Comparison of LDPI to SPECT perfusion imaging using Tc-99m-sestamibi and Tc-99m-pyrophosphate in a murine ischemic hind limb model of neovascularization

Background: We aimed to determine the accuracy of laser Doppler perfusion imaging (LDPI) in an animal model for hind limb ischemia. Methods: We used a murine (C57Bl/6 mice) ischemic hind limb model in which we compared LDPI with the clinically used Tc-99m-sestamibi SPECT perfusion imaging (n = 7). In addition, we used the SPECT tracer Tc-99m-pyrophosphate (Tc-99m-PyP) to image muscular damage (n = 6). Results: LDPI indicated a quick and prominent decrease in perfusion immediately after ligation, subsequently recovering to 21.9 and 25.2 % 14 days later in the Tc-99m-sestamibi and Tc-99m-PyP group, respectively. Tc-99m-sestamibi SPECT scans also showed a quick decrease in perfusion. However, nearly full recovery was reached 7 days post ligation. Muscular damage, indicated by the uptake of Tc-99m-PyP, was highest at day 3 and recovered to baseline levels at day 14 post ligation. Postmortem histology supported these findings, as a significantly increased collateral diameter was found 7 and 14 days after ligation and peak macrophage infiltration and TUNEL positivity was found on day 3 after ligation. Conclusions: Here, we indicate that LDPI strongly underestimates perfusion recovery in a hind limb model for profound ischemia.