CARDIAC PHASE-SYNCHRONIZED MYOCARDIAL TL-201 SINGLE-PHOTON EMISSION TOMOGRAPHY USING LIST MODE DATA-ACQUISITION AND ITERATIVE TOMOGRAPHIC RECONSTRUCTION

The purpose of this study was to determine whether data acquisition in the list mode and iterative tomographic reconstruction would render f easible cardiac phase-synchronized thallium-201 single-photon emission tomography (SPET) of the myocardium under routine conditions without modifications in tracer dose, acquisition time, or number of steps of the a gamma camera, Seventy non-selected patients underwent Tl-201 SPE T imaging according to a routine protocol (74 MBq/2 mCi Tl-201, 180 de grees rotation of the gamma camera, 32 steps, 30 min), Gamma camera da ta, EGG, and a time signal were recorded in list mode. The cardiac cyc le was divided Into eight phases, the end-diastolic phase encompassing the QRS complex, and the end-systolic phase the T wave, Both phase- a nd non-phase-synchronized tomograms based on the same list mode data w ere reconstructed iteratively. Phase-synchronized and non-synchronized images were compared. Patients were divided into two groups depending on whether or not coronary artery disease had been definitely diagnos ed prior to SPET imaging. The numbers of patients in both groups demon strating defects visible on the phase-synchronized but not on the non- synchronized images were compared, It was found that both postexercise and redistribution phase tomograms were Suited for interpretation. Th e changes from end-diastolic to end-systolic images allowed a comparat ive assessment of regional wall motility and tracer uptake. End-diasto lic tomograms provided the best definition of defects. Additional defe cts not apparent on non-synchronized images were visible in 40 patient s, six of whom did not show any defect on the non-synchronized images, Of 42 patients: in whom coronary artery disease had been definitely d iagnosed, 19 had additional defects not visible on the non-synchronize d images, in comparison to 21 of 28 in whom coronary artery disease wa s suspected (P<0.02; chi(2)) It is concluded that cardiac phase-synchr onized Tl-201 SPET of the myocardium was made feasible by list mode da ta acquisition and iterative reconstruction. The additional findings o n the phase-synchronized tomograms, not visible on the non-synchronize d ones, represented genuine defects, Cardiac phase-synchronized Tl-201 SPET is advantageous in allowing simultaneous assessment of regional wall motion and tracer uptake, and in visualizing smaller defects.