[Myocardial perfusion imaging with 99mTc-SQ30217: application of three-headed SPECT system]

The early dynamic change of a new myocardial imaging agent, 99mTc-SQ30217, was investigated in SPECT study. A three-headed high sensitivity SPECT system was employed to evaluate the serial changes of accumulation pattern in the heart, lung and liver using a "continuous repetitive acquisition" mode. The myocardial activity reached a peak rapidly and decreased with rapid clearance rate. The analysis of myocardial clearance curve showed a T1/2 of 2.8 minutes (k1 = 0.25 +/- 0.12/min) in the rapid phase, and a T1/2 of 57 minutes (k2 = 0.012 +/- 0.011/min) in the slow phase. The tracer clearance in the lung was more rapid, while the hepatic uptake reached a peak approximately 10 to 15 minutes after injection. When the serial SPECT images were reviewed, the early 3-minute acquisition within 10 minutes after injection showed better image quality than the images obtained after 10 minutes. The hepatic activity did not obscure the infero-septal wall in the earlier images, but did in the images 10 minutes after injection. Thus, quick SPECT data acquisition seemed to be desirable for this agent. We concluded that 99mTc-SQ30217 was a promising radiopharmaceutical for myocardial perfusion imaging.