Routine 3D magnetic resonance imaging of joints

Optimization of 3D imaging time reduction by assessing spatial resolution in the slice selective direction using the ladder method

PURPOSE

Assessing spatial resolution in MRI is challenging due to non-linearity. Despite the widespread use of 3D imaging in clinical practice for lesion detection and multi-planar reconstruction (MPR), the extended acquisition time poses a shortcoming. To address this, the "Slice resolution" parameter is utilized; however, its impact on MPR images is unclear. This study aims to assess spatial resolution using the ladder method, investigate the effects of diverse slice resolution settings in various imaging sequences, and propose optimal conditions.

METHODS

Images were acquired using various 3D imaging sequences-SPACE T1WI, SPACE T2WI, and VIBE T1WI-with different slice resolutions. Axial cross-section images were acquired and reconstructed into coronal cross-sections. The ladder method was employed for objective evaluation, including spatial frequency analysis. Additionally, visual evaluation was conducted and compared with ladder method results.

RESULTS

For three imaging sequences, the evaluated value of ladder method remained relatively constant from 100 % to 80 % slice resolution. However, the evaluated value decreased in low-spatial frequency for slice resolution below 70 %.

CONCLUSIONS

Results from both ladder method and visual evaluations indicated image quality remained stable when the slice resolution was decreased to 80 %, potentially enabling a 20 % reduction in imaging time while preserving resolution in other cross-sections reconstructed by MPR.

Application of three-dimensional (3D) magnetic resonance (MR) Multi-Echo iN Steady-state Acquisition sequences in preoperative evaluation of lumbar disc herniation: a prospective study

Background

Conventional spinal magnetic resonance imaging (MRI) cannot provide accurate diagnosis and surgical planning; thin-layer scanning can enhance the diagnostic efficacy. This study aimed to investigate the value of 3-dimensional (3D) magnetic resonance (MR) in preoperative evaluation of lumbar disc herniation, with a focus on the application of Multi-Echo iN Steady-state Acquisition (MENSA) sequence.

Methods

A total of 51 patients who underwent lumbar disc herniation surgery in West China Hospital of Sichuan University from June 2021 to December 2021 were prospectively enrolled. A cross-sectional study was conducted on those patients. The Cube group was scanned using 3D-FSE-Cube sequence, the Cube stir group was scanned using 3D-FSE-Cube Short Tau Inversion Recovery (STIR) sequence, and the MENSA group was scanned using MENSA sequence. Signal and noise values of nerve, herniated disc, ligamentum flavum (LF), and soft tissue were measured on the 3 groups. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Objective scores were calculated by analysis of variance (ANOVA). Image quality was scored by a 5-point method. Friedman test was used to compare subjective scores, and Kappa test was used to evaluate the consistency of 2 readers' scores.

Results

The nerve root SNRs in the MENSA and Cube stir groups were higher than that in the Cube group (P<0.01), but there was no substantial statistical difference between the 2 groups. The herniated disc and LF SNRs of the MENSA group were greater than those of the Cube stir and Cube groups (P<0.01). Soft tissue SNR was greater in the MENSA group compared with the Cube stir group (P<0.01), which was greater than the SNR in the Cube group (P<0.01). The nerve root CNR of the Cube group (102.88±73.19) was greater than that of the MENSA group (55.98±25.26, P<0.01), which was higher than the CNR in the Cube Stir group (29.42±16.22, P<0.01). The herniated disc CNR was higher in the MENSA and Cube groups than that in the Cube Stir group. The CNR of LF was greater in the MENSA group (37.71±16.87) compared to the Cube group (29.76±25.73, P=0.03), which was greater than that in the Cube stir group (10.50±7.75, P<0.01). Among the subjective ratings of 2 reviewers, MENSA sequence scored highest in the qualitative measures of image quality. In the consistency test, the Kappa values of 2 readers for 3 groups of images were all greater than 0.73, indicating good consistency. The differences of subjective scores among all groups were statistically significant (P<0.05). Overall, it was indicated that the consistency test results of the 2 readers were statistically significant and consistent. The MENSA group had the highest accuracy in diagnosing nerve compression. In addition, MENSA sequence ranked highest among the 3 sequences with 94.1% diagnostic accuracy.

Conclusions

The preoperative 3D MRI MENSA sequence can clearly depict the nerve roots and offer desirable contrast between the nerve roots, LF, bone, and intervertebral discs (IVDs). Patients with lumbar degeneration can effectively benefit from MENSA sequence since it provides useful imaging information to help understand disc herniation and compression of adjacent tissues when developing preoperative surgical strategies.

Diagnosing periprosthetic hip joint infection with new-generation 0.55T MRI

PURPOSE

To assess the accuracy of 0.55 T MRI in diagnosing periprosthetic joint infection (PJI) in patients with symptomatic total hip arthroplasty (THA).

MATERIAL AND METHODS

0.55 T MRI of patients with THA PJI (Group A) and noninfected THA (Group B), including aseptic loosening (Group C, subgroup of B) performed between May 2021 and July 2023 were analysed retrospectively. Two musculoskeletal fellowship-trained radiologists independently identified MRI bone and soft tissue changes including: marrow oedema, periosteal reaction, osteolysis, joint effusion, capsule oedema and thickening, fluid collections, muscle oedema, bursitis, inguinal adenopathy, and muscle tears. The diagnostic performance of MRI discriminators of PJI was evaluated using Fisher's exact test (p < 0.05) and interrater reliability was determined. 61 MRI scans from 60 THA patients (34 female, median age 68, range 41-93 years) in Group A (n = 9; female 4; median age 69, range 56-82 years), B (n = 51; 30; 67.5, 41-93 years), and C (10; 6; 67; 41-82 years) were included.

RESULTS

Capsule oedema (sensitivity 89 %, specificity 92 %,), intramuscular oedema (89 %, 82 %) and joint effusion (89 %, 73 %) were the best performing discriminators for PJI diagnosis (p ≤ 0.001), when viewed individually and had combined 70 % sensitivity and 100 % specificity for PJI diagnosis in parallel testing. For the differentiation between PJI and aseptic loosening, intramuscular oedema (89 %, 80 %) and capsule oedema (89 %, 80 %) were significant discriminators (p ≤ 0.001) with combined 64 % sensitivity and 96 % specificity for PJI.

CONCLUSIONS

New generation 0.55 T MRI may aid in the detection of PJI in symptomatic patients. Oedema of the joint capsule, adjacent muscles as well as joint effusion were indicative of the presence of PJI.

Radial Planes in Hip Magnetic Resonance Imaging: Techniques, Applications, and Perspectives

The hip cartilage and labrum, as the main targets of femoroacetabular impingement, sports-related or traumatic damage, as well as congenital and developmental abnormalities, have attracted increasing attention with the development of magnetic resonance imaging (MRI) and hip arthroscopy. MRI is a commonly used imaging modality to noninvasively visualize the hip cartilage and labral lesions. However, conventional orthogonal MRI planes encounter unique challenges given the ball-and-socket configuration of the hip joint, its anatomically abducted and anteverted orientation, and the thin, closely apposed cartilage enveloping the femoral head and acetabulum. Advancements in hip MRI's radial plane, which is acquired through the center of the hip joint, offer a solution. This technology provides true cross-sectional images of the cartilage and labrum perpendicular to the curvature of the joint, thereby mitigating the partial-volume-averaging effects. The integration of 3.0-Tesla high field strength and three-dimensional (3D) acquisition techniques further enhances the capabilities of the radial plane. This combination yields a high signal-to-noise ratio, high spatial resolution, high contrast between intraarticular structures, while minimizing partial-volume-averaging effects. Such improvements potentially facilitate the comprehensive detection of even minor chondral and labral lesions. The capability for multiplanar reconstruction from a single 3D volumetric acquisition further strengthens the usefulness of the radial plane by aiding in precise localization of hip cartilage and labral lesions, in line with hip arthroscopy findings. These advancements have the potential to standardize MRI evaluations and radiographic reporting systems for hip cartilage and labrum, offering precise guidance for hip arthroscopy. This article presents a comprehensive review of radial plane technology applied to the hip MRI, and discusses the morphological assessment and localization of hip cartilage and labral lesions utilizing this advanced imaging technique. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 2.

Thin-slice 2D MR Imaging of the Shoulder Joint Using Denoising Deep Learning Reconstruction Provides Higher Image Quality Than 3D MR Imaging

PURPOSE

This study was conducted to evaluate whether thin-slice 2D fat-saturated proton density-weighted images of the shoulder joint in three imaging planes combined with parallel imaging, partial Fourier technique, and denoising approach with deep learning-based reconstruction (dDLR) are more useful than 3D fat-saturated proton density multi-planar voxel images.

METHODS

Eighteen patients who underwent MRI of the shoulder joint at 3T were enrolled. The denoising effect of dDLR in 2D was evaluated using coefficient of variation (CV). Qualitative evaluation of anatomical structures, noise, and artifacts in 2D after dDLR and 3D was performed by two radiologists using a five-point Likert scale. All were analyzed statistically. Gwet's agreement coefficients were also calculated.

RESULTS

The CV of 2D after dDLR was significantly lower than that before dDLR (P < 0.05). Both radiologists rated 2D higher than 3D for all anatomical structures and noise (P < 0.05), except for artifacts. Both Gwet's agreement coefficients of anatomical structures, noise, and artifacts in 2D and 3D produced nearly perfect agreement between the two radiologists. The evaluation of 2D tended to be more reproducible than 3D.

CONCLUSION

2D with parallel imaging, partial Fourier technique, and dDLR was proved to be superior to 3D for depicting shoulder joint structures with lower noise.

3D isotropic MRI of ankle: review of literature with comparison to 2D MRI

The ankle joint has complex anatomy with different tissue structures and is commonly involved in traumatic injuries. Magnetic resonance imaging (MRI) is the primary imaging modality used to assess the soft tissue structures around the ankle joint including the ligaments, tendons, and articular cartilage. Two-dimensional (2D) fast spin echo/turbo spin echo (FSE/TSE) sequences are routinely used for ankle joint imaging. While the 2D sequences provide a good signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) with high spatial resolution, there are some limitations to their use owing to the thick slices, interslice gaps leading to partial volume effects, limited fluid contrast, and the need to acquire separate images in different orthogonal planes. The 3D MR imaging can overcome these limitations and recent advances have led to technical improvements that enable its widespread clinical use in acceptable time periods. The volume imaging renders the advantage of reconstructing into thin continuous slices with isotropic voxels enabling multiplanar reconstructions that helps in visualizing complex anatomy of the structure of interest throughout their course with improved sharpness, definition of anatomic variants, and fluid conspicuity of lesions and injuries. Recent advances have also reduced the acquisition time of the 3D datasets making it more efficient than 2D sequences. This article reviews the recent technical developments in the domain 3D MRI, compares imaging with 3D versus 2D sequences, and demonstrates the use-case scenarios with interesting cases, and benefits of 3D MRI in evaluating various ankle joint components and their lesions.

2D versus 3D MRI of osteoarthritis in clinical practice and research

Accurately detecting and characterizing articular cartilage defects is critical in assessing patients with osteoarthritis. While radiography is the first-line imaging modality, magnetic resonance imaging (MRI) is the most accurate for the noninvasive assessment of articular cartilage. Multiple semiquantitative grading systems for cartilage lesions in MRI were developed. The Outerbridge and modified Noyes grading systems are commonly used in clinical practice and for research. Other useful grading systems were developed for research, many of which are joint-specific. Both two-dimensional (2D) and three-dimensional (3D) pulse sequences are used to assess cartilage morphology and biochemical composition. MRI techniques for morphological assessment of articular cartilage can be categorized into 2D and 3D FSE/TSE spin-echo and gradient-recalled echo sequences. T2 mapping is most commonly used to qualitatively assess articular cartilage microstructural composition and integrity, extracellular matrix components, and water content. Quantitative techniques may be able to label articular cartilage alterations before morphological defects are visible. Accurate detection and characterization of shallow low-grade partial and small articular cartilage defects are the most challenging for any technique, but where high spatial resolution 3D MRI techniques perform best. This review article provides a practical overview of commonly used 2D and 3D MRI techniques for articular cartilage assessments in osteoarthritis.

Arthritis Foundation/HSS Workshop on Hip Osteoarthritis, Part 2: Detecting Hips at Risk: Early Biomechanical and Structural Mechanisms

Far more publications are available for osteoarthritis of the knee than of the hip. Recognizing this research gap, the Arthritis Foundation (AF), in partnership with the Hospital for Special Surgery (HSS), convened an in-person meeting of thought leaders to review the state of the science of and clinical approaches to hip osteoarthritis. This article summarizes the recommendations gleaned from 5 presentations given in the "early hip osteoarthritis" session of the 2023 Hip Osteoarthritis Clinical Studies Conference, which took place on February 17 and 18, 2023, in New York City. It also summarizes the workgroup recommendations from a small-group discussion on clinical research gaps.

Glenohumeral osteoarthritis: what the surgeon needs from the radiologist

Glenohumeral osteoarthritis (GHOA) is a widely prevalent disease with increasing frequency due to population aging. Both clinical manifestations and radiography play key roles in the initial diagnosis, staging, and management decisions. Radiographic disease progression evaluation is performed using validated staging systems, such as Kellgren and Lawrence, Samilson, and Hamada. For young patients with mild to moderate GHOA and failed conservative treatment, arthroscopic preservation surgery (APS) is usually considered. Older patients and those with severe GHOA benefit from different types of arthroplasties. Preoperative magnetic resonance imaging (MRI) is essential for APS surgical planning, as it maps repairable labral, cartilage, and rotator cuff lesions. For arthroplasty planning, the status of glenoid cartilage and intactness of rotator cuff as well as glenoid morphology represent key factors guiding the decision regarding the most suitable hardware design, whether resurfacing, partial, total, or reverse joint replacement. Pre-surgical MRI or alternatively computed tomography arthrogram is employed to evaluate the cartilage and rotator cuff. Finally, three-dimensional computed tomography (3D CT) is indicated to optimally assess the glenoid morphology (to determine Walch classification, version, inclination, and bone loss) and analyze the necessity for glenoid osteotomy or graft augmentation to correct the glenoid structural abnormalities for future success and longevity of the shoulder implants or chosen constructs. Understanding the purpose of each imaging and treatment modality allows more efficient image interpretation. This article reviews the above concepts and details what a surgeon needs from a radiologist and could benefit from accurate reporting of preoperative imaging studies.

Diagnostic performance of a 3D double-echo steady-state sequence at 3 T using radial reformats for detecting and grading rotator cuff tears: a pilot diagnostic accuracy study with magnetic resonance imaging and arthroscopic correlation

BACKGROUND

In diagnosing rotator cuff tears (RCTs), magnetic resonance imaging (MRI) is the imaging modality of choice, and its accuracy is improving constantly.

PURPOSE

To evaluate the diagnostic performance of a high-resolution 3D double-echo steady-state (DESS) sequence with radial and paracoronal 3-T MRI regarding the grading of RCTs in correlation with conventional 2D MRI and arthroscopic findings.

MATERIAL AND METHODS

We retrospectively compared arthroscopic findings of RCTs with preoperative MRI, including conventional 2D sequences and radial and paracoronal DESS images in 20 patients. Two observers evaluated supraspinatus (SSP), infraspinatus (ISP), and subscapularis (SSC) tendon tears using a grading system. For statistical analysis, arthroscopy was used as the reference standard.

RESULTS

Inter-observer agreement for detecting and grading SSP, ISP, and SSC tendon tears on radial and paracoronal sliced 3D DESS MRI was excellent (intraclass-correlation [ICC] = 0.92-0.98; all P < 0.001). Regarding the detection of SSP lesions, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 93.8%, 50%, 88.2%, and 66.7% for both radial and paracoronal DESS imaging. A sensitivity of 100%, specificity of 61.1%, PPV of 22.2%, and NPV of 100% were noted for detecting ISP tendon tears using radially reformatted DESS images. Regarding detecting SSC tendon tears using radially reformatted DESS images, sensitivity, specificity, PPV, and NPV were 100%, 81.3%, 50%, and 100%, respectively. The results with standard 2D MRI were similar.

CONCLUSION

The DESS technique with radially reformatted images provided excellent sensitivity and high inter-observer agreement in detecting RCTs. It showed a moderate to high correlation between MRI and arthroscopy for diagnosing SSP and SSC tendon tears.

Deep Learning for Medical Image-Based Cancer Diagnosis

(1) Background: The application of deep learning technology to realize cancer diagnosis based on medical images is one of the research hotspots in the field of artificial intelligence and computer vision. Due to the rapid development of deep learning methods, cancer diagnosis requires very high accuracy and timeliness as well as the inherent particularity and complexity of medical imaging. A comprehensive review of relevant studies is necessary to help readers better understand the current research status and ideas. (2) Methods: Five radiological images, including X-ray, ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI), positron emission computed tomography (PET), and histopathological images, are reviewed in this paper. The basic architecture of deep learning and classical pretrained models are comprehensively reviewed. In particular, advanced neural networks emerging in recent years, including transfer learning, ensemble learning (EL), graph neural network, and vision transformer (ViT), are introduced. Five overfitting prevention methods are summarized: batch normalization, dropout, weight initialization, and data augmentation. The application of deep learning technology in medical image-based cancer analysis is sorted out. (3) Results: Deep learning has achieved great success in medical image-based cancer diagnosis, showing good results in image classification, image reconstruction, image detection, image segmentation, image registration, and image synthesis. However, the lack of high-quality labeled datasets limits the role of deep learning and faces challenges in rare cancer diagnosis, multi-modal image fusion, model explainability, and generalization. (4) Conclusions: There is a need for more public standard databases for cancer. The pre-training model based on deep neural networks has the potential to be improved, and special attention should be paid to the research of multimodal data fusion and supervised paradigm. Technologies such as ViT, ensemble learning, and few-shot learning will bring surprises to cancer diagnosis based on medical images.

Water excitation with LIBRE pulses in three-dimensional variable flip angle fast spin echo for fat-free and large field of view imaging at 3 tesla

PURPOSE

To develop and evaluate a sequence in which water excitation with lipid insensitive binomial off-resonant radio frequency excitation (LIBRE) pulses is incorporated into three-dimensional (3D) variable flip angle fast spin echo (LIBRE-vf-FSE) for fat-free and large field of view imaging at 3 Tesla (T).

MATERIALS AND METHODS

Numerical simulation was conducted to optimize the parameters of LIBRE pulses, including the flip angle, pulse duration, and frequency offset, for maximizing the fat suppression effect of the proposed LIBRE-vf-FSE sequence. The sequence was then implemented at 3 T and assessed in phantoms, lower extremity imaging of 8 healthy volunteers, and head/neck imaging of 5 healthy volunteers. Conventional water excitation (WE) and fat saturation (FatSat) were also performed for comparison. Signal-to-noise ratio (SNR) of fat and contrast-to-noise ratio (CNR) between fat and water were used to evaluate the level of fat suppression. Standard deviation (SD) of SNR was used to evaluate the uniformity of fat suppression.

RESULTS

The numerical simulation demonstrated that LIBRE-vf-FSE enables large volume imaging with uniform fat suppression, which was further confirmed by phantom and healthy volunteer experiments. LIBRE provided the lowest fat SNR and offered more uniform fat suppression compared with the WE and FatSat. Specifically, average oil SNRs obtained by LIBRE (1.10 ms, 360 Hz, and 60°), WE, and FatSat were (180.1 vs. 280.2 vs. 811.2) in phantom experiments, and average fat SNRs and SDs in legs obtained by LIBRE (1.10 ms, 360 Hz, and 60°), WE, and FatSat were (85.1 vs. 105.0 vs. 105.1) and (22.4 vs. 27.4 vs. 56.4) in vivo experiments, respectively.

CONCLUSION

The proposed LIBRE-vf-FSE sequence allows for fat suppression and large field of view imaging at 3 T. It could be an alternative approach for fat-free vf-FSE scan.

Anatomical variants of the acromioclavicular joint influence its visibility in the standard MRI protocol in patients aged 18-31 years

Purpose

Visualization of a structure in orthogonal planes is essential for correct radiological assessment. The aim was to assess the utility of the standard MRI protocol for the shoulder in the assessment of the acromioclavicular joint (ACJ).

Methods

A total of 204 MRI scans of the shoulder were re-reviewed. Visibility of the ACJ in orthogonal planes was assessed, and the type of acromion and the angle between the ACJ and the glenoid cavity were assessed by two observers.

Results

Agreement in the assessment of ACJ visibility was moderate to substantial. The ACJ was visible in the three anatomical views in 48% (confidence interval [CI] 95% = [41–54%]) of the examinations, and no significant difference regarding gender or age was noticed. The mean angle between the ACJ and the glenoid cavity was 41.12 deg. CI95% = (39.72, 42.53) in the axial plane, 33.39 deg. CI95% = (31.33, 35.45) in the coronal plane and 52.49 deg. CI95% = (50.10, 54.86) in the sagittal plane. When the ACJ was visible in the sagittal and axial planes, significant differences were noticed in the remaining planes (p < .05).

Conclusion

Anatomical variations of the ACJ influence its visibility in the standard MRI protocol for examining the shoulder, making this protocol insufficient for ACJ assessment in the examined population.

Diagnostic advantage of thin slice 2D MRI and multiplanar reconstruction of the knee joint using deep learning based denoising approach

The purpose of this study is to evaluate whether thin-slice high-resolution 2D fat-suppressed proton density-weighted image of the knee joint using denoising approach with deep learning-based reconstruction (dDLR) with MPR is more useful than 3D FS-PD multi planar voxel image. Twelve patients who underwent MRI of the knee at 3T and 13 knees were enrolled. Denoising effect was quantitatively evaluated by comparing the coefficient of variation (CV) before and after dDLR. For the qualitative assessment, two radiologists evaluated image quality, artifacts, anatomical structures, and abnormal findings using a 5-point Likert scale between 2D and 3D. All of them were statistically analyzed. Gwet's agreement coefficients were also calculated. For the scores of abnormal findings, we calculated the percentages of the cases with agreement with high confidence. The CV after dDLR was significantly lower than the one before dDLR (p < 0.05). As for image quality, artifacts and anatomical structure, no significant differences were found except for flow artifact (p < 0.05). The agreement was significantly higher in 2D than in 3D in abnormal findings (p < 0.05). In abnormal findings, the percentage with high confidence was higher in 2D than in 3D (p < 0.05). By applying dDLR to 2D, almost equivalent image quality to 3D could be obtained. Furthermore, abnormal findings could be depicted with greater confidence and consistency, indicating that 2D with dDLR can be a promising imaging method for the knee joint disease evaluation.

3D MRI of the Knee

Three-dimensional (3D) magnetic resonance imaging (MRI) of the knee is widely used in musculoskeletal (MSK) imaging. Currently, 3D sequences are most commonly used for morphological imaging. Isotropic 3D MRI provides higher out-of-plane resolution than standard two-dimensional (2D) MRI, leading to reduced partial volume averaging artifacts and allowing for multiplanar reconstructions in any plane with any thickness from a single high-resolution isotropic acquisition. Specifically, isotropic 3D fast spin-echo imaging, with options for tissue weighting similar to those used in multiplanar 2D FSE imaging, is of particular interest to MSK radiologists. New applications for 3D spatially encoded sequences are also increasingly available for clinical use. These applications offer advantages over standard 2D techniques for metal artifact reduction, quantitative cartilage imaging, nerve imaging, and bone shape analysis. Emerging fast imaging techniques can be used to overcome the long acquisition times that have limited the adoption of 3D imaging in clinical protocols.

3D MRI of the Rheumatic Diseases

Magnetic resonance imaging (MRI) is commonly used to evaluate musculoskeletal pathologies due to its high spatial resolution and excellent tissue contrast. The diagnosis of rheumatic diseases can often be challenging. Investigation with conventional two-dimensional MRI is helpful for diagnosis and monitoring treatment. In the past few years, three-dimensional (3D) MRI has been more commonly used to assess joint pathologies including inflammatory and rheumatic diseases. This review discusses the techniques and protocols of 3D MRI and its diagnostic yield in the assessment of rheumatic diseases, along with different examples.

3D MRI of the Shoulder

Magnetic resonance imaging provides a comprehensive evaluation of the shoulder including the rotator cuff muscles and tendons, glenoid labrum, long head biceps tendon, and glenohumeral and acromioclavicular joint articulations. Most institutions use two-dimensional sequences acquired in all three imaging planes to accurately evaluate the many important structures of the shoulder. Recently, the addition of three-dimensional (3D) acquisitions with 3D reconstructions has become clinically feasible and helped improve our understanding of several important pathologic conditions, allowing us to provide added value for referring clinicians. This article briefly describes techniques used in 3D imaging of the shoulder and discusses applications of these techniques including measuring glenoid bone loss in anterior glenohumeral instability. We also review the literature on routine 3D imaging for the evaluation of common shoulder abnormalities as 3D imaging will likely become more common as imaging software continues to improve.

Comparison of CAIPIRINHA-accelerated 3D fat-saturated-SPACE MRI with 2D MRI sequences for the assessment of shoulder pathology

OBJECTIVES

To compare the performance of 6-min MRI with a fat-saturated 3D-controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) Sampling perfection with application-optimized contrast using different flip angle evolution (SPACE) TSE protocol with 10-min 2D TSE MRI protocol for assessment of abnormalities of the shoulder.

METHODS

Forty-nine subjects underwent both 3D fat-saturated-CAIPIRINHA SPACE and 2D TSE sequences of the shoulder on a 3.0-T system. Following randomization and anonymization, two musculoskeletal radiologists evaluated the 2D and 3D images independently for image quality and diagnostic capability. Descriptive statistics, inter-observer, and inter-method concordance were investigated. p values < 0.05 were considered significant.

RESULTS

For image quality assessment, 2D images were similar to 3D CAIPIRINHA SPACE images (p = 0.05). 3D had lower noise standard deviation (SD) and higher fluid CNR than 2D images (p = 0.00). For diagnostic capability assessment, using 2D TSE as a standard of reference, sensitivity, specificity, and accuracy of 3D SPACE were, respectively, 94.81%, 94.12%, and 94.39% for tendon abnormalities; 97.06%, 80.00%, and 91.84% for acromioclavicular joint abnormalities; 88.89%, 100.00%, and 93.89% for adjacent bone alterations; and 97.30%, 100%, and 97.96% for joint fluid/effusion assessment. The inter-method concordance was moderate to almost perfect. The inter-observer-concordance of the shoulder assessment was also moderate to almost perfect, with SSP lesions demonstrating the greatest concordance.

