Lumbar disc herniation (LDH) always causes the compression of lumbosacral nerve, which is the main cause of the low back pain. Traditional MRI examination is the major diagnostic technique for nerve root compression, but it cannot provide the specific location and the characteristics of nerve compression because of the complexity of adjacent structures and nerve contorts. Recently, the interactive Dixon water-fat separation with echo asymmetry and least-squares estimation technique (IDEAL) was proposed for fat suppression and water-fat separation^[1,2]. The IDEAL acquisition and reconstruction methods can generate a water-only, fat-only, in-phase and out-phase data sets for clear tissue differentiation in a single sequence. It offers a great opportunity for imaging the nerve root compression. In this work, the IDEAL technique was used to image nerve roots to find out the difference between normal and lumbar disc herniation nerve roots. One patient with LDH was examined using a 3.0T MR scanner (GE Discovery MR750 with an 8-channel CTL Target Array Coil). Routine MRI scans with additional IDEAL sequence were conducted. Prior consent form was obtained. The following imaging parameters were used for IDEAL sequence: TR = 6453 ms, TE = 120 ms, FOV = 32 x 32 cm, ETL = 16, NEX = 3, slice-thickness = 1.2 mm, slice-gap = 0 mm, acquisition-matrix = 320 x 224, bandwidth = 83.33 kHz. Post-processing techniques were performed on ADW4.5 workstation, including reformatting of 3D-maximum intensity projection (MIP), multi-planar reconstruction (MPR) and curved-planar reformation (CPR). To ensure that all the nerve roots and DRGs from L1-S1 were displayed well, all the measurements including observing the characteristic of anatomic structure and the whole contort were conducted on MPR and MIP images. Curved planar reformation images were prepared along the nerve in the axial plane, and all the diagnostic analyses were done on CPR images. The evaluation of both sides’ lumbosacral nerve roots from L1 to S1 included the detection rate of lumbosacral nerve roots, the length of preganglionic nerve, the width and length of DRGs, the length of nerve root sheath, the characteristic of nerve compression and anatomical relationship between lesion and adjacent structures.The anatomic structure and the whole contort of nerve roots from L4 were demonstrated in Figure 1. It can be seen that the nerve roots were well depicted in both original image and processed images, including preganglionic nerve and DRGs, part segments of the posterior to the ganglions. It can be seen in Figure 1(c) that its branches could also be visualized well from L3 to S1 level nerves. It had a great advantage that the integrality of lumbosacral nerve roots was maintained. The microstructural of nerve in lumbar lateral recess segment and the nerve in vertebral canal could be observed clearly on curved-planar reformation imaging (see Figure 2). The nerve roots appeared as linear structure with low signal intensity and delineated well within the high signal CSF. Findings of nerve compression, including the local defect impression of nerve root, the changes of the trunk and contort of nerve root (raising or displacement), the changes of morphological characteristics of nerve root (local swelling or widening, unclear displayed, even manifests discontinuity or breaking), unclear limit between adjacent tissue (local conglutination, edge blur), and narrowing or disappearing of CSF spaces.In this case study, we demonstrated the feasibility of IDEAL sequence to image the anatomic structure and the whole contort of the lumbosacral nerve roots as well as the microstructural of lumbosacral nerve on the canals of lumbar spinal nerves is possible. We were able to make accurate positioning and diagnostic assessment of compressed or damaged nerve through the analysis of lumbosacral nerve roots imaging and the relationship between nerve and its adjacent structures. IDEAL imaging on lumbosacral nerve roots can be valuable for clinical diagnosis to estimate the nerve compression or nerve injury, and provide detailed information for the right treatment at early-stage and for the observation of clinical efficacy.