An Updated Review of Magnetic Resonance Neurography for Plexus Imaging

Magnetic resonance neurography (MRN) is increasingly used to visualize peripheral nerves in vivo. However, the implementation and interpretation of MRN in the brachial and lumbosacral plexi are challenging because of the anatomical complexity and technical limitations. The purpose of this article was to review the clinical context of MRN, describe advanced magnetic resonance (MR) techniques for plexus imaging, and list the general categories of utility of MRN with pertinent imaging examples. The selection and optimization of MR sequences are centered on the homogeneous suppression of fat and blood vessels while enhancing the visibility of the plexus and its branches. Standard 2D fast spin-echo sequences are essential to assess morphology and signal intensity of nerves. Moreover, nerve-selective 3D isotropic images allow improved visualization of nerves and multiplanar reconstruction along their course. Diffusion-weighted and diffusion-tensor images offer microscopic and functional insights into peripheral nerves. The interpretation of MRN in the brachial and lumbosacral plexi should be based on a thorough understanding of their anatomy and pathophysiology. Anatomical landmarks assist in identifying brachial and lumbosacral plexus components of interest. Thus, understanding the varying patterns of nerve abnormalities facilitates the interpretation of aberrant findings.

Diagnosis of Infectious Spondylitis Using Non-Contrast Enhanced MRI With Axial Diffusion-Weighted Images: Comparison With Gadolinium-Enhanced MRI

Purpose@#To assess the diagnostic performances of diffusion-weighted imaging (DWI)-included non-contrast magnetic resonance imaging (MRI) compared to standard contrastenhanced MRI for infectious spondylitis. @*Materials and Methods@#This study involved 154 participants: a spondylitis group (n = 76) and a control group (n = 78) with Modic type 1 degeneration or recent compression fractures. Two readers independently reviewed paraspinal soft tissue signal change and abscess with 5-scale confidence scores based on two image sets: one featuring both non-contrast-enhanced MRI (NCEI) and DWI and the other consisting of NCEI and contrast-enhanced fat-suppressed T1-weighted imaging (CEFST1). The diagnostic performance of the two image sets was compared using McNemar tests for sensitivity, specificity, and area under the receiver operating characteristics (AUROC) analysis. Interobserver agreements (κ) for each images sets were also calculated. @*Results@#The sensitivity and specificity for infectious spondylitis were 90.8% and 69.2% for NCEI + DWI, 96.1% and 60.3% for NCEI + CEFST1 in reader 1, whereas it was 92.1% and 66.7% for NCEI + DWI, and 96.1% and 68.0% for NCEI + CEFST1 in reader 2. Sensitivities and specificities were not significantly different between NCEI + DWI and NCEI + CEFST1 (reader 1: p = 0.289, 0.065; reader 2: p = 0.250, > 0.999, respectively). However, the AUROC was not considerably different between the two modalities in only one reader (p = 0.306 in reader 1, p = 0.031 in reader 2). Interobserver agreement for infectious spondylitis was moderate (κ = 0.55) in NCEI + DWI and substantial (κ = 0.66) in NCEI + CEFST1. @*Conclusion@#Non-contrast enhanced MRI with additional DWI is as effective for diagnosing infectious spondylitis as a contrast-enhanced MRI.

Recent Issues in Musculoskeletal Anatomy Research and Correlation with MRI

MRI is a valuable imaging technique for the evaluation of intraarticular diseases. Accurate interpretation of joint MRI necessitates sound knowledge of anatomy. In the field of joint anatomy, in addition to the discovery of new structures, previously reported joint components of unexplained function are also detected. In this review, joint anatomy researched actively over the last decade is discussed. Joint components including the rotator cable and the superior capsule of the shoulder, posterolateral corner and the anterolateral ligament complex of the knee, and the distal tibiofibular syndesmosis of the ankle joint are introduced and correlated with their MRI features.

