Skeletal Scintigraphy Flashcards
Radiotracers used for skeletal scintigraphy
Tc 99m hydroxymethylene disphosphonate
Tc 99m methylene disphosphonate
HMDP or MDP
Radiotracers uptake
Tc 99 HMDP/HDP and MDP localize to areas of bone repair. Excreted in urine so will see kidneys and bladder too.
half life 24 hr
Sacroiliac joints, iliac wings due to proximity, costochondral junction,
Abnormal soft tissue might also show uptake
Mechanisms of Increased Activity on Bone Scan
increased osteoid formation
increased blood flow
increased mineralization of osteoid
interrupted sympathetic nerve supply
4 phases of bone scan
flow - up to 5 sec
blood pool - up to 5 min
delayed- 2-4 hours
delayed- up to 24 hr (useful if pt has poor renal clearance to improve target to background ratio)
Cellulitis
angio + blood pool phase increased
Osteomyelitis
angio+ blood pool+ delayed increased
Often times can go bone scan, then confirm with WBC scan
In-111 WBC can be used for
diabetic osteo of the feet
grafts/prosthesis
Fever of Unknown Origin
Gallium-67
osteo of spine
septic arthritis
positive 3 phases on BOTH sides of joint
diskitis
Increased activity on both sides of vertebral bodies
superscan
Clue: significantly decreased renal activity with diffusely increased activity through out the axial skeleton.
usually due to neoplasm (esp prostate),
renal osteodystrophy
in absence of neoplasm likely 2/2 metabolic disorder such as hyperparathyroidism. hot skull, distal extremities, lung or stomach activity suggest hyperparathyroidism.
Osteomalacia
Paget disease
Hot on all 3 phases of bone scan
osteomyelitis
acute fracture
hypervascular tumor
Complex Regional Pain Syndrome
Neuropathic joint
Mimics of osteomyelitis on 3 phase bone scan
Osteoarthritis Gout Fracture Stress fracture Healing osteonecrosis Charcot joint Osteotomy Complex regional pain syndrome
