Maximizing thallium stress/redistribution scans.

TO THE EDITOR: In an effort to maximize the utility of the thallium scan, the subject of the reinjection of thallium has become an issue of recent concern (1). The rationale of the reinjection procedure is the observation that a stress/reinjection comparison does a better job of identifying viable myocardium than a stress/redistribution scan. Some authors propose performing stress/redistribution scans with reinjection of thallium in those patients with a fixed defect on the redistribution scan (2,3). The problem with this technique is that it involves a third set of images and is disruptive of the imaging schedule. Some laboratories prefer a 24-hr delayed im aging session, but this is also disruptive to a busy schedule as well as inconvenient for outpatients. Some authors (4) propose a reinjection of thallium 20 mm before the performance of the redistribution scan. The problem with this approach is the fact that a very tight stenosis of a coronary vessel (the type that causes †̃pseudo-fixed' stress-induced defects) can cause defects on rest studies that †̃fill-in' over time