Functional MR Neurography in Evaluation of Peripheral Nerve Trauma and Postsurgical Assessment

Noguerol, Teodoro Martín; Barousse, Rafael; Cabrera, Marta Gómez; Socolovsky, Mariano; Bencardino, Jenny T.; Luna, Antonio

doi:10.1148/rg.2019180112

Cited by 54 publications

(27 citation statements)

References 78 publications

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“…The FA values are high (close to unity) along the peripheral nerve because of the restricted water diffusion along the axonal direction as guided by the epineurium, perineurium, endoneurium, and myelin sheath in myelinated axons. Because of the predominantly unidirectional nature of the nerve fibers, fewer diffusional gradient directions are required in peripheral nerve DTI than in the brain for quantifying white matter fiber tracts 49 . In the 1990s, peripheral nerve anisotropy was overserved in works on human sciatic nerve 50 and tibial nerve 51 .…”

Section: Peripheral Nerve Magnetic Resonance Imagingmentioning

confidence: 99%

Peripheral nerve magnetic resonance imaging

Chen

Haacke

2019

F1000Res

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Magnetic resonance imaging (MRI) has been used extensively in revealing pathological changes in the central nervous system. However, to date, MRI is very much underutilized in evaluating the peripheral nervous system (PNS). This underutilization is generally due to two perceived weaknesses in MRI: first, the need for very high resolution to image the small structures within the peripheral nerves to visualize morphological changes; second, the lack of normative data in MRI of the PNS and this makes reliable interpretation of the data difficult. This article reviews current state-of-the-art capabilities in in vivo MRI of human peripheral nerves. It aims to identify areas where progress has been made and those that still require further improvement. In particular, with many new therapies on the horizon, this review addresses how MRI can be used to provide non-invasive and objective biomarkers in the evaluation of peripheral neuropathies. Although a number of techniques are available in diagnosing and tracking pathologies in the PNS, those techniques typically target the distal peripheral nerves, and distal nerves may be completely degenerated during the patient’s first clinic visit. These techniques may also not be able to access the proximal nerves deeply embedded in the tissue. Peripheral nerve MRI would be an alternative to circumvent these problems. In order to address the pressing clinical needs, this review closes with a clinical protocol at 3T that will allow high-resolution, high-contrast, quantitative MRI of the proximal peripheral nerves.

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Section: Peripheral Nerve Magnetic Resonance Imagingmentioning

confidence: 99%

Peripheral nerve magnetic resonance imaging

Chen

Haacke

2019

F1000Res

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“…The highly organized microstructure of a nerve's axon bundles directionally restricts diffusion (anisotropy), in comparison to an unconstrained space where water molecules freely diffuse in all directions (isotropy). By applying diffusion tensor imaging (DTI), it is possible to quantify the degree of diffusion anisotropy within a nerve via a variety of parameters, the most commonly analyzed of which is the fractional anisotropy (FA) metric …”

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confidence: 99%

“…Second, high in‐ and through‐plane spatial resolution with a voxel size of <2 mm 3 is typically needed to image peripheral nerves in the extremities, most of which are less than 5 mm in diameter. Third, several excitations (NEX) (>3) are often prescribed to increase SNR by averaging, but this results in increased scan time and Rician noise bias. In order to achieve a clinically feasible scan time (<5–6 min to minimize motion artifact), acceleration methods can be employed, but these in turn lower SNR.…”

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confidence: 99%

Denoising of diffusion MRI improves peripheral nerve conspicuity and reproducibility

Sneag

Zochowski

Tan

et al. 2019

Magnetic Resonance Imaging

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Background Quantitative diffusion MRI is a promising technique for evaluating peripheral nerve integrity but low signal‐to‐noise ratio (SNR) can impede measurement accuracy. Purpose To evaluate principal component analysis (PCA) and generalized spherical deconvolution (genSD) denoising techniques to improve within‐subject reproducibility and peripheral nerve conspicuity. Study Type Prospective. Subjects Seven healthy volunteers and three peripheral neuropathy patients. Field Strength/Sequence 3T/multiband single‐shot echo planar diffusion sequence using multishell 55‐direction scheme. Assessment Images were processed using four methods: "original" (no denoising), "average" (10 repetitions), "PCA‐only," and "PCA + genSD." Tibial and common peroneal nerve segmentations and masks were generated from volunteer diffusion data. Quantitative (SNR and contrast‐to‐noise ratio [CNR]) values were calculated. Three radiologists qualitatively evaluated nerve conspicuity for each method. The two denoising methods were also performed in three patients with peripheral neuropathies. Statistical Tests For healthy volunteers, calculations included SNR and CNRFA (computed using FA values). Coefficient of variation (CV%) of CNRFA quantified within‐subject reproducibility. Groups were compared with two‐sample t‐tests (significance P < 0.05; two‐tailed, Bonferroni‐corrected). Odds ratios (ORs) quantified the relative rates of each of three radiologists confidently identifying a nerve, per slice, for the four methods. Results "PCA + genSD" yielded the highest SNR (meanoverall = 14.83 ± 1.99) and tibial and common peroneal nerve CNRFA (meantibial = 3.45, meanperoneal = 2.34) compared to "original" (P SNR < 0.001; P CNR = 0.011) and "PCA‐only" (P SNR < 0.001, P CNR < 0.001). "PCA + genSD" had higher within‐subject reproducibility (low CV%) for tibial (6.04 ± 1.98) and common peroneal nerves (8.27 ± 2.75) compared to "original" and "PCA‐only." The mean FA was higher for "original" than "average" (P < 0.001), but did not differ significantly between "average" and "PCA + genSD" (P = 0.14). "PCA + genSD" had higher tibial and common peroneal nerve conspicuity than "PCA‐only" (ORtibial = 2.50, P < 0.001; ORperoneal = 1.86, P < 0.001) and "original" (ORtibial = 2.73, P < 0.001; ORperoneal = 2.43, P < 0.001). Data Conclusion PCA + genSD denoising method improved SNR, CNRFA, and within‐subject reproducibility (CV%) without biasing FA and nerve conspicuity. This technique holds promise for facilitating more reliable, unbiased diffusion measurements of peripheral nerves. Level of Evidence: 2 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2020;51:1128–1137.

