Quantification of myocardial perfusion based on signal intensity of flow sensitized MRI

Abstract

Summary A new method to quantify myocardial perfusion was developed based on slice select (MS) and non-select (MG) inversion recovery acquisitions at a single inversion time. A modified Bloch equation was solved to obtain an analytical expression for perfusion (P) in terms of ΔMSG =M S-MG The average myocardial perfusion of healthy C57BL/6 mice measured using this technique (P=5.7±0.4 ml/g/min) agreed with that measured using traditional techniques and it had a high reproducibility with mean standard deviation of 3.6% between repeated measures. Perfusion maps of ischemia-reperfusion mice showed significantly low perfusion (P=1.6±0.3 ml/g/min) in the infarcted regions compared to that of remote regions (P=4.1±0.3 ml/g/min,p=0.004). Background The arterial spin labeling technique based on the T1 relaxation time of tissue (T1 method) can be used to quantify myocardial perfusion without the use of exogenous contrast materials[1]. However accurate estimation of T1 relaxation times in the heart, especially in mice is difficult and can require long scan time. As an alternative, we developed a method to quantify myocardial perfusion based on the signal intensity(SI method)of flow sensitized MRI. Methods Myocardial tissue was modeled as intra and extra vascular compartments with fast exchange of spins in between them[1]. The flow sensitization was achieved by slice select (MS) and non-select (MG) inversion recovery acquisitions at a single inversion time. A steady state gradient echo image (Msa) was also acquired to normalize receiver characteristics. A modified Bloch equation was solved for this acquisition scheme to obtain an analytical expression for perfusion (P) in terms of ΔMSG = MS-MG as follows: