DI I Final Flashcards
List 10 indicators for when to order diagnostic imaging.
trauma unexplained weight los night pain neuromotor deficit inflammatory arthrirtis hx of malignancy fever of unknown origin abnormal labs deformity failure to respond to tx medicolegal implications >50 yrs drug/alcohol abuse coricosteroid use unavailability of alernate imaging unavailable/lost/technically inadequate previous studies research contributional/systemic disease Recent immigration therapeuti risk assessment Therapeutic response
NON-INDICATORS - pt education, routine screening, habit, discharge assessment, financial gain, pregnancy, pre-employment status, physical limitations of pt
What is conventional tomography? Is it used much?
old fashioned xray tube and receptor that moves
not used much
What is the difference in appearance between a plain x-ray and conventional tomography?
not much
multiple xray absorption measurements made around the periphery of body
xray source produces fan shaped beam that rotates around pt - irradiating slice pf pt ranging from 0.5mm to 10mm (more slices = more radiation)
cross sectional images stacked and reformatted for 3D images
Which imaging plane is commonly used in computed tomography (CT)? Can more than one imaging plane be demonstrated with CT?
transverse cross section in the AXIAL plane
Images can be reformatted to view 3D in many planes
What is the difference between CT soft tissue and bone window?
Bone window - better visualization of fine details of osseous structures
Soft tissue - better visualization of soft tissues - cant differentiate medullary bone from cortical bone
What is the appearance of bone in a soft tissue window of CT?
Can’t differentiate cortical bone from medullary bone - just looks white
What is the appearance of bone in a bone window?
Cortical bone is differentiated from medullary bone
Does CT utilize the theory of attenuation (absorption of x-rays)?
YES
Which is more sensitive in the differentiation of tissue densities, CT or plain x-ray?
CT
What is the appearance of fat on CT vs. MRI?
High signal in MRI (white)
Black in CT (like xray)
By what routes can CT contrast material be administered?
Iodine - IV injection
Barrium - swallowed
How does MRI acquire images?
Nuclei of hydrogen atoms align themselves with magnetic field
Image reflects the concentration of hydrogen and associated bonds/motion
Things that move (blood) is black
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?
T1 - fat appears whiter than water (high signal)
T2 - water (CSF) appears whiter than fat (high signal) - or as white as fat
Cortical bone will be black (signal void) on both T1 and T2
Ligaments/Tendons produce little signal - grayish
Which modality would best demonstrate dehydration (dessication) of the nucleus pulposis, CT or MRI?
MRI - T2 shows discs
Which modality would best demonstrate an intervertebral disc herniation, CT or MRI?
MRI
CT can also be performed with myelographic contrast which may add to dx accuracy
What is the contrast called that is sometimes used with MRI and why is it used?
Gadolinium - goes to areas of increased vascularity with T1 weighted images only (malignant tumors, trauma, and bone/joint infections)
Where is the contrast material placed in myelography?
Radiopaque contrast in CSF - Subarachnoid space
Used to see lesions within spinal cord - when MRI is contraindicated (herniation, tumor, hematoma, osteophyte, inflammation)
What modality besides plain film radiography is myelography often used with?
CT-myelo - often done pre-surgery
When is myelography utilized?
used to visualize indirectly a lesion within the spinal canal - when CT or MRI is contraindicated
What is a “hot spot” in bone scan (scintigraphy)?
Nuclear medicine uses intravenous injection of radionucleide selecetively taken up by tissue (technetium in bone) photoscanner used to measure radioactivity from the nuclear substance high sensitivity (sees 3-5% bone loss) and low specificity Focal area to look for find tumors, infection, and fracture using 3 phases (flow, blood pool, and delayed/bone scan) Increased cellular activity is seen through 'hot spots' that indicate bone destruction
When might SPECT scan be useful?
Single Photon Emission Computed Tomography is similar to scintigraphy/ nuclear medicine/ bone scan but uses CT to display the tracer in selected image planes to provide better localization of bone lesions - used to confirm ‘fatigue fracture’ in pars
When might PET scan be useful?
When might PET scan be useful?
PET utilizes radiopharmaceuticals to emit gamma rays that can be visualized with greater resolution than either SPECT or scintigraphy
Used to localize tumors (lymph nodes) and ascertain treatment success but is expensive and often not readily available
Also used to visualize brain activity and lesions in brain
When might discography be useful?
Discography uses injection of radioopaque contrast into intervertrebral disc to provoke low back pain and demonstrated dessicated/herniated disc
Indicated to locate specific disc source of pain and examine disc integrity
Before surgery - identify specific disc
When might diagnostic ultrasound be useful?
SOFT TISSUE Evaluate fetus Diagnose gall bladder disease Evaluate flow in blood vessels Guide needle biopsy Guide biopsy and treatment of tumors Check thyroid gland Study the heart Diagnose some infections Diagnose some cancers Reveal abnormalities in scrotum/prostate
Which modality would be most appropriate to evaluate an intervertebral disc protrusion?
Discography
Which modality would be most appropriate to evaluate a stress fracture?
MRI (Nuclear medicine - bone scan/scintigraphy is also good, but MRI is better)
Which modality would be most appropriate to confirm or rule out an occult fracture or questionable fracture initially discovered on plain x-ray?
Nuclear medicine - bone scan/scintigraphy
Which modality would be most appropriate to evaluate avascular necrosis?
MRI
Which modality would be most appropriate to evaluate most chest and abdomen pathologies?
MRI
What are the relative radiation doses for each imaging modality discussed?
Plain film radiography - minimal radiation
CT - more radiation
MRI - none
Bone scan/nuc med - variable
