Assessment of cerebral perfusion by first-pass, dynamic, contrast-enhanced, steady-state free-precession MR imaging: an animal study.

The purpose of this study was to determine whether cerebral perfusion could be assessed with a conventional 1.5-T MR imaging system by applying a steady-state free-precession (SSFP) technique during bolus IV injection of contrast material (gadoteridol). Normal and abnormal perfusion states and the effect of the dose of contrast material were studied in cats.Nine healthy anesthetized cats were imaged after administration of 0.5 mmol/kg (n = 5), 0.25 mmol/kg (n = 2), and 0.1 mmol/kg (n = 2) of gadoteridol. Six cats with an acute infarct of the middle cerebral artery (five cats 10 min after and one cat 1 hr after vessel occlusion) were evaluated at a dose of 0.5 mmol/kg. The middle cerebral artery was ligated in each instance by use of a snare placed around the vessel during surgery, which was performed via a transorbital approach. Each animal was imaged with spin-echo T2-weighted (3000/45,90 [TR/TE]) and T1-weighted (500/10) techniques before contrast material was injected. SSFP images (12/18, 80 degrees tip angle) were acquired sequentially (each with a 1-sec acquisition time and no interimage delay) immediately before and for 45 sec after IV injection of a bolus of gadoteridol.The first-pass effect in both normal gray and white matter was dose dependent, with a greater magnitude of change seen at higher doses of contrast material. A 55% decrease in signal intensity of normal peripheral gray matter was observed during the first pass after bolus injection of 0.5 mmol/kg gadoteridol, compared with a 23% decrease and a 17% decrease at doses of 0.25 and 0.1 mmol/kg, respectively. High temporal (one image per second) and spatial (1.5 x 1.5 x 6.0 mm) resolution was achieved, with sufficient sensitivity that both visual and statistical differentiation of normal and abnormal gray and white matter was possible. Ten minutes after vessel occlusion, the change in signal intensity during the first pass was 45 +/- 5% and 27 +/- 9% for normal central gray and white matter, respectively, as compared with 20 +/- 2% and 11 +/- 5% for ischemic central gray and white matter, respectively.Cerebral perfusion can be assessed on conventional 1.5-T MR imaging systems by combining high-dose IV bolus injection of contrast material (in this instance, using gadoteridol) with dynamic SSFP imaging.