Pulsatile cycle-specific data acquisition in carotid MR angiography with segmented FLASH sequence: Experimental and clinical investigation

Abstract

The authors evaluated the usefulness of diastolic data acquisition in magnetic resonance (MR) angiography of the carotid artery. MR angiographic images of phantom models of 30%, 40%, and 50% stenosis were obtained at different pulsatile cycles by using variable delay times from the electrocardiogram triggering with segmented fast low-angle shot sequences (14/7.3 [repetition time msec/echo time msec]) with k-space segmentation. The degree of stenosis was measured on the MR angiographic images by three observers. Poststenotic signal intensity loss was analyzed by measuring the signal intensity on the axial image acquired 10 mm distal to the stenotic portion of the 50% stenosis phantom at variable delay time from triggering. Six patients with stenosis of the internal carotid artery also underwent conventional and MR angiography. The degree of stenosis depicted on diastolic- and systolic-phase MR angiographic images was measured by three observers and compared with that shown on the conventional angiographic images. The diastolic-phase images more accurately depicted the degree of stenosis than did the systolic-phase images in the phantom and all six patients, although the degree of stenosis tended to be overestimated on both images. The degree of stenosis was most overestimated with triggering that occurred at the time of peak flow velocity. In the phantom with 50% stenosis, the signal intensity 10 mm distal to the stenotic portion was decreased in the systolic phase. Diastolic data acquisition is a useful method of reducing intra- and poststenotic signal intensity loss in the carotid artery.