Evaluation of sympathetic nervous system function in normal and spontaneously hypertensive rat hearts with dynamic SPECT imaging

¹²³I-MIBG is an analogue of the norepinephrine uptake in the presynaptic portion of the sympathetic neurons that innervate the heart. The abnormal metabolism of ¹²³I-MIBG is used to diagnose potential heart failure. This paper quantitatively compares the metabolism of ¹²³I-MIBG in SHRs and Wistar-Kyoto normal rats. Dynamic projection data were acquired for 100 min in 1-sec time frames with an angular step of 2 degrees per frame on a dual-head GE Millennium VG Hawkeye SPECT/CT scanner equipped with custom pinhole collimators. The time activity curves of radiotracer in blood pool and myocardium were extracted from the projections through the spatiotemporal dimension reduction method developed previously for dynamic cardiac SPECT reconstruction. The kinetic parameters were estimated by fitting the estimate time activity curves to a compartmental model. The distribution volumes (DVs) of the radiotracer in the myocardium were calculated. The DV of SHRs was greater (p=2.4E-4) than that of WKY normal rats, indicating the development of cardiac hypertrophy in the SHRs.