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“…Other novel diagnostic tools such as diffusion tensor imaging aim at delivering information about a nerve's functional integrity by distinguishing between its myelin sheath and axons (37). This imaging tool was further supported by experimental trials demonstrating a correlation between DTI-derived information and histological data of injured nerves (42,43), as well as clinical trials comparing electrophysiological data with DTIderived information in healthy patients (44) and patients with neuropathic changes (45).…”

Section: Discussionmentioning

confidence: 96%

“…its wide applicability, MR neurography is susceptible to imaging artifacts, lacks specificity in T2WI, and, most notably, does not provide crucial data on axonal transport and thus functional continuity of axons (8,37). In order to optimize signal specificity of lesioned nerves, various studies investigated contrast agentenhanced MR neurography (13)(14)(15)(16)(17)(18)(19)(20)(21).…”

Section: Discussionmentioning

confidence: 99%

MR Imaging of Peripheral Nerves Using Targeted Application of Contrast Agents: An Experimental Proof-of-Concept Study

et al. 2020

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Introduction: Current imaging modalities for peripheral nerves display the nerve's structure but not its function. Based on a nerve's capacity for axonal transport, it may be visualized by targeted application of a contrast agent and assessing the distribution through radiological imaging, thus revealing a nerve's continuity. This concept has not been explored, however, may potentially guide the treatment of peripheral nerve injuries. In this experimental proof-of-concept study, we tested imaging through MRI after administering gadolinium-based contrast agents which were then retrogradely transported.Methods: We synthesized MRI contrast agents consisting of paramagnetic agents and various axonal transport facilitators (HSA-DTPA-Gd, chitosan-DTPA-Gd or PLA/HSA-DTPA-Gd). First, we measured their relaxivity values in vitro to assess their radiological suitability. Subsequently, the sciatic nerve of 24 rats was cut and labeled with one of the contrast agents to achieve retrograde distribution along the nerve. One week after surgery, the spinal cords and sciatic nerves were harvested to visualize the distribution of the respective contrast agent using 7T MRI. In vivo MRI measurements were performed using 9.4 T MRI on the 1st, 3rd, and the 7th day after surgery. Following radiological imaging, the concentration of gadolinium in the harvested samples was analyzed using inductively coupled mass spectrometry (ICP-MS).Results: All contrast agents demonstrated high relaxivity values, varying between 12.1 and 116.0 mM−1s−1. HSA-DTPA-Gd and PLA/HSA-DTPA-Gd application resulted in signal enhancement in the vertebral canal and in the sciatic nerve in ex vivo MRI. In vivo measurements revealed significant signal enhancement in the sciatic nerve on the 3rd and 7th day after HSA-DTPA-Gd and chitosan-DTPA-Gd (p < 0.05) application. Chemical evaluation showed high gadolinium concentration in the sciatic nerve for HSA-DTPA-Gd (5.218 ± 0.860 ng/mg) and chitosan-DTPA-Gd (4.291 ± 1.290 ng/mg).Discussion: In this study a novel imaging approach for the evaluation of a peripheral nerve's integrity was implemented. The findings provide radiological and chemical evidence of successful contrast agent uptake along the sciatic nerve and its distribution within the spinal canal in rats. This novel concept may assist in the diagnostic process of peripheral nerve injuries in the future.

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Functional MR Neurography in Evaluation of Peripheral Nerve Trauma and Postsurgical Assessment

Cited by 54 publications

References 78 publications

Peripheral nerve magnetic resonance imaging

Peripheral nerve magnetic resonance imaging

Denoising of diffusion MRI improves peripheral nerve conspicuity and reproducibility

MR Imaging of Peripheral Nerves Using Targeted Application of Contrast Agents: An Experimental Proof-of-Concept Study

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