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Bone scintigraphy
Tc-99m MDP or HDP is adsorbed onto hydroxyapatite where there is blood flow and bone formation, so bone scintigraphy shows the bone's response — highly sensitive for osteoblastic metastases, fractures and infection, but non-specific and blind to purely lytic lesions.
Why it matters in the exam
The exam shows an image and asks about a pattern. A "superscan" — diffuse increased uptake throughout the skeleton with faint or absent kidneys — is caused by widespread metastases (prostate, breast) or metabolic disease (hyperparathyroidism, osteomalacia). The "flare phenomenon" — new or stronger lesions in the first months after starting treatment — reflects healing, not progression. "Cold" lesions: multiple myeloma, lytic metastases from kidney and thyroid, early osteonecrosis and a radiation field. In myeloma the scan is almost worthless; whole-body low-dose CT, MRI or FDG PET are preferred.
Three-phase scintigraphy — flow, blood pool and delayed phase — separates osteomyelitis (focal uptake in all three phases) from cellulitis (uptake only in the early phases, diffuse). With a fracture, previous surgery or a Charcot foot specificity falls and labelled leucocytes are added. In sports medicine: a stress fracture — focal, fusiform cortical uptake in all phases; "shin splints" — linear uptake along the posteromedial tibial margin on the delayed phase only. Osteoid osteoma — a "double density" around the nidus.
In osteoporosis the scan does not diagnose the disease but finds fractures and estimates their age: horizontal uptake in a collapsed vertebra, and a sacral insufficiency fracture in an "H" shape. Paget disease — intense uptake in the whole bone with expansion. Hypertrophic osteoarthropathy — parallel lines of uptake along the cortex of long bones, linked to lung cancer. In children the growth plates take up intensely and reduce contrast; hydration, bladder emptying and weight-based activity per the EANM dosage card improve quality. NaF PET is more sensitive than the conventional scan.
Key points
- Bone scintigraphy shows bone formation and blood flow.
- Superscan — diffuse uptake with faint kidneys.
- Myeloma — cold lesions; the scan is not suitable.
- Three-phase — osteomyelitis versus cellulitis.
- A flare after treatment is healing.
Summary table
| Pattern | Diagnosis | Note |
|---|---|---|
| Superscan — diffuse uptake, faint kidneys | Widespread metastases or metabolic disease | Prostate, breast, hyperparathyroidism |
| New lesions after starting treatment | Flare | Healing, not progression |
| Cold lesions | Myeloma, lytic metastases, early necrosis | Myeloma — CT, MRI or PET |
| Focal uptake in all three phases | Osteomyelitis | Cellulitis — early phases only |
| Linear along the tibia on the delayed phase | Shin splints | Stress fracture — focal and fusiform |
| Horizontal vertebral uptake | Osteoporotic compression fracture | "H" in the sacrum — insufficiency fracture |
A free exam question
מה הממצא האופייני במיפוי בבן 60 עם spondyloarthropathy seronegative ? (the question as examined, in Hebrew)
- א. קליטה פתולוגית בעמוד השדרה במיפוי כבד וטחול
- ב. גסטרופרזיס במיפוי התרוקנות קיבה
- ג. Honda Sign במיפוי עצם
- ד. אנטזופתיה במיפוי עצם
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
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Sources
- EANM Practice Guidelines for Bone Scintigraphy, 2016 — Indications, three-phase technique and interpretation
- SNMMI Procedure Standard for Bone Scintigraphy, 2023 — Patterns, pitfalls and paediatric considerations
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.