Comparison of gradient- and spin-echo imaging: CBF, CBV, and MTT measurements by bolus tracking

The authors measured cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) in pigs by gadodiamide bolus injections and the bolus tracking technique. Two different pulse sequences were applied and compared: gradient-echo (GE) and spin-echo (SE) echoplanar imaging (EPI). After normalization of CBF and CBV values to the area under the arterial input function (AIF), a linear relation between the two methods was found, suggesting that a previous normalization approach for determining absolute CBF by SE EPI may be extended to GE EPI measurements. The ratio between CBV values measured with GE and SE [CBV (GE)/CBV (SE)] was 2.96. Assuming that the GE acquisition reflects total CBV, our findings suggest that SE is sensitive to 34% (1/2.96) of the total vasculature. The corresponding ratio for CBF was 2.53. There was no significant difference in these two ratios, suggesting that MTT estimates derived from GE and SE EPI measurements are comparable. The findings suggest that SE and GE are equally useful in clinical measurements of functional parameters such as CBF, CBV, and MTT in the brain. J. Magn. Reson. Imaging 2000;12:411-416.