167 0361 -803X/90/155i-0i67 C American Roentgen Ray Society Three-Dimensional Phase- Contrast MR Angiography in the Head and Neck: Preliminary Report :t!i1M Joseph R. Pernicon& James E. Siebert1 E. James Potchen1 Abraham Pera2 Charles L. Dumoulin3 Steven P. Souza3 Received March 14, 1989; revision requested May 12, 1989; revision received October 17, 1989; accepted November 2, 1989. 1 Department of Radiology, Michigan State Uni- versity, B220 Clinical Center, East Lansing, Ml 48824. Address reprint requests to J. R. Pemicone. 2 Hemet valley Imaging Medical Group, Inc., P. 0. Box 3897, Hemet, CA 92343. 3 General Electric Company, Corporate Re- search and Development, P. 0. Box 8, Schenec- tady, NY 12301. Morbidity and possible mortality associated with contrast angiography lead to its cautious use. A noninvasive method for screening and further delineating known abnor- malities would be welcomed. This article reviews the initial results and application of MR imaging to vascular imaging in the head and neck. By using the three-dimensional phase-sensitive method of Dumoulin, Souza, and collaborators, we acquired MR angio- grams in 37 mm and portrayed blood flow in all the major arteries and veins. Feeding arteries and draining veins of artenovenous malformations were well delineated; aneu- rysms as small as 3-4 mm were shown, and obstructed cerebral vessels and the patency of a highly stenotic internal carotid artery were demonstrated. MR angiography of the head or neck offers great promise as a noninvasive means of studying vascular abnormalities. AJNR 11:457-466, May/June 1990; AJR 155:167-176, July 1990 Contrast angiography is a reliable method for obtaining morphologic, and to some extent, hernodynamic information about blood vessels. Morbidity associated with angiographic procedures, however, includes the possibility of stroke, renal failure, and patient discomfort from catheter insertion and contrast injection [1 ]. A noninvasive alternative would be clearly desirable. This article discusses and gives examples ofour initial experience with a phase-sensitive method of MR angiography [2-5], a totally noninvasive procedure. Our efforts have been directed toward continued development of the technique and the determination of clinical protocols in preparation for future prospective clinical studies. Materials and Methods Data are acquired by using a three-dimensional (3D) gradient-refocused spin-warp scan technique (General Electric 1 .5-T MR imager, Version 3.2.C) that incorporates bipolar mag- netic gradient pulses for phase-sensitive flow encoding [3]. Figure 1 depicts the RF and magnetic gradient pulse sequence used. The repetition time (TR) was 22.3 msec, the echo time (TE) was 14.7 msec, and the RF flip angle ranged from 15#{176} to 30#{176}. The number of excitations (NEX) per phase-encoding step was two. Flow-encoding gradient-pulse lobes were half-period sine functions of typically 3-msec duration with a peak value of 9.0 mT/m. Before the MR study, the referring clinician is consulted to define the anatomic extent of interest to determine the minimum appropriate field of view (FOV) to be imaged. Table 1 presents frequently used selections for acquisition matrix and FOVs. All options listed have the same number of phase-encoding steps and, hence, the same acquisition times. The options are listed in order of decreasing acquisition voxel (effective volume element) size, the smallest voxel size being (0.78 mm)3. Since currently only one flow direction can be encoded in an acquisition, three sequential acquisitions were performed for total flow information. The scanning time was approximately 12 mm for each of the three directions of flow encoding. Hence, the total scan time was approximately 37 mm. The three single-flow component volume images were then combined by vector addition to form a total-flow magnitude image.