Quantification of myocardial blood flow and flow reserve in rats using arterial spin labeling MRI: comparison with a fluorescent microsphere technique

To quantify noninvasively myocardial blood flow (MBF) and MBF reserve in isoflurane‐anesthetized rats using the Look‐Locker flow‐alternating inversion recovery gradient‐echo arterial spin labeling technique (LLFAIRGE‐ASL), and to compare the results with the fluorescent microsphere (FM) technique. Male Wistar rats (weight = 200–240 g, n = 21) were anesthetized with 2.0% isoflurane. Hemodynamic parameters were recorded. In seven rats, MBF was assessed on a Bruker Biospec 4.7T MR system using an ECG‐ and respiration‐gated LLFAIRGE‐ASL (pixel size = 234 × 468µm², TE = 1.52ms) at rest and during adenosine infusion (140 µg/kg/min). A mixture of 200 000 FM was injected into a second group of rats at rest and during adenosine infusion (n = 7 each), under similar physiologic conditions. Hearts and skeletal muscle samples were processed for fluorescence spectroscopy. Two‐tailed unpaired, paired Student's t‐test and ANOVA were used to compare groups. MBF measured with LLFAIRGE‐ASL was 5.2 ± 1.0 mL/g/min at rest and 13.3 ± 3.0 mL/g/min during adenosine infusion. Results obtained with fluorescent microspheres yielded 5.9 ± 2.3 mL/g/min (nonsignificant vs. LLFAIRGE‐ASL, p = 0.9) at rest and 13.1 ± 2.1 mL/g/min (nonsignificant vs. LLFAIRGE‐ASL, p = 0.4) during adenosine infusion. Myocardial blood flow reserve measured using LLFAIRGE‐ASL and FM were not significantly different (2.5 ± 0.6 vs. 2.4 ± 0.9, respectively; p = 0.8). Hemodynamic parameters during the experiments were not different between the groups. The myocardial blood flow reserve determined under isoflurane anesthesia was 2.5 ± 0.6, which was not different from the value obtained with FM. LLFAIRGE‐ASL provided MBF maps with high spatial resolution in rats under isoflurane anesthesia. LLFAIRGE‐ASL is a noninvasive measure to assess myocardial blood flow reserve and provides an interesting tool for cardiovascular research. Copyright © 2011 John Wiley & Sons, Ltd.