CONCLUSIONS

The performance of 6-min 3D fat-saturated-CAIPIRINHA SPACE MRI for shoulder MRI is similar to that of 10-min 2D TSE MRI. 3D fat-saturated-CAIPIRINHA SPACE MRI can be utilized to reduce scan time without degradation in image quality.

KEY POINTS

• CAIPIRINHA acceleration 3D fat-saturated-MRI of the shoulder is achievable in 6 min with high spatial resolution. • 3D fat-saturated CAIPIRINHA MRI is similar to 2D MRI in the shoulder assessment. • 3D CAIPIRINHA MRI images enable rapid diagnosis of shoulder abnormalities without image quality degradation.

How to Measure Glenoid Bone Stock and Version and Why It Is Important: A Practical Guide

Shoulder osteoarthritis (OA) is a common and debilitating condition and a source of high morbidity and medical expenditures across the world among individuals older than 60 years. Shoulder OA results in the gradual destruction of articular cartilage of the humeral head and glenoid component, causing inflammation, pain, and a restricted range of motion. Most patients are diagnosed with shoulder OA after experiencing shoulder pain and stiffness, and the diagnosis is often made after medical and physical histories are obtained and physical and imaging examinations are performed. Use of various surgical techniques such as total anatomic or reverse shoulder arthroplasty and hemiarthroplasty has increased in recent years, resulting in reduced morbidity and improved functional status of patients. However, the rate of surgical complications such as premature loosening of components is significant, reducing the effectiveness of such procedures. Data in the literature indicate that high-grade fatty infiltration of the rotator cuff muscle before surgery is associated with postoperative glenoid component loosening. High-grade rotator cuff fatty infiltration and atrophy have been found to be associated with more severe Walch classification-based glenoid morphology subtypes, increased joint line medialization, glenoid bone loss, and increased pathologic glenoid version. The authors describe how advanced imaging techniques are used for preoperative evaluation of the shoulder and discuss how to measure glenoid version and bone stock and classify glenoid morphology types on the basis of Walch classification, as these parameters are commonly used in surgical planning. Methods involving the use of Friedman and paleoglenoid lines for respective measurements are illustrated by using three-dimensional CT and MRI case examples. ^©RSNA, 2020.

Evaluation of an accelerated 3D modulated flip-angle technique in refocused imaging with an extended echo-train sequence with compressed sensing for imaging of the knee: comparison with routine 2D MRI sequences

AIM

To accelerate the acquisition of high-resolution magnetic resonance imaging (MRI) by using the three-dimensional (3D) matrix sequence with compressed sensing and to compare it with conventional two-dimensional (2D) proton-density (PD) and fast spin-echo (FSE) sequences.

MATERIALS AND METHODS

3D matrix, 2D FSE, and PD sequences were acquired from 68 participants using 3 T magnetic resonance imaging (MRI). Two radiologists scored image quality independently on a four-point scale. The structural similarity index (SSIM), and signal- (SNRs) and contrast-to-noise ratios (CNRs) of different anatomical structures of the knee were assessed and compared between sequences using Wilcoxon signed-rank tests and Cohen's kappa.

RESULTS

The median acquisition time reduction was 44.5%. There was a substantial to perfect agreement for the rating between the 3D matrix FSE and 2D FSE or PD sequences when evaluating cartilage, subchondral bone, and ligaments (κ=0.783-872, p>0.05). The mean SSIM values between the 3D matrix FSE and 2D FSE, and between the 3D matrix PD and 2D PD sequences was 0.994 and 0.971, respectively, which are acceptable. No significant differences were found in SNR between the 3D matrix FSE and 2D FSE, and between the 3D matrix PD and 2D PD sequences, even though the SNR appeared to be higher on routine 2D sequences. The CNR of subchondral bone-meniscus, subchondral bone-joint fluid, and meniscus-joint fluid did not differentiate significantly between the 3D matrix sequence and routine 2D sequences.

CONCLUSIONS

3D matrix reduced the acquisition time in routine clinical knee MRI without the loss in image quality, SNR, and CNR.

3T magnetic resonance for evaluation of adult pulmonary tuberculosis

OBJECTIVES

To evaluate image quality and detection rate of four 3T magnetic resonance imaging (MRI) sequences and MRI performances in pulmonary tuberculosis (TB) when compared to computed tomography (CT).

METHODS

Forty patients with pulmonary tuberculosis separately underwent CT and 3T-MRI with T1-weighted free-breathing star-volumetric interpolated breath-hold examination (Star-VIBE) and standard VIBE, T2-weighted two-dimensional fast BLADE turbo spin-echo (2D-fBLADE TSE) and three-dimensional isotropic turbo spin-echo (3D-SPACE). Four MRI sequences were compared in terms of detection rate and image quality, which consisted of signal to noise ratio (SNR), contrast to noise ratio (CNR) and 5-point scoring scale. The total sensitivity was also compared between CT and MRI. Inter-observer agreement on 5-point scoring scale was calculated by Cohen's kappa (k). SNR, CNR and 5-point scoring scale were compared using two-tailed pared t-test. Using CT as a reference, the MRI detection rate of pulmonary abnormality was evaluated by Pearson's Chi-square test. Furthermore, the sizes of the nodules (≥5 mm) were compared using intraclass correlation coefficient.

RESULTS

In this study, Free-breathing Star-VIBE had significantly better SNR and identical CNR compared with standard VIBE. 2D-fBLADE TSE had statistically higher SNR but uniform or inferior CNR compared with 3D-SPACE. Inter-observers showed excellent agreement on 5-point scoring scale. The average score of Star-VIBE and VIBE had no difference. The average score of 2D-fBLADE TSE was higher than 3D-SPACE. There were no statistical differences in the detection rates of non-calcified parenchymal lesions between Star-VIBE and standard VIBE, 2D-fBALDE TSE and 3D-SPACE. MRI is comparable to CT in detecting consolidation, cavity, non-calcified nodules of ≥5 mm and tree-in-bud signs compared to CT. MRI detected non-calcified nodules of ＜5 mm, 5-10 mm, ≥10 mm and calcified nodules with sensitivity of 69.6%, 90.6%, 100% and 89.5% respectively. In addition, the sizes of the nodules (≥5 mm) had statistical consistency. MRI is more sensitive in detecting caseous necrosis, liquefaction, active cavity, abnormalities of lymph nodes and pleura.

CONCLUSIONS

T1-weighted free-breathing Star-VIBE and T2-weighted 2D-fBLADE TSE, both with satisfactory image quality, are suitable for patients with pulmonary TB who need long-term follow-ups in clinical routine, especially for children, young women and pregnant women.

Baseline and early 3D-CUBE volume reconstruction of locally advanced rectal cancer to predict tumor response after neoadjuvant chemotherapy

PURPOSE

To explore whether volumetric measurements of 3D-CUBE sequences based on baseline and early treatment time can predict neoadjuvent chemotherapy (NCT) efficacy of locally advanced rectal cancer (LARC).

MATERIAL AND METHOD

73 patients with LARC were enrolled from February 2014 to January 2018. All patients underwent MRIs during the baseline period before NCT (BL-NCT) and the first month of NCT (FM-NCT), and tumor volume (TV) was measured using 3D-CUBE, and tumor volume reduction (TVR) and tumor volume reduction rate (TVRR) were calculated. In addition, tumor invasion depth, tumor maximal length, range of tumor involvement in the circumference of intestinal lumen and distance from inferior part of tumor to the anal verge were measured using baseline high-spatial-resolution T2-weighted MRIs. All patients were categorized into sensitive and insensitive groups based on post-surgical pathology after completion of the full courses of NCT. The receiver operating characteristic (ROC) curve was used to analyze the value of different MRI parameters in predicting efficacy of NCT.

RESULTS

Statistically significant differences in TV of BL-NCT, TVR and TVRR from BL-NCT to FM-NCT were detected between sensitive and insensitive groups (P < 0.05, respectively). The areas under the curves (AUC) of ROC of TVR and TVRR in predicting efficacy of NCT (0.890 [95% CI, 0.795∼0.951], 0.839 [95% CI, 0.735∼0.915]) were significantly better than that of TV (0.660 [95% CI, 0.540∼0.767]) (P < 0.05, respectively).

CONCLUSION

Reconstruction of 3D-CUBE volume in the first month of NCT is necessary, and both TVR and TVRR can be used as early predictors of NCT efficacy.

