RADIONUCLEOTIDE IMAGING

Question 1

radionuclide imaging equals?

Answer 1

functional (physiologic) imaging

Question 2

so bone scanning is considered ancillary imaging, what is still considered the 1st choice?

Answer 2

radiograph

Question 3

why do bone scanning?

Answer 3

suspect bone pathology and x-rays were normal (stage 0 Charcot)

bony pathology takes time to develop (10 days)

small boney lesions less than 1.0 cm

Question 4

what are plain film radiographs lacking?

Answer 4

they are static

takes time for bone pathology to show up (10 days OM)

high insensitive to demineralization (30-50% bone loss before showing up)

radiograph accuracy for diagnosing OM is 50-60%

Question 5

what is a major bone scan use in podiatry?

Answer 5

early detection of OM

Question 6

what is the gold standard?

complications?

Answer 6

Bone Biopsy

can have false negative, 50%

culture contamination

pathologic fractures

Question 7

bone scanning is very sensitive to pathology but not very specific to what type, T/F?

Answer 7

T

Question 8

what are the indications of bone scanning?

Answer 8

evaluate bone pain 
diagnose OM before plain film radiographs
aid in diagnosis of cellulitis  from OM
aid in developing diabetic foot
aid in diagnosis of CPRS

Question 9

main radiopharmaceutical for bone scanning?

Answer 9

technetium-99m

Question 10

what are the main characteristics of technetium-99m?

what part of the bone attracts the 99mTc?

Answer 10

short 1/2 life 6 hrs
complexed to polyphosphates for bone affinity, so no inherent bone affinity by itself

hydrated shell, not phosphorus

Question 11

MOA of 99mTc?

Answer 11

tracer adsorbs (solid holds onto a molecule) onto inorganic matrix of bomne

Question 12

bio distribution of 99mTc?

*have injected dose is excreted in?

Answer 12

compartmentalized at certain spots at predictable times

tracer remains in vascular pool for a very short time

rapid equilibrations w/ ECF volume

rapid localization in bone (hours)

*4 hrs

Question 13

how safe is bone scanning?

Answer 13

Tc-MDP is low toxicity

short 1/2 life (6 hrs)

rapidly cleared

caution in pediatric patients due to marrow distribution

Question 14

what is the normal distribution in a scan?

Answer 14

intense in:
physes
cancellous
axial skeleton
bladder/kidney

normal symmetry

posterior scan
-ribs, scapula, vertebral bodies, SI joints

Question 15

things that will increase bone turnover and those that will increase vascularity?

examples?

Answer 15

hot spots (area of increased uptake)

sepsis: OM, septic arthritis, abscesses
fracture
metastases
aseptic bone
misc: Charcot joint, RSD, CRPS

Question 16

very early (1st 24 hrs) of neonatal HOM

early bone infarcts

avascular lesions

Answer 16

cold spots