Assessment of the Location of the Peroneus Longus Tendon in the Cuboid Groove Using 3D Isotropic Fast Spin-Echo MRI

Purpose@#To investigate normal location of the peroneus longus tendon (PL) in the cuboid groove by evaluating it between ankles with no significant abnormality (asymptomatic group) and those with retromalleolar PL dislocation (dislocation group) using three-dimensional isotropic fast spin-echo (3D-FSE) magnetic resonance imaging (MRI) of the ankle. @*Materials and Methods@#Thirty-six and 32 3D-FSE ankle MRI were assigned to the asymptomatic group and the dislocation group, respectively. Using multiplanar reformatted 3D-FSE, qualitative PL location (i.e., outside, overlying, and inside in relation to the cuboid groove), quantitative PL location (i.e., distance between the proximal margins of PL and cuboid groove), and cuboid groove size were measured in lateral, middle, and medial levels of the cuboid groove. @*Results@#In the asymptomatic group, 64%, 42%, and 11%, respectively, had the outside or overlying-located PL in lateral, middle, and medial levels of the cuboid groove and the quantitative location gradually decreased from lateral to medial level.Qualitative and quantitative PL locations were not significantly different between the asymptomatic group and dislocation group. Cuboid groove size showed significant negative correlation with quantitative PL location in both groups. @*Conclusion@#Outside- or overlying-located PL in lateral and middle levels of the cuboid groove would be a normal finding, regardless of PL status at the retromalleolar level.

Where Is the Ulnar Styloid Process? Identification of the Absolute Location of the Ulnar Styloid Process Based on CT and Verification of Neutral Forearm Rotation on Lateral Radiographs of the Wrist

BACKGROUND: The location of the ulnar styloid process can be confusing because the radius and the hand rotate around the ulna. The purpose of this study was to identify the absolute location of the ulnar styloid process, which is independent of forearm pronation or supination, to use it as a reference for neutral forearm rotation on lateral radiographs of the wrist. METHODS: Computed tomography (CT) images of 23 forearms taken with elbow flexion of 70° to 90° were analyzed. The axial CT images were reconstructed to be perpendicular to the distal ulnar shaft. The absolute location of the ulnar styloid process in this study was defined as the position of the ulnar styloid process on the axial plane of the ulnar head relative to the long axis of the humeral shaft with the elbow set in the position for standard lateral radiographs of the wrist. To identify in which direction the ulnar styloid is located on the axial plane of the ulnar head, the angle between “the line of humeral long axis projected on the axial plane of the ulna” and “the line passing the center of the ulnar head and the center of the ulnar styloid” was measured (ulnar styloid direction angle). To identify how volarly or dorsally the ulnar styloid should appear on the true lateral view of the wrist, the ratio of “the volar-dorsal diameter of the ulnar head” and “the distance between the volar-most aspect of the ulnar head and the center of the ulnar styloid” was calculated (ulnar styloid location ratio). RESULTS: The mean ulnar styloid direction angle was 12° dorsally. The mean ulnar styloid location ratio was 1:0.55. CONCLUSIONS: The ulnar styloid is located at nearly the ulnar-most (the opposite side of the humerus with the elbow flexed) and slightly dorsal aspects of the ulnar head on the axial plane. It should appear almost midway (55% dorsally) from the ulnar head on the standard lateral view of the wrist in neutral forearm rotation. These location references could help clinicians determine whether the forearm is in neutral or rotated position on an axial CT/magnetic resonance imaging scan or a lateral radiograph of the wrist.

Diagnosis of Rotator Cuff Tears with Non-Arthrographic MR Imaging: 3D Fat-Suppressed Isotropic Intermediate-Weighted Turbo Spin-Echo Sequence versus Conventional 2D Sequences at 3T

PURPOSE: To assess the diagnostic performance in detecting rotator cuff tears at 3T of non-arthrographic shoulder magnetic resonance imaging (MRI) using 3D isotropic turbo spin-echo (TSE-SPACE) sequence as compared with 2D sequences. MATERIALS AND METHODS: Seventy-four patients who were arthroscopically confirmed to have underwent non-arthrographic shoulder MRI with 2D sequences and TSE-SPACE were included. Three independent readers retrospectively scored supraspinatus and infraspinatus tendon (SST-IST) and subscapularis tendon (SCT) tears on 2D sequences and TSE-SPACE. RESULTS: The mean sensitivity, specificity, and accuracy of the three readers were 95%, 100%, and 95% on TSE-SPACE and 99%, 93%, and 98% on 2D sequences for detecting SST-IST tears, respectively, whereas those were 87%, 49%, and 68% on TSE-SPACE and 88%, 66%, and 77% on 2D sequences for detecting SCT tears, respectively. There was no statistical difference between the two sequences, except for in the specificity of one reader for detecting SCT tears. The mean AUCs of the three readers on TSE-SPACE and 2D sequences were 0.96 and 0.98 for detecting SST-IST tears, respectively, which were not significantly different, while those were 0.71 and 0.82 for detecting SCT tears, respectively, which were significantly different (P < 0.05). CONCLUSION: TSE-SPACE may have accuracy and reliability comparable to conventional 2D sequences for SST-IST tears at non-arthrographic 3T shoulder MRI, whereas TSE-SPACE was less reliable than conventional 2D sequences for detecting SCT tears.