Diagnostic performance of 3D-multi-Echo-data-image-combination (MEDIC) for evaluating SLAP lesions of the shoulder

Background

Superior labral anterior to posterior (SLAP) lesions remain a clinical and diagnostic challenge in routine (non-arthrographic) MR examinations of the shoulder. This study prospectively evaluated the ability of 3D-Multi-Echo-Data-Image-Combination (MEDIC) compared to that of routine high resolution 2D-proton-density weighted fat-saturated (PD fs) sequence using 3 T-MRI to detect SLAP lesions using arthroscopy as gold standard.

Methods

Seventeen consecutive patients (mean age, 51.6 ± 14.8 years, 11 males) with shoulder pain underwent 3 T MRI including 3D-MEDIC and 2D-PD fs followed by arthroscopy. The presence or absence of SLAP lesions was evaluated using both sequences by two independent raters with 4 and 14 years of experience in musculoskeletal MRI, respectively. During arthroscopy, SLAP lesions were classified according to Snyder’s criteria by two certified orthopedic shoulder surgeons. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 3D-MEDIC and 2D-PD fs for detection of SLAP lesions were calculated with reference to arthroscopy as a gold standard. Interreader agreement and sequence correlation were analyzed using Cohen’s kappa coefficient.

Figure 1 demonstrates the excellent visibility of a proven SLAP lesion using the 3D-MEDIC and Fig. 2 demonstrates a false-positive case.

Results

Arthroscopy revealed SLAP lesions in 11/17 patients. Using 3D-MEDIC, SLAP lesions were diagnosed in 14/17 patients by reader 1 and in 13/17 patients by reader 2. Using 2D-PD fs, SLAP lesions were diagnosed in 11/17 patients by reader 1 and 12/17 patients for reader 2. Sensitivity, specificity, PPV, and NPV of 3D-MEDIC were 100.0, 50.0, 78.6, and 100.0% for reader 1; and 100.0, 66.7, 84.6, and 100% for reader 2, respectively. Sensitivity, specificity, PPV, and NPV of 2D-PD fs were 90.9, 83.3, 90.9, and 83.3% for reader 1 and 100.0, 83.3, 91.7, and 100.0% for reader 2. The combination of 2D-PD fs and 3D-MEDIC increased specificity from 50.0 to 83.3% for reader 1 and from 66.7 to 100.0% for reader 2. Interreader agreement was almost perfect with a Cohen’s kappa of 0.82 for 3D-MEDIC and 0.87 for PD fs.

Conclusions

With its high sensitivity and NPV, 3D-MEDIC is a valuable tool for the evaluation of SLAP lesions. As the combination with routine 2D-PD fs further increases specificity, we recommend incorporation of 3D-MEDIC as an additional sequence in conventional shoulder protocols in patients with non-specific shoulder pain.

Gadoterate Meglumine Administration in Multiple Sclerosis has no Effect on the Dentate Nucleus and the Globus Pallidus Signal Intensities

RATIONALE AND OBJECTIVES

Previous studies on possible accumulation of gadolinium-based contrast agents (GBCA) in the brain suggest that macrocyclic GBCA are less likely to accumulate than linear GBCA. However, conflicting results have been reported, especially in MS. The aim of this study is to investigate retrospectively the correlation between gadoterate-meglumine (macrocyclic GBCA) use and T1 signal intensity changes (SI) in the dentate nucleus and the GP on unenhanced T1-weighted images in a large cohort of MS patients.

MATERIALS AND METHODS

Unenhanced T1-weighted images of 232 MS patients who previously received multiple intravenous administrations of 0.1 mmol/kg of gadoterate-meglumine were reviewed. The change in T1 SI ratios of dentate nucleus/central pons (DN/CP) and globus pallidus/centrum semiovale (GP/CSO) was calculated between the first and last MRIs and correlated with age, number of injections, time interval between MRIs, disease duration, activity, and therapy.

RESULTS

DN/CP ratio showed no significant changes whereas the GP/CSO ratio showed a significant decrease (p < 0.0001) between the first and last MRIs. Multivariable analyses of both ratios, controlling for age, disease duration, and time interval between MRIs, showed no significant correlation between the number of gadolinium injections and the differences in DN/CP (standardized beta = -0.018, p = 0.811) or GP/CSO SI ratios (standardized beta = -0.049, p = 0.499).

CONCLUSION

Repeated administration of gadoterate-meglumine in MS patients did not result in increased T1 SI in the DN or the GP. The significant decrease of GP/CSO ratio between the first and last MRIs is not due to gadolinium accumulation but rather to varying MR parameters.

Patterns of cartilage degeneration in knees with medial tibiofemoral offset

OBJECTIVE

To determine if radiographic medial tibiofemoral offset (MTFO) is associated with: (1) magnetic resonance imaging (MRI) pathology of cartilage, meniscus, and ligament; and (2) a distinct pattern of lateral cartilage degeneration on MRI.

MATERIALS AND METHODS

Three hundred consecutive adult knee MRIs with anteroposterior (AP) radiographs were retrospectively reviewed, and 145 studies were included. MTFO was defined as a medial extension of the medial femoral condyle beyond the articular surface of the medial tibial plateau on weight-bearing AP radiographs. The patients were then divided into the MTFO (n = 61) or no-offset (n = 84) groups. On MRI data obtained on a 1.5-Tesla system, articular cartilage of the femoral condyle and tibial plateau were graded using a modified Outerbridge classification (36 sub-regions similar to whole-organ MRI Score (WORMS) system). In addition, MR pathology of the ACL, MCL, LCL, medial and lateral menisci, were determined.

RESULTS

Significantly increased (ANOVA p < 0.007) MR grade of the ligaments, menisci, and cartilage in the MTFO group (ranging from 0.3 to 2.5) compared to the control group (0.2 to 1.1). Color maps of the cartilage grades suggested a marked difference in both severity of degeneration and regional variations between the groups. MTFO group exhibited focally increased cartilage grades in the central, non-weight regions of lateral compartment (region p = 0.07 to 0.12, interaction p = 0.05 to 0.1).

CONCLUSIONS

MTFO is associated with overall degeneration of the knee and features a distinct lateral cartilage degeneration pattern, which may reflect non-physiologic contact of the cartilage between the lateral tibial eminence and lateral central femoral condyle.

Utility of radial reformation of three-dimensional fat-suppressed multi-echo gradient-recalled-echo images for the evaluation of acetabular labral injuries and femoroacetabular impingement

OBJECTIVES

To assess the utility of the radial reformation of three-dimensional fat-suppressed multi-echo gradient-recalled-echo (3D FS me-GRE) for evaluating acetabular labral injuries and femoroacetabular impingement (FAI).

MATERIALS AND METHODS

A total of 25 patients with suspected acetabular labral injuries were examined using 3D FS me-GRE and radial 2D T2*-weighted imaging (T2*WI) on a 3-T magnetic resonance imaging (MRI) scanner. The range of acetabular labral injuries was evaluated by radial reformation through the center of the acetabulum perpendicular to the plane across the entire acetabular rim (type 1 radial reformation) of 3D FS me-GRE and radial 2D T2*WI. To evaluate the FAI morphology, we performed radial reformation perpendicular to the central axis of the femoral head and neck (type 2 radial reformation) of 3D FS me-GRE.

RESULTS

Acetabular labral injuries were identified in 23 patients, and no acetabular labral injury was seen in two patients on type 1 radial reformation of 3D FS me-GRE and radial 2D T2*WI. The diagnostic concordance rate for the range of acetabular labral injuries between the two imaging methods was 76.0%, and there was excellent agreement for the injured angles (r = 0.977, p < 0.001). FAI morphology could be evaluated in all patients (no FAI, n = 8; cam, n = 10; pincer, n = 4; combined cam and pincer, n = 3) using type 2 radial reformation of 3D FS me-GRE.

CONCLUSIONS

Type 1 and type 2 radial reformations of 3D FS me-GRE imaging were useful for evaluating acetabular labral injuries and determining whether patients with acetabular labral injuries have FAI, respectively.

Increased diagnostic confidence in the diagnosis of pituitary micro-lesions with the addition of three-dimensional sampling perfection with application-optimized contrasts using different flip-angle evolutions sequences

BACKGROUND

Conventional magnetic resonance imaging (MRI) is adversely affected by thick slices, small intersection gaps, and the partial volume effect, leading to the missed diagnosis or misdiagnosis of pituitary micro-lesions.

PURPOSE

To evaluate the diagnostic yield of three-dimensional sampling perfection with application-optimized contrasts using different flip-angle evolutions (3D-T2 SPACE) sequences compared with a standard MRI protocol for the diagnosis of pituitary micro-lesions.

MATERIAL AND METHODS

The MRI findings of 664 patients with clinically suspected pituitary lesions were retrospectively analyzed. All patients underwent coronal 3D-T2 SPACE sequences followed by T1-weighted (T1W) imaging. Conventional scanning sequences included coronal and sagittal T1W imaging and post-contrast enhanced coronal and sagittal T1 imaging. All images were independently evaluated by two experienced neuroradiologists. The inter-observer agreement was analyzed using kappa statistics.

RESULTS

Compared with conventional sequences, there was an increase in diagnostic confidence of 60.3% for the diagnosis of pituitary micro-lesions with the addition of 3D-T2 SPACE sequences. The lesion conspicuity scores of combined conventional and 3D-T2 SPACE sequences were significantly higher than those of conventional imaging (z = -6.403, P < 0.01) and 3D-T2 SPACE sequences (z = -4.243, P < 0.01). In addition, the inter-observer agreement of 3D-T2 SPACE sequences was good (κ = 0.826).

CONCLUSION

Combined with routine sequences, post-contrast enhanced 3D-T2 SPACE sequences effectively improve diagnostic confidence in the diagnosis of pituitary micro-lesions. Post-contrast enhanced 3D-T2 SPACE is suitable for detecting pico-adenomas, micro-lesions adjacent to the cavernous sinuses or sellar floor, lesions between the anterior and posterior lobes, and lesions with early phase enhancement.

Assessment of Anterolateral Complex Injuries by Magnetic Resonance Imaging in Patients With Acute Rupture of the Anterior Cruciate Ligament

PURPOSE

To assess anterolateral complex (ALC) injuries in patients with acute anterior cruciate ligament (ACL) rupture on magnetic resonance imaging (MRI).

METHODS

Patients with acute ACL rupture who underwent ACL surgery between 2015 and 2017 and underwent MRI within 6 weeks of the initial trauma were included. Two radiologists assessed magnetic resonance images retrospectively for the status of the ALC, including the iliotibial band (ITB), Kaplan fibers, and anterolateral ligament (ALL), as follows: grade 0, normal; grade 1, periligamentous edema; grade 2, partial tear; and grade 3, complete tear. The findings were analyzed using the Friedman test and weighted κ values.

RESULTS

Sixty-nine MRI scans were reviewed. Of the 69 patients, 51% had associated injuries to the ITB (grade 1, n = 31; grade 2, n = 4), 33% had associated injuries to the Kaplan fibers (grade 1, n = 21; grade 2, n = 2), and 57% had associated injuries to the ALL (grade 1, n = 12; grade 2, n = 22; grade 3, n = 5). We found a significant difference in the frequency and grading between ITB, Kaplan fiber, and ALL injuries (P ≤ .032). Inter-reader agreement for assessing the ALC on MRI was almost perfect (κ ≥ 0.922).

CONCLUSIONS

On the basis of MRI analysis, ALL injuries were found with varying degrees of severity and intensity with noted injuries to associated surrounding fibers in patients with acute ACL rupture.

LEVEL OF EVIDENCE

Level IV, case series.

Evaluation of diagnostic value and T2-weighted three-dimensional isotropic turbo spin-echo (3D-SPACE) image quality in comparison with T2-weighted two-dimensional turbo spin-echo (2D-TSE) sequences in lumbar spine MR imaging

Purpose

to evaluate diagnostic value and image quality of T2-weighted Three-dimensional isotropic turbo spin-echo (SPACE) in comparison with T2-weighted two-dimensional turbo spin-echo (TSE) sequences for comprehensive evaluation of lumbar spine pathologies.

Materials and methods

Thirty-five participants with lumbar discopathy were examined on a 1.5-T MRI system with both 2D TSE and 3D SPACE sequences. Obtained images were analyzed with synedra view personal (V 17.0.0.2) software in terms of calculating image quality factors such as signal to noise ratio (SNR) and contrast to noise ratio (CNR) for selected regions of interest. In addition, images were referred to radiologists to report their pathologic indexes. The visibility of anatomical structures in the 3D and 2D sequences was qualitatively assessed by two radiologists independently. Cohen's kappa (k) and Wilcoxon signed rank test was used for the statistical analysis.

Results

In this study, the 3D SPACE T2-weighted sequence showed significant higher SNR and CNR as well as visibility in all of the regions of interest except vertebrae and intervertebral discs (p-value < 0.05). Inter-observer agreement for visibility of regions of interest was substantial and perfect (k > 0.6). Also, inter-observer and inter-method agreements for pathologic indexes were substantial and perfect for all of the pathologic indexes (k > 0.6). Inter-observer agreement for 3D SPACE sequence was higher (k = 0.793) in comparison with 2D-TSE sequence (k = 0.603). 3D SPACE sequence and its multi-planar reconstructions (MPR) scan time were less (192 s) than 2D TSE in the sagittal, axial and coronal planes (209 s).

Conclusion

3D SPACE sequence for lumbar spine MRI proved to have higher SNR, CNR, and visibility for all regions of lumbar spine except vertebrae and disc. Inter-observer and inter-method agreements for pathologic indexes between 3D SPACE and 2D TSE sequences were substantial and 3D SPACE had a higher inter-observer agreement and less scan time. Therefore, T2 weighted 3D SPACE sequence, and its MPR might be an excellent alternative for 2D TSE in sagittal, axial, and coronal planes, especially for patients with abnormal curvature of the lumbar spine.

Feasibility of 3D black-blood variable refocusing angle fast spin echo cardiovascular magnetic resonance for visualization of the whole heart and great vessels in congenital heart disease

BACKGROUND

Volumetric black-blood cardiovascular magnetic resonance (CMR) has been hampered by long scan times and flow sensitivity. The purpose of this study was to assess the feasibility of black-blood, electrocardiogram (ECG)-triggered and respiratory-navigated 3D fast spin echo (3D FSE) for the visualization of the whole heart and great vessels.

METHODS

The implemented 3D FSE technique used slice-selective excitation and non-selective refocusing pulses with variable flip angles to achieve constant echo signal for tissue with T1 (880 ms) and T2 (40 ms) similar to the vessel wall. Ten healthy subjects and 21 patients with congenital heart disease (CHD) underwent 3D FSE and conventional 3D balanced steady-state free precession (bSSFP). The sequences were compared in terms of ability to perform segmental assessment, local signal-to-noise ratio (SNRl) and local contrast-to-noise ratio (CNRl).

RESULTS

In both healthy subjects and patients with CHD, 3D FSE showed superior pulmonary vein but inferior coronary artery origin visualisation compared to 3D bSFFP. However, in patients with CHD the combination of 3D bSSFP and 3D FSE whole-heart imaging improves the success rate of cardiac morphological diagnosis to 100% compared to either technique in isolation (3D FSE, 23.8% success rate, 3D bSSFP, 5% success rate). In the healthy subjects SNRl for 3D bSSFP was greater than for 3D FSE (30.1 ± 7.3 vs 20.9 ± 5.3; P = 0.002) whereas the CNRl was comparable (17.3 ± 5.6 vs 17.4 ± 4.9; P = 0.91) between the two scans.

CONCLUSIONS

The feasibility of 3D FSE for whole-heart black-blood CMR imaging has been demonstrated. Due to their high success rate for segmental assessment, the combination of 3D bSSFP and 3D FSE may be an attractive alternative to gadolinium contrast enhanced morphological CMR in patients with CHD.

Super-resolution musculoskeletal MRI using deep learning

PURPOSE

To develop a super-resolution technique using convolutional neural networks for generating thin-slice knee MR images from thicker input slices, and compare this method with alternative through-plane interpolation methods.

METHODS

We implemented a 3D convolutional neural network entitled DeepResolve to learn residual-based transformations between high-resolution thin-slice images and lower-resolution thick-slice images at the same center locations. DeepResolve was trained using 124 double echo in steady-state (DESS) data sets with 0.7-mm slice thickness and tested on 17 patients. Ground-truth images were compared with DeepResolve, clinically used tricubic interpolation, and Fourier interpolation methods, along with state-of-the-art single-image sparse-coding super-resolution. Comparisons were performed using structural similarity, peak SNR, and RMS error image quality metrics for a multitude of thin-slice downsampling factors. Two musculoskeletal radiologists ranked the 3 data sets and reviewed the diagnostic quality of the DeepResolve, tricubic interpolation, and ground-truth images for sharpness, contrast, artifacts, SNR, and overall diagnostic quality. Mann-Whitney U tests evaluated differences among the quantitative image metrics, reader scores, and rankings. Cohen's Kappa (κ) evaluated interreader reliability.

RESULTS

DeepResolve had significantly better structural similarity, peak SNR, and RMS error than tricubic interpolation, Fourier interpolation, and sparse-coding super-resolution for all downsampling factors (p < .05, except 4 × and 8 × sparse-coding super-resolution downsampling factors). In the reader study, DeepResolve significantly outperformed (p < .01) tricubic interpolation in all image quality categories and overall image ranking. Both readers had substantial scoring agreement (κ = 0.73).

CONCLUSION

DeepResolve was capable of resolving high-resolution thin-slice knee MRI from lower-resolution thicker slices, achieving superior quantitative and qualitative diagnostic performance to both conventionally used and state-of-the-art methods.

Accelerated MRI of the Lumbar Spine Using Compressed Sensing: Quality and Efficiency

BACKGROUND

Decreasing MRI scan time is a key factor to increase patient comfort and compliance as well as the productivity of MRI scanners.

PURPOSE/HYPOTHESIS

Compressed sensing (CS) should significantly accelerate 3D scans. This study evaluated the clinical application and cost effectiveness of accelerated 3D T₂ sequences of the lumbar spine.

STUDY TYPE

Prospective, cross-sectional, observational.

POPULATION

Twenty healthy volunteers and 10 patients.

FIELD STRENGTH/SEQUENCE

A 3D T₂ TSE sequence, identical 3D sequences with three different parallel imaging and CS accelerating factors, and 2D TSE sequences as a clinical reference were obtained on a 3T scanner.

ASSESSMENT

Three readers evaluated the sequences for delineation of anatomical structures and image quality. A quantitative analysis consisting of root mean square error, structural similarity index, signal-to-noise ratio, and contrast-to-noise ratio were performed. The scan times were used to calculate cost differences for each sequence.

STATISTICAL TESTS

An analysis of variance with repeated measurements and the Friedman test were used to test for potential differences between the sequences. Post-hoc analysis was made with the chi-squared and Tukey-Kramer test.

RESULTS

CS with factor 4.5 results in unchanged image quality compared to the T₂ TSE for volunteers and patients (overall image impression: 4.75 vs. 4.20 [P = 0.73] and 4.90 vs. 4.47 [P = 0.44]). The CS 4.5 scan is 167 seconds (-39%) faster than the 3D and 216.5 seconds (-45%) faster than the 2D sequences. No significant differences was found for the diagnostic certainty in the volunteers and patients between 2D TSE and 3D CS 4.5 (P = 0.89 and P = 0.43). A reduction of scan time to 148 seconds (CS 8) was still rated acceptable for most diagnosis.

DATA CONCLUSION

CS accelerates the 3D T₂ without compromising image quality. The 3D sequences offer comparable diagnostic quality to the clinical 2D standard with less scan time (-45%), potentially increasing the productivity of MRI scanners.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 6 J. Magn. Reson. Imaging 2019;49:e164-e175.

Medial meniscal extrusion: Detection, evaluation and clinical implications

The menisci play an important role in knee kinematics. Their unique anatomy allows them to channel forces generated during knee movements through the larger tibio-femoral condylar surfaces while simultaneously resisting deleterious hoop stresses. Although physiologic meniscal extrusion occurs with every knee joint movement, pathologic meniscal extrusion subjects the knee to persistent and excessive load transmission. This renders the knee structures susceptible to injury or exacerbates worsening of existing knee joint internal derangement. Detection and quantification of meniscus extrusion is important given its association with underlying pathological processes and internal derangements such as cartilage loss, osteoarthritis and meniscal tears. The medial and lateral menisci vary in size, attachments and load transmission, and the medial meniscus is more susceptible to injury. In this article, the authors illustrate the role of meniscus kinematics, and the identification and quantification of medial meniscal extrusion. Multimodality imaging appearances and implications of presence of medial meniscal extrusion in different knee joint pathologies are discussed with review of the relevant literature.

Accuracy of 3 Tesla magnetic resonance imaging using detection of fiber loss and a visual analog scale for diagnosing partial and complete cranial cruciate ligament ruptures in dogs

Canine cranial cruciate ligament rupture is often bilateral and asymmetrical, ranging from partial to complete rupture. The purpose of our diagnostic accuracy study was to assess the accuracy of 3 Tesla magnetic resonance imaging (MRI) detection of fiber loss and use of a visual analog scale in the diagnosis of complete versus partial cranial cruciate ligament rupture in 28 clinical dogs with unilateral complete rupture and contralateral partial rupture. Three Tesla MRI was performed on 56 stifles using sagittal sequences (T2-weighted fast spin echo with fat saturation, proton density fast spin echo, and T2-weighted 3D fast spin echo CUBE). Two MRI observers assessed the cranial cruciate ligament for fiber loss and completed a visual analog scale. The MRI data were compared to arthroscopy and clinical status. Accuracy classifying partial or complete rupture was assessed using receiver operating characteristic analysis. Compared to arthroscopy, for complete cranial cruciate ligament rupture, sensitivity, specificity, and accuracy of MRI detection of fiber loss were 0.78, 0.50-0.60, and 0.68-0.71, respectively, and, for partial tears, specificity was 1.00. An MRI visual analog scale score ≥79 was indicative of complete cranial cruciate ligament rupture (sensitivity 0.72-0.94 and specificity 0.71-0.84). Using a visual analog scale cut-point ≥79, observers achieved good accuracy discriminating clinical status of partial or complete cranial cruciate ligament rupture (area under the curve 0.87-0.93). MRI evaluation for fiber loss and use of a visual analog scale are specific in stifles with clinically stable partial cranial cruciate ligament rupture. In stifles with clinically unstable complete cranial cruciate ligament rupture, both MRI tests are sensitive though not specific compared to arthroscopy. As a diagnostic imaging method, MRI may help guide treatment in patients with cranial cruciate ligament damage, particularly for stable partial rupture.

Routine clinical knee MR reports: comparison of diagnostic performance at 1.5 T and 3.0 T for assessment of the articular cartilage

OBJECTIVE

Accurate assessment of knee articular cartilage is clinically important. Although 3.0 Tesla (T) MRI is reported to offer improved diagnostic performance, literature regarding the clinical impact of MRI field strength is lacking. The purpose of this study is to compare the diagnostic performance of clinical MRI reports for assessment of cartilage at 1.5 and 3.0 T in comparison to arthroscopy.

MATERIALS AND METHODS

This IRB-approved retrospective study consisted of 300 consecutive knees in 297 patients who had routine clinical MRI and arthroscopy. Descriptions of cartilage from MRI reports of 165 knees at 1.5 T and 135 at 3.0 T were compared with arthroscopy. The sensitivity, specificity, percent of articular surfaces graded concordantly, and percent of articular surfaces graded within one grade of the arthroscopic grading were calculated for each articular surface at 1.5 and 3.0 T. Agreement between MRI and arthroscopy was calculated with the weighted-kappa statistic. Significance testing was performed utilizing the z-test after bootstrapping to obtain the standard error.

RESULTS AND CONCLUSIONS

The sensitivity, specificity, percent of articular surfaces graded concordantly, and percent of articular surfaces graded within one grade were 61.4%, 82.7%, 62.2%, and 77.5% at 1.5 T and 61.8%, 80.6%, 59.5%, and 75.6% at 3.0 T, respectively. The weighted kappa statistic was 0.56 at 1.5 T and 0.55 at 3.0 T. There was no statistically significant difference in any of these parameters between 1.5 and 3.0 T. Factors potentially contributing to the lack of diagnostic advantage of 3.0 T MRI are discussed.

MRI anatomical preoperative evaluation of distally based peroneus brevis muscle flap in reconstructive surgery of the lower limb

BACKGROUND

The distally based peroneus brevis muscle flap has proved to be a simple solution for small- to moderate-sized wounds of the lower limb. The length of the muscle belly suitable for coverage is a crucial parameter. In this study, we evaluated the capability of 3D MRI of the lower limb to measure it preoperatively.

METHODS

Between 2008 and 2017, 32 patients with lower limb defects underwent preoperative MRI to measure the peroneus brevis muscle length. All patients underwent reconstruction, and the muscle was measured again intraoperatively during surgical dissection. Surgical measurements were then compared to the MRI ones.

RESULTS

MRI measures of the peroneus brevis muscle belly ranged from 9 to 21 cm (μ = 14.44 ± 3.43 cm), and intraoperative measures ranged from 9 to 20 cm (μ = 14.2 ± 2.3 cm). Thirty of 32 intraoperative measures corresponded to the MRI ones (variation = ± 1 cm, r = 0.92, p = 0.002). One patient showed an intraoperative muscle length 3 cm shorter than the MRI measure, and another patient had intraoperative muscle length 3 cm longer than the MRI one. All flaps survived, and no secondary local flap coverage was required, with no flap-related complication, limited donor site morbidity, and acceptable patient discomfort.

CONCLUSIONS

The reverse peroneus brevis muscle flap is a versatile alternative to free flap reconstruction in small- to moderate-sized defects of the lower limb. Preoperative 3D MRI is accurate to evaluate the anatomy of the muscle when performed by an expert radiologist. In our experience, it should become part of preoperative workup before performing a peroneus brevis flap procedure.

3D double-echo steady-state sequence assessment of hip joint cartilage and labrum at 3 Tesla: comparative analysis of magnetic resonance imaging and intraoperative data

OBJECTIVES

To assess the diagnostic accuracy of a high-resolution, three-dimensional (3D) double-echo steady-state (DESS) sequence with radial imaging at 3 Tesla (T) for evaluating cartilage and labral alterations in the hip.

METHODS

Magnetic resonance imaging (MRI) data obtained at 3 T, including radially reformatted DESS images and intraoperative data of 45 patients (mean age 42 ± 13.7 years) who underwent hip arthroscopy, were compared. The acetabular cartilage and labrum of the upper hemisphere of the acetabulum and the central femoral head cartilage were evaluated. Sensitivity, specificity, accuracy, and negative and positive predictive values were determined.

RESULTS

Sensitivity, specificity and accuracy of the DESS technique were 96.7%, 75% and 93.7% for detecting cartilage lesions and 98%, 76.2% and 95.9% for detecting labral lesions. The positive and negative predictive values for detecting or ruling out cartilage lesions were 96% and 78.9%. For labral lesions, the positive and negative predictive values were 97.5% and 80%.

CONCLUSION

A high-resolution, 3D DESS technique with radial imaging at 3 T demonstrated high accuracy for detecting hip cartilage and labral lesions with excellent interobserver agreement and moderate correlation between MRI and intraoperative assessment.

KEY POINTS

• High-resolution, 3D DESS with radial imaging allows accurate cartilage and labrum evaluation. • DESS demonstrated high sensitivity, specificity, accuracy for detecting cartilage and labral lesions. • Highly accurate sequence may influence treatment decisions in patients with hip pain.

MR arthrography of the shoulder: evaluation of isotropic 3D intermediate-weighted FSE and hybrid GRE T1-weighted sequences

PURPOSE

To compare the diagnostic accuracy of three-dimensional (3D) fast spin echo (FSE) intermediate-weighed (IW-3D) and 3D hybrid double-echo steady-state T1-weighted sequences (Hy-3D) and two-dimensional (FSE) images (2D) at shoulder MR arthrography (MRA).

MATERIALS AND METHODS

Institutional review board approval was obtained and informed consent was waived for this retrospective study. From September 2011 to October 2014, 102 patients who had undergone 1.5 Tesla MRA of the shoulder, including conventional 2D-FSE and IW-3D and Hy-3D images were included in our study. The mean interval between MRA and surgery was 21 days (range 2-70 days). MR images were retrospectively and independently reviewed by two experienced radiologists blinded to the clinical and surgical data. Supraspinatus tendon (SST), infraspinatus tendon (IST) and subscapularis tendon (SCT) tears, as well as antero-inferior, superior and posterior labral lesions were assessed, using surgery as the reference standard. Each reader's performance in assessing rotator cuff and labrum abnormalities was evaluated using the area under the receiver operating characteristic curve (AUC) and 95% confidence intervals (CIs). The difference was evaluated using a univariate z test. The sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV) and accuracy (Acc) for all types of rotator cuff tears and labral lesions were calculated. A value of p < 0.05 was considered statistically significant. Inter-observer agreement was calculated using kappa statistics.

RESULTS

The difference of diagnostic accuracy achieved was not significant (p > 0.05). In particular, differences in AUC values ranged from 0.002 (p = 0.98) to 0.014 (p = 0.82) as regards the comparison between 2D and IW-3D images, from 0.002 (p = 0.98) to 0.034 (p = 0.08) concerning the comparison between 2D and Hy-3D images and from 0.010 (p = 0.82) to 0.032 (p = 0.09) when comparing Hy-3D to IW-3D images. Accuracy values in evaluating RC lesions and labral lesions were 95.1, 92.1, 91.2, 93.1, 93.1 and 94.1% by reading 2D, Hy-3D and IW-3D images, respectively. The difference of diagnostic accuracy achieved using the datasets analyzed was not significant (p > 0.05). Inter-observer agreement was very good for each of the datasets that were evaluated, with near-perfect agreement for 2D dataset (k = 0.86), Hy-3D (k = 0.81) and IW-3D (k = 0.83).

CONCLUSIONS

The accuracy of IW-3D and Hy-3D images was not significantly higher than the 2D sequences in evaluating RC and labral lesions.

Comparing an accelerated 3D fast spin-echo sequence (CS-SPACE) for knee 3-T magnetic resonance imaging with traditional 3D fast spin-echo (SPACE) and routine 2D sequences

PURPOSE

To compare a faster, new, high-resolution accelerated 3D-fast-spin-echo (3D-FSE) acquisition sequence (CS-SPACE) to traditional 2D and high-resolution 3D sequences for knee 3-T magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Twenty patients received knee MRIs that included routine 2D (T1, PD ± FS, T2-FS; 0.5 × 0.5 × 3 mm³; ∼10 min), traditional 3D FSE (SPACE-PD-FS; 0.5 × 0.5 × 0.5 mm³; ∼7.5 min), and accelerated 3D-FSE prototype (CS-SPACE-PD-FS; 0.5 × 0.5 × 0.5 mm³; ∼5 min) acquisitions on a 3-T MRI system (Siemens MAGNETOM Skyra). Three musculoskeletal radiologists (MSKRs) prospectively and independently reviewed the studies with graded surveys comparing image and diagnostic quality. Tissue-specific signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were also compared.

RESULTS

MSKR-perceived diagnostic quality of cartilage was significantly higher for CS-SPACE than for SPACE and 2D sequences (p < 0.001). Assessment of diagnostic quality of menisci and synovial fluid was higher for CS-SPACE than for SPACE (p < 0.001). CS-SPACE was not significantly different from SPACE but had lower assessments than 2D sequences for evaluation of bones, ligaments, muscles, and fat (p ≤ 0.004). 3D sequences had higher spatial resolution, but lower overall assessed contrast (p < 0.001). Overall image quality from CS-SPACE was assessed as higher than SPACE (p = 0.007), but lower than 2D sequences (p < 0.001). Compared to SPACE, CS-SPACE had higher fluid SNR and CNR against all other tissues (all p < 0.001).

CONCLUSIONS

The CS-SPACE prototype allows for faster isotropic acquisitions of knee MRIs over currently used protocols. High fluid-to-cartilage CNR and higher spatial resolution over routine 2D sequences may present a valuable role for CS-SPACE in the evaluation of cartilage and menisci.

T2 shuffling: Sharp, multicontrast, volumetric fast spin-echo imaging

PURPOSE

A new acquisition and reconstruction method called T2 Shuffling is presented for volumetric fast spin-echo (three-dimensional [3D] FSE) imaging. T2 Shuffling reduces blurring and recovers many images at multiple T2 contrasts from a single acquisition at clinically feasible scan times (6-7 min).

THEORY AND METHODS

The parallel imaging forward model is modified to account for temporal signal relaxation during the echo train. Scan efficiency is improved by acquiring data during the transient signal decay and by increasing echo train lengths without loss in signal-to-noise ratio (SNR). By (1) randomly shuffling the phase encode view ordering, (2) constraining the temporal signal evolution to a low-dimensional subspace, and (3) promoting spatio-temporal correlations through locally low rank regularization, a time series of virtual echo time images is recovered from a single scan. A convex formulation is presented that is robust to partial voluming and radiofrequency field inhomogeneity.

RESULTS

Retrospective undersampling and in vivo scans confirm the increase in sharpness afforded by T2 Shuffling. Multiple image contrasts are recovered and used to highlight pathology in pediatric patients. A proof-of-principle method is integrated into a clinical musculoskeletal imaging workflow.

CONCLUSION

The proposed T2 Shuffling method improves the diagnostic utility of 3D FSE by reducing blurring and producing multiple image contrasts from a single scan. Magn Reson Med 77:180-195, 2017. © 2016 Wiley Periodicals, Inc.

A narrative overview of the current status of MRI of the hip and its relevance for osteoarthritis research - what we know, what has changed and where are we going?

OBJECTIVE

To review and discuss the role of magnetic resonance imaging (MRI) in the context of hip osteoarthritis (OA) research.

DESIGN

The content of this narrative review, based on an extensive PubMed database research including English literature only, describes the advances in MRI of the hip joint and its potential usefulness in hip OA research, reviews the relevance of different MRI features in regard to symptomatic and structural progression in hip OA, and gives an outlook regarding future use of MRI in hip OA research endeavors.

RESULTS

Recent technical advances have helped to overcome many of the past difficulties related to MRI assessment of hip OA. MRI-based morphologic scoring systems allow for detailed assessment of several hip joint tissues and, in combination with the recent advances in MRI, may increase reproducibility and sensitivity to change. Compositional MRI techniques may add to our understanding of disease onset and progression. Knowledge about imaging pitfalls and anatomical variants is crucial to avoid misinterpretation. In comparison to research on knee OA, the associations between MRI features and the incidence and progression of disease as well as with clinical symptoms have been little explored. Anatomic alterations of the hip joint as seen in femoro-acetabular impingement (FAI) seem to play a role in the onset and progression of structural damage.

CONCLUSIONS

With the technical advances occurring in recent years, MRI may play a major role in investigating the natural history of hip OA and provide an improved method for assessment of the efficacy of new therapeutic approaches.