Distortion-free diffusion tensor imaging for evaluation of lumbar nerve roots: Utility of direct coronal single-shot turbo spin-echo diffusion sequence

A novel simultaneous three-dimensional volumetric morphological imaging and T2-mapping method, multi-interleaved X-prepared turbo-spin echo with intuitive relaxometry provides more accurate quantification of cervical spinal nerves

PURPOSE

MIXTURE is a simultaneous morphological and quantitative imaging sequence developed by Philips that provides high-resolution T2 maps from the imaged series. We aimed to compare the T2 maps of MIXTURE and SHINKEI-Quant (S-Q) in the cervical spine and to examine their usefulness in the functional diagnosis of cervical radiculopathy.

METHODS

Seven healthy male volunteers (mean age: 31 ± 8.0 years) and one patient with cervical disc herniation (44 years old, male) underwent cervical spine magnetic resonance imaging (MRI), and T2-mapping of each was performed simultaneously using MIXTURE and S-Q in consecutive sequences in one imaging session. The standard deviation (SD) of the T2 relaxation times and T2 relaxation times of the bilateral C6 and C7 dorsal root ganglia (DRG) and C5/6 level cervical cord on the same slice in the 3D T2-map of the cervical spine coronal section were measured and compared between MIXTURE and S-Q.

RESULTS

T2 relaxation times were significantly shorter in MIXTURE than in S-Q for all C6, C7 DRG, and C5/6 spinal cord measurements. The SD values of the T2 relaxation times were significantly lower for MIXTURE in the C5/6 spinal cord and C7 DRG. In cervical disc herniation, MRI showed multiple intervertebral compression lesions with spinal canal stenosis at C5/6 and disc herniation at C6/7.

CONCLUSION

MIXTURE is useful for preoperative functional diagnosis. T2-mapping using MIXTURE can quantify cervical nerve roots more accurately than the S-Q method and is expected to be clinically applicable to cervical radiculopathy.

Clinical Value and Reliability of Quantitative Assessments of Lumbosacral Nerve Root Using Diffusion Tensor and Diffusion Weighted MR Imaging: A Systematic Review

BACKGROUND

Lumbosacral radicular pain diagnosis remains challenging. Diffusion tensor imaging (DTI) and diffusion weighted imaging (DWI) have potential to quantitatively evaluate symptomatic nerve root, which may facilitate diagnosis.

PURPOSE

To determine the ability of DTI and DWI metrics, namely fractional anisotropy (FA) and apparent diffusion coefficient (ADC), to discriminate between healthy and symptomatic lumbosacral nerve roots, to evaluate the association between FA and ADC values and patient symptoms, and to determine FA and ADC reliability.

STUDY TYPE

Systematic review.

SUBJECTS

Eight hundred twelve patients with radicular pain with or without radiculopathy caused by musculoskeletal-related compression or inflammation of a single, unilateral lumbosacral nerve root and 244 healthy controls from 29 studies.

FIELD STRENGTH/SEQUENCE

Diffusion weighted echo planar imaging sequence at 1.5 T or 3 T.

ASSESSMENT

An extensive systematic review of the literature was conducted in Embase, Scopus, and Medline databases. FA and ADC values in symptomatic and contralateral lumbosacral nerve roots were extracted and summarized, together with intra- and inter-rater agreements. Where available, associations between DWI or DTI parameters and patient symptoms or symptom duration were extracted.

STATISTICAL TESTS

The main results of the included studies are summarized. No additional statistical analyses were performed.

RESULTS

The DTI studies systematically found significant differences in FA values between the symptomatic and contralateral lumbosacral nerve root of patients suffering from radicular pain with or without radiculopathy. In contrast, identification of the symptomatic nerve root with ADC values was inconsistent for both DTI and DWI studies. FA values were moderately to strongly correlated with several symptoms (eg, disability, nerve dysfunction, and symptom duration). The inter- and intra-rater reliability of DTI parameters were moderate to excellent. The methodological quality of included studies was very heterogeneous.

DATA CONCLUSION

This systematic review showed that DTI was a reliable and discriminative imaging technique for the assessment of symptomatic lumbosacral nerve root, which more consistently identified the symptomatic nerve root than DWI. Further studies of high quality are needed to confirm these results.

EVIDENCE LEVEL

N/A TECHNICAL EFFICACY: Stage 2.

Quantitative Evaluation of Intraspinal Lumbar Disc Herniation-related Lumbosacral Radiculopathy Before and After Percutaneous Transforaminal Endoscopic Discectomy Using Diffusion Tensor Imaging

STUDY DESIGN

A prospective study.

