PULSATILE CYCLE-SPECIFIC DATA-ACQUISITION IN CAROTID MR-ANGIOGRAPHY WITH SEGMENTED FLASH SEQUENCE - EXPERIMENTAL AND CLINICAL INVESTIGATION

Rationale and Objectives. The authors evaluated the usefulness of dias tolic data acquisition in magnetic resonance (MR) angiography of the c arotid artery. Materials and Methods. MR angiographic images of phanto m models of 30%, 40%, and 50% stenosis were obtained at different puls atile cycles by using variable delay times from the electrocardiogram triggering with segmented fast low-angle shot sequences (14/7.3 [repet ition time msec/echo time msec]) with k-space segmentation. The degree of stenosis was measured on the MR angiographic images by three obser vers, Poststenotic signal intensify loss was analyzed by measuring the signal I intensity on the axial image acquired 10 mm distal to the st enotic 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 stenosi s depicted on diastolic-and systolic-phase MR angiographic images was measured by three observers and compared with that shown on the conven tional angiographic images. Results. The diastolic-phase images more a ccurately depicted the degree of stenosis than did the systolic-phase images in the phantom and all six patients, although the degree of ste nosis tended to be overestimated on both images. The degree of stenosi s was most overestimated with triggering that occurred at the time of peak flow velocity. In the phantom with 50% stenosis, the signal inten sity 10 mm distal to the stenotic portion was decreased in the systoli c phase. Conclusion. Diastolic data acquisition is a useful method of reducing intra-and poststenotic signal intensity loss in the carotid a rtery.