Comparison of Myocardial Imaging with Iodine- 123-Iodophenyl-9-Methyl Pentadecanoic Acid and Thallium-201-Chloride for Assessment of Patients with Exercise-Induced

Iodine-123-iodophenyl-9-methyl-pentadecanoic acid ([1231] MPDA) and thallium-201 (2°1TI) were sequentially injected in 11 patients during exercise-induced myocardial ische-mia. Simultaneous dual-energy planar images w re ob-tained at 5 min, 3 and 5 hr. All studies were concordantly either positive (8/11) or negative (3/11) by both radio-nuclides. Exact agreement for segmental uptake was 93%, 94 % and 94 % for 5-min, 3- and 5-hr images, respectively. Exact agreement for defect reversibility by 3 and 5 hr were 95 % and 92%. The initial defect contrasts and myocardial-to-lung ratios were similar by both agents but myocardial-to-liver ratio was lower by [12at]MPDA at 5 min, which became similar to 2°1TI at 5 hr. Normal percent myocardial clearances of both agents were comparable and signifi-cantly higher than those in defect zones. Thus [1231]MPDA is suitable for myocardial imaging and correlates closely with 2°1TI for initial postexercise myocardial uptake and defect reversibility. Defect reversibility appears to esult from differential myocardial clearance from normal and ischemic regions. J Nucl Med 1991; 32:447-452 Assessment of regional myocardial perfusion and viability has prognostic and therapeutic mplications in patients with coronary artery disease. Thallium-201 (2°~T1) myocardial imaging has been widely applied for these assessments. Thallium-201, however, is not opti-mal for assessing myocardial viability because nonre-versible defects may be observed in viable myocardial regions (1-4). Myocardial viability may also be assesse