liveonearth (liveonearth) wrote,

Diagnostic Imaging: Final Exam Study Guide

1. List 10 indications for ordering imaging.
trauma, unexplained wt loss, night pain, neuromotor deficit, RA, hx of malignancy, FUO, abn blood finding, deformity, failure to respond to therapy, medicolegal

2. What is CONVENTIONAL tomography? Is it used much?
aka Plain film tomography, it's radiography of slices of anatomy taken with moving camera and film to see small area, is cost effective with little radiation exposure but not great image, blurry, not used much anymore

3. What's the diff in appearance between plain x-ray and conventional tomography?
x-ray is clearer and goes through whole body, conventional tomog is just a slice and is blurry

4. Which imaging plane is usu seen in computed tomography (CT)? Can more than one imaging plane be demonstrated with CT?
usu axial but can do coronal or sagittal plane if part will fit in tube

5. What's the diff btw CT soft tissue and bone window?
soft tissue window shows variation btw different types of soft tissue, bone is all white, bone window shows difference between cortical and medullary bone

6. What's the appearance of bone in soft tissue window?
solid white

7. What's the appearance of bone in bone window?
cortical bone is white, medullary is gray

8. Does CT utilize theory of attentuation (absorbtion of x-rays)?

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

10. What is the appearance of fat on CT vs MRI?
on CT fat is black, on MRI fat is white in T1, gray in T2

11. By what routes can CT contrast material be administered?
oral (barium swallow), anal (barium enema), intravenous (IV iodine), intrathecal (in CSF)

12. How does MRI acquire images?
nuclei spin randomly, atoms align with magnetic field, radio frequency tips axis off alignment with magnetic field, then radio frequency stopped and released energy measured as alignment to field resumes. Uses mostly hydrogen atoms because there are many of them and they are small and responsive.

13. What does a T1 weighted MRI look like compared to T2? What's high vs low signal?
T1: fat is white/bright (high signal), CSF darker than cord, precise anatomy
T2: water/CSF is bright, CSF lighter than cord, fat is gray, less precise detail, normal discs bright
Both: ligaments and tendons are dark (low signal)

14. Which modality best demonstrates dessication of nucleus pulposis (between CT and MRI)?
MRI (usu healthy disc on T2 is white, darker when dry/degenerated)
("CT for anatomy, MRI for physiology")

15. Which modality best demonstrates intervertebral disc herniation (CT or MRI)?
MRI: T2 edema is white, T1 edema is black
(CT is OK when used w/ contrast injected into CSF: myelography)

16. What is the contrast sometimes used with MRI and why is it used?
gadolinium dt effect of strongly decreasing the T1 relaxation times of the tissues to which it has access, also, goes to areas of increased vascularity, increases clarity of T1 image

17. Where is contrast material placed in myelography?
subarachnoid space (CSF)

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

19. When is myelography utilized?
to visualize lesion in spinal column, disc herniation, tumor (SOL), osteophytes, inflam, presurgery, when CT and MRI are not available or contra-indicated

20. What is a "hot spot" in bone scan?
3-5%+ bone destruction-->tissue has increased metabolic rate or vascularity (bone turnover)
metastases, stress fractures, infection

21. When might SPECT be useful?
to confirm a fatigue fracture of pars interarticularis (usu @ L5)
100pics/page, yellow, looks like bone scan w/ better resolution

22. When might PET scan be useful?
tumor localization, LN's, lymphoma, brain function

23. When might discography be useful?
provocative test, document specific disc as pain source and examine disc integrity

24. When might diagnostic ultrasound be useful?
soft tissue, preg, DVT, thyroid, gall stones, kidney stones, liver, breast
guide needle biopsy

25. Which modality is most appropriate to eval an intervertebral disc protrusion?
MRI is best for all joints

26. Which modality is best to eval a stress fx?
MRI or bone scan (MRI T2 shows edema in bone)
(CT also, last choice)

27. Which modality is best to confirm or R/O occult fx or questionable fx intitially discovered on plain x-ray?
MRI or bone scan

28. Which modality is best to eval avascular necrosis?
MRI, best for marrow replacement processes too

29. Which modality is best to eval most chest and abdomen pathologies?
after x-ray, CT becuz it's a faster shoot (you only have to hold breath for 30sec-1min instead of 45 mins w/ MRI =-[ )

30. What are the relative radiation doses for each imaging modality?
MRI - none
Diagnostic Ultrasound - none
xray - minimal
conventional tomography - minimal
myelography - same as CT or xray, depending on which used
nuclear medicine/bone scan/scintigraphy - minimal - injecting radioactive substance into body
SPECT - another one in which radiactive stuff ("tracer") is injected - minimal?
PET = injected radiopharmaceuticals - more
CT - more to most depending on specific scan done

(TABLE 1 from
(dose in miliseverts)
(article indicates that pt cumulative exposure by CT is increasing LOTS)
Chest radiography,posteroanterior and lateral 0.06
Screening mammography 0.6
Gastric emptying study 1.4
Kidney-ureter-bladder radiography 1.7
CT of the head 1.8
Lumbar spine radiography 2.1
Background radiation, annual dose 3.6
Radionuclide bone scan 4.4
Ventilation-perfusion (V/Q) scan 6.8
CT of the pelvis 7.1
CT of the abdomen 7.6
CT of the chest 7.8
Barium enema radiography 8.7
CT angiography of coronary arteries 10
Positron emission tomography, whole body 14
Small bowel series (barium swallow x-ray study) 15
Intravenous pyelography 10.0–20.0
Whole-body screening CT 22.5
Three-phase hepatic CT scan 29.9
Dual-isotope myocardial rest 32.5
stress perfusion CT study CT urographic study 44.1
Tags: diagnosis, imaging, nd2, radiation, spine

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