Lee-Ren Yeh

Tibiofibular syndesmosis: high-resolution MRI using a local gradient coil.

PURPOSE Our goal was to correlate high-resolution MR images of the tibiofibular syndesmosis with anatomic sections. METHOD MRI was performed inside a local gradient coil on six cadaveric feet taped in 10-20 degrees dorsiflexion and 40-50 degrees plantar flexion by using axial and coronal T1-weighted SE sequences. After imaging, the specimens were frozen and sectioned into 3-mm-thick slices along the MR planes. Images were correlated with the anatomic sections. RESULTS MRI depicted the anatomy of the tibiofibular syndesmosis and surrounding structures. With the foot taped in dorsiflexion, axial imaging provided optimum views of the anterior, posterior, interosseous, and transverse tibiofibular ligaments. Coronal images allowed visualization of the entire course of the anterior, posterior, and transverse tibiofibular ligaments. The multifascicular appearance of the anterior tibiofibular ligament was best visualized in coronal sections. With the foot taped in dorsiflexion or in plantar flexion, it was possible to distinguish the posterior tibiofibular ligament and transverse tibiofibular ligament from the posterior talofibular ligament in all specimens. CONCLUSION High-resolution MRI using a local gradient coil provides excellent delineation of the ligaments of the distal tibiofibular syndesmosis.

Intracapsular origin of the long head of the biceps tendon

Abstract A developmental anomaly of the long head of the biceps tendon was found in a cadaveric shoulder. Findings on arthroscopy, routine MR imaging, and MR arthrography were compared and correlated with results of anatomic dissection. MR arthrography appears to be a very good diagnostic imaging method for depicting this anomaly prior to arthroscopy.

Transverse ligament and its effect on meniscal motion. Correlation of kinematic MR imaging and anatomic sections.

RATIONALE AND OBJECTIVES To evaluate the effect of the transverse ligament on translation of the menisci. METHODS Six cadaveric knees were examined by MR imaging inside a positioning device before and after transecting the transverse ligament. The knees were examined at various positions: extension, 30 degrees of flexion, 60 degrees of flexion, and full flexion. Sagittal T1-weighted spin-echo images were generated at each knee position and evaluated for statistical differences with regard to anterior-posterior meniscal excursion. RESULTS Statistically significant differences in meniscal excursion were found before and after transsecting the transverse ligament for anterior-posterior meniscal motion of the anterior horn of the medial meniscus at 30 degrees of knee flexion. No such significant differences were found, however, at 60 degrees of flexion and full flexion in anterior-posterior meniscal excursion of the anterior or posterior horn of either meniscus before and after transsecting the transverse ligament. CONCLUSIONS The transverse ligament has a restricting effect on anterior-posterior excursion of the anterior horn of the medial meniscus at lower degrees of knee flexion.

Posterior Reversible Encephalopathy Syndrome: Magnetic Resonance Imaging and Diffusion-Weighted Imaging in 12 Cases

Posterior reversible encephalopathy syndrome (PRES) is a potentially devastating neurologic syndrome, but timely treatment may lead to complete reversal of the disease course. We reviewed 12 cases of PRES and describe the clinical history and imaging findings, including conventional magnetic resonance imaging (MRI), diffusion‐weighted imaging (DWI), and calculated apparent diffusion coefficient (ADC) maps, used to establish the diagnosis of PRES. Three male and nine female patients aged between 11 and 70 years (mean, 37 years) with clinical and imaging findings consistent with PRES were enrolled in the study. All patients had undergone conventional MRI and 10 had undergone additional DWI studies. Ten patients had follow‐up MRI studies. DWI was performed using a 1.5T system with a single‐shot spin‐echo echo‐planar pulse sequence. Initial and follow‐up neuroimaging and clinical history were reviewed. Lesions were almost always present over the posterior circulation, mainly the parieto‐occipital region, affecting primarily the white matter. The anterior circulation region, brainstem, cerebellum, deep cerebral white matter, and thalamus were also involved in five cases. Conventional MRI revealed hyperintensity on T2‐ weighted and fluid‐attenuated inversion recovery images. DWI showed isointensity and increased signal intensity on ADC values in all cases, indicating vasogenic edema. Clinical and MRI follow‐up showed that the symptoms and radiologic abnormalities could be reversed after appropriate treatment of the causes of PRES in most patients (9 of 10). In one patient, the ADC value was lower on follow‐up images, indicating cytotoxic edema with ischemic infarct. DWI was a useful complement to MRI in the diagnosis of PRES.

Isolated intraosseous gout in hallux sesamoid mimicking a bone tumor in a teenaged patient

We are reporting an unusual case of isolated intraosseous tophus in medial hallux sesamoid presenting as tumor-like lesion in a teenage patient without prior history of gouty attack and underlying systemic disorders. The lesion manifested isointensity to surrounding muscles with internal low signal on spin echo (SE) T1-weighted images, and heterogeneous low signal intensity on fast spin echo (FSE) T2-weighted images. Computed tomography (CT) scan disclosed expansion and diffusely increased attenuation of the medial hallux sesamoid with focal cortical erosion and extraosseous extension of high attenuation content. The subsequent resection and pathology revealed intraosseous tophus deposition, which is particularly rare at this site and at this age. Imaging studies revealed some characteristic imaging features which can retrospectively be attributed to gouty tophus. When an expansile osteolytic lesion manifesting low signal intensity on T2-weighted image and internal calcifications on CT scan is encountered, the possibility of intraosseous tophus should be included in the list of differential diagnoses, even in a teenage patient without prior history of gout.

MRI Diagnosis of Contracture of the Gluteus Maximus Muscle

OBJECTIVE The objective of our study was to describe MRI features of contracture of the gluteus maximus muscle after providing a retrospective review of the MRI studies of 21 patients. CONCLUSION Gluteal contracture manifests characteristic features on MRI, including an intramuscular fibrotic cord extending to the thickened distal tendon with atrophy of the gluteus maximus muscle and posteromedial displacement of the iliotibial tract. In advanced cases, medial retraction of the muscle and its tendon results in a depressed groove at the muscle-tendon junction and external rotation of the proximal femur. Clinical correlation and meticulous physical examination may confirm the MR diagnosis.

Optimizing Scanning Phases in Detecting Small (<2 cm) Hepatocellular Carcinoma: Whole-liver Dynamic Study With Multidetector Row Ct

Objective: To define the optimal scanning phases for detecting small hepatocellular carcinomas (HCCs) with whole-liver dynamic helical computed tomography. Methods: Sixty-one patients with 112 hypervascular HCCs smaller than 2 cm underwent 7-phase dynamic study from the early arterial to the late equilibrium phases of the entire liver. Proof of neoplasms was based on biopsy results and computed tomography with iodized oil. Time-density curves of the individual tumor and the liver were compared. Results: Of 112 hypervascular nodules, the late arterial phase had the best liver-tumor conspicuity (P < 0.001). Ninety-one nodules (81%) had peak liver-tumor contrast in late arterial phase, and only 21 (19%) in the early arterial phase. All the hypervascular HCCs became isoattenuating to the regional parenchyma before the late portal venous phase (120th second). Conclusion: The late arterial and late portal venous phases are recommended for detecting small HCC smaller than 2 cm.

Focal Bone Abnormality as a Complication of Ultrasound Diathermy: A Report of Eight Cases

PURPOSE To review the magnetic resonance (MR) imaging findings in eight patients who developed marrow lesions after undergoing physiotherapy with use of ultrasound diathermy. MATERIALS AND METHODS The authors retrospectively reviewed the medical charts and MR images of eight patients (six women and two men aged 22-69 years) who received ultrasound diathermy treatment for a variety of soft tissue injuries involving primarily the knee, shoulder, and wrist. All patients underwent MR imaging without the use of intravenous gadolinium-based contrast material. The institutional review board approved the study, and the requirement to obtain informed consent was waived. RESULTS MR imaging of all patients revealed subcortical rim or arc lesions with low signal intensity on T1-weighted images and high signal intensity on T2-weighted images, without involvement of the deeper aspect of the bone marrow. The imaging features of the lesions were similar to those of focal osteonecrosis. Follow-up MR imaging performed in three patients approximately 2-