DI 1- Final

Question 1

List 10 indicators for when to order diagnostic imaging (Probable and Possible)

Answer 1

• -Probable: trauma, unexplained weight loss, night pain, inflamm. Arthritis, Neuromotor deficit, hx of malignancy, fever of unknown origin, abN blood finding, medicolegal implications, failure to respond to therapy, deformity (scoliosis, etc)
• -Possible: >50 y.o, drug/alcohol abuse, corticosteroid use, Recent immigration, therapeutic response, therapeutic risk assessment, Unavailability of alternate imaging, outdated previous studies, Unavailable/lost/technically inadequate previous studies, Constitutional/systemic dz, research
• -(in older people, can look for metastasis, osteoporosis, dried out/smaller discs)

Question 2

What is conventional tomography? Is it used much? Dis/Adv?

Answer 2

• -Requires specific area to be visualized, b/c difficult to see on plain films and is clinically necessary to see. Creates small focal point to be clear & other portions in picture to be blurry.
• -move x-ray X-ray source and film in opposite directions during exposure -> structures in focal plane appear sharper, while structures in other planes appear blurred. By modifying the direction and extent of movement, can select different focal planes
• -Not used much
• -Adv: cost effective, minimal radiation, & bony anatomy visualized
• Disadv: visualize only small areas

Question 3

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

Answer 3

• -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 tissues are also seen)

Question 4

Which imaging plane is commonly used in computed tomography (CT)?

Answer 4

Axial (same as transverse/horizontal)

Question 5

Can more than one imaging plane be demonstrated with CT?

Answer 5

Yes, but the resolution is decreased (reconstructed images in sagittal or coronal or direct (sp?)-small body parts

Question 6

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

Answer 6

• -Soft tissue window= better visualization of soft tissues, and can be differentiated between different planes of tissues.
• -Bone window= better visualization of the fine details of the osseous structures. Cortical bone can be differentiated from cancellous (medullary) bone.

Question 7

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

Answer 7

Bone appears as uniformly white without distinction between cortical & medullary bone.

Question 8

What is the appearance of bone in a bone window?

Answer 8

Cortex and medullary bone are distinctly different in contrast. The cortex is whiter, and the medullary bone is more lucent (different contrast).

Question 9

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

Answer 9

Yes. Each pixel of the final image gets its color based on how much radiation hit it, and consequently represents the amount of attenuation.
(plain is controlled by kVp)
–CT is a result of electric manipulation of the digital image, namely window width and leveling setting

Question 10

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

Answer 10

CT= more sensitive to structural 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 11

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

Answer 11

MRI= TIwhite (T2 dark)
CT= black (second to air)

Question 12

By what routes can CT contrast material be administered?

Answer 12

Oral (barium to see tumors) or IV (liver and kidney will take up contrast-w/o contrast liver and kidney will look like muscle) or myleographic or intra-articular

Question 13

How does MRI acquire images?

Answer 13

No radiation. Nuclei of atoms have spin randomly (usually the dipole moment). That dipole moment of the spin aligns with the magnetic field. Then the field stops and the amount of energy released from going back to equilibrium gives us the picture of densities

Question 14

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

Answer 14

• -T1 (short TE & short TR)= fat image, fat is bright, precise anatomy, Low signal cortical bone spinal cord, CSF intermediate, medullary bone
• -lightest to darkest: fat, marrow, brain & spinal cord, muscle & CSF, fluid filled cavities, & compact bone. *Cord is brighter than CSF
• -T2 (long TE & long TR)= water image, less precise detail, normal discs bright, CSF is bright
• -lightest to darkest: CSF (water base), edema & normal disc, marrow & spinal cord, muscle, ligaments, & compact bone. *CSF is brighter than cord
• -(T tests are based on H atoms. If you have a high concentration of H atoms-like water or fat-they appear white)

Question 15

What structures are high signal (white) vs. low signal (dark) on each weighting?

Answer 15

T1= fat will appear bright/white
T2= water will appear bright (i.e. CSF)
T1 & T2= ligaments and tendons produce little or no signal, and cortical bone will appear as a signal void

Question 16

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

Answer 16

MRI

Question 17

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

Answer 17

MRI (mb discography)

Question 18

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

Answer 18

• -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
• -helps get a clear and detailed picture internal organs, tissues, bones & vessels. Highlights tumors & infections.

Question 19

Where is the contrast material placed in myelography?

Answer 19

Subarachnoid space (by injection)

Question 20

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

Answer 20

Usually followed by a CT to better define the anatomy and any abnormalities. Often performed pre-surgically.

Question 21

When is myelography utilized?

Answer 21

When CT & MRI are not available, or when MRI can’t find source of pain. Used to visualize indirectly a lesion within the spinal canal (i.e. disc herniation, tumor, hematoma, osteophyte, inflammation, developmental anomaly)

Question 22

What is a “hot spot” in bone scan?

Answer 22

• -area where a large amount of radionuclide migrates to because of increased cellular activity. They appear black (or “bright” if background is black)
• -Small areas of destruction or accumulation of bone (increased cell activity due to fracture or tumor)
• -Areas of rapid bone growth or repair, i.e. arthritis, presence of tumor, fracture, or infection. Only 3-5% bone destruction needed to see “hot areas” on scan, but don’t specify process.
• -(“cold”/white spots absorb little to no amount of tracer and indicate a lack of blood supply or certain types of cancer)

Question 23

When might SPECT scan be useful?

Answer 23

• Better localization of a lesion

- Confirming a fatigue fracture in the pars interarticularis

Question 24

When might PET scan be useful?

Answer 24

• Tumor localization
• Ascertaining treatment 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 25

When might discography be useful?

Answer 25

• Provocative test for low back pain (may demonstrate dessicated discs & herniated discs).
• Document specific disc as source of pain & examine disc integrity

Question 26

When might diagnostic ultrasound be useful?

Answer 26

evaluate a fetus		
diagnose gallbladder dz
guide a needle biopsy	
evaluate flow in blood vessels
check thyroid gland		
guide biopsy & treatment of a tumor
study the heart		
diagnose some forms of infection/cancer
reveal abnormalities in the scrotum & prostate

Question 27

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

Answer 27

MRI or bone scan

Question 28

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

Answer 28

1) plain film x-ray
2) bone scan
3) MRI or CT

Question 29

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

Answer 29

1) bone scan

2) MRI or CT

Question 30

Which modality would be most appropriate to evaluate avascular necrosis?

Answer 30

1) plain film x-ray

2) MRI or bone scan if suspected, but x-ray negative

Question 31

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

Answer 31

CT-since it is fast

US good for many abdomen dzs

Question 32

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

Answer 32

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

Question 33

Know your imaging planes (i.e. axial, coronal, sagittal).

Answer 33

• Coronal= A/P view or P/A view
• Sagittal= Left to Right, or Right to Left
• Axial= Top to bottom, or Bottom to top

Question 34

Be able to identify each of the imaging studies discussed in this course, whether contrast is used, which window (CT) or weighting (MRI – T1 or T2) is demonstrated, and identify basic anatomy.

Answer 34

……