Luis S. Beltran

Articular Cartilage: In Vivo Diffusion-Tensor Imaging

PURPOSE To investigate technical feasibility, test-retest reproducibility, and the ability to differentiate healthy subjects from subjects with osteoarthritis (OA) with diffusion-tensor (DT) imaging parameters and T2 relaxation time. MATERIALS AND METHODS This study was approved by the institutional review board and was HIPAA compliant. All subjects provided written informed consent. DT imaging parameters and T2 (resolution=0.6×0.6×2 mm) of patellar cartilage were measured at 7.0 T in 16 healthy volunteers and 10 patients with OA with subtle inhomogeneous signal intensity but no signs of cartilage erosion at clinical magnetic resonance (MR) imaging. Ten volunteers were imaged twice to determine test-retest reproducibility. After cartilage segmentation, maps of mean apparent diffusion coefficient (ADC), fractional anisotropy (FA), and T2 relaxation time were calculated. Differences for ADC, FA, and T2 between the healthy and OA populations were assessed with nonparametric tests. The ability of each MR imaging parameter to help discriminate healthy subjects from subjects with OA was assessed by using receiver operating characteristic curve analysis. RESULTS Test-retest reproducibility was better than 10% for mean ADC (8.1%), FA (9.7%), and T2 (5.9%). Mean ADC and FA differed significantly (P<.01) between the OA and healthy populations, but T2 did not. For ADC, the optimal threshold to differentiate both populations was 1.2×10(-3) mm2/sec, achieving specificity of 1.0 (16 of 16) and sensitivity of 0.80 (eight of 10). For FA, the optimal threshold was 0.25, yielding specificity of 0.88 (14 of 16) and sensitivity of 0.80 (eight of 10). T2 showed poor differentiation between groups (optimal threshold=22.9 msec, specificity=0.69 [11 of 16], sensitivity=0.60 [six of 10]). CONCLUSION In vivo DT imaging of patellar cartilage is feasible, has good test-retest reproducibility, and may be accurate in discriminating healthy subjects from subjects with OA. ADC and FA are two promising biomarkers for early OA.

The distal semimembranosus complex: normal MR anatomy, variants, biomechanics and pathology

ObjectiveTo describe the normal MR anatomy and variations of the distal semimembranosus tendinous arms and the posterior oblique ligament as seen in the three orthogonal planes, to review the biomechanics of this complex and to illustrate pathologic examples.Results and conclusionThe distal semimembranosus tendon divides into five tendinous arms named the anterior, direct, capsular, inferior and the oblique popliteal ligament. These arms intertwine with the branches of the posterior oblique ligament in the posterior medial aspect of the knee, providing stability. This tendon-ligamentous complex also acts synergistically with the popliteus muscle and actively pulls the posterior horn of the medial meniscus during knee flexion. Pathologic conditions involving this complex include complete and partial tears, insertional tendinosis, avulsion fractures and bursitis.

Entrapment Neuropathies III: Lower Limb

Clinicians frequently encounter compressive neuropathies of the lower extremity. The clinical history and physical examination, along with electrodiagnostic testing and imaging studies, lead to the correct diagnosis. The imaging characteristics of the compression neuropathies can include acute and chronic changes in the nerves and the muscles they innervate. We provide a detailed review of compression neuropathies of the lower extremity with an emphasis on magnetic resonance (MR) imaging characteristics. We discuss the clinical presentation, etiology, anatomical location, and MR imaging appearance of these neuropathies, including the piriformis syndrome, iliacus syndrome, saphenous neuropathy, obturator neuropathy, lateral femoral cutaneous neuropathy (meralgia paresthetica), proximal tibial neuropathy, common peroneal neuropathy, deep peroneal neuropathy, superficial peroneal neuropathy, tarsal tunnel syndrome, Baxters neuropathy, joggers foot, sural neuropathy, and Mortons neuroma.

The Rotator Interval: A Review of Anatomy, Function, and Normal and Abnormal MRI Appearance

OBJECTIVE The purpose of this article is to review imaging of the rotator interval, an anatomically complex region in the shoulder that plays an important role in the normal function of the shoulder joint. The rotator interval can be difficult to evaluate by imaging, and it is not routinely evaluated arthroscopically unless the clinical examination or imaging findings suggest an abnormality of the rotator interval. Rotator interval pathology is implicated in glenohumeral instability, biceps instability and adhesive capsulitis-entities which remain a challenge to diagnose and treat. CONCLUSION Imaging can play an important role in increasing suspicion for injury to the rotator interval so that this region can be evaluated and appropriate treatment can be initiated.

The middle glenohumeral ligament: normal anatomy, variants and pathology

The middle glenohumeral ligament frequently presents variations of the normal anatomy and it is often injured in patients suffering trauma to the glenohumeral joint. The purpose of this pictorial assay is to illustrate the normal anatomy, biomechanics, normal variants and pathology of the middle glenohumeral ligament, as shown on MRI and MR arthrography of the shoulder.

The proximal hamstring muscle–tendon–bone unit: A review of the normal anatomy, biomechanics, and pathophysiology

Proximal hamstring injuries occur during eccentric contraction with the hip and the knee on extension; hence they are relatively frequent lesions in specific sports such as water skiing and hurdle jumping. Additionally, the trend toward increasing activity and fitness training in the general population has resulted in similar injuries. Myotendinous strains are more frequent than avulsion injuries. Discrimination between the two types of lesions is relevant for patient management, since the former is treated conservatively and the latter surgically. MRI and Ultrasonography are both well suited techniques for the diagnosis and evaluation of hamstring tendon injuries. Each one has its advantages and disadvantages. The purpose of this article is to provide a comprehensive review of the anatomy and biomechanics of the proximal hamstring muscle-tendon-bone unit and the varied imaging appearances of hamstring injury, which is vital for optimizing patient care. This will enable the musculoskeletal radiologist to contribute accurate and useful information in the treatment of athletes at all levels of participation.

Current Status of Hybrid PET/MRI in Oncologic Imaging

OBJECTIVE This review article explores recent advancements in PET/MRI for clinical oncologic imaging. CONCLUSION Radiologists should understand the technical considerations that have made PET/MRI feasible within clinical workflows, the role of PET tracers for imaging various molecular targets in oncology, and advantages of hybrid PET/MRI compared with PET/CT. To facilitate this understanding, we discuss clinical examples (including gliomas, breast cancer, bone metastases, prostate cancer, bladder cancer, gynecologic malignancy, and lymphoma) as well as future directions, challenges, and areas for continued technical optimization for PET/MRI.

Imaging Evaluation of Traumatic Ligamentous Injuries of the Ankle and Foot

Sports ankle injuries are very common worldwide. In the United States, it is estimated that 2 million acute ankle sprains occur each year, averaging to

Imaging Evaluation of Developmental Hip Dysplasia in the Young Adult

318 to

Imaging and evaluation of patients with high-risk prostate cancer.

914 per sprain. Magnetic resonance imaging is excellent for depicting normal ankle anatomy and can elegantly demonstrate ligamentous injuries of the ankle and associated conditions after ankle sprain. This article encompasses epidemiology, biomechanics, normal anatomy, and pathologic conditions of the ankle and foot ligaments. The specific ligaments discussed include the syndesmotic ligaments, lateral ligament complex of the ankle, deltoid ligament, spring ligament, ligaments of the sinus tarsi, and the Lisfranc ligament.