 in your book
Shape Distortion
• Misrepresentation of the shape of an
object
• Controlled by alignment of the beam, part
(object), & image receptor
• Influences: Central ray angulation & body
part rotation
Bone Classification
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•
•
•
Long
Flat
Short
Irregular
Centers of Endochondral
Ossification
• Primary center- midbody or diaphysis
• Secondary center- ends or extremities of
the long bones or epiphysis
– Epiphyseal plates: found between the
diaphysis and the epiphysis until skeletal
growth is complete
Anatomic Position
• Upright, arms adducted,
palms forward, head and
feet directed straight
ahead
• Viewing Radiographs:
Display x-rays so that the
patient is facing the
viewer in anatomic
position
R
Body Planes, Sections and Lines
• Sagittal- any longitudinal plane dividing
the body into right and left parts
• Mid-sagittal or median plane- divides the
body into equal right and left halves
• Coronal- longitudinal plane dividing the
body into anterior and posterior parts
• Mid-coronal- divides the body into equal
anterior and posterior parts
• Horizontal or axial plane- transverse
plane passing through the body at right
angles to the longitudinal plane; divides
into superior and inferior portions
• Oblique plane- longitudinal or transverse
that is on an angle or slant to the sagittal,
coronal or horizontal planes.
Understanding CT and MRI
Images
• Longitudinal sections can be taken in
sagittal, coronal or oblique planes
• Transverse (axial) or cross sections
Gastrointestional Fluoroscopy
•
•
•
•
•
•
•
Esophogram/Barium Swallow
Modified Barium Swallow/Dysphgiagram
Upper GI
Small Bowel Series
Enteroclysis
Contrast Enema
Defecography
Single Contrast vs
Double Contrast
• Single Contrast
– Generally uses just thin Barium
– Distends lumen with high density material
– Easier for patient/less mucosal detail
• Double Contrast/Air Contrast
– Thick barium coats lumen
– Effervescent tablets ingested to distend lumen with air
– Produces ‘see-through’ images with greater mucosal
detail
– Greater sensitivity for small lesions, polyps, ulcers
Contrast Enemas
•
•
•
•
Barium or Gastrograffin
Double contrast or single contrast
Generally less sensitive than endoscopy
Requires bowel prep to assess for
mucosal lesions
• Requires some element of patient
cooperation
Hysterosalpingogram
• Used to evaluate endometrial canal and
fallopian tubes
• Infertility and uterine anomalies
• Dye injected into cervical os under fluoro
• Injection continued with goal to opacify the
fallopian tubes and spill contrast into
peritoneum
Magnetic Resonance Imaging (MRI)
• Multi-planar scanning
• Without ionizing radiation
• Images generated using powerful magnets
and pulsed radio waves passing through the
body
• Data from Pt’s body used to generate image
• Field strength of magnets 0.3-3.0 Tesla
MR Contrast Agents
• Intravenous contrast---Gadolinium chelatebased contrast agents
• Gadolinium is a paramagnetic lanthanide
that is toxic as a free metal
• Contrast to evaluate BBB, intracranial
edema and hemorrhage
• Novel agents being developed as tagged
Monoclonal antibodies for Molecular
Imaging
MR Applications
• Neuro-imaging
-Excellent tool due to high soft tissue
contrast resolution
-Abundant water content of CNS allows for
imaging soft intracranial tissue
• Head and Neck imaging
-Multi-planar capability allows for monitoring
extent of disease
-Differentiating subtle soft tissue boundaries of
head and neck
Aims:
Basics•
Best exam results•
Appreciate the role radiology plays•
Densities
The big two densities are:
(1) WHITE - Bone
(2) BLACK - Air
The others are:
(3) DARK GREY- Fat
(4) GREY- Soft tissue/water
And if anything Man-made is on the film, it is:
(5) BRIGHT WHITE - Man-made
Inspiration/Expiration
Anatomy
Heart (continued)
Lateral CXR (continued)
Heart
Size of heart•
Size of individual •
chambers of heart
Size of pulmonary •
vessels
Evidence of stents, clips, •
wires and valves
Outline of aorta and IVC •
and SVC
Typical Mammography Unit
Equipment is
C-arm
SID is fixed at
24 – 26”
Compression Device
Made of firm plastic
Amount of compression:
between 25 and 40
pounds pressure
Compression may be
uncomfortable!
Digital Mammography
State of the art!
• No film or chemical processing
• Images easily sent over internet
• Much better definition
Routine mammography projections
Craniocaudal (CC)
Mediolateral oblique
(MLO)
CT Terminology
• Attenuation is measured in Hounsfield
units
– Scale -1000 to 1000
• -1000 is air
• 0 is water
• 1000 is cortical bone
• Attenuation
– Hyperattenuating (hyperdense)
– Hypoattenuating (hypodense)
– Isoattenuating (isodense)
CT Terminology
• What we can see
– The brain is grey
•
•
•
•
White matter is usually dark grey (40)
Grey matter is usually light grey (45)
CSF is black (0)
Things that are brite on CT
–
–
–
–
–
Bone or calcification (>300)
Contrast
Hemorrhage (Acute ~ 70)
Hypercellular masses
Metallic foreign bodies
CT Terminology
• Window Width
– Number of Hounsfield units from black to
white
• Level or Center
– Hounsfield unit approximating mid-gray
CT Terminology
• DICOM
– Digital Imaging and Communications in
Medicine
– DICOM provides standardized formats for
images, a common information model,
application service definitions, and protocols
for communication.
Radiation Safety
• Terminology
– Gy = Gray is the absorbed dose (SI unit)
• The equivalent of 1 joule/kg of tissue
• Rad = radiation absorbed dose
– Sv = Sievert is the dose equivalent (SI unit)
• Absorbed dose multiplied by a quality factor
• Rem = radiation equivalent man
Radiation Safety
•
Effects of X rays.
–
–
Absorption of photons by biological
material leads to breakage of chemical
bonds.
The principal biological effect results
from damage to DNA caused by either
the direct or indirect action of radiation.
Good Luck