High-resolution diffusion-weighted MR imaging of the human lumbosacral plexus and its branches based on a steady-state free precession imaging technique at 3T

Identifying lumbosacral plexus nerve root abnormalities in patients with sciatica using 3T readout-segmented echo-planar diffusion weighted MR neurography

Objectives

To investigate the accuracy of Diffusion Weighted Imaging (DWI) using the Readout Segmentation of Long Variable Echo-trains (RESOLVE) sequence in detecting lumbosacral nerve abnormalities.

Methods

Following institutional ethics committee approval, patients with sciatica-type lower limb radicular symptoms (n = 110) were recruited and prospectively scanned using 3T MRI. Additional participants (n = 17) who underwent neurophysiological testing (EMG/NCV), were also prospectively studied. In addition to routine lumbar spine MRI, a DWI-RESOLVE sequence of the lumbosacral plexus was performed. Two radiologists, blinded to the side of patient symptoms, independently evaluated the MR images. The size and signal intensity changes of the nerves were evaluated using ordinal 4-point Likert-scales. Signal-to-noise ratio (SNR), apparent diffusion coefficient (ADC) and size were measured for affected and normal nerves. Inter-observer agreement was determined with kappa statistics; κ.

Results

In patients who did not undergo EMG/NCV testing (n = 110), the DWI-RESOLVE sequence detected lumbosacral nerve abnormalities that correlated with symptoms in 36.3% (40/110). This is a similar percentage to patients who underwent EMG/NCV testing, which was positive and correlated with symptoms in 41.2% (7/17). Inter-observer agreement for evaluation of lumbosacral nerve abnormalities was excellent and ranged from 0.87 to 0.94. SNR and nerve size measurements demonstrated statistically significant differences for the L5 and S1 nerves (p value < 0.05) for patients who did not undergo EMG/NCV testing.

Conclusion

The DWI-RESOLVE sequence is a promising new method that may permit accurate detection and localization of lumbar nerve abnormalities in patients with sciatica.

Three-dimensional reversed fast imaging with steady-state precession diffusion-weighted imaging for the detection of middle ear cholesteatoma

AIM

To determine the usefulness of three-dimensional reversed fast imaging with steady-state precession diffusion-weighted imaging (3D-PSIF DWI) for the detection of middle ear cholesteatoma.

MATERIALS AND METHODS

The study population consisted of 81 patients who underwent 3D-PSIF-DWI at 3 T. They included cholesteatoma in 73 cases, otitis media in five, and cholesterol granuloma in three. Two observers independently performed qualitative evaluations for the detection of cholesteatoma and measured apparent diffusion coefficient (ADC) values and ADC ratios of the lesions. Kappa (κ) statistics, the intraclass correlation coefficient (ICC), the independent t-test, and receiver operating characteristic (ROC) analysis were used for statistical analysis. Pair-wise comparison of the ROC curves was performed using the area under the ROC curve (AUC).

RESULTS

Interobserver agreement and ICC for the qualitative and quantitative evaluations were excellent (κ=0.92 and ICC=0.90-0.92, respectively). The ADC value and the ADC ratio were significantly lower for cholesteatoma than non-cholesteatoma lesions (p<0.0001). In <5 mm cholesteatoma group, the diagnostic performance of the ADC value (AUC=0.97) and the ADC ratio (AUC=1) was significantly superior to qualitative 3D-PSIF-DWI (AUC=0.76; p=0.0001 and <0.0001, respectively). For ≥5 mm cholesteatoma group, there were no significant differences in diagnostic performance among the three parameters.

CONCLUSION

3D-PSIF-DWI sequence is useful for the detection of middle ear cholesteatomas, especially <5 mm lesions.

Value of Visualization of the Intraparotid Facial Nerve and Parotid Duct Using a Micro Surface Coil and Three-Dimensional Reversed Fast Imaging With Steady-State Precession and Diffusion-Weighted Imaging Sequence

OBJECTIVE

To explore the value of micro surface coil combined with three-dimensional reversed fast imaging with steady-state precession and diffusion-weighted imaging (3D-PSIF-DWI) in displaying intraparotid facial nerves and parotid ducts.

