bone scintigraphy

bone functions

support, movement, protection, blood cell formation, mineral storage

bone formation

osteoblasts lay down osteoid (organic matrix) → amorphous calcium phosphate (ACP) salts convert to crystalline hydroxyapatite (HA) and solidify the matrix to remodel bone (HA and ACP are in inorganic matrix)

osteogenic/osteoprogenitor cells

unspecialised stem cells that develop into osteoblasts

osteoblasts

build bone, synthesise soft matter in the matrix which is hardened by mineral deposition

osteocytes

former osteoblasts trapped in their matrix to maintain calcium and phosphate ion levels

osteoclasts

dissolve bone

how does bone remodeling occur?

remodeling results from bone dissolving osteoclasts and bone depositing osteoblasts

bone radiopharmaceuticals

99mTc MDP (methylene diphosphonate)
99m Tc HDP (hydroxy methylene diphosphonate)

bone typical administered activity

~800MBq +- 10%

bone radiopharmaceutical administration

Injected intravenously (IV)

bone radiopharmaceutical mechanism of localisation

diphosphonates bind to calcium ions in the inorganic matrix (chemisorption)
hydroxl in HDP also binds to Calcium → tridentate binding
amorphous calcium phosphate (ACP) salts bind well to diphosphonate
hydroxyapatite (HA) crystals do not bind as well to radiopharmaceutical → less uptake of radiopharmaceutical in mature bone compared to immature bone
difference in HA and ACP uptake allows for detection of lesions in areas of increased osteoblastic activity
more osteoblastic activity → more ACP that converts to HA → more radiopharmaceutical uptake

bone dynamic scanning

(128x128) 2-3sec/frame 20 frames

consider 5sec/frame for extremities

bone blood pool scanning

a. statics: 500K counts or 2 min/image (128x128)
b. whole body: 25cm/min (1024x256)

bone delayed scanning

(2.5-4 hours later)
a. statics: 500K counts or 5 min/image (256x256)
b. whole body: 10cm/min (1024x256)
c. SPECT/CT: 15secs/frame, 64 frames (32 each head)

when is a 3 phase bone scan used?

when assessment of inflammation and/or vascularity is important → osteomyelitis (infection), fractures, inflammatory arthropathy

when is a 2 phase bone scan used?

when assessment of inflammation and/or vascularity is important → inflammatory arthritis, osteolytic bone lesions

when a single phase bone scan used?

when assessment of inflammation/vascularity is NOT important → metastatic disease with osteosclerotic lesions (breast and prostate cancer)

bone desired image analysis

normal biodistribution is SYMMETRICAL some areas may be hotter/colder, may be due to positioning/distance from detectors - CHECK IF IT MATCHES BOTH SIDES

bone patient history of interest

medications, allergies, history of cancer, past surgeries, falls or incidents causing injury, breastfeeding/pregnant, history of broken bones or fractures, type of pain and duration of pain

bone patient advice

avoid pregnant women/children

what are the 3 main primary bone tumours?

1. osteosarcoma

2. chondrosarcoma

3. Ewing’s sarcoma

primary malignant bone tumour

originate from bone itself

secondary malignant bone tumour

metastasise to bone from other body parts such as breast or prostate

osteosarcoma

(most common primary bone cancer) → develops from osteoblasts and most common in metaphyseal region of long bones, (50% knee) → good outcomes if amputation is possible

REQUIRES 3 PHASE BONE SCAN

chondrosarcoma

malignant bone cancer starting in cartilage cells → relatively slowly growing

REQUIRES 3 PHASE BONE SCAN

Ewing’s sarcoma

develops in mesenchyme in bone marrow (embryonic mesoderm with loosely packed unspecialised cells) → common in long bones and pelvis

REQUIRES 3 PHASE BONE SCAN

osteochondroma

(benign bone tumours) → common, develop from growth plates → no symptoms, can be discovered incidentally → can be attached directly to bone or connected by a stem like structure

REQUIRES 3 PHASE BONE SCAN

secondary malignant bone tumour from thyroid, bronchus, lymphoma or renal carcinoma primaries

