DI 1 Final Flashcards
Name 10 probable indications for diagnostic imaging
- trauma
- unexplained wt loss
- night pain
- inflammatory arthritis
- neuromotor deficit
- hx of malignancy
- fever of unk origin
- abn blood findings
- medicolegal implications
- failure to respond to therapy
- deformity (scoliosis, etc.)
Name 10 possible indications for diagnostic imaging
- > 50 yo
- drug/EtOH abuse
- corticosteroid use
- recent immigration
- therapeutic response
- therapeutic risk assessment
- unavailability of other imaging
- outdated previous studies
- unavailable/lost/technically inadequate previous studies
- constitutional/systemic dz
- research
what is conventional tomography? is it used much?
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
advantages and disadvantages of conventional tomography
adv: cost effective, minimal radiation, bony anatomy can be visualized
disadv: visualize only small areas
difference in appearance b/w plain x-ray and conventional tomography?
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)
which imaging plane is commonly used in conventional tomography?
axial (transverse/horizontal)
can more than one plane be demonstrated with CT?
yes, but resolution is decreased b/c it is a reconstructed image in sagittal, coronal or direct
what is the difference b/w CT soft tissue and bone window?
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
what is the appearance of bone in a soft tissue window?
bone appears as uniformly white w/o distinction b/w cortical and medullary bone
what is the appearance of bone in a bone window?
cortex and medullary bone are distinctly different in contrast; the cortex is whiter and the medullary bone is more lucent (dark) (different contrast)
does CT utilize theory of attenuation (absorption of x-rays)?
yes (plain is controlled by kVp); CT is a result of electric manipulation of the digital image, namely window width and leveling
which is more sensitive in the differentiation of tissue densities, CT or plain x-ray?
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
what is the appearance of fat on CT vs MRI?
fat on CT is dark (black, second to air)
fat on MRI is light (white, as long as T2 image)
by what routes can CT contrast material be administered?
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
how does MRI acquire images?
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
what does a T1 weighted MRI image look like compared to a T2 weighted image?
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
what are T tests based on?
based on H atoms, if you have a high concentration of H atoms, like water or fat, they appear white
which modality would best demonstrate dehydration (dessication) of the nucleus pulposus, CT or MRI?
MRI
which modality would best demonstrate an intervertebral disc herniation?
MRI, mb discography
what is the contrast called that is sometimes used w/MRI and why is it used?
gadolinum, used to help physicians get a clear and detailed picture of the patients’ internal organs, tissues, bones and vessels, highlights tumors and infection
where is the contrast material placed in myelography?
subarachnoid space (by injection)
which modality besides plain film radiography is myelography often used with?
usu followed by CT or better to define the anatomy and any abn; often performed pre-surgery
when is myelography utilized?
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)
what is a “hot spot” in a bone scan?
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
when might SPECT scan be useful?
better localization of a lesion
confirming a fatigue fracture in the pars interarticularis
when might PET scan be useful?
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
when might discography be useful?
provocative test for low back pain (may demonstrate dessicated discs and herniated discs)
document specific disc as source of pain and examine disc integrity
when might diagnostic U/S be useful? (name 5)
- evaluate a fetus
- guide a needle bx
- check thyroid
- study heart
- reveal abn in scrotum and prostate
- dx gallbladder dz
- evaluate flow in bvs
- guide bx and tx of tumor
- dx some forms of infxn/CA
which modality would be most appropriate to eval an intervertebral disc protrusion?
MRI or bone scan
which modality would be most appropriate to eval a stress fracture?
MRI or bone scan
which modality would be most appropriate to confirm or r/o an occult fracture or questionable fracture initially discovered on plain x-ray?
MRI
which modality would be most appropriate to evaluate avascular necrosis?
MRI
which modality would be most appropriate to eval most chest and abd pathologies?
CT- since it’s fast
what are the relative radiation doses for each imaging modality discussed?
MRI= no radiation–> x-ray –> CT –> bone scan= most radiation
imaging planes (name them)
coronal (front from back)
sagittal (L from R)
axial/horizontal/transverse (top from bottom)