METHODS

In total 24 healthy volunteers with no parotid disease underwent scanning of head and neck coil and 4-cm micro surface coil combined with 3D-PSIF-DWI prospectively. The obtained original images were processed through maximum intensity projection, multiplanar reconstruction, and curved planar reconstruction. The magnetic resonance imaging (MRI) signal characteristics of intraparotid structure, the subjective score of image quality, the signal intensity ratio (SIR) of facial nerve/parotid tissues (SIRN), and SIR of parotid duct/parotid tissues (SIRD) were calculated, and the displaying rates of the facial nerves and parotid ducts were observed. The Wilcoxon matched-sample signed rank sum test was used to compare the scores of head and neck coil and micro surface coil 3D-PSIF-DWI sequence images; paired-t test was used to compare SIRN and SIRD of the 2 groups; χ test was used to compare the displaying rate of the facial nerves and parotid ducts in the 2 groups.

RESULTS

In total 24 volunteers successfully underwent MRI scan of parotid glands. On 3D-PSIF-DWI images, the parotid gland showed slightly low signal intensity, muscle tissues showed intermediate intensity, while the vessels showed slightly high or equal intensity; the parotid segment of facial nerves was displayed as a tortuous line-like high intensity, and the parotid duct showed curved high intensity, lymph nodes showed kidney-shaped, oval, or spindle-shaped high intensity. The subjective scores for head and neck coil and small coil images were (2.2 ± 0.7) and (1.5 ± 0.3) respectively, with significant difference (Z = -2.714, P = 0.007), and image quality of micro surface coils was better than that of head and neck coil. The SIRNs of head and neck coil and micro surface coil images were 1.6 ± 0.5 and 2.2 ± 1.1 respectively; the SIRDs were 2.0 ± 0.6 and 2.8 ± 1.4 respectively, which showed significant differences (t = 3.440, 3.639 respectively, P value was 0.001, 0.001 respectively). All facial nerve trunks could be displayed by head and neck coils and micro surface coils. On head and neck coil images, 46 sides of temporofacial division, 47 sides of cervicofacial division, 21 sides of temporal branches, 22 sides of zygomatic branches, 29 sides of buccal branches, 30 sides of marginal mandibular branches, 32 sides of cervical branches, and 28 sides of the parotid duct could be displayed. On micro coil images, 48 sides of temporofacial division, 48 sides of cervicofacial division, 37 sides of temporal branches, 39 sides of zygomatic branches, 42 sides of buccal branches, 35 sides of marginal mandibular branches, 46 sides of cervical branches, and 28 sides of the parotid duct could be displayed. The display number of first branches of the intraparotid facial nerve by these 2 methods had no significant difference, the number of the secondary branches and parotid duct had significant differences.

CONCLUSION

Micro surface coil surpassed parotid MRI with 3D-PSIF-DWI sequence than neck coil, which can simultaneously clearly display the trunk and branches of the intraparotid facial nerves and parotid ducts.

ACR Appropriateness Criteria® Plexopathy

MRI without and with contrast is the most accurate imaging method to determine whether a process is intrinsic or extrinsic to a nerve of the brachial or lumbosacral plexus. However, there are no Current Procedural Terminology codes to correspond to imaging studies of the brachial or lumbar plexus discretely. This assessment uses "MRI of the brachial plexus" or "MRI of the lumbosacral plexus" as independent entities given that imaging acquisition for the respective plexus differs in sequences and planes compared with those of a routine neck, chest, spine, or pelvic MRI, yet acknowledges the potential variability of ordering practices across institutions. In patients unable to undergo MRI, CT offers the next highest level of anatomic evaluation. In oncologic patients, PET/CT imaging can identify the extent of tumor involvement and be beneficial to differentiate radiation plexitis from tumor recurrence but provides limited resolution of the plexus itself. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Comparison Between Three-Dimensional Diffusion-Weighted PSIF Technique and Routine Imaging Sequences in Evaluation of Peripheral Nerves in Healthy People

Introduction:

The present study aims to evaluate the Three-Dimensional Diffusion-Weighted reversed fast imaging with steady state free precession (3D DW-PSIF) sequence with respect to imaging of the peripheral nerves; the tibial, medial, and lateral plantar nerves in the lower extremity, ulnar and median nerve in the upper extremity, sciatic nerve, brachial plexus, and lumbosacral plexus, and also to compare its usefulness with the current two-dimensional sequences on a 1.5 T MR scanner.

Methods:

A total of 25 healthy subjects underwent MR imaging of peripheral nerves, 5 subjects in each area. In each imaging sequence, including T2W SPAIR and 3D DW-PSIF, images were evaluated for ability to identify the nerves in the related area using a 3-score scale (0–2). Then, by summing up the conspicuity scores, a total certainty score was recorded for each sequence.

