SUMMARY: 3D diffusion-weighted steady-state free precession imaging (3D DW-SSFP) with isotropic resolution was performed to delineate structures of the human lumbosacral plexus (LSP). 3D DW-SSFP clearly revealed detailed anatomy of the LSP and its branches. Our data suggest that the sequence based on 3D DW-SSFP can be used for high-resolution MR imaging of the peripheral nervous system. MR imaging evaluation of the normal peripheral nerve anatomy and diseases is mainly dependent on 2D MR imaging techniques, including T1-weighted spin-echo, T2-weighted fast spin-echo, and inversion-recovery sequences with fat saturation.1-7 Although these techniques can produce excellent-quality images, they have limitations in describing deliberate orientations of the targeted nerves, in that section gaps in these techniques lead to lower anatomic coverage and less quantitative information. Furthermore, T2-weighted spin-echo techniques cannot image smaller nerves in the periphery because the nerves cannot be distinguished from blood vessels on T2-weighted spin-echo images.8 A combination of diffusion-weighted imaging (DWI) with fat-suppressed T2-weighted sequences has been proposed to overcome these technical limitations. Additionally, DWI based on spin-echo with an echo-planar readout has been used to evaluate the anatomy of the peripheral nervous system. 9-10 However, these conventional techniques have limited spatial resolution or low signal-to-noise ratio and often produce severe image distortion. 8,11 It is difficult to reveal the detailed anatomy of the lumbosacral plexus (LSP) by using conventional MR imaging in that many important branches of the LSP are small, and contrast of the various anatomic structures is not sufficient to exhibit their discrete identification. The purpose of this study is to describe a high-spatial-resolution 3D diffusion-weighted steady-state free precession (3D DW-SSFP) sequence and prospectively evaluate its feasibility in human LSP imaging at 3T. Materials and MethodsTwenty-four healthy subjects (10 men, 14 women; mean age, 42.2 years; range, 24 -69 years) underwent high-spatial-resolution T2-weighted 3D DW-SSFP imaging with a generalized autocalibrating partially parallel acquisition (GRAPPA) technique on a clinical 3T MR imager (Trio; Siemens Medical Solutions, Erlangen, Germany) with 2-element circularly polarized (CP) phased-array body coils combined with CP phased-array spinal coils.After optimization of the sequence in 3 healthy subjects (1 woman and 2 men, 30 -36 years of age), we used the following parameters: TR/TE, 14.16/4.61 ms; flip angle, 30°; FOV, 360 mm; matrix, 512 ϫ 512; bandwidth, 184 Hz per pixel; fat suppression, water excitation technique; diffusion moments, 90 mT/m (*)msec; 3D slab thickness, 256 mm; voxel dimension, 0.8 ϫ 0.8 ϫ 0.8 mm (320 partitions); number of acquisitions, 1; acquisition time, 10 minutes 49 seconds. The diagram of the 3D DW-SSFP sequence used in this study is shown in Fig 1. The postprocessing techniques, including maximum intensity projection and mul...
The 3-dimensional DW-SSFP MRI with high spatial and sufficient contrast is an excellent technique to define the nature of sciatica and assists in prognostication and possibly in management.
Purpose: To evaluate the image quality of segmented echo planar MRI with inversion recovery magnetization preparation (seg-IR-EPI) to depict the anatomy and pathologic changes involving the brachial plexus. Materials and Methods:The coronal seg-IR-EPI sequence was performed on 30 healthy volunteers and 20 patients. Postprocessing techniques were used to generate images of brachial plexus and the images acquired were qualitatively evaluated by two experienced radiologists based on grading of the morphological images. Signal-to-noise ratios (SNRs) and nerve soft tissue contrast-to-noise-ratios (CNRs) were calculated and the normalized SNR (SNRn) and the normalized CNR (CNRn) were compared with the STIR TSE sequence. Results:Although seg-IR-EPI had more ghosting artifacts than STIR TSE, excellent general image appearance with minor blurring can be achieved with seg-IR-EPI. In all healthy volunteers the means of CNRn were significantly greater for seg-IR-EPI than for STIR-TSE, while the means of SNRn were significantly lower for seg-IR-EPI than for STIR-TSE. Conclusion:In the present study the seg-IR-EPI sequence obtained uniform fat suppression and high-contrast T2-weighted images of brachial plexus. Our data suggest that the seg-IR-EPI sequence may provide high fidelity in evaluating brachial plexus. MAGNETIC RESONANCE IMAGING (MRI) is the preferred technique for visualizing the brachial plexus and most of its branches because of its multiplanar capabilities and increased contrast between soft tissues. Many MRI techniques have been developed to identify the components of the brachial plexus and the surrounding anatomy (1-9). However, the inadequate fat suppression can degrade the image quality because of the magnetic susceptibility differences at air-tissue interfaces and the insufficient contrast between nerves and surrounding tissues which could greatly affect the accurate diagnosis of diseases involving brachial plexus. Short inversion time (TI) inversion-recovery spin echo imaging (STIR) and iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) method can provide uniform fat suppression. However, the overall scan efficiency of these methods is reduced by the requirement of the extra preparation pulses (7,8). During echo planar imaging (EPI) scanning, which is generated by an oscillating readout gradient scanning, a limited portion or segment of data is collected within each repetition time (TR) interval and the data from all the segments are interleaved prior to image reconstruction with segmented echo-planar imaging (10). In this method, interleaving minimizes signal intensity fluctuations that occur from the end of one segment to the beginning of another. The purpose of this study was to evaluate the image quality of segmented echo planar MRI with inversion recovery magnetization preparation (seg-IR-EPI) to depict the anatomy and pathologic changes involving the brachial plexus. MATERIALS AND METHODS Study PopulationsThis study was performed on 30 healthy volunteer...
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