DI 1 Final

Question 1

Name 10 probable indications for diagnostic imaging

Answer 1

1. trauma
2. unexplained wt loss
3. night pain
4. inflammatory arthritis
5. neuromotor deficit
6. hx of malignancy
7. fever of unk origin
8. abn blood findings
9. medicolegal implications
10. failure to respond to therapy
11. deformity (scoliosis, etc.)

Question 2

Name 10 possible indications for diagnostic imaging

Answer 2

1. > 50 yo
2. drug/EtOH abuse
3. corticosteroid use
4. recent immigration
5. therapeutic response
6. therapeutic risk assessment
7. unavailability of other imaging
8. outdated previous studies
9. unavailable/lost/technically inadequate previous studies
10. constitutional/systemic dz
11. research

Question 3

what is conventional tomography? is it used much?

Answer 3

requires specific area to be visualized b/c it is difficult to see on plain films and is clinically significant to see
creates small focal pt to be clear & other portions in picture to be blurry
it is not used often

Question 4

advantages and disadvantages of conventional tomography

Answer 4

adv: cost effective, minimal radiation, bony anatomy can be visualized
disadv: visualize only small areas

Question 5

difference in appearance b/w plain x-ray and conventional tomography?

Answer 5

plain x-ray does not allow you to see slight bone destruction (need about 30-50%) or axial images and usually a broad area of focus
conventional tomography has radiographic ‘slices’ taken with moving camera and film where thin ‘slices’ of bony anatomy are visualized but can only visualize a small area (soft tissue also seen)

Question 6

which imaging plane is commonly used in conventional tomography?

Answer 6

axial (transverse/horizontal)

Question 7

can more than one plane be demonstrated with CT?

Answer 7

yes, but resolution is decreased b/c it is a reconstructed image in sagittal, coronal or direct

Question 8

what is the difference b/w CT soft tissue and bone window?

Answer 8

soft tissue window: better visualization of soft tissues and can be differentiated b/w different planes of tissues
bone window: better visualization of fine details of the osseous structures, cortical bone can be differentiated from cancellous (medullary) bone

Question 9

what is the appearance of bone in a soft tissue window?

Answer 9

bone appears as uniformly white w/o distinction b/w cortical and medullary bone

Question 10

what is the appearance of bone in a bone window?

Answer 10

cortex and medullary bone are distinctly different in contrast; the cortex is whiter and the medullary bone is more lucent (dark) (different contrast)

Question 11

does CT utilize theory of attenuation (absorption of x-rays)?

Answer 11

yes (plain is controlled by kVp); CT is a result of electric manipulation of the digital image, namely window width and leveling

Question 12

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

Answer 12

CT= more sensitive to structure density, CT is superior for soft tissue contrast
x-ray is manipulated by how much radiation is emitted whereas CT uses electronic manipulation of the digital image

Question 13

what is the appearance of fat on CT vs MRI?

Answer 13

fat on CT is dark (black, second to air)

fat on MRI is light (white, as long as T2 image)

Question 14

by what routes can CT contrast material be administered?

Answer 14

oral (barium to see tumors), intravenous (liver and KD will take up contrast, w/o contrast liver and KD will look like muscle), intra-articular and myelographic

Question 15

how does MRI acquire images?

Answer 15

NO RADIATION. nuclei of atoms have spin randomly (usu dipole moment), the dipole moment of the spin aligns w/magnetic field then the field stops and the amount of energy released from going back to equilibrium gives us the picture of densities

Question 16

what does a T1 weighted MRI image look like compared to a T2 weighted image?

Answer 16

T1= short TE and short TR, spinal cord is bright (light, white); fat density items are brighter; fat image
T2= long TE and long TR, CSF is bright (light, white); water density items are brighter, water image

Question 17

what are T tests based on?

Answer 17

based on H atoms, if you have a high concentration of H atoms, like water or fat, they appear white

Question 18

which modality would best demonstrate dehydration (dessication) of the nucleus pulposus, CT or MRI?

Answer 18

MRI

Question 19

which modality would best demonstrate an intervertebral disc herniation?

Answer 19

MRI, mb discography

Question 20

what is the contrast called that is sometimes used w/MRI and why is it used?

Answer 20

gadolinum, used to help physicians get a clear and detailed picture of the patients’ internal organs, tissues, bones and vessels, highlights tumors and infection

Question 21

where is the contrast material placed in myelography?

Answer 21

subarachnoid space (by injection)

Question 22

which modality besides plain film radiography is myelography often used with?

Answer 22

usu followed by CT or better to define the anatomy and any abn; often performed pre-surgery

Question 23

when is myelography utilized?

Answer 23

when CT and MRI are not available or when MRI cannot find source of pain; used to visualize, indirectly, a lesion w/in the spinal canal (disc herniation, tumor, hematoma, osteophyte, inflammation, developmental anomaly)

Question 24

what is a “hot spot” in a bone scan?

Answer 24

small areas of destruction or accumulation of bone (increased cell activity dt fracture or tumor)
areas of rapidly growing bone or repair absorb increased amounts of tracer and show up as bright or “hot spots” (arthritis, infection, fracture or tumor)
“cold”/dark spots absorb little to no tracer and indicate a lack of blood supply or with certain types of cancer

Question 25

when might SPECT scan be useful?

Answer 25

better localization of a lesion

confirming a fatigue fracture in the pars interarticularis

Question 26

when might PET scan be useful?

Answer 26

tumor localization
ascertaining tx success
has better resolution than SPECT or scintigraphy
dx a health condition/find out how it’s developing
used alongside x-rays or MRI to get more data

Question 27

when might discography be useful?

Answer 27

provocative test for low back pain (may demonstrate dessicated discs and herniated discs)
document specific disc as source of pain and examine disc integrity

Question 28

when might diagnostic U/S be useful? (name 5)

Answer 28

1. evaluate a fetus
2. guide a needle bx
3. check thyroid
4. study heart
5. reveal abn in scrotum and prostate
6. dx gallbladder dz
7. evaluate flow in bvs
8. guide bx and tx of tumor
9. dx some forms of infxn/CA

Question 29

which modality would be most appropriate to eval an intervertebral disc protrusion?

Answer 29

MRI or bone scan

Question 30

which modality would be most appropriate to eval a stress fracture?

Answer 30

MRI or bone scan

Question 31

which modality would be most appropriate to confirm or r/o an occult fracture or questionable fracture initially discovered on plain x-ray?

Answer 31

MRI

Question 32

which modality would be most appropriate to evaluate avascular necrosis?

Answer 32

MRI

Question 33

which modality would be most appropriate to eval most chest and abd pathologies?

Answer 33

CT- since it’s fast

Question 34

what are the relative radiation doses for each imaging modality discussed?

Answer 34

MRI= no radiation–> x-ray –> CT –> bone scan= most radiation

Question 35

imaging planes (name them)

Answer 35

coronal (front from back)
sagittal (L from R)
axial/horizontal/transverse (top from bottom)