Distribution of cardiac perfusion in growing rats: Serial examination in the SPECT/CT for small animals and Quantitative perfusion SPECT

Purpose: There are few studies that evaluate normal rat’s myocardial perfusion in the process of growing using in-vivo imaging. The purpose of the study was to evaluate serial change of cardiac perfusion distribution during the growth of normal rats using SPECT/CT for small animals and Quantitative perfusion SPECT (QPS; Cedars-Sinas) software with 99mTc-sestamibi. Method: We performed SPECT/CT in 6 normal rats serially from 8 to 28 weeks after their birth. Rats received an intravenous 99mTc-sestamibi (185MBq) via tail vein before 20 minutes of SPECT to reduce the physiological uptake in the liver. The rats were scanned under anesthesia (1-2% isoflurane) for 15 min in prone position. Then we made cardiac perfusion polar maps using QPS software. By using 17 segments system as has been used in clinical study, we calculated the % uptake of each segment. We assessed the change of the % uptake of each segment during the growing. Result: The apical segment showed lowest uptake over the entire period (% uptake is 67 ± 3.7%). The mid anterolateral segment showed highest %uptake over the entire period (89 ± 3.9%). There were no significant differences in % segmental uptake in all weeks in basal anterior, basal anteroseptal, basal inferior, mid anterior, mid anteroseptal, mid inferoseptal, mid inferior, mid inferolateral, mid anterolateral, apical anterior, apical inferior, apical lateral and apex area (13 out of 17 segments). Significant differences in % segmental uptake were observed in basal inferoseptal (between at 10 and 21 week), in basal inferolateral (between at 12 and 28 week), basal anterolateral (between at 8 and 28 weeks, at 10 and 28 week), in apical septal (between at 8 and 21 week). We guess that change of % uptake tends to occur in some of the basal segments because of some fluctuation of the edge detection. Other than basal segments, % uptakes were quite stable in the process of growing. Conclusion: We analyzed the rat cardiac perfusion distribution in every week from 8 to 28 weeks after their birth using 99mTc-sestamibi SPECT/CT with QPS software. Other than basal area, the distribution of perfusion in normal rats was quite stable during growth, therefore, single normal data base could be applied for the evaluation of perfusion abnormality at least from 8 to 28 week-old-rats.