A method is presented in which an extended longitudinal field of view (FOV), as required for whole-body MRI or MRA peripheral runoff studies, is acquired in one seamless image. Previous methods typically either acquired 3D data at multiple static "stations" which covered the extended FOV or as a series of 2D axial sections. The method presented here maintains the benefits of 3D acquisition while removing the discrete nature of the multistation method by continuous acquisition of MR data as the patient Since first introduced a number of years ago, contrastenhanced 3D MR angiographic methods (MRA) have been applied to a number of vascular regions, including the aorta, carotid, pulmonary, renal, coronary, and peripheral vasculature (1-7). With the exception of "runoff" studies of the peripheral vasculature, most contrast-enhanced MRA studies can generally be performed using a spatially limited anatomic region which can be contained within the effective imaging volume of the MR scanner. However, for visualization of the spatially extended vascular anatomy necessary for peripheral runoff studies, the required longitudinal field of view (FOV) can be well over 100 cm. This value is much higher than the dimension of the imaging volume of virtually all whole-body scanners. In order to cover an FOV of this extent, a variety of methods have been developed (8 -22) in which 3D acquisitions are done at each of several "stations," the FOV of each station falling within the largest imaging volume possible as limited by magnetic field homogeneity and gradient linearity. Contrast agent is administered intravenously and the most superior station is then typically imaged first, followed by inferiorly positioned ones, a succession designed to allow the discrete imaged FOVs to nominally match the timecourse of the contrast bolus.Although effective peripheral runoff MRA studies have been generated using such fixed station techniques, the approach is not without its limitations. First, similar to single-FOV contrast-enhanced 3D MRA, is the issue of timing. It is necessary to time the central k-space views to the arterial phase of the contrast bolus (23). However, for the peripheral runoff case the timing requirements are stricter: it is not only necessary to determine the bolus transit time to the first station, but it is also desirable to know the rate of transit to the subsequent stations. A second issue is time efficiency. Ideally, MR data which contribute to the MR angiogram are acquired throughout the entire time that the contrast material is in the arterial phase of the vasculature. With the discrete, multistation approach there are losses in efficiency due to the time required for table repositioning between stations, time spent for dummy repetitions of the pulse sequence to establish steady state at each station, and effective losses of time due to overlap of FOVs in the longitudinal direction for adjacent stations. Yet a third possible limitation is the potential for artifact at the interface or intersection of the FOVs betwe...

This study shows that the BOLD technique can noninvasively detect change in intra-renal oxygenation during an acute reduction of RBF. This study provides a strong rationale for developing the BOLD method for the detection and evaluation of renal hypoxia induced by RAS, which may be potentially applicable in humans.

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Technical reliability was determined for triggering three-dimensional (3D) contrast material-enhanced magnetic resonance (MR) angiography with MR fluoroscopy. Technical requirements for high reliability were also identified. Reliability was evaluated in 330 consecutive patient studies of the neck, thorax, abdomen, and pelvis. Contrast material arrival was detected fluoroscopically in 325 of the 330 studies (98.5%), and the 3D sequence was successfully triggered in 321 of 330 studies (97.3%). Fluoroscopic triggering of centrically encoded 3D MR angiographic acquisitions is a highly reliable means of obtaining 3D MR angiograms with high spatial resolution.