Diffusion tensor MRI of the healthy brachial plexus

Abstract

IntroductionDiffusion Tensor MRI (DT-MRI) is a promising tool for the evaluation of brachial plexus pathology. Therefore, we introduce and evaluate a fast DT-MRI protocol (8min33s scanning with 5–10 min postprocessing time) for the brachial plexus.Materials and methodsThirty healthy volunteers within three age-groups (18–35, 36–55, and > 56) received DT-MRI of the brachial-plexus twice. Means of fractional-anisotropy (FA), mean-diffusivity (MD), axial-diffusivity (AD), and radial-diffusivity (RD) for the individual roots and trunks were evaluated. A stepwise forward approach was applied to test for correlations with age, sex, body-mass-index (BMI), bodysurface, height, and bodyweight. Within-subject, intra-rater, and inter-rater repeatability were assessed using Bland-Altman analysis, coefficient of variation (CV), intraclass-correlation (ICC), and minimal detectable difference (MDD).ResultsNo differences between sides and root levels were found. MD, AD, and RD correlated (P < 0.05) with bodyweight. Within-subject quantification proved repeatable with CVs for FA, MD, AD, and RD of 16%, 12%, 11%, and 14%, respectively.DiscussionThe DT-MRI protocol was fast and repeatable. Found correlations should be considered in future studies of brachial plexus pathology.

Diffusion Tensor Imaging for Diagnosing Root Avulsions in Traumatic Adult Brachial Plexus Injuries: A Proof-of-Concept Study

“…Our findings are in agreement with the limited literature concerning DTI of the brachial plexus at 3 Tesla (22)(23)(24), all of which report deterministic tractography in healthy volunteers. We based on work on that of Tagliafico et al (22); their FA values ranged from 0.27 to 0.43 (mean 0.34) and the MD ranged from 1.4 × 10 −3 to 1.8 × 10 −3 mm 2 /s (mean 1.6 × 10 −3 mm 2 /s), although they omitted to describe which anatomical structure from which these values were derived which might explain the disparity with our data.…”

“…In their report, their FA values were ∼10% higher and MD 0.2 × 10 −3 mm 2 /s lower than our data. Similarly, Oudeman et al (24) Ouderman's work compared to ours and Tagliafico's might be explained by differences in the b-value (29) and other experimental conditions (e.g., methods of averaging, partial volume effects, etc.). Overall, our data adds to the literature and suggests that deterministic tractography and FA/MD extraction from the brachial plexus is both possible and of potential clinical utility.…”

“…There are a number of potential reasons to explain why we and others (22)(23)(24) are currently unable to have confidence in diffusion data acquired from the T1 root. The T1 root will be affected by susceptibility artifact due to the diamagnetic and paramagnetic effects of 1st rib and air in the apical lung, respectively, causing signal loss due to T2 * -dephasing and mis-mapping.…”

Top-Ten Tips for Imaging the Brachial Plexus with Ultrasound and MRI

“…Postprocessing DTI data to visualize the nerve tracts is known as tractography. A fast DTI-MRI protocol with 8.5 minutes of scanning time and 5 to 10 minutes of postprocessing time was introduced, 16 using a tissue susceptibility matching pillow in conjunction with an image-based shimming method. Using this fast technique, diagnostic quality DTI was obtainable for the C5-C8 roots in all subjects, although the T1 root could not be reconstructed to Erb's point in 50% of subjects.…”

“…Repeatability variance of $ 12% for MD and 15% for FA was achieved. 16,17 Readout segmented DTI seems to provide higher image quality with less distortion than single-shot echo planar DTI. 18 Respiratory triggering using a respiratory bellows strap around the chest during image acquisition led to a significant reduction in ghost artifact (odds ratio [OR]: 0.21) and an improvement in overall image quality (OR: 4.88) as well as increased diagnostic confidence (OR: 3.72) in brachial plexus imaging with only a small increase ($ 1.5 minutes) in scan time.…”