[Property of electrocardiogram gated single photon emission tomography by 99mTc-methoxy isobutyl isonitrile]

99mTc-methoxy isobutyl isonitrile (MIBI) is a new developed myocardial perfusion imaging agent. Because this compound has higher photon energy than thallium (Tl), electrocardiogram gated single photon emission tomography (SPECT): end-diastolic (ED) and end-systolic (ES) short axis (SA) images could be taken. To investigate property of gated MIBI SPECT, MIBI myocardial scintigraphy, Tl scintigraphy (TMS) and analysis of left ventricular wall motion were performed in 6 patients with myocardial infarction. Left ventricle was divided into 8 segments. Perfusion defect (PD) was scored: "0" (normal), "1" (hypo-perfusion), "2" (defect). Wall motion abnormality (WMA) was also scored: "0" (normokinesis), "1" (hypo-kinesis), "2" (a-, dys-kinesis). Severity and extent of PD and WMA were calculated. Severity of WMA was 3.0 +/- 2.0 (M +/- SD), severity of PD was 3.3 +/- 1.7 in TMS, 3.7 +/- 1.3 in no-gated MIBI, 5.0 +/- 0.6 in ES-MIBI, 7.3 +/- 2.0 in ED-MIBI. Extent of WMA was 2.3 +/- 1.0. Extent of PD was 2.5 +/- 1.3 in TMS, 3.0 +/- 1.6 in no-gated MIBI, 3.5 +/- 0.8 in ES-MIBI, 4.8 +/- 1.0 in ED-MIBI. Compared with wall motion abnormality, severity and extent of PD in ED-MIBI was larger. From our data, it is concluded that perfusion defect in ED-MIBI was overestimated significantly. When we evaluate gated MIBI image, we must consider this property.