Diffusion tensor imaging of the roots of the brachial plexus: a systematic review and meta-analysis of normative values

Wade, Ryckie G.; Whittam, Alexander J.; Teh, Irvin; Andersson, Gustav; Yeh, Fang‐Cheng; Wiberg, Mikael; Bourke, Gráinne

doi:10.1007/s40336-020-00393-x

Cited by 8 publications

(8 citation statements)

References 46 publications

(93 reference statements)

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“…Although our findings are in agreement with the metrics reported in many DTI studies of the brachial plexus 4 – 7 , 9 , 10 , 26 (Supplementary Table 2 ), our FA values are slightly lower. FA is a function of numerous factors such as the b-value and number of diffusion encoding directions 27 , 28 .…”

Section: Discussionsupporting

confidence: 92%

Fractional anisotropy thresholding for deterministic tractography of the roots of the brachial plexus

Wade

Teh

Andersson

et al. 2021

Sci Rep

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Diffusion tensor imaging (DTI) metrics, such as the fractional anisotropy (FA) and estimates of diffusivity are sensitive to the microstructure of peripheral nerves and may be displayed as tractograms. However, the ideal conditions for tractography of the roots of the brachial plexus are unclear, which represents the rationale for this study. Ten healthy adults were scanned using a Siemens Prisma (3T) and single-shot echo-planar imaging (b-value 0/1000 s/mm2, 64 directions, 2.5 mm3 with 4 averages; repeated in opposing phase encoding directions). Susceptibility correction and tractography were performed in DSI Studio by two independent raters. The effect of FA thresholding at increments of 0.01 (from 0.04 to 0.10) were tested. The mean FA varied between subjects by 2% (95% CI 1%, 3%). FA thresholds of 0.04, 0.05 and 0.06 all propagated 96% of tracts representing the roots; thresholding at 0.07 yielded 4% fewer tracts (p = 0.2), 0.08 yielded 11% fewer tracts (p = 0.008), 0.09 yielded 15% fewer tracts (p = 0.001) and 0.1 yielded 20% fewer tracts (p < 0.001). There was < 0.1% inter-rater variability in the measured FA and 99% agreement for tractography (κ = 0.92, p < 0.001). The fractional anisotropy thresholds required to generate tractograms of the roots of the brachial plexus appears to be lower than those used in the brain. We provide estimates of the probability of generating true tracts for each spinal nerve root of the brachial plexus, at different fractional anisotropy thresholds.

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Section: Discussionsupporting

confidence: 92%

Fractional anisotropy thresholding for deterministic tractography of the roots of the brachial plexus

Wade

Teh

Andersson

et al. 2021

Sci Rep

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“…Numerous studies in the brain have shown dMRI metrics and streamlines to be dependent on scanner hardware, acquisition settings, preprocessing techniques, reconstruction algorithms and extraction methods 2,[9][10][11][12][13][14] . Recent work has shown similar dependence in the brachial plexus 15 and median nerve in the hand 16 . Therefore, before researchers and clinicians can reliably use dMRI to assess the 'health' of the major nerves of the upper limb, there is a need to de ne the range of "normal" values and how they vary with experimental conditions.…”

Section: Introductionmentioning

confidence: 78%

Meta-Analysis of the Normal Diffusion Tensor Imaging Values of the Peripheral Nerves in the Upper Limb

