HIGH YIELD

Question 1

radionuclide imaging equals bone scanning, T/F?

Answer 1

F

Question 2

why perform a bone scan?

Answer 2

suspect bone pain
plain film fails
takes time to develop
small bony lesions <1.0 cm

Question 3

bone scan is more specific or sensitive in the early detection of OM?

Answer 3

specific

Question 4

what remains the gold standard diagnostic for OM?

Answer 4

Bone biopsy

Question 5

complications of bone biopsy?

Answer 5

sampling error
false negative w/ antibiotics
invasive 
culture contamination from soft tissue
false-negative bone in up to 50%

Question 6

bone scanning is a dynamic imaging modality that looks at?

Answer 6

bone activity, not static changes which take time

Question 7

what percent of bone loss is needed to become visible on radiograph?

Answer 7

30-50%

Question 8

plain films are static, T/F?

Answer 8

static

Question 9

bone scanning equals? while, which is greater, sensitivity or specificity?

Answer 9

dynamic imaging

sensitivity

Question 10

in bone scanning, after IV injection, what happens to the tracer?

Answer 10

tracer accretes in areas of increased vascular flow and bone turnover, no 7-10 day wait for osteoid to mineralize

Question 11

indications for bone scanning?

Answer 11

evaluate bone pain in presence of normal radiographs

aid in evaluating diabetic foot

screen for occult skeletal lesions

aid in diagnosis of:

• OM before plain film change evident
• diagnosis of stress fractures
• cellulitis form OM
• RSD/CRPS
• diagnosis of fracture delayed and/or non-unions

Question 12

what makes bone immature? mature?

Answer 12

highly hydrated
low density
low Ca/P molar ratio (1.35)

moderate hydration
high density
high Ca/P molar ratio (1.66)

Question 13

why are radiopharmaceuticals the ideal bone scanning agent?

Answer 13

readily available
high concentration at site of pathology
high bone/soft tissue uptake
minimal extra-osseous site uptake
minimum tissue radiation

Question 14

whats a popular radiopharmaceutical?

Answer 14

technetium-99m

Tc-MDP/HDP

Question 15

main characteristics of technetium-99m?

*what to note especially?

Answer 15

short half life-6.02 hours

complexed to polyphosphates to attract hydroxyapatite crystals especially to new bonenformation

*no inherent bone affinity

Question 16

Tc-MDP/HDP mechanism of uptake?

Answer 16

tracer preferentially adsorbs onto inorganic (calcium) matrix of bone (2x), 42:1 affinity so much higher affinity for inorganic matrix of bone

Question 17

major biodistribution of Tc-MDP/HDP?

Answer 17

remains in vascular pool for a very short time

rapid equilibration with ECF volume

rapid localization in bone

Question 18

radiopharmaceuticals are recorded using what instrument?

Answer 18

the anger camera, windows in on photo peak of radiopharmaceutical (140 keV)

Question 19

safety considerations of Tc-MDP/HDP?

Answer 19

low toxicity
short half life
rapidly cleared from body
marrow distribution is considerable, caution with peds

Question 20

what is the normal scan using Tc-MDP/HDP pick up?

Answer 20

intense in bladder, kidneys

bone uptake

• intense in physes
• cancellous, much greater in cortical bone

posterior body scan

• ribs
• scapula
• vertebral bodies
• SI joint

Question 21

hot spots picked up byTc-MDP/HDP?

important misc hot spot?

Answer 21

sepsis
fractures
metastases
primary bone tumors
aseptic bone
metabolic bone disease

reflex dystrophy (RSD, CRPS)
*string of lights sign

Question 22

cold spots picked up byTc-MDP/HDP?

Answer 22

avascular region

• very early neonatal hematogenous OM
• early bone infarction
• avascular lesions, gangrene
• osteonecrosis
• sometimes cancer