Bone Scan (Technetium Scintigraphy)

What It Shows

• Osteoblastic (bone-forming) metastases — most commonly from prostate, breast, and lung cancer
• Whole-skeleton assessment in a single study — from skull to feet
• Symptomatic bone lesion assessment when X-ray is normal (bone scan positive 3–6 months earlier than X-ray)
• Monitoring treatment response in bone metastases
• Distinguishing solitary bone lesions (metastasis vs benign)

How It Works

99mTc-MDP is injected intravenously. The bisphosphonate compound accumulates in areas of active bone remodelling proportional to blood flow and osteoblastic activity. Imaging is performed 2–4 hours after injection. A gamma camera acquires anterior and posterior whole-body images. SPECT (single-photon emission CT) can be added for 3D imaging of specific regions, improving specificity. A nuclear medicine physician reports the distribution of tracer uptake against normal physiological patterns.

• Staging in prostate cancer (PSA > 20, Gleason 8–10, T3/T4 disease)
• Staging in breast cancer with locally advanced or inflammatory disease
• Evaluation of bone pain in known cancer patients
• Monitoring response of bone metastases to treatment
• Assessment when X-ray is normal but bone pain persists

Bone scan has decades of validated use in cancer staging. It detects bone metastases 3–6 months earlier than plain X-ray. Sensitivity for osteoblastic metastases is 75–95%. However, specificity is lower (60–85%) as many benign conditions (arthritis, fractures, Paget's disease) cause increased uptake, requiring clinical correlation. In prostate cancer, PSMA PET outperforms bone scan significantly (sensitivity 97% vs 73%, proPSMA trial) and is replacing it in high-income settings. For breast cancer with bone metastases, whole-body MRI shows superior sensitivity for marrow disease. Bone scan remains valuable in resource-limited settings and for initial staging where PET is unavailable.

Preparation & What to Expect

No fasting required. Drink plenty of water before and after injection to flush kidneys. Void bladder immediately before imaging. Arrive 30 minutes before injection. Return 2–4 hours later for imaging. Remove jewellery and metal objects. Total time: approximately 4–5 hours (including wait between injection and imaging).

• Low specificity — arthritis, fractures, and Paget's disease all show increased uptake
• Cannot detect osteolytic (bone-destroying) metastases reliably — myeloma and renal cell often missed
• PSMA PET superior for prostate cancer in centres where available
• Whole-body MRI superior for myeloma and marrow assessment
• SPECT required to improve specificity at equivocal sites — adds time and cost

• Low radiation dose (~6 mSv) — safe but avoid in pregnancy
• Patient is mildly radioactive for several hours post-injection — limit close contact with young children
• Bisphosphonate component of tracer rarely causes flushing or bone pain (transient)