Bone scans



Technetium 99m labelled MDP (Mono - diphosphonate)




1.  Pure gamma emitter


2.  Half life only 6 hours

- limits radiation exposure


3.  Localises in bone

- chemical interaction on the surface of the hydroxyapatite crystal of bone

- phosphorous component interacts with the endogenous calcium

- produces insoluble technetium calcium phosphate complexes.




50% goes to bone

50% in equilibrium throughout soft tissues

Excreted in urine


Uptake occurs in areas of


1.  Increased blood flow

- e.g. hypervascular tumours, fractures, inflammatory process


2.  Increased cellular activity and mineral turnover

- osteoblastic activity produces immature osteoid

- this has numerous binding sites for developing apatite crystals

- i.e. healing fractures, inflammatory foci, growth plates

- remodelling of trabeculae in response to stress


3.  Metabolic bone disease

- where there may be abundant immature unmineralised collagen


Imaging protocol


IV injection of 550 to 740 MBq of Tc 99 MDP


Patient encouraged to drink several glasses of water and micturate frequently

- dilute radiation dose to bladder wall

- accumulates in bladder

- a full bladder may obscure posterior abdominal wall


Gamma camera picks up emitted gamma rays


Anterior and posterior

- if just take anterior picture, posterior gamma rays will be absorbed by anterior body wall


3 phase scan


1. Flow phase

- patient positioned under camera

- images taken at 5 second intervals after injection into antecubital vein


2. Blood pool phase

- within next 5 - 10 minutes

- shows extent of soft tissue and bone hyperaemia

- shows soft tissue component of lesions

- i.e. cellulitis around osteomyelitis, soft tissue extent of bony tumours

- synovial hyperaemia in inflammatory arthritis


Bone Scan Blood Pool PhaseBone Scan Blood Pool Phase 2


3. Delayed scan

- 2-4 hours later

- soft tissue activity has cleared

- skeletal structures demonstrated

- separate anterior + posterior scans obtained

- takes 15-30 minutes


Bone Scan Static Bone Images


SPECT (Single photon emission CT)


Tomographic examination

- rotate gamma camera around the patient

- creates CT like slice

- useful in spine i.e. spondylysis


Normal scan



- overall very active

- hot symmetrical epiphyseal growth zones



- slightly hot at ends of long bones, SI joints, tips of scapulae, nasal cavity

- age related changes (ACJ, DDD)


Bone Scan Normal Adult


Hot Lesions on Bone Scan



Primary Malignant Bone Tumour


Trauma / Stress Fracture

Osteoid Osteoma


Fibrous dysplasia


Locally increased blood flow

Primary hyperparathyroidism

Renal osteodystrophy


Specific Conditions


1.  Investigation for bony metastases


Bone Scan MetastasisBone scan Metastasis0001Bone scan Metastasis0002


95% sensitivity

- multiple scattered focal hot spots in axial skeleton



- can occur if metastases coalesce


False Negative Bone Scan

- osteolytic and osteoblastic components are balanced

- multiple myeloma, melanoma, renal cell carcinoma


2. Primary malignant bone tumours



- detects metastasis

- detects extent of lesion for resection / skip lesions


3. Benign bone tumours


Most show low grade uptake


Giant cell tumours / osteoid osteomas

- have intense uptake


4. Fractures



- detection of stress fractures

- scaphoid fractures

- myositis ossificans



- initially blood flow & blood pool phases hot

- then only delayed scan positive which remains hot for several months

- when a fracture fails to unite, blood pool phase negative with delayed scan mildly positive


Sacral insufficiency fracture

- H / Honda sign

- bilateral linear uptake in sacral alar

- transverse uptake in mid sacrum


5. Infection



- Hot flow and pool phases, negative delayed scan



- All 3 phases positive


6. Investigation of pain around prostheses


Bone scan becomes normal at 12 months

- persistently positive scan means loosening or infection


Bone Scan TKRBone Scan Loose Revision TKR


7. Arthritis


Can differentiate between degenerative + inflammatory arthritis



- negative blood pool phase, positive delayed scan



- all three phases positive


8. Avascular necrosis


Ischaemic bone cold, surrounding bone hot

- doughnut appearance in hip


9. Paget's disease


Intensely hot on all three

Pagets Bone Scan


10. Fibrous dysplasia


11. Superscan


Metabolic bone disease

- osteomalacia

- hyperparathyroidism

- enal osteodystrophy



Disseminating coalescing metastasis


12. Undiagnosed bone pain


May reveal an osteoid osteoma / unsuspected AVN / microfractures / low grade osteomyelitis


Gallium Scan


Gallium Scan




Gallium 67 citrate

- localises in areas of inflammation and neoplasia

- due to exudation of labelled serum proteins




Delayed imaging at 24-48 hrs


Frequently used in combination with a technetium bone scan

- a double tracer technique


Less dependent on vascular flow than technetium


Difficulty in distinguishing between cellulitis and osteomyelitis


Technetium or Indium  111-Labelled White cell scan




Label patients own WBC's with radioactive tracer


Labelled white cells accumulate in areas of inflammation but not in areas of neoplasia


Useful in diagnosing osteomyelitis or infection around joint replacement


Unlike gallium also useful in the presence of pseudarthrosis


Leukocyte ScanBone scan and Leucocyte Scan Infected TKR