HIGH YIELD II Flashcards
the triphasic technetium scan improves?
specificity
what are the phases of triphasic technetium scan?
phase 1-dynamic images
phase 2-blood pool image
phase 3-delayed/static image
phase 4-24 hour delay
name this phase of the technetium scan?
series of rapid 2-5 second images as tracer passes through vascular compartment (perfusion)
bulk of tracer is intravascular-radionuclide angiogram
strong gradient towards ECF
phase 1, dynamic images
name this phase of the technetium scan?
after 5 min, 20-30% of injected tracer remains intravascular
images acquired after 5-15 min
reflects tracer redistribution into ECF, relative hyperemia
areas of inflammation cause capillaries to dilate, increasing blood flow
phase 2, blood pool image
name this phase of the technetium scan?
after 4 hours, 55-60% of the initial dose is retained in skeleton, remaining 30-40% excreted via urine
reflects relative bone turnover
retained ECF tracer=unwanted background noise
phase III, delayed/static image
name this phase of the technetium scan?
uptake in the lamellar bone ends at 4 hours and continues next 24 hours in woven bone
higher lesion to background ratio
PVD, vascularity compound
phase IV, 24 hour delay
complicating factors of bone scans?
active sterile inflammation
- recent fracture
- diabetic foot
- neoplasm
early neonatal HOM
septic arthritis
false negatives w/ AB tx
what are the reliability issues with bone scans?
remain hot for 9-12 months after major bone trauma, not 6 months
for bone scans, how do we improve specificity?
sequential scanning via
scintigraphic modalities
gallium
WBC scans
antibody labeled WBCs
what is the main mechanism of uptake with gallium scanning?
used as an inflammatory scan that binds to transferrin
also lactoferrin, found in high concentrations in inflammatory foci
what is significant of Ga in OM imaging?
*when may it be more accurate?
2 isotopes with mulitple imaging sessions over many days
high radiation dosage
more accurate in monitoring OM therapy
vertebral OM
*monitoring therapy
what does indium scanning look for?
WBC scan, non inflammatory
indium scanning technique?
40-50 ml blood drawn and sent out
WBCs separated
re-inject into patient 2-3 hrs later
scan pt 24 hrs later
when does indium photopeak? Tc?
half life of indium vs Tc?
173/247 keV, 140 KeV
2.8 days, 6 hrs
T/F, for indium scanning, labeled WBCs do not usually accumulate at sites of increased bone mineral turnover in the absence of infection?
T
major problems with in-WBC scanning?
rapid forming non-infected DNOAP
indium localization occurs at non-infected acute fracture sites
not bone seeking resulting in poor spatial resolution
in labeled WBCs determine? Tc images provide?
presence of infection, providing sensitivity and specificity
anatomic detail like infection of bone, ST, both
T/F, in Charcot arthropathy, WBC uptake within bone cannot automatically be equated with OM?
this leads to false positives, name some?
T
acute fracture
increased bone remodeling
fibre-osseous metaplasia
name some disorders associated with increased WBC uptake?
acute fracture active RA Charcot joints displacement or reactivation of marrow heterotrophic bone acute bone infarction
what was the affect of Charcot pathology on marrow?
usually inactive, but yellow marrow is turned into red active marrow
- active post traumatic arthropathy
- early post op changes can lead to ectopic active marrow
this type of marrow scan doesn’t have a tendency to accrete in infected marrow and provides an accurate map of active red marrow, exudes infected marrow? asymmetry indicates?
why is indium important?
Tc-sulfur colloid scan; infection
*labeled WBC activity outside normal marrow distribution represents infection
used to detect both sterile and infected reactivated marrow, reactivation can cause false positive indium scans
this is a reliable way to diagnose marrow from infection and is superior to T3 bone or Tc/In scanning?
WBC/marrow scintigraphy