Diagnosis of Nerve Root Compromise of the Lumbar Spine: Evaluation of the Performance of Three-dimensional Isotropic T2-weighted Turbo Spin-Echo SPACE Sequence at 3T

OBJECTIVE: To explore the performance of three-dimensional (3D) isotropic T2-weighted turbo spin-echo (TSE) sampling perfection with application optimized contrasts using different flip angle evolution (SPACE) sequence on a 3T system, for the evaluation of nerve root compromise by disc herniation or stenosis from central to extraforaminal location of the lumbar spine, when used alone or in combination with conventional two-dimensional (2D) TSE sequence. MATERIALS AND METHODS: Thirty-seven patients who had undergone 3T spine MRI including 2D and 3D sequences, and had subsequent spine surgery for nerve root compromise at a total of 39 nerve levels, were analyzed. A total of 78 nerve roots (48 symptomatic and 30 asymptomatic sites) were graded (0 to 3) using different MRI sets of 2D, 3D (axial plus sagittal), 3D (all planes), and combination of 2D and 3D sequences, with respect to the nerve root compromise caused by posterior disc herniations, lateral recess stenoses, neural foraminal stenoses, or extraforaminal disc herniations; grading was done independently by two readers. Diagnostic performance was compared between different imaging sets using the receiver operating characteristics (ROC) curve analysis. RESULTS: There were no statistically significant differences (p = 0.203 to > 0.999) in the ROC curve area between the imaging sets for both readers 1 and 2, except for combined 2D and 3D (0.843) vs. 2D (0.802) for reader 1 (p = 0.035), and combined 2D and 3D (0.820) vs. 3D including all planes (0.765) for reader 2 (p = 0.049). CONCLUSION: The performance of 3D isotropic T2-weighted TSE sequence of the lumbar spine, whether axial plus sagittal images, or all planes of images, was not significantly different from that of 2D TSE sequences, for the evaluation of nerve root compromise of the lumbar spine. Combining 2D and 3D might possibly improve the diagnostic accuracy compared with either one.

Measurement and Compensation of Respiration-Induced B0 Variations in Lumbar Spine Bone Marrow Fat Quantification

PURPOSE: To investigate and compensate the effects of respiration-induced B0 variations on fat quantification of the bone marrow in the lumbar spine. MATERIALS AND METHODS: Multi-echo gradient echo images with navigator echoes were obtained from eight healthy volunteers at 3T clinical scanner. Using navigator echo data, respiration-induced B0 variations were measured and compensated. Fat fraction maps were estimated using T2*-IDEAL algorithm from the uncompensated and compensated images. For manually drawn bone marrow regions, the estimated B0 variations and the calculated fat fractions (before and after compensations) were analyzed. RESULTS: An increase of temporal B0 variations from inferior level to superior levels was observed for all subjects. After compensation using navigator echo data, the effects of the B0 variations were reduced in gradient echo images. The calculated fat fractions show significant differences (P < 0.05) in L1 and L3 between the uncompensated and the compensated. CONCLUSION: The results of this study raise the need for considering respiration-induced B0 variations for accurate fat quantification using gradient echo images in the lumbar spine. The use of navigator echo data can be an effective way for the reduction of the effects of respiratory motion on the quantification.