OBJECTIVE

The aim of this study was to investigate the relationship between diffusion tensor imaging (DTI) derived parameters of compressed nerve roots at subregions and the corresponding clinical symptoms to evaluate the patients with intraspinal lumbar disc herniation (LDH)-related lumbosacral radiculopathy pre- and postoperatively.

SUMMARY OF BACKGROUND DATA

It is crucial to explore whether magnetic resonanve imaging (MRI) can quantitatively evaluate intraspinal LDH-related lumbosacral radiculopathy before and after surgery.

METHODS

In all, 66 patients underwent MRI scans and Clinical assessment before and after percutaneous transforaminal endoscopic discectomy (PTED). Pre- and postoperative findings of the related lumbar disk and nerve tractography were compared with two-way contingency table analysis. The embedded paired t test toolbox was applied to respectively compare the fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of nerves at the symptomatic and asymptomatic sides in three subregions pre- and postoperatively. The correlation of clinical Japanese Orthopedic Association (JOA) scores and FA/ADC values of nerves at three sub-regions was analyzed by stepwise multiple linear regression analysis.

RESULTS

The postoperative FA values were significantly higher than the corresponding preoperative values (P < 0.001), while comparable ADC values were found. Using tractography, a notable improvement of compressed nerve was revealed after surgery (61 cases, 92.4%). Additionally, multiple linear regression analysis identified significant associations between JOA scores and FA values of the compressed nerves with the greatest effect at the proximal region.

CONCLUSION

The FA values at subarticular zone can reflect the microstructural changes of the corresponding compressed nerves and well associate with clinical symptoms. Therefore, the DTI parameter FA can be considered an effective tool in clinic to quantitatively evaluate intraspinal LDH-related lumbosacral radiculopathy before and after PTED surgery.Level of Evidence: 3.

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

Editor's Note.-Articles in the RadioGraphics Update section provide current knowledge to supplement or update information found in full-length articles previously published in RadioGraphics. Authors of the previously published article provide a brief synopsis that emphasizes important new information such as technological advances, revised imaging protocols, new clinical guidelines involving imaging, or updated classification schemes. Articles in this section are published solely online and are linked to the original article. ^©RSNA, 2021.

Effect of b Value on Imaging Quality for Diffusion Tensor Imaging of the Spinal Cord at Ultrahigh Field Strength

Objective

To explore the optimal b value setting for diffusion tensor imaging of rats' spinal cord at ultrahigh field strength (7 T).

Methods

Spinal cord diffusion tensor imaging data were collected from 14 rats (5 healthy, 9 spinal cord injured) with a series of b values (200, 300, 400, 500, 600, 700, 800, 900, and 1000 s/mm²) under the condition that other scanning parameters were consistent. The image quality (including image signal-to-noise ratio and image distortion degree) and data quality (i.e., the stability and consistency of the DTI-derived parameters, referred to as data stability and data consistency) were quantitatively evaluated. The min-max normalization method was used to process the calculation results of the four indicators. Finally, the image and data quality under each b value were synthesized to determine the optimal b value.

Results

b = 200 s/mm² and b = 900 s/mm² ranked in the top two of the comprehensive evaluation, with the best image quality at b = 200 s/mm² and the best data quality at b = 900 s/mm².

Conclusion

Considering the shortcomings of the ability of low b values to reflect the microstructure, b = 900 s/mm² can be used as the optimal b value for 7 T spinal cord diffusion tensor scanning.

A quantitative and clinical evaluation of nerve roots in lumbosacral radiculopathy using diffusion tensor imaging

PURPOSE

This study aimed to investigate the relationship between the fractional anisotropy (FA) values of compressed nerves derived in diffusion tensor imaging (DTI) and the corresponding clinical symptoms for quantitative and clinical evaluation in patients with lumbosacral radiculopathy.

METHODS

Thirty-six patients and ten volunteers participated in the study and measured with DTI. The resultant FA values for L5-S1 lumbar nerve roots were calculated at three sub-regions. Additionally, the DTI relevant tractography was also performed on L4-S1 nerve roots. Clinical symptoms were performed by Japanese Orthopedic Association (JOA) scoring for each patient and volunteer.

RESULTS

The FA values of the nerves at the symptomatic side were significantly lower than those at the asymptomatic side (p < 0.001). Diffusion tensor tractography distinctly showed abnormalities in the symptomatic nerve tracts. There was a significant correlation between JOA scores and the FA values of the compressed nerves at middle and distal sub-regions (p < 0.005).

