The absolute perfusion and the intracapillary or regional blood volume (RBV) in murine myocardium were assessed in vivo by spin labeling magnetic resonance imaging. Pixel-based perfusion and RBV maps were calculated at a pixel resolution of 469 x 469 mum and a slice thickness of 2 mm. The T(1) imaging module was a segmented inversion recovery snapshot fast low angle shot sequence with velocity compensation in all three gradient directions. The group average myocardial perfusion at baseline was determined to be 701 +/- 53 mL (100 g . min)(-1) for anesthesia with isoflurane (N = 11) at a mean heart rate (HR) of 455 +/- 10 beats per minute (bpm). This value is in good agreement with perfusion values determined by invasive microspheres examinations. For i.v. administration of the anesthetic Propofol, the baseline perfusion decreased to 383 +/- 40 mL (100 g . min)(-1) (N = 17, P < 0.05 versus. isoflurane) at a mean heart rate of 261 +/- 13 bpm (P < 0.05 versus isoflurane). In addition, six mice with myocardial infarction were studied under isoflurane anesthesia (HR 397 +/- 7 bpm). The perfusion maps showed a clear decrease of the perfusion in the infarcted area. The perfusion in the remote myocardium decreased significantly to 476 +/- 81 mL (100 g . min)(-1) (P < 0.05 versus sham). Regarding the regional blood volume, a mean value of 11.8 +/- 0.8 vol % was determined for healthy murine myocardium under anesthesia with Propofol (N = 4, HR 233 +/- 17 bpm). In total, the presented techniques provide noninvasive in vivo assessment of the perfusion and the regional blood volume in the murine myocardium for the first time and seem to be promising tools for the characterization of mouse models in cardiovascular research.
(c) 2005 Wiley-Liss, Inc.