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Page 849
Chapter 20 Goals
Students will be able to:
 List the physical properties of x-rays.
 Identify diagnostic techniques use by radiologist &
nuclear physicians
 Name the x-ray views & patient position used in x-ray
examinations
 Describe the role of radioactivity in the diagnosis of
disease
 Recognize medical terms used in the specialties of
radiology & nuclear medicine
 Apply your new knowledge to understanding medical
terms in their proper contexts, such as medical reports
& records.
Radiology &
Nuclear
Medicine
Chapter 20
Pages 849 – 880
Page 850
Introduction
 Radiology
is the medical specialty concerned with
the study & application of x-rays & other
technology (such as ultrasound & magnetic
resonance) to produce & interpret images of the
human body for the diagnosis of disease.
 Nuclear medicine is the medical specialty that
uses radioactive substances in the diagnosis &
treatment of disease.
 The professionals involved in these medical fields
differ in practice & level of education or training.
Page 850
Introduction: Cont.
 Radiologist
= a physician who specializes in the
practice of diagnostic radiology.
 Nuclear medicine physician = specializes in
diagnostic radionuclide scanning procedures.
 Radiologic technologists = allied health care
professionals who work with physicians in the
fields of radiology & nuclear medicine. Different
types radiologic technologists are:
• Radiographers; Nuclear medicine
technologists; & Sonographers
Pages 850 – 851
Radiology
Characteristics of X-Rays
1.
Ability to cause exposure of a photographic plate
2.
Ability to penetrate different substances to
varying degrees
3.
Invisibility
4.
Travel in straight lines
5.
Scattering of x-rays
6.
Ionization
Page 852
Radiology: Cont.
Diagnostic Techniques – X-Ray Studies
 X-ray imaging is used in a variety of ways to
detect pathologic conditions. Digital radiology is a
form of x-ray imaging in which digital x-ray
sensors are used instead of traditional
photographic film. Thus images can be enhanced
& transferred easily, & less radiation can be used
than in conventional radiography.
Page 852
Radiology: Cont.
Diagnostic Techniques – X-Ray Studies
Computed Tomography (CT)
 The CT scan is made by beaming x-rays at
multiple angles through a section of the patient’s
body. The absorption of all of these x-rays, after
they pass through the body, is recorded & used by
a computer to create multiple cross-sectional
images. The ability of a CT scanner to detect
abnormalities is increased with the use of iodinecontaining contrast agents, which outline blood
vessels & confer additional density to soft tissues.
Pages 852 – 854
Radiology: Cont.
Diagnostic Techniques – X-Ray Studies
Contrast Studies
 In radiography, the natural differences in the density
of body tissues produce contrasting shadows on the
radiographic image. However, when x-rays pass
through two adjacent body parts composed of
substances of the same density, their shadow cannot
be distinguished from one another on the film or on
the screen. It is necessary, then, to place a contrast
medium into the structure or fluid to be visualized so
that a specific part, organ, tube, or liquid can be seen
as a negative imprint on the dense contrast agent.
Page 854
Radiology: Cont.
Diagnostic Techniques – X-Ray Studies
Contrast Studies – Iodine Compounds
angiography
X-ray image of blood vessels &
heart chambers is obtained after
contrast is injected through a
catheter into the appropriate
blood vessel or heart chamber
X-ray imaging after contrast
cholangiography
injection into bile ducts
Page 855
Radiology: Cont.
Diagnostic Techniques – X-Ray Studies
Contrast Studies – Iodine Compounds
digital
subtraction
angiography
(DSA)
X-ray image of contrast-injected blood
vessels is produced by taking two x-ray
pictures (first without contrast) & using
a computer to subtract obscuring
shadows from the second image
myelography
X-ray imaging of the spinal cord after
injection of contrast agent in the
subarachnoid space surrounding the
spinal cord.
Pages 855 – 856
Radiology: Cont.
Diagnostic Techniques – X-Ray Studies
Contrast Studies – Iodine Compounds
X-ray record of
endometrial cavity &
fallopian tubes is obtained
hysterosalpingography after injection of contrast
material through the
vagina & into the
endocervical canal
X-ray imaging of the renal
pyelography
pelvis & urinary tract
Page 856
Radiology: Cont.
