Peripheral nerves, particularly pure sensory nerves, are sometimes very small in caliber (< 2 mm) and their oblique course through intra- and intermuscular planes throughout the extremities as well as within the neck (i.e. brachial plexus) and the abdomen (i.e. lumbosacral plexus) make anatomic mapping and visualization difficult with traditional planes and sequences. Peripheral nerves commonly run in a ‘neurovascular bundle’ and thus confidently distinguishing between the nerve and vessel can be impossible even with high field-strength and multichannel coils. The brachial plexus may be the most challenging structure due to respiratory and cardiac motion as well as inhomogeneous fat suppression related to inherent neck curvature and adjacent lung air that cause a large variation in B0 inhomogeneity. Volumetric acquisition also allows reformatting into arbitrary planes to delineate the longitudinal course of the nerve in one or two slices and for creation of maximal intensity projection (MIP) “thick slab” images. In this study, we aimed to address these issues by employing a high-resolution 3D fast spin echo technique with 2-point Dixon fat/water separation (CUBE-FLEX) capability [1] and a black-blood flow-saturation prep (FSP) pulse [2] with venous suppression capabilities. The purpose of this particular abstract is to highlight the diagnostic benefit of such a sequence.Peripheral nerve imaging was performed on 71 consented patients on a GE 3T 60cm bore scanner (MR750) using a 16channel Flexible extremity array (for upper extremities) or 32ch body array (for brachial or lumbosacral plexi). A 3D fast spin echo technique with modulated flip angle (CUBE) was used to enable long echo train length (ETL) with reduced blurring. The flow-sat-preparation module consisted of a 90x 180y -90x RF train, with 2 velocity encoding/dephasing gradients between the 90x & 180y, and between the 180x & -90y (Fig 1). A VENC of 100mm/sec in most cases provided sufficient suppression for venous signal. We applied this technique to peripheral nerve imaging of various anatomical locations including the brachial and lumbosacral plexi, deep pelvis, and upper extremities. Parameters were adjusted based on the anatomy but an example of the CUBE-FLEX FSP protocol for bilateral imaging of the brachial plexus was: FOV:36cm(SI)x36cm(LR); Matrix: 256(freq) x 256(phase), TR/TE:2000ms/75ms, ETL: 120, BW:±125kHz, Slice thickness:1.6mm, NEX:1, Acceleration: 1.5, # slices: 232, scan time: 4-6min. Image quality, artifact, fat suppression quality and venous suppression quality were noted.The DIXON method of fat suppression applied in this sequence is less sensitive to B0 inhomogeneity as compared to chemical shift-selective fat suppression and adiabatic spectral inversion recovery techniques (Fig. 1), which may fail to provide adequate suppression in the neck region for imaging of the brachial plexus. While STIR can provide homogeneous fat suppression, it suffers from reduced signal-to-noise (SNR) ratio as compared to the DIXON technique. The CUBE-FLEX FSP sequence, combined with a maximal intensity projection (MIP), is helpful for delineating the entire, longitudinal course of branches of the brachial plexus from their origin proximally to their target muscle of innervation. This helps increase confidence in diagnosis, particularly when evaluating smaller nerves that may take a circuitous course, and can also be applied in the extremities (Figs. 2-4). Optimizing contrast differences between nerves and muscles is of utmost importance when evaluating both the brachial plexus, as it courses through the interscalene triangle, and the lumbosacral plexus as some branches weave through and around the psoas musculature (Fig. 5, A and B). Evaluating the pudendal nerve in Alcock’s canal in the pelvis, the most common site of entrapment of this nerve, is a common imaging conundrum as its small branches run immediately alongside a prominent venous plexus. CUBE-FLEX FSP affords adequate vascular suppression for distinguishing the nerve from the vessels (Fig. 5, C and D).In this work, we demonstrated the feasibility and diagnostic utility of CUBE-FLEX FSP technique in peripheral nerve imaging. We have observed improved fat suppression, excellent contrast between nerves and surrounding tissues, and the added advantage of venous suppression with this sequence. Remaining challenges to be addressed are B1 inhomogeneity creating a shading effect, typically on one side of the patient’s body, and incomplete signal suppression of slow flow veins, particularly in the extremities.