MSK

Question 1

MSK NM radiotracer

Answer 1

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

Question 2

phases of exam with Tc99m MDP

Answer 2

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

Question 3

pattern of low probability metastatic disease

Answer 3

• single focus of rib uptake
• uptake in 2 adjacent ribs (trauma)
• mutliple adjacent photopenic bone lesions (recent infarct, AVN, sequelae of radiation therapy)

Question 4

pattern of high probability metastatic disease

Answer 4

• single sternal lesion in breast cancer
• multifocal areas of increased rib activity
• single photopenic lesion in pt of known malignancy (neuroblastoma, RCC, thyroid)

Question 5

pattern of increased soft tissue uptake

Answer 5

• 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)

Question 6

NM superscan

Answer 6

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

Question 7

indications for bone scan

Answer 7

• 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

Question 8

NM: primary bone tumor pattern (osteosarcoma, ewing, osteoid osteoma)

Answer 8

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

Question 9

NM bone scan: double density sign

Answer 9

intense focus of uptake corresponding to nidus with relative increased uptake

osteoid osteoma vs brodie abscess, less likely stress fracture

Question 10

NM bone scan: fracture

Answer 10

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

Question 11

NM bone scan: stress fracture

Answer 11

fracture due to abnormal stress; typically tibial diaphysis, femoral neck, metatarsals (90% in foot/ankle in 2nd-3rd metatarsals)

Question 12

NM bone scan: shin splints

Answer 12

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

Question 13

NM bone scan: insufficiency fracture

Answer 13

fracture to normal stress in abnormal bone due to osteoporosis

sacral insufficiency fracture shows “H” shaped sacral fracture; honda sign

Question 14

NM bone scan: prosthesis evaluation

Answer 14

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

Question 15

NM bone scan: osteomyelitis

Answer 15

WBC imaging (indium 111 or Tc99 labeled WBC) with sulfur colloid marrow; gallium 67

positive on all 3 phases

Question 16

NM bone scan: cellulitis

Answer 16

increased MDP activity during blodo flow and soft tissue phase, not on skeletal phase

Question 17

NM bone scan: septic arthritis

Answer 17

positive on all three phases on both sides of joint

Question 18

hypertrophic pulmonary osteoarthropathy

Answer 18

long bone diaphyseal periosteal reaction due to pulmonary disease; lung cancer

parallel lines of activity along cortex of bones

Question 19

bone scan: AVN

Answer 19

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

Question 20

NM bone scan: Paget disease

Answer 20

heterogenously increased uptake due to lytic/mixed/sclerotic uptake corresponding to phases

may degenerate into osteosarcoma

Question 21

NM bone scan: complex regional pain syndrome/reflex sympathetic dystrophy

Answer 21

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)