CT And MRI Flashcards
Which has better special resolution?
A. MRI
B. Radiograph
C. CT
B. Radiograph
Special resolution- ability of an imaging systems to differentiate between two adjacent objects
Which has the best contrast resolution ? A. Film radiograph B. Digital radiograph C. CT D. MRI
D. MRI
MRI > CT> DR > Film
This can also be manipulated post processing
What is used in CT to enhance the visibility of blood vessels, vascular leaks, and GI tract?
Contrast medium
Eg. Iodinated given IV
What are uses of CT??
Nasal disease Thoracic masses, respectable Elbow dysplasia Portal vein anomalies Radiation therapy planning
Is contrast resolution better in an MRI or in CT?
MRI
How does an MRI produce an image?
Magnets cause hydrogen atoms to align in the body, and turned at at 90degree angle by a radio wave
Misaligned protons rotate and crate a signal -> detected and turned into image
T/F: most lesions have increased water
True
What signals does a T1 sequence primarily produce in MRI
Fat
A T2 sequence MRI will primarily pick up what signals ?
Free and tissue water
Fat
A FLAIR sequence will pick up what signals?
Tissue water and fat
A STIR image will produce sequences form ?
Free water and tissue water
NOT fat
What substance is used as a contrast medium for MRI?
Gadolinium
- paramagnetic compound that speeds up proton relaxation
- Useful for detecting defective blood-brain barrier or inflammation
- Only used in T1 sequence
What imaging method is best suited for neuroimaging
MRI
What are the 5 radiographic opacities?
Air Fat Water Bone Metal
If a dog is lying in R recumbency, and you have both femurs in a radiograph, the left appears larger than the right, this is likely due to _________
Magnification,
Farther from the cassette -> image is larger and less sharp
What is distortion in an X-ray?
Special case of unreal magnification.
Eg. If a limb is not flat to the cassette, and is at an angle, it will appear shorter and larger at the elevated end
What is superimposition?
A real structure is projected in an unexpected location and is misinterpreted as a lesion
What is summation?
Two structures overlap and create a summation opacity that is not actually present in the patient
What is a silhouette sign?
The effacement of the border of two structures of the same radiographic opacity that are in contact
How should radiographs be named?
Point of entrance - point of exit
Correct an atomic terminology
What are the 6 roentgen signs used to describe changes in a radiograph?
Size Shape Number Location Margination Opacity
