[Phase I clinical study on 99mTc-MIBI].

A phase I clinical study on 99mTc-hexakis 2-methoxy isobutylisonitrile (99mTc-MIBI) was carried out in 6 normal volunteers. There was no significant change in vital signs and laboratory parameters attributing to the reagent other than complaint of slight and transient metallic taste immediately after the injection in 4 volunteers. The highest dosimetry was calculated as 1.1 mGy/37 MBq at lower large intestine, which was within the acceptable range. 99mTc-MIBI was rapidly cleared from the blood and accumulated in the heart immediately after the injection with 1.4% dose and 1.8% dose at 5 min at rest and at stress, respectively. The retention of radioactivity in the heart well continued for at least several hours. The heart-to-lung ratio was over 2.00 at 5 min and heart-to-liver ratio was over 1.00 at 60 min. Myocardial planar and SPECT images were obtained with high quality. In conclusion, 99mTc-MIBI is a useful myocardial perfusion imaging agent.