Selective visualization of pelvic splanchnic nerve and pelvic plexus using readout-segmented echo-planar diffusion-weighted magnetic resonance neurography: A preliminary study in healthy male volunteers

Abstract

Purpose: To evaluate the potential of readout-segmented echo-planar diffusion-weighted magnetic resonance neurography (RS-EPI DW-MRN) for the selective visualization of pelvic splanchnic nerve and pelvic plexus in healthy male volunteers.

Materials and methods: Institutional review board approval and written informed consent were obtained. RS-EPI DW-MRN images were acquired from thirteen healthy male volunteers aged 25-48 years between September 2013 and December 2013. For RS-EPI DW-MRN, the following parameters were used: spatial resolution, 1.1×1.1×2.5mm; b-value, 250s/mm²; number of readout-segments, seven; and acquisition time, 7min 45s. For qualitative assessment, two abdominal radiologists independently evaluated the visibility of the pelvic splanchnic nerves and pelvic plexuses bilaterally in each subject on oblique coronal thin-slab 10-mm-thick maximum intensity projection images and scored it with a 4-point grading scale (excellent, good, fair, poor). Both readers scored twice at 6-month intervals. Inter-observer and intra-observer variability were evaluated using Cohen's quadratically weighted κ statistics. Image artifact level was scored on a 4-point grading scale by other two abdominal radiologists in order to evaluate the correlation between the nerve visibility and the severity of imaging artifacts using the Spearman's correlation coefficient.

Results: Qualitative grading showed the following success rate (number of nerves qualitatively scored as excellent or good divided by total number of nerves): reader 1 (first set), 73% (19/26); reader 2 (first set), 77% (20/26); reader 1 (second set), 81% (21/26); and reader 2 (second set), 77% (20/26). Inter-observer agreement between readers 1 and 2 was excellent: κ=0.947 (first set) and 0.845 (second set). Intra-observer agreement was also excellent: κ=0.810 (reader 1) and 0.946 (reader 2). The visibility of pelvic splanchnic nerve and pelvic plexus showed a moderate correlation with the image artifact level (ρ=0.54, p=0.004).

Conclusion: This study demonstrated that RS-EPI DW-MRN is a promising approach for selectively visualizing the pelvic splanchnic nerve and pelvic plexus.

Keywords: Magnetic resonance neurography; Nerve-preserving surgery; Pelvic autonomic innervation; Pelvic plexus; Pelvic splanchnic nerve; Readout-segmented echo-planar diffusion-weighted imaging.