Final I

Question 1

List 10 indicators for when to order diagnostic imaging. PROBABLE causes

Answer 1

Trauma – recent, old
Unexplained weight loss
Night pain
Neuromotor deficit
Inflammatory arthritis
History of malignancy
Fever of unknown origin (>100 F)
Abnormal blood finding
Deformity (Scoliosis, etc.)
Failure to respond to therapy
Medicolegal implications

Question 2

2. What is conventional tomography? Is it used much?

Answer 2

Conventional tomography is an x-ray slice that focuses on a small area of the body. Because of the movement of the x-ray source, everything around the area of interest is blurred.

Tomography has been rendered obsolete by computed tomography (CT)

Question 3

3. What is the difference in appearance between a plain x-ray and conventional tomography?

Answer 3

Plain x-ray is 2-D with everything superimposed.

Conventional tomography blurs everything not in the plane of focus, thus removing some of the difficulties in reading images.

Question 4

4. Which imaging plane is commonly used in computed tomography (CT)? Can more than one imaging plane be demonstrated with CT?

Answer 4

CT commonly takes axial slices of the body. From these axial slices, other image planes can be constructed, but at lower resolution.

Question 5

5. What is the difference between CT soft tissue and bone window?

Answer 5

CT Soft tissue window has the contrast adjusted to make soft tissue more visible. Bone window makes the details of bony structures more visible so that cortex and medullary bone can be easily distinguished.

Question 6

6. What is the appearance of bone in a soft tissue window?

Answer 6

It all looks very white.

Question 7

7. What is the appearance of bone in a bone window?

Answer 7

Much less white with details easily visualized.

Question 8

8. Does CT utilize the theory of attenuation (absorption of x-rays)?

Answer 8

Yes. Each pixel of the final image gets its color based on how much radiation hit it, and consequently represents the amount of attenuation.

Question 9

9. Which is more sensitive in the differentiation of tissue densities, CT or plain
   x-ray?

Answer 9

CT provides much better soft tissue contrast

Question 10

10. What is the appearance of fat on CT vs. MRI?

Answer 10

On a CT, fat will be rather dark, whereas on a T1 weighted MRI, it will be white

Question 11

11. By what routes can CT contrast material be administered?

Answer 11

Oral and intravenous

Question 12

12. How does MRI acquire images?

Answer 12

MRI uses a super huge magnet which aligns hydrogen protons. When the magnet moves, the hydrogen goes back to a relaxed state. The energy released is measured by a computer and turned into a meaningful image.

Question 13

13. What does a T1 weighted MRI image look like compared to a T2 weighted image? What structures are high signal (white) vs. low signal (dark) on each weighting

Answer 13

T1 = Fat is white, compact bone is dark T2 = Water is white, compact bone is dark

Question 14

14. Which modality would best demonstrate dehydration (dessication) of the nucleus pulposis, CT or MRI?

Answer 14

MRI because the nucleus pulposis will show up as a darker color due to the lesser water content

Question 15

15. Which modality would best demonstrate an intervertebral disc herniation, CT or MRI?

Answer 15

MRI would show it better since it shows all soft tissue better

Question 16

What is the contrast called that is sometimes used with MRI and why is it used?

Answer 16

Gadolinium is an intravenous contrast agent that is sometimes used with MRI
It goes to areas of increased vascularity. Performed with T1 weighted images only

Question 17

16. Where is the contrast material placed in myelography?

Answer 17

Into the subarachnoid space

Question 18

17. What modality besides plain film radiography is myelography often used with?

Answer 18

CT

Question 19

18. When is myelography utilized?

Answer 19

When MRI or CT would be contraindicated, or with a CT pre-surgery

Question 20

19. What is a “hot spot” in bone scan?

Answer 20

A hot spot is an area where a large amount of radionuclide migrates to because of increases cellular activity. They appear black

Question 21

20. When might SPECT scan be useful?

Answer 21

To localize a lesion better, particularly good for a fatigue fracture of the pars interarticularis

Question 22

• When might PET scan be useful?

Answer 22

Excellent for tumor localization, grading and ascertaining treatment success. look for lymph node mets, look at brain activity, lesions

Question 23

• When might discography be useful?

Answer 23

May demonstrate dessicated discs and herniated discs. Document specific disc as source of pain, Examine disc integrity

Question 24

When might diagnostic ultrasound be useful?

Answer 24

Evaluate a fetus, Diagnose gallbladder disease, stones, Evaluate flow in blood vessels, Guide a needle biopsy, Guide the biopsy and treatment of a tumor, Check thyroid gland, Study the heart, Diagnose some forms of infection, Diagnose some forms of cancer, Reveal abnormalities in the scrotum and prostate, could help you find an occult fracture

Question 25

21. Which modality would be most appropriate to evaluate an intervertebral disc protrusion?

Answer 25

MRI

Question 26

22. Which modality would be most appropriate to evaluate a stress fracture?

Answer 26

Plain film X-ray ?

Question 27

23. Which modality would be most appropriate to confirm or rule out an occult fracture or questionable fracture initially discovered on plain x-ray?

Answer 27

Diagnostic ultrasound

Question 28

24. Which modality would be most appropriate to evaluate avascular necrosis?

Answer 28

MRI

Question 29

25. Which modality would be most appropriate to evaluate most chest and abdomen pathologies?

Answer 29

CT because you don’t have to worry about movement and you get a good image of soft tissue

Question 30

26. What are the relative radiation doses for each imaging modality discussed?

Answer 30

MRI = No radiation -> X-ray -> CT -> Bone scan = most radiation