CONCLUSION

The clinical symptoms associated robustly with the DTI derived FA values of the compressed nerves in patients with lumbosacral radiculopathy. Therefore, the FA values can be a potential clinical tool to evaluate the nerve roots in lumbosacral radiculopathy quantitatively.

Functional Assessment of Lumbar Nerve Roots Using Coronal-plane Single-shot Turbo Spin-echo Diffusion Tensor Imaging

We investigated the usefulness of diffusion tensor imaging using single-shot turbo spin-echo sequence (TSE–DTI) in detecting the responsible nerve root by multipoint measurements of fractional anisotropy (FA) values. Five patients with bilateral lumbar spinal stenosis showing unilateral neurological symptoms were examined using TSE–DTI. In the spinal canal, FA values in the symptomatic side were lower than those in the asymptomatic side. TSE–DTI using multipoint measurements of FA values can differentiate the responsible lumbar nerve root.

Diffusion-weighted imaging and diffusion tensor imaging as adjuncts to conventional MRI for the diagnosis and management of peripheral nerve sheath tumors: current perspectives and future directions

Peripheral nerve sheath tumors (PNSTs) account for ~ 5% of soft tissue neoplasms and are responsible for a wide spectrum of morbidities ranging from localized neuropathy to fulminant metastatic spread and death. MR imaging represents the gold standard for identification of these neoplasms, however, current anatomic MR imaging markers do not reliably detect or differentiate benign and malignant lesions, and therefore, biopsy or excision is required for definitive diagnosis. Diffusion-weighted MR imaging (DWI) serves as a useful tool in the evaluation and management of PNSTs by providing functional information regarding the degree of diffusion, while diffusion tensor imaging (DTI) aids in determining the directional information of predominant diffusion and has been shown to be particularly useful for pre-operative planning of these tumors by delineating healthy and pathologic fascicles. The article focuses on these important neurogenic lesions, highlighting the current utility of diffusion MR imaging and future directions including computerized radiomic analysis. KEY POINTS: • Anatomic MRI is moderately accurate in differentiating benign from malignant PNST. • Diffusion tensor imaging facilitates pre-operative planning of PNSTs by depicting neuropathy and tractography. • Radiomics will likely augment current observer-based diagnostic criteria for PNSTs.

Artifact-robust diffusion-weighted whole-body imaging with background suppression at 3 T using improved turbo spin-echo diffusion-weighted imaging

OBJECTIVE:

To compare single-shot turbo spin-echo (TSE) diffusion-weighted whole-body imaging with background suppression (DWIBS) and echo-planar imaging (EPI) DWIBS to determine the feasibility of direct-coronal TSE-DWIBS.

METHODS:

All measurements were performed using a 3.0 T MRI scanner. In the phantom study, we compared the contrast ratios (CRs) of tumor-mimicking phantom (tumor) to muscle-mimicking phantom (muscle) and water to muscle and the signal-to-noise ratio (SNR) between TSE-DWIBS and EPI-DWIBS. In the volunteer study, 10 healthy volunteers were whole-body scanned with direct-coronal TSE-DWIBS, direct-coronal EPI-DWIBS (corEPI-DWIBS), and transverse EPI-DWIBS (traEPI-DWIBS). Two radiologists assessed the image distortion, uniformity of fat suppression, overall artifacts, and overall image quality in maximum intensity projection (MIP) images from each DWIBS image using a 5-point scale.

RESULTS:

In the phantom study, the CR of tumor to muscle was found to be lower for TSE-DWIBS (10.57 ± 0.45) than for EPI-DWIBS (15.38 ± 0.27), and the CR of water to muscle was higher for TSE-DWIBS (9.61 ± 0.66) than for EPI-DWIBS (2.52 ± 0.60). The volunteer study revealed good inter observer agreement between TSE-DWIBS and EPI-DWIBS with respect to image distortion, uniformity of fat suppression, overall artifacts, and overall image quality, with weighted Cohen's κ coefficients of 0.91, 0.74, 0.87, and 0.72, respectively. Qualitative analysis scores for image distortion, uniformity of fat suppression, overall artifacts, and overall image quality were significantly higher for TSE-DWIBS than for corEPI-DWIBS or traEPI-DWIBS (p < 0.05).

CONCLUSION:

Direct-coronal TSE-DWIBS is robust against magnetic field inhomogeneity. High-quality images without distortion or fat suppression inhomogeneity were obtained.

ADVANCES IN KNOWLEDGE:

Many studies on DWIBS have been previously reported; however, these studies used EPI read-out. To the best of our knowledge, no studies using TSE read-out have been reported. In this study, we examined the feasibility of TSE-DWIBS with lesser artifacts than EPI-DWIBS.