REQUIRES 2 PHASE BONE SCAN

secondary malignant bone tumour from breast, prostate or gastric primaries

REQUIRES SINGLE PHASE BONE SCAN

osteolytic lesions

where there is a loss of bone density → structural instability

REQUIRES 2 PHASE BONE SCAN

3 main causes of osteolytic bone lesions

1. multiple myeloma

2. primary bone lymphoma

3. metastatic bone cancer

multiple myeloma

cancer of plasma cells

REQUIRES 2 PHASE BONE SCAN

primary bone lymphoma

non Hodgkin lymphoma affecting bone that leads to bone destruction and osteolytic lesions

REQUIRES 2 PHASE BONE SCAN

metastatic bone cancer

due to release of factors that stimulate bone breakdown by osteoclasts → primary cancers breast, lung, prostate, kidney

REQUIRES SINGLE/2 PHASE BONE SCAN

osteosclerotic bone lesions

where there is increased bone density or thickening → can be benign or malignant

REQUIRES 2 PHASE BONE SCAN

osteosclerotic bone lesions potential causes

1. metastatic cancer

2. Paget’s disease

3. osteopetrosis

4. infection

Paget’s disease

excessive breakdown and formation of bone tissue → monostotic (one bone) or polystotic (multiple bones)

REQUIRES SINGLE/2 PHASE BONE SCAN

osteopetrosis

dense and brittle bones

REQUIRES 2 PHASE BONE SCAN

what is a superscan

metastatic lesions uniform across entire skeleton → absence of kidneys or bladder → everywhere is dark

what is an osteoblastic flare phenomenon

occurs <3 months chemotherapy treatment → existing lesions very hot, small lesions become visible → result of chemo treatment → new lesions after 6 months could be disease progression

types of benign bone tumours

1. osteoid osteoma

2. fibrous dysplasia

3. osteochondroma

osteoid osteoma

rare, affects young individuals → for young children it can deform bone or cause increased bone size

REQUIRES 3 PHASE BONE SCAN

fibrous dysplasia

abnormal growth or development of fibrous tissue within bone → can affect single or multiple bones → caused by genetic mutation leading to replacement of normal bone with fibrous tissue → can be monostotic (single bone) or polystotic (multiple bones)

REQUIRES 2 PHASE BONE SCAN

rheumatoid arthritis

autoimmune disease, inflammation in joints, common in women

REQUIRES SINGLE/2 PHASE BONE SCAN
- consider including plantar and palmar scans

avascular necrosis

aka osteonecrosis → bone tissue dies due to lack of blood supply → affects epiphysis of long bones at weight bearing joints → common at femoral head, knee, talus of foot and humeral head

REQUIRES 3 PHASE BONE SCAN

osteomyelitis

infection of bone usually by bacteria → can be acute (initial stage) or chronic (when acute is not adequately treated)

acute can develop quickly and requires prompt treatment → rapid onset of symptoms
chronic → persistent infection and inflammation often leading to bone necrosis

REQUIRES 3 PHASE BONE SCAN

hematogenous osteomyelitis

bacteria from a distant infection site (skin infection or UTI) travels through bloodstream and settles in blood → often in children long bones and adult vertebrae or pelvis

REQUIRES 3 PHASE BONE SCAN

contiguous osteomyelitis

infection spreads to bone from adjacent infected tissue (ie. open fracture, bone exposed to outside environment), infected joint replacement, infected soft tissue around bone

REQUIRES 3 PHASE BONE SCAN

bacterial osteomyelitis

caused by bacteria such as Staphylococcus aureus

REQUIRES 3 PHASE BONE SCAN

fungal osteomyelitis

less common, but can occur in immunocompromised individuals

REQUIRES 3 PHASE BONE SCAN

prosthetic loosening

detachment of movement of artificial joint from the bone it was implanted in → causes general reduction in quality of life

REQUIRES 3 PHASE BONE SCAN
- prosthetic seen as cold spot

symphysis menti

at chin

sternal notch

top of sternum

xiphoid process

bottom of sternum

right and left costal margins

ends of ribs

(anterior superior) iliac crest

hips

greater trochanter

proximal femur

vertebral column numbers

cervical: 7 C1-C7
thoracic: 12 T1-T12
lumbar: 5 L1-L5
sacrum: 5 fused
coccyx: 4 fused