Diagnostic Imaging Flashcards
Adjacent structures can be seen in radio imaging when they have different
Radiodensities
The radiodensities are:
- ) Foreign metals
- ) Enamel
- ) Bone
- ) Water density
- ) Fat
- ) Air
Which is the most dense and which is the least dense?
Most dense = foreign metals
Least dense = Air
More radiodense structures are referred to as
Radio opaque
Less radiodense structures are referred to as
Radiolucent
Anything that has a different radiodensity than it’s nabor can be
Identified
What are some examples of water density?
Muscle, connective tissue, blood, cartilage, etc
Muscle can be distinguished from an adjacent bone, but can we distinguish ligaments from cartilage?
No
A growth plate within a bone can be seen because the growth plate is
Cartilage
Contrast material with high (or low) radiodensity can be placed into hollow organs to provide contrast that otherwise would not
Exist
When contrast material is placed into blood vessels
Angiography
When contrast material is placed into the subarachnoid space
Myelography
When contrast material is placed into the kidneys
Pyelography
When contrast material is placed into the digestive tract
Barium contrast and/or air contrast
Because materials of higher radiodensity absorb more x-ray than do material of low radiodensity, less radiation reaches the
Film
Film that is less exposed will be
Whiter than more exposed film
In radiography:
- ) High radiodensity structures appear
- ) Low radiodensity structures appear
- ) Whiter
2. ) Blacker
In modern radiography, electronic capture of the x-ray replaces film and then a computer assigns the
Gray scale
The same grey scale used for radiography can be applied to CT scans but NOT to
-because they are not dependent on radiodensity
MRI
Are two dimensional images of three dimensional structures
-so ventral structures will be superimposed on dorsal structures
Radiographs
A single radiograph does not allow you to determine which structure is
In “front” of the other
Orientation of the patient relative to the x-ray source and the film (detector)
-named based off of which surface of patients body is closest to film
Projection
Patient’s anterior side faces the film and their posterior side faces the x-ray source
Anterior projection (PA projection)
The patients posterior side faces the film and the anterior side faces x-ray source
Posterior projection (AP projection)
When the patients left side faces the film
Left lateral projection
When the patients right side faces the film
Right lateral projection
Always viewed as if you are facing the patient (i.e. patient’s right is on your left), regardless of whether it is an anterior or a posterior projection
Frontal projections (anterior (PA) or posterior (AP))
It is common to take two images of the same region that are in projections that are
Perpendicular
Allow you to view an image that appears to be a section through the body
CT (computerized tomograph) and MRI scans
X-rays are passed through the body from multiple directions and collected by sensors in
CT
These signals are then analyzed and transformed into a gray scale by a computer to provide an image of a
particular level of the
Body
Uses a magnetic field and pulse radiofrequency (RF) waves
MRI
After each RF pulse, the emitted energy from the body is collected and analyzed and converted into an
Image
Since CT and MRI are based on different technologies, the interpretation of their gray scale is
Different
In a CT, fat is usually very
Dark (radiotranslucent)
In an MRI, fat is usually very
White (high signaling)
Are always viewed as if you are looking up into a supine patient from the patients feet
Axial (cross-sectional) images
Let’s say you are looking at two images both focused on the heart, but in one image the heart is much larger than the other. Which image has the heart closer to the film?
Objects closer to film = smaller
Objects further from film = larger