Results:

With combining the results of all studies, the conspicuity mean (SD) score was 1.57(0.67) on the 3D DW-PSIF images, and 0.74(0.76) on the T2-weighted images (P<0.001). Regarding the lumbosacral plexus, the corresponding certainty mean (SD) scores were 1.80(0.40) and 1.07(0.74) (P<0.001) and with regard to the brachial plexus, they were 1.23(0.83) and 0.75(0.84), (P<0.001). Regarding the ankle/hind foot they were 1.87(0.35) and 0.40(0.50) (P<0.001) and in the wrist/proximal hand, 1.70(0.48) and 0.50(0.52) (P<0.001). Regarding the sciatic nerve, they were 1.80(0.44) and 0.20(0.44) (P=0.003).

Conclusion:

3D DW PSIF provides better manifestation of nerves compared to routine imaging sequences particularly fat saturated T2W images. This novel imaging technique can be used in MR neurography examination protocol for exact localization of the nerve and evaluation of the nerve pathology.

An Amendment to the Neidre and MacNab Classification System for Lumbosacral Nerve Root Anomaly and Its Implication in Percutaneous Endoscopic Lumbar Discectomy

BACKGROUND

Lumbar disc herniation complicated with nerve root anomaly presents great challenges to diagnosis and treatment. Improper selection of surgical procedures may cause inferior outcomes and neurologic injury.

CASE DESCRIPTION

A 66-year old man presented with low back pain and radicular symptoms involving bilateral L5 and S1 nerve roots. Instead of percutaneous endoscopic lumbar discectomy, aggressive decompression was carried out because of a deviation between the examination and imaging findings. Surgical detection disclosed a confluent nerve root comprising 2 adjacent contributions that arose from the thecal sac exiting from the left L5/S1 foramen, in the absence of the root otherwise exiting through the caudal foramen. We found that the overwhelming left radicular symptoms were attributable to compression on this swelling anomalous root by a narrowed L5/S1 root cannula. Aggressive decompression and distraction of the intervertebral space successfully released the nerve root. Twenty months postoperatively, the patient experienced evident relief of the radicular symptoms and improvement of muscle strength with no complication.

CONCLUSIONS

Lumbosacral nerve root anomaly should be remembered and ruled out before selecting surgical methods. Inappropriate procedures can not alleviate the symptoms associated with the anomalous roots and may expose such patients to the risk of neural injury. In clinical practice, surgeons should select percutaneous endoscopic lumbar discectomy with caution, and stop the procedure instantly when unexplainable radicular irritation is evoked.

The role of magnetic resonance imaging in the evaluation of peripheral nerves following traumatic lesion: where do we stand?

BACKGROUND

Peripheral nerve injury is a common and important cause of morbidity and disability in patients who have suffered a traumatic injury, particularly younger people. Various different injuries can result in damage to specific nerves. In patients with multiple trauma, the prevalence of peripheral nerve injury is estimated at 2.8%, but can reach 5% with the inclusion of brachial plexus involvement. Physical examination, as well as the origin and location of the trauma, can indicate the nerve involved and the type of nerve damage. However, the depth and severity of damage, and the structures involved often cannot be determined initially, but depend on longer periods of observation to reach a definitive and accurate diagnosis for which treatment can be proposed. Current approaches to locate and assess the severity of traumatic nerve injury involve clinical and electrodiagnostic studies. From a clinical and neurophysiological point of view, nerve injuries are classified in an attempt to correlate the degree of injury with symptoms, type of pathology, and prognosis, as well as to determine the therapy to be adopted.

OBJECTIVES

MRI in the diagnosis of traumatic peripheral nerve injury has increasingly been used by surgeons in clinical practice. In this article, we analyze the use of magnetic resonance (MR) for the evaluation of traumatic peripheral nerve diseases that are surgically treatable. We also consider basic concepts in the evaluation of technical and MR signs of peripheral nerve injuries.

MATERIALS AND METHODS

Studies were identified following a computerized search of MEDLINE (1950 to present), EMBASE (1980 to present), and the Cochrane database. The MEDLINE search was conducted on PUBMED, the EMBASE search was conducted on OVID, and the Cochrane database was conducted using their online library. A set was created using the terms: 'traumatic', 'nerve', and 'resonance'.