Wade

BaMed

Poruslrani

et al. 2022

Preprint

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Introduction: Peripheral neuropathy affects ~1 in 10 adults over the age of 40 years. Given the absence of a reliable diagnostic test, there has been a surge of research into diffusion tensor imaging (DTI) because it characterises nerve microstructure and provides reproducible proxy measures of myelination, axon diameter, fibre density and organisation. Before researchers and clinicians can reliably use diffusion tensor imaging to assess the ‘health’ of the major nerves of the upper limb, we must understand the “normal” range of values and how they vary with experimental conditions. Methods: We searched PubMed, Embase, medRxiv and bioRxiv for studies which reported the findings of DTI of the upper limb in healthy adults. Four review authors independently triple extracted data. Using the meta suite of Stata 17, we estimated the normal fractional anisotropy (FA) and diffusivity (mean, MD; radial, RD; axial AD) values of the median, radial and ulnar nerve in the arm, elbow and forearm. Using meta-regression, we explored how DTI metrics varied with age and experimental conditions. Results: We included 20 studies reporting data from 391 limbs, belonging to 346 adults (189 males and 154 females, ~1.2M:1F) of mean age 34 years (median 31, range 20-80). In the arm, there was no difference in the FA (pooled mean 0.59 mm2/s [95% CI 0.57, 0.62]; I2 98%) or MD (pooled mean 1.13 x10-3 mm2/s [95% CI 1.08, 1.18]; I2 99%) of the median, radial and ulnar nerves. Around the elbow, the ulnar nerve had a 12% lower FA than the median and radial nerves (95% CI -0.25, 0.00) and significantly higher MD, RD and AD. In the forearm, the FA (pooled mean 0.55 [95% CI 0.59, 0.64]; I2 96%) and MD (pooled mean 1.03 x10-3 mm2/s [95% CI 0.94, 1.12]; I2 99%) of the three nerves were similar. Multivariable meta regression showed that the b-value, TE, TR, spatial resolution and age of the subject were clinically important moderators of DTI parameters in peripheral nerves. Conclusions: We show that subject age, as well as the b-value, TE, TR and spatial resolution are important moderators of DTI metrics from healthy nerves in the adult upper limb. The normal ranges shown here may inform future clinical and research studies.

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“…However, the proximity of peripheral nerves and skeletal muscles, similar FA values of both tissues, spatial resolution, algorithm type, different ROIs sizes, numbers and locations of the ROIs ( 40 ) may cause contamination by skeletal muscle fibers (e.g., scalene muscles), when MRT of the BP nerve bundles is performed.…”

Section: Discussionmentioning

confidence: 99%

Magnetic resonance tractography of the brachial plexus: step-by-step

Ibrahim¹,

Škoch²,

Herynek³

et al. 2022

Quant Imaging Med Surg

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Background: Magnetic resonance (MR) tractography of the brachial plexus (BP) is challenging due to different factors such as motion artifacts, pulsation artifacts, signal-to-noise ratio, spatial resolution; eddy currents induced geometric distortions, sequence parameters and choice of used coils. Notably challenging is the separation of the peripheral nerve bundles and skeletal muscles as both structures have similar fractional anisotropy values. We proposed an algorithm for robust visualization and assessment of BP root bundles using the segmentation of the spinal cord (SSC, C4-T1) as seed points for the initial starting area for the fibre tracking algorithm.Methods: Twenty-seven healthy volunteers and four patients with root avulsions underwent magnetic resonance imaging (MRI) examinations on a 3T MR scanner with optimized measurement protocols for diffusion-weighted images and coronal T2 weighted 3D short-term inversion recovery sampling perfection with application optimized contrast using varying flip angle evaluation sequences used for BP fibre reconstruction and MR neurography (MRN). The fibre bundles reconstruction was optimized in terms of eliminating the skeletal muscle fibres contamination using the SSC and the tracking threshold of the normalized quantitative anisotropy (NQA) on reconstruction of the BP. In our study, the NQA parameter has been used for fiber tracking instead of fractional anisotropy (FA). The diffusion data were processed in individual C4-T1 root bundles using the generalized q-sampling imaging (GQI) algorithm. Calculated diffusion parameters were statistically analysed using the two-sample t-test. The MRN was performed in MedINRIA and post-processed using the maximum intensity projection (MIP) method to demonstrate BP root bundles in multiple planes.Results: In control subjects, no significant effect of laterality in diffusion parameters was found (P>0.05) in the BP. In the central part of the BP, a significant difference between control subjects and patients at P=0.02 was found in the NQA values. Other diffusion parameters were not significantly different.Conclusions: Using NQA instead of FA in the proposed algorithm allowed for a better separation of muscle and root nerve bundles. The presented algorithm yields a high quality reconstruction of the BP bundles that may be helpful both in research and clinical practice.

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Diffusion tensor imaging of the roots of the brachial plexus: a systematic review and meta-analysis of normative values

Cited by 8 publications

References 46 publications

Fractional anisotropy thresholding for deterministic tractography of the roots of the brachial plexus

Fractional anisotropy thresholding for deterministic tractography of the roots of the brachial plexus

Meta-Analysis of the Normal Diffusion Tensor Imaging Values of the Peripheral Nerves in the Upper Limb

Magnetic resonance tractography of the brachial plexus: step-by-step

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