Background and aim: Extra-cardiac activity can interfere with observer interpretation of myocardial perfusion single photon emission computed tomography (SPECT) images. Fatty meals and drinks to reduce interference have been tested; however, a simple study of delayed imaging with Tc-tetrofosmin and Tc-sestamibi has not been specifically addressed. The aim was to quantify the effects of imaging time, radiopharmaceutical and oral administration of full fat milk and water on interfering activity.
Methods: Myocardial perfusion SPECT images were acquired using either tetrofosmin or sestamibi. Patients were imaged at 0.5, 1 or 2 h post-injection (tetrofosmin, 59; sestamibi, 72). Additional groups of patients were imaged either with or without milk (tetrofosmin, 54; sestamibi, 45) and with milk and water (sestamibi, 30). A myocardial region was drawn on the anterior projection and a thin adjacent extra-cardiac region was generated automatically. The count density ratio was calculated and validated with a trial of five observers. A decreasing ratio correlated significantly with observer rank of increasing interference with SPECT image interpretation (r=0.95, P=0.001).
Results: The ratio improved significantly as the imaging time increased for both tetrofosmin and sestamibi groups (P>0.05). The groups given milk or milk plus water showed no significant improvement against control groups (P≥0.2). There was no significant difference between tetrofosmin and sestamibi at any time point (P≥0.4).
Conclusions: Image interpretation may be improved by delayed imaging for tetrofosmin and sestamibi. However, in contrast with common practice, the administration of milk or water appears to be of no clinical value compared with delayed imaging, and there is no significant difference between interfering activity from tetrofosmin and sestamibi.
Peace RA, Lloyd JJ. The effect of imaging time, radiopharmaceutical, full fat milk and water on interfering extra-cardiac activity in myocardial perfusion single photon emission computed tomography. Nucl Med Commun 2005; 26: 17-24.
Dr. Richard Peace RVI Unit, Newcastle upon Tyne. Tel: +44 (0)191-233-6161.
Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, NE7 7DN, UK.
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