RESULTS

The included articles were identified using a computerized search and the resulting databases were then sorted according to the inclusion and exclusion criteria. This yielded 10,340 articles (MEDLINE, n = 758; EMBASE, n = 9564; and Cochrane, n = 18). A search strategy was then built by excluding articles that only concern plexus injury and adding the terms 'neuropathies', 'DTI' and 'neurotmesis'. In total, seven studies were included in the review effectively addressing the role of MRI in the evaluation of traumatic peripheral nerve injury. We extracted all relevant information on the imaging findings and the use of magnetic resonance in trauma. We did not include technical or specific radiological aspects of the imaging techniques.

CONCLUSIONS

These seven articles were subsequently evaluated by analyzing their results, methodological approach, and conclusions presented.

Magnetic resonance neurography in the diagnosis of neuropathies of the lumbosacral plexus: a pictorial review

Magnetic resonance neurography (MRN) is an important tool to detect abnormalities of peripheral nerves. This pictorial review demonstrates the MRN features of a variety of neuropathies affecting the lumbosacral plexus (LSP) and lower extremity nerves, drawn from over 1200 MRNs from our institution and supplemented by the literature. Abnormalities can be due to spinal compression, extraspinal compression, malignancy, musculoskeletal disease, iatrogenesis, inflammation, infection, and idiopathic disorders. We discuss indications and limitations of MRN in diagnosing LSP neuropathies. As MRN becomes more widely used, physicians must become familiar with the differential diagnosis of abnormalities detectable with MRN of the LSP.

Diffusion weighted magnetic resonance imaging and its recent trend-a survey

Since its inception in 1985, diffusion weighted magnetic resonance imaging has been evolving and is becoming instrumental in diagnosis and investigation of tissue functions in various organs including brain, cartilage, and liver. Even though brain related pathology and/or investigation remains as the main application, diffusion weighted magnetic resonance imaging (DWI) is becoming a standard in oncology and in several other applications. This review article provides a brief introduction of diffusion weighted magnetic resonance imaging, challenges involved and recent advancements.

MR Imaging of the Lumbosacral Plexus: A Review of Techniques and Pathologies

The lumbosacral plexus is a complex anatomic area that serves as the conduit of innervation and sensory information to and from the lower extremities. It is formed by the ventral rami of the lumbar and sacral spine which then combine into larger nerves serving the pelvis and lower extremities. It can be a source of severe disability and morbidity for patients when afflicted with pathology. Patients may experience motor weakness, sensory loss, and/or debilitating pain. Primary neurologic processes can affect the lumbosacral plexus in both genetic and acquired conditions and typically affect the plexus and nerves symmetrically. Additionally, its unique relationship to the pelvic musculature and viscera render it vulnerable to trauma, infection, and malignancy. Such conditions are typically proceeded by a known history of trauma or established pelvic malignancy or infection. Magnetic resonance imaging is an invaluable tool for evaluation of the lumbosacral plexus due to its anatomic detail and sensitivity to pathologic changes. It can identify the cause for disability, indicate prognosis for improvement, and be a tool for delivery of interventions. Knowledge of proper MR protocols and imaging features is key for appropriate and timely diagnosis. Here we discuss the relevant anatomy of the lumbosacral plexus, appropriate imaging techniques for its evaluation, and discuss the variety of pathologies that may afflict it.

Diffusion-weighted MR neurography of the brachial and lumbosacral plexus: 3.0 T versus 1.5 T imaging

PURPOSE

To compare intraindividually the nerve conspicuity of the brachial and lumbosacral plexus on diffusion-weighted (DW) MR neurography (MRN) at two different field strengths.

MATERIALS AND METHODS

16 healthy volunteers were investigated at 3.0 T and 1.5 T applying optimized variants of a DW spin-echo echo-planar imaging sequence with short TI inversion recovery fat suppression. Full-volume (FV) and curved sub-volume (CSV) maximum intensity projection (MIP) images were reconstructed and nerve conspicuity was visually assessed. Moreover, visible length and sharpness of the nerves were quantitatively analyzed.

RESULTS

On FV MIP images, nerve conspicuity at 3.0 T compared to 1.5 T was worse for brachial plexus (P=0.00228), but better for lumbosacral plexus (P=0.00666). On CSV MIP images, nerve conspicuity did not differ significantly for brachial plexus, but was better at 3.0 T for lumbosacral plexus (P=0.00091). The visible length of the analyzed nerves did not differ significantly with the exception of some lumbosacral nerves, which were significantly longer at 3.0 T. The sharpness of all investigated nerves was significantly higher at 3.0 T by about 40-60% for cervical and 97-169% for lumbosacral nerves.