Platelet Indices Are Associated with Disease Activity Scores and the Severity of Sacroiliitis on Magnetic Resonance Imaging in Axial Spondyloarthritis Patients

OBJECTIVE: To investigate the associations among platelet indices, disease activity scores, and inflammatory markers in axial spondyloarthritis, and to determine the relation between platelet indices and inflammation measured on magnetic resonance imaging (MRI). METHODS: The study included 161 patients who fulfilled Assessment of Spondyloarthritis International Society criteria. Platelet indices such as mean platelet volume (MPV), plateletcrit (PCT), platelet large cell ratio (PLCR), and platelet distribution width (PDW) were measured. Ninety patients underwent sacroiliac (SI) MRI at baseline. Bone marrow edema (BME) and erosion on MRI were scored using the SPondyloArthritis Research Consortium of Canada (SPARCC) method. Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), Ankylosing Spondylitis Disease Activity Score (ASDAS) and spinal radiologic progression were also assessed. The associations among platelet indices and disease activity scores and inflammatory markers were evaluated. RESULTS: Of the 161 patients, 130 (81%) were male. MPV, PLCR, and PDW were negatively associated with ASDAS and inflammatory marker expression, whereas PCT was positively associated with these parameters. MPV, PLCR, and PDW were negatively associated with BME and erosion scores on SI MRI. However, platelet indices were not associated with the BASDAI and BASFI. The mean erythrocyte sedimentation rate, C-reactive protein, and BME and erosion scores were significantly higher in patients with low MPV. Changes in MPV, PCT, and PDW at baseline and after one year were associated with changes in ASDAS and inflammatory marker expression. CONCLUSION: Platelet indices are associated with ASDAS, inflammatory marker levels, and severity of BME and erosion measured on MRI.

MR Findings of the Osteofibrous Dysplasia

OBJECTIVE: The aim of this study was to describe MR findings of osteofibrous dysplasia. MATERIALS AND METHODS: MR images of 24 pathologically proven osteofibrous dysplasia cases were retrospectively analyzed for a signal intensity of the lesion, presence of intralesional fat signal, internal hypointense band, multilocular appearance, cortical expansion, intramedullary extension, cystic area, cortical breakage and extraosseous extension, abnormal signal from the adjacent bone marrow and soft tissue and patterns of contrast enhancement. RESULTS: All cases of osteofibrous dysplasia exhibited intermediate signal intensity on T1-weighted images. On T2-weighted images, 20 and 4 cases exhibited heterogeneously intermediate and high signal intensity, respectively. Intralesional fat was identified in 12% of the cases. Internal low-signal bands and multilocular appearance were observed in 91%. Cortical expansion was present in 58%. Intramedullary extension was present in all cases, and an entire intramedullary replacement was observed in 33%. Cortical breakage (n = 3) and extraosseous mass formation (n = 1) were observed in cases with pathologic fractures only. A cystic area was observed in one case. Among 21 cases without a pathologic fracture, abnormal signal intensity in the surrounding bone marrow and adjacent soft tissue was observed in 43% and 48%, respectively. All cases exhibited diffuse contrast enhancement. CONCLUSION: Osteofibrous dysplasia exhibited diverse imaging features ranging from lesions confined to the cortex to more aggressive lesions with complete intramedullary involvement or perilesional marrow edema.

Preliminary Experience Using Dynamic MRI at 3.0 Tesla for Evaluation of Soft Tissue Tumors

OBJECTIVE: We aimed to evaluate the use of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) at 3.0 T for differentiating the benign from malignant soft tissue tumors. Also we aimed to assess whether the shorter length of DCE-MRI protocols are adequate, and to evaluate the effect of temporal resolution. MATERIALS AND METHODS: Dynamic contrast-enhanced magnetic resonance imaging, at 3.0 T with a 1 second temporal resolution in 13 patients with pathologically confirmed soft tissue tumors, was analyzed. Visual assessment of time-signal curves, subtraction images, maximal relative enhancement at the first (maximal peak enhancement [Emax]/1) and second (Emax/2) minutes, Emax, steepest slope calculated by using various time intervals (5, 30, 60 seconds), and the start of dynamic enhancement were analyzed. RESULTS: The 13 tumors were comprised of seven benign and six malignant soft tissue neoplasms. Washout on time-signal curves was seen on three (50%) malignant tumors and one (14%) benign one. The most discriminating DCE-MRI parameter was the steepest slope calculated, by using at 5-second intervals, followed by Emax/1 and Emax/2. All of the steepest slope values occurred within 2 minutes of the dynamic study. Start of dynamic enhancement did not show a significant difference, but no malignant tumor rendered a value greater than 14 seconds. CONCLUSION: The steepest slope and early relative enhancement have the potential for differentiating benign from malignant soft tissue tumors. Short-length rather than long-length DCE-MRI protocol may be adequate for our purpose. The steepest slope parameters require a short temporal resolution, while maximal peak enhancement parameter may be more optimal for a longer temporal resolution.