Diagnostic Techniques – Ultrasound Imaging
 A transducer (probe) is placed near or on the skin,
which is covered with a thin coating of gel to
ensure good transmission of sound waves. The
transducer emits sound waves in short, repetitive
pluses. The ultrasound waves move through body
tissues & detect interfaces between tissues of
different densities. An echo reflection of the sound
waves is formed as they hit the various body
tissues & bounce back to the transducer.
Pages 856 – 858
Radiology: Cont.
 These
ultrasonic echoes are then recorded as a
composite picture of the area of the body over which
the instrument has passed. The record produced by
ultrasound imaging is called a sonogram.
 Ultrasound imaging has several advantages in that the
sound waves are not ionizing & do not injure tissues
at the energy ranges used for diagnostic purpose.
Because water is an excellent conductor of the
ultrasound beams, patients are requested to drink
large quantities of water before examination so that
the urinary bladder will be distended, allowing better
viewing of pelvic & abdominal organs.
Page 858
Radiology: Cont.
Diagnostic Techniques – Magnetic Resonance
Imaging
 MRI uses magnetic fields & radio-waves rather than
x-rays. Hydrogen protons are aligned & synchronized
by placing the body in a strong magnetic field &
exposing it to radio-waves. The rates of alignment &
relaxation vary from one tissue to the next, producing
a sharply defined picture. Because bone is virtually
devoid of water, it is not well visualized on MRI. This
technique produces sagittal (lateral), frontal (coronal),
& axial (cross-sectional) images as well as images in
oblique (slanted) planes.
Page 859
Radiology: Cont.
 MRI
provides excellent soft tissue images, detecting
edema in the brain, providing direct imaging of the
spinal cord, detecting tumors in the chest & abdomen,
& visualizing the cardiovascular system.
 MRI is contraindicated for patients with pacemakers
or metallic implants because the powerful magnet can
alter position & functioning of such devices.
However, the FDA has recently approved new
pacemakers that can be safely used with MRI. The
sounds (loud tapping) heard during the test are caused
by the pulsing of the magnetic field components as
the device scans the body.
Page 859
Radiology: Cont.
X-Ray Positioning
 In order to take the best picture of the part of the body
being radiographed, the patient, detector, & x-ray tube
must be positioned in the most favorable alignment
possible. Radiologist use special terms to refer to the
direction of travel of the x-rays through the patient’s
body.
 Listed next are terms for radiographic views that are
defined by the direction of the x-ray beam relative to
the patient, who is positioned between the source &
the detector.
Page 859
Radiology: Cont.
X-rays travel from a posteriorly
Posteroanterior
placed source to an anteriorly placed
(PA) view
detector
X-rays travel from an anteriorly
Anteroposterior
placed source to a posteriorly placed
(AP) view
detector
X-ray travel from a source located
Lateral view
to the right of the patient to a detect
placed to the left of the patient
X-rays travel in a slanting direction
Oblique view
at an angle from the perpendicular
plane.
Page 860
Radiology: Cont.
movement away from the midline of the
abduction
body
movement away toward the midline of the
adduction
body
decubitus Lying down
eversion
Turning outward
extension Lengthening or straightening a flexed limb
flexion
Bending a part of the body
inversion
Turning inward
prone
Lying on the belly (face down)
recumbent Lying down (may be prone or supine)
supine
Lying on the back (face up)
Page 860
Nuclear Medicine
Radioactivity & Radionuclides
 Radioactivity = the spontaneous emission of energy
in the form of particles or rays coming from the
interior of a substance.
 Radionuclide = a substance that gives off highenergy particles or rays as it disintegrates.
 Radionuclides emit three types of radioactivity: alpha
particles, beta particles, & gamma rays. Gamma rays,
which have greater penetrating ability than alpha &
beta particles, & more ionizing power, are especially
useful to physicians in both the diagnosis & the
treatment of disease.
Pages 860 – 864
Nuclear Medicine: Cont.
Nuclear Medicine Tests: In Vitro & In Vivo
Procedures
 Nuclear medicine physicians use two types of tests in
the diagnosis of disease: in vitro (in the test tube)
procedures & in vivo (in the body) procedures.
 In vitro procedures involve analysis of blood & urine
specimens using radioactive chemicals.
 In vivo tests trace the amounts of radioactive
substances within the body. They are given directly to
the patient to evaluate the function of an organ or to
image it.