CONCLUSION

DW MRN imaging at 3.0 T compared to 1.5 T is superior for lumbosacral plexus, but not for brachial plexus.

Diffusion tensor imaging and T2 relaxometry of bilateral lumbar nerve roots: feasibility of in-plane imaging

Lower back pain is a common problem frequently encountered without specific biomarkers that correlate well with an individual patient's pain generators. MRI quantification of diffusion and T2 relaxation properties may provide novel insight into the mechanical and inflammatory changes that occur in the lumbosacral nerve roots in patients with lower back pain. Accurate imaging of the spinal nerve roots is difficult because of their small caliber and oblique course in all three planes. Two-dimensional in-plane imaging of the lumbosacral nerve roots requires oblique coronal imaging with large field of view (FOV) in both dimensions, resulting in severe geometric distortions using single-shot echo planar imaging (EPI) techniques. The present work describes initial success using a reduced-FOV single-shot spin-echo EPI acquisition to obtain in-plane diffusion tensor imaging (DTI) and T2 mapping of the bilateral lumbar nerve roots at the L4 level of healthy subjects, minimizing partial volume effects, breathing artifacts and geometric distortions. A significant variation in DTI and T2 mapping metrics is also reported along the course of the normal nerve root. The fractional anisotropy is statistically significantly lower in the dorsal root ganglia (0.287 ± 0.068) than in more distal regions in the spinal nerve (0.402 ± 0.040) (p < 10(-5) ). The T2 relaxation value is statistically significantly higher in the dorsal root ganglia (78.0 ± 11.9 ms) than in more distal regions in the spinal nerve (59.5 ± 7.4 ms) (p < 10(-5) ). The quantification of nerve root DTI and T2 properties using the proposed methodology may identify the specific site of any degenerative and inflammatory changes along the nerve roots of patients with lower back pain.

Magnetic resonance neurography: diffusion tensor imaging and future directions

Magnetic resonance (MR) neurography has progressed in the past 2 decades because of rapid technological developments in both hardware and software. In addition to improvements in high-resolution anatomic pulse sequences, functional techniques are becoming feasible. This article presents the current state-of-the-art three-dimensional anatomic techniques, discusses the advantages of functional techniques being exploited, and portrays novel contrast types and molecular techniques that are under development and promise a bright future for this rapidly evolving technique.

Rapid high resolution MR neurography with a diffusion-weighted pre-pulse

PURPOSE

To introduce, optimize, and assess the feasibility of a new scheme to rapidly acquire high-resolution volumetric neurographic images using a three-dimensional turbo spin-echo sequence combined with a diffusion-weighted pre-pulse called improved motion-sensitized driven equilibrium (iMSDE): Diffusion-prepared MR Neurography (D-prep MRN).

METHODS

In order to optimize the signal suppression of blood vessels and muscle at D-prep MRN, coronal lumbosacral plexus images were acquired in five volunteers at 3T, and the following parameters were examined: iMSDE gradient-strength (b-value) of 0, 2 and 10 s/mm² (with the aim to suppress blood vessels) and iMSDE preparation duration (iMSDEprep-time) of 18, 50 and 100 ms (with the aim to suppress muscle signal). Subsequently, the feasibility of the optimized D-prep MRN sequence in visualizing the brachial plexus, lumbosacral plexus, and cranial nerves was evaluated in 5 healthy volunteers.

RESULTS

A higher b-value of 10 s/mm² was better in signal suppression of blood vessels, whereas an intermediate iMSDEprep-time of 50 ms provided the best compromise between suppression of muscle signal and minimization of signal loss of nerves. With these parameters, the normal nerve structures showed high signal intensity, while the blood vessels and muscles were effectively suppressed. The optimized D-prep MRN sequence clearly showed the three-dimensional trajectory of the brachial plexus, lumbosacral plexus, and cranial nerves.

CONCLUSION

D-prep MRN was introduced and optimized, and clearly showed detailed anatomy of the brachial plexus, lumbosacral plexus, and cranial nerves. These results suggest that the D-prep MRN can be used for fast, high-resolution, volumetric imaging of the peripheral nervous system.

High-resolution MRI of the intraparotid facial nerve based on a microsurface coil and a 3D reversed fast imaging with steady-state precession DWI sequence at 3T

BACKGROUND AND PURPOSE

3D high-resolution MR imaging can provide reliable information for defining the exact relationships between the intraparotid facial nerve and adjacent structures. The purpose of this study was to explore the clinical value of using a surface coil combined with a 3D-PSIF-DWI sequence in intraparotid facial nerve imaging.

MATERIALS AND METHODS

Twenty-one healthy volunteers underwent intraparotid facial nerve scanning at 3T by using the 3D-PSIF-DWI sequence with both the surface coil and the head coil. Source images were processed with MIP and MPR to better delineate the intraparotid facial nerve and its branches. In addition, the SIR of the facial nerve and parotid gland was calculated. The number of facial nerve branches displayed by these 2 methods was calculated and compared.

RESULTS

The display rates of the main trunk, divisions (cervicofacial, temporofacial), and secondary branches of the intraparotid facial nerve were 100%, 97.6%, and 51.4% by head coil and 100%, 100%, and 83.8% by surface coil, respectively. The display rate of secondary branches of the intraparotid facial nerve by these 2 methods was significantly different (P < .05). The SIRs of the intraparotid facial nerve/parotid gland in these 2 methods were significantly different (P < .05) at 1.37 ± 1.06 and 1.89 ± 0.87, respectively.

CONCLUSIONS

The 3D-PSIF-DWI sequence combined with a surface coil can better delineate the intraparotid facial nerve and its divisions than when it is combined with a head coil, providing better image contrast and resolution. The proposed protocol offers a potentially useful noninvasive imaging sequence for intraparotid facial nerve imaging at 3T.

3T MR neurography using three-dimensional diffusion-weighted PSIF: technical issues and advantages

Three-dimensional (3D) diffusion-weighted reversed fast imaging with steady state precession (3D DW-PSIF) MR sequence has the potential to create nerve-specific images. The authors describe the technical issues and their initial experience with this imaging technique employed for peripheral MR neurography.

Simultaneous visualization of nerves and vessels of the lower extremities using magnetization-prepared susceptibility weighted magnetic resonance imaging at 3.0 T

BACKGROUND

Identifying the extent of involvement of the vessel and nerve, particularly in regard to preoperative evaluation and precise localization of the tumor and its relation to the structures of the extremities, has important applications for advancing the treatment of lower extremity diseases.

OBJECTIVE

To review the technical feasibility of simultaneous visualization of nerves and vessels of the lower extremities by using magnetization-prepared susceptibility-weighted magnetic resonance (MR) imaging (MP-SWI) at 3.0T.

METHODS

Ten healthy volunteers and 10 patients were studied. Optimized MP-SWI, MR neurography (MRN) based on 3D diffusion-weighted steady-state free precession imaging and contrast-enhanced MR angiography (CE-MRA) sequences were performed for each subject. The means of signal-to-noise ratio (SNR)n, SNRv, SNRm, contrast-to-noise ratio (CNR)n,m and CNRv,m were calculated and the certainty of identifying nerves and vessels was determined. CNRn,m between MP-SWI and MRN, and CNRv,m between MP-SWI and CE-MRA were compared.

RESULTS

MP-SWI provides slightly poorer CNRv,m than CE-MRA, whereas MP-SWI provides a better CNRn,m than MRN. In thin-slice-thickness maximum-intensity projection arbitrary planes, the sciatic nerve and its branches were clearly identified (score 1 or 2 of 2) in 17 subjects (85%); the femoral artery and the main branches were identified (score 1 or 2 of 2) in all 20 subjects (100%). The nerves are isointense to slightly hypointense to muscle, and the vessels show a more obvious hyperintense signal than muscle in MP-SWI.

CONCLUSION

The proposed MP-SWI demonstrates the feasibility of simultaneously visualizing nerves and vessels of the lower extremities without using an exogenous contrast agent. It may enable straightforward localization of a disease process to a specific nerve and vessel.

New methods in diffusion-weighted and diffusion tensor imaging

Considerable strides have been made by countless individual researchers in diffusion-weighted imaging (DWI) to push DWI from an experimental tool, limited to a few institutions with specialized instrumentation, to a powerful tool used routinely for diagnostic imaging. The field of DWI constantly evolves, and progress has been made on several fronts. These developments are primarily composed of improved robustness against patient and physiologic motion, increased spatial resolution, new biophysical and tissue models, and new clinical applications for DWI. This article aims to provide a succinct overview of some of these new developments and a description of some of the major challenges associated with DWI.