A 58-year-old man with angina and known triple-vessel disease undergoes stress and 4-hour delayed Tl-201 myocardial scintigraphy. A lateral wall defect seen immediately after stress fills in completely on the delayed images. This pattern indicates:

• A Non-viable transmural infarct in the lateral wall
• B Normal homogeneous perfusion
• C Artifact from diaphragmatic attenuation
• D Viable, ischaemic (hibernating) myocardium likely to improve after revascularization ✓

Explanation

Thallium behaves as a potassium analogue: myocytes actively extract it via the Na/K ATPase pump, so any cell with intact membrane transport gradually clears and redistributes the tracer. Complete fill-in of a stress defect on delayed images means living myocytes supplied by a stenosed artery, predicting functional recovery after revascularization. A fixed defect persisting on delayed imaging signifies scar. Attenuation artifacts do not show true redistribution kinetics.

Reference: Mettler, Essentials of Nuclear Medicine Imaging, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.