Improved visualization of diffusion-prepared MR neurography (SHINKEI) in the lumbosacral plexus combining high-intensity reduction (HIRE) technique

3D MR neurography with gadolinium contrast to improve the visualization of pelvic nerves and the branches

Objective

To evaluate the effectiveness of 3D NerveVIEW sequence with gadolinium contrast on the visualization of pelvic nerves and their branches compared to that without contrast.

Methods

Participants were scanned twice using 3D NerveVIEW sequence with and without gadolinium contrast to acquire pelvic nerve images. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and contrast ratio of the nerves were calculated and compared to determine the quality of images. To subjectively assess, using a 3-point scale, branch nerves critical to therapeutic decision-making, including the pelvic splanchnic nerve and pelvic plexus, the superior gluteal nerve, and the pudendal nerve.

Results

In the 32 eligible participants after using contrast, the CNRs of the images of nerve-to-bone and nerve-to-vessel significantly increased (p < 0.05). The CR of the images with contrast of all nerve-to-surrounding tissues (i.e., bone, muscle, blood vessels, and fat) were also found significantly higher (p < 0.05). The assessment of observers also shows higher scores for images with contrast compared to images without contrast.

Conclusion

The 3D NerveVIEW sequence combined with gadolinium contrast improved vascular suppression, increased the contrast between pelvic nerves and surrounding tissue, and enhanced the visualization of nerves and their branches. This study may be helpful for the technically challenging preoperative planning of pelvic diseases surgery.

Lumbosacral plexus MR tractography: A novel diagnostic tool for extraspinal sciatica and pudendal neuralgia?

BACKGROUND

Diagnosing extraspinal sciatica and pudendal neuralgia remains a clinical challenge. MRI and MR Neurography (MRN) are currently the standard techniques used to support the diagnosis of extraspinal lumbosacral plexus entrapments; however, for the intrapelvic portions of the lumbosacral plexus their accuracy is still limited. MR Tractography (MRT) feasibility to image the lumbosacral plexus has been demosntrated, but its clinical applications have yet to be determined.

PURPOSE

To correlate MRT with intraoperative findings in patients undergoing laparoscopic treatment of intrapelvic entrapments of the lumbosacral plexus and compare its accuracy with Neuropelveological clinical assessment and MRN.

MATERIALS AND METHODS

This is a retrospective analysis of MRT reconstructions of diffusion tensor imaging (DTI) sequences acquired for the MRN collected from a cohort of 13 patients undergoing laparoscopic detrapment of the lumbosacral plexus. The primary outcome of this study was the correlation of MRT reconstruction with intraoperative findings. Secondary outcomes included the correlation of MRN, preoperative Neuropelveological clinical diagnoses and the diffusion-weighted imaging (DWI) fractional anisotropy (FA) and Apparent Diffusion Coefficient (ADC) in patients undergoing pelvic MRI and MRN for the investigation of intrapelvic nerve entrapments.

RESULTS

MRT correlated with intraoperative findings in 11 of 13 patients (85%). Neuropelveological clinical assessment was able to accurately diagnose a pelvic nerve entrapment in 12/13 patients (92%) and MRN agreed with surgical findings in only 2/13 (15%) patients. MRT was significantly superior to MRN (p < 0.001). FA and ADC did not correlate with the identification of a nerve entrapment, likely due to limitations regarding the placement of the seedpoints.

CONCLUSIONS

This initial, retrospective analysis, suggests that MRT is superior to MRN at diagnosing intrapelvic entrapments of the lumbosacral plexus. A prospective, double-blinded study is underway to validate this data, but these initial findings show great potential for MRT as a diagnostic tool for extraspinal sciatica and pudendal neuralgia. Clinical Trials Registry: U1111-1261-4910 (REBEC - Brazilian Registry for Clinical Trials).

Magnetic resonance neurography of the lumbosacral plexus at 3 Tesla - CSF-suppressed imaging with submillimeter resolution by a three-dimensional turbo spin echo sequence

PURPOSE

To investigate magnetic resonance neurography (MRN) of the lumbosacral plexus (LSP) with cerebrospinal fluid (CSF) suppression by using submillimeter resolution for three-dimensional (3D) turbo spin echo (TSE) imaging.

MATERIALS AND METHODS

Using extended phase graph (EPG) analysis, the signal response of CSF was simulated considering dephasing from coherent motion for frequency-encoding voxel sizes ranging from 0.3 to 1.3 mm and for CSF velocities ranging from 0 to 4 cm/s. In-vivo MRN included 3D TSE data with frequency encoding parallel to the feet/head axis from 15 healthy adults (mean age: 28.5 ± 3.8 years, 5 females; acquisition voxel size: 2 × 2 × 2 mm³) and 16 pediatric patients (mean age: 6.7 ± 4.1 years, 7 females; acquisition voxel size: 0.7 × 0.7 × 1.4 mm³) acquired at 3 Tesla. Five of the adults were scanned repetitively with changing acquisition voxel sizes (1 × 2 × 2 mm³, 0.7 × 2× 2 mm³, and 0.5 × 2 × 2 mm³). Measurements of the bilateral ganglion of the L5 nerve root, averaged between sides, as well as the CSF in the thecal sac were obtained for all included subjects and compared between adults and pediatric patients and between voxel sizes, using a CSF-to-nerve signal ratio (CSFNR).

RESULTS

According to simulations, the CSF signal is reduced along the echo train for moving spins. Specifically, it can be reduced by over 90% compared to the maximum simulated signal for flow velocities above 2 cm/s, and could be most effectively suppressed by considering a frequency-encoding voxel size of 0.8 mm or less. For in-vivo measurements, mean CSFNR was 1.52 ± 0.22 for adults and 0.10 ± 0.03 for pediatric patients (p < .0001). Differences in CSFNR were significant between measurements using a voxel size of 2 × 2 × 2 mm³ and measurements in data with reduced voxel sizes (p ≤ .0012), with submillimeter resolution (particularly 0.5 × 2 × 2 mm³) providing highest CSF suppression.

CONCLUSIONS

Applying frequency-encoding voxel sizes in submillimeter range for 3D TSE imaging with frequency encoding parallel to the feet/head axis may considerably improve MRN of LSP pathology in adults in the future because of favorable CSF suppression.