CT And MRI

Question 1

Which has better special resolution?
A. MRI
B. Radiograph
C. CT

Answer 1

B. Radiograph

Special resolution- ability of an imaging systems to differentiate between two adjacent objects

Question 2

Which has the best contrast resolution ?
A. Film radiograph 
B. Digital radiograph 
C. CT
D. MRI

Answer 2

D. MRI

MRI > CT> DR > Film
This can also be manipulated post processing

Question 3

What is used in CT to enhance the visibility of blood vessels, vascular leaks, and GI tract?

Answer 3

Contrast medium

Eg. Iodinated given IV

Question 4

What are uses of CT??

Answer 4

Nasal disease 
Thoracic masses, respectable 
Elbow dysplasia 
Portal vein anomalies 
Radiation therapy planning

Question 5

Is contrast resolution better in an MRI or in CT?

Answer 5

MRI

Question 6

How does an MRI produce an image?

Answer 6

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

Question 7

T/F: most lesions have increased water

Answer 7

True

Question 8

What signals does a T1 sequence primarily produce in MRI

Answer 8

Fat

Question 9

A T2 sequence MRI will primarily pick up what signals ?

Answer 9

Free and tissue water

Fat

Question 10

A FLAIR sequence will pick up what signals?

Answer 10

Tissue water and fat

Question 11

A STIR image will produce sequences form ?

Answer 11

Free water and tissue water

NOT fat

Question 12

What substance is used as a contrast medium for MRI?

Answer 12

Gadolinium

• paramagnetic compound that speeds up proton relaxation
• Useful for detecting defective blood-brain barrier or inflammation
• Only used in T1 sequence

Question 13

What imaging method is best suited for neuroimaging

Answer 13

MRI

Question 14

What are the 5 radiographic opacities?

Answer 14

Air 
Fat
Water
Bone 
Metal

Question 15

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 _________

Answer 15

Magnification,

Farther from the cassette -> image is larger and less sharp

Question 16

What is distortion in an X-ray?

Answer 16

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

Question 17

What is superimposition?

Answer 17

A real structure is projected in an unexpected location and is misinterpreted as a lesion

Question 18

What is summation?

Answer 18

Two structures overlap and create a summation opacity that is not actually present in the patient

Question 19

What is a silhouette sign?

Answer 19

The effacement of the border of two structures of the same radiographic opacity that are in contact

Question 20

How should radiographs be named?

Answer 20

Point of entrance - point of exit

Correct an atomic terminology

Question 21

What are the 6 roentgen signs used to describe changes in a radiograph?

Answer 21

Size 
Shape
Number
Location 
Margination 
Opacity