PURPOSE In this study,we applied a sparse sampling prototype sequence with variable-density poisson incoherent sampling pattern for TOF-MRA imaging(TOFu-MRA).The purpose was to compare TOF-MRA and TOFu-MRA for assessment of atherosclerotic disease of the carotid and cranial vasculature,using DSA as a reference standard.METHOD AND MATERIALS 10 volunteers and 28 patients participated in this study.The MRI exam included TOF-MRA and a prototype sequence for TOFu-MRA.All data were acquired on a MAGNETOM Skyra 3T MR scanner(Siemens Healthcare,Erlangen,Germany).DSA was performed as clinically indicated.All subjects underwent TOF-MRA and TOFu-MRA.The 28 patients underwent as well DSA.All patient data were used,irrespectively of the presence or absence of pathology.Lesions identified on angiography were optically magnified,and the relative stenosis diameter was measured.The post-processing of the TOF-MRA data and TOFu-MRA data used a maximum intensity projection algorithm.Two experienced neuroradiologists,blinded to the results of DSA evaluated the TOF-MRA and the TOFu-MRA images independently.The lesions were measured using a zoom factor of 6.The stenosis grades were based on the North American Symptomatic Carotid Endarterectomy(NASCET)Trial criteria: <50%stenosis(low moderate),50 to 69%stenosis(high moderate),70 to 99%stenosis(high-grade),and occlusion.Because of the small number of lesions and the multiple vessels involved in this study,the arteries were grouped into <50%and ≥50%stenosis for most of the analyses.RESULTS Fig.1 shows a stenosis of A1 and M2 in TOF-MRA and TOFu-MRA,compared with DSA.The two high-grade stenoses of A1 and M2,which were documented by DSA,are seen on TOF-MRA as well as on TOFu-MRA.Nonetheless,the degree of stenosis for TOFu-MRA was closer to that in DSA than for TOF-MRA.Fig.2 shows TOF-MRA and TOFu-MRA in carotid arteries of a volunteer.It can be observed that all the arteries shown in TOF-MRA are visible in TOFu-MRA.Tinier branch arteries are only visible in TOFu-MRA.On DSA,there were 30 vascular stenoses >=50%identified,which were all visible in TOF-MRA and TOFu-MRA.On DSA,there were 42 vascular stenoses <50%identified,32 vascular stenoses were visible in TOF-MRA,and 38 vascular stenoses were visible in TOFu-MRA.Among the stenosis missing in the TOF and TOFu-MRA data,10 vascular stenoses in TOFMRA and 4 vascular stenoses in TOFu-MRA were judged as stenosis >=50%.CONCLUSION Using TOFu-MRA,it was possible to shorten the scan time and provide clinical information as good as routine TOF-MRA.For neck artery imaging,TOFu-MRA had better depiction than standard TOF-MRA when visualizing non-perpendicular arteries.CLINICAL RELEVANCE/APPLICATION Contrast-free MRA in cranial and carotid vasculature has been used broadly in Asia.With shorter scanning time than TOF-MRA,TOFu-MRA presented higher-quality images,and showed tiny artery branches and stenosis closer to DSA,especially in imaging neck arteries.