MSK Flashcards
MSK NM radiotracer
Tc 99m MDP
- disphosphonate
- 20mCi dosage
- image 2-4 hrs after administration
- renal uptake (void before imaging); diffuse soft tissue uptake seen with renal vailure
phases of exam with Tc99m MDP
1) angiogram flow taken every few seconds; increase flow = hyperemia
2) blood pool following extracellular distribution
3) standard delayed (skeletal) images ~3 hrs after injection
pattern of low probability metastatic disease
- single focus of rib uptake
- uptake in 2 adjacent ribs (trauma)
- mutliple adjacent photopenic bone lesions (recent infarct, AVN, sequelae of radiation therapy)
pattern of high probability metastatic disease
- single sternal lesion in breast cancer
- multifocal areas of increased rib activity
- single photopenic lesion in pt of known malignancy (neuroblastoma, RCC, thyroid)
pattern of increased soft tissue uptake
- increased brain/heart may be due to recent infarct
- malignant pleural effusion can have increased uptake
- soft tissue mets containing calcium (osteosarcoma, neuroblastoma, mucin producing tumors like GI and ovary)
- focal intense breast uptake (or recent procedure)
- inflammatory diseases (myosititis ossificans, dermatomyositis, rhabdomyolysis)
NM superscan
diffusely increased osseous uptake, usually due to metastatic prostate cancer (less lymphoma, breast cancer)
-nonvisualization of kidneys
if due to metabolic cause (primary/secondary hyperparathyroidism) then long bones are also well seen
indications for bone scan
- evaluate mets
- primary bone tumors
- fractures (stress/insufficienc, child abuse, pathologic)
- shin splints
- prostehsis evaluation
- osteomyelitis
- hypertrophic pulmonary osteoarthropathy
- AVN
- paget
- complex regional pain syndrome/reflex sympathetic dystrophy
NM: primary bone tumor pattern (osteosarcoma, ewing, osteoid osteoma)
osteosarcoma: increased uptake; even in entire limb
ewing sarcoma: intense homogenous activity; positive on all three phases of scan
osteoid osteoma: vascular central nidus with intense activity
NM bone scan: double density sign
intense focus of uptake corresponding to nidus with relative increased uptake
osteoid osteoma vs brodie abscess, less likely stress fracture
NM bone scan: fracture
increased uptake 3-4 weeks after injury; positive after one day in pts <65yo
skull fractures rarely show activity
can be used in children with limping if radiographs negative
NM bone scan: stress fracture
fracture due to abnormal stress; typically tibial diaphysis, femoral neck, metatarsals (90% in foot/ankle in 2nd-3rd metatarsals)
NM bone scan: shin splints
pain from periostitis at tibial insertions of anterior tibialis and soleus muscles
normal blood flow/blood pool images; linear increased uptake on delayed/skeletal phase
NM bone scan: insufficiency fracture
fracture to normal stress in abnormal bone due to osteoporosis
sacral insufficiency fracture shows “H” shaped sacral fracture; honda sign
NM bone scan: prosthesis evaluation
loosening/infection of hardware
normal: increased activity around cemented prosthesis up to 12 months; non cemented 2 years
abnormal: increased activity past these borders
generalized increased activity: osteomyelitis
mild/moderate greater trochanter region = heterotopic ossification
NM bone scan: osteomyelitis
WBC imaging (indium 111 or Tc99 labeled WBC) with sulfur colloid marrow; gallium 67
positive on all 3 phases
NM bone scan: cellulitis
increased MDP activity during blodo flow and soft tissue phase, not on skeletal phase
NM bone scan: septic arthritis
positive on all three phases on both sides of joint
hypertrophic pulmonary osteoarthropathy
long bone diaphyseal periosteal reaction due to pulmonary disease; lung cancer
parallel lines of activity along cortex of bones
bone scan: AVN
decreased uptake in affected region followed by hyperemic phase
rim of increased uptake with central photopenia in hip
increased uptake in medial knee due to spontaneous osteonecrosis of knee (SONK); atraumatic knee pain
NM bone scan: Paget disease
heterogenously increased uptake due to lytic/mixed/sclerotic uptake corresponding to phases
may degenerate into osteosarcoma
NM bone scan: complex regional pain syndrome/reflex sympathetic dystrophy
persistent pain, tenderness, swelling due to minor trauma
increased juxta-articular activity in multiple small joints of hand/foot on delayed images
variable uptake on blood pool/soft tissue phase (mildly increased usually)
