1011-117 Comparison of 82Rubidium Positron Emission Tomography to 99Technetium-Methoxyisobutyl Isonitrile Perfusion Imaging

Abstract

This study was designed to prospectively compare myocardial perfusion imaging with rubidium-82 ( 82 Rb) by positron emission tomography (PET) to technetium-99 m –methoxyisobutyl isonitrile (MIBI) by single photon emission computed tomography (SPECT). Detection of inducible ischemia and prior infarction was assessed in 53 patients (pts) with known coronary artery disease (CAD) who had undergone quantitative coronary angiography. To assign independently myocardial viability both techniques were compared to resting, glucose loaded myocardial uptake of fluorine-18 fluorodeoxyglucose (FDG) PET in a subgroup of 27 pts. with left ventricular wall motion abnormalities. Intravenous dipyridamole vasodilatation (0.7 mg/kg) was used as myocardial stress modality, with 82 Rb and MIBI being injected simultaneously under identical hemodynamic conditions. SPECT and PET results were scored in a 13 segment model of the left ventricle as normal, inducible ischemia, infarction or infarction with adjacent ischemia. There were concordant findings in 48 out of 53 analysed pts. (91%). However, in 5 pts. (9%) MIBI-SPECT showed fixed perfusion defects but ischemia by 82 Rb-PET and evidence of viable myocardium with FDG-PET, whereas there was no segment with infarction in 82 Rb-PET and ischemia in SPECT. We conclude that MIBI-SPECT detects less inducible ischemia but more fixed perfusion defects compared to 82 Rb-PET in the same patient population. Sensitivity of stress/rest 82 Rb-PET in detection of ≥ 70% stenosed vessel was 33/33 (100%) in LAD territory respectively 31/32 (97%) in LCx/RCA territory with specificity of 93%. MIBI SPECT sensitivity in the same group was 29/33 (88%) for LAD and 31/32 (97%) for LCx/RCA territory with specificity of 90% in LAD territory respectively 71% in LCx/RCA. These data strongly suggest that MIBI-SPECT underestimates the presence of ischemic and still viable myocardium in comparison to 82 Rb- and FDG-PET. In contrast myocardial viability as assessed by 82 Rb- and FDG-PET correlated well. Thus stress/rest 82 Rb-PET holds promise for reliable assessment of reversible ischemia and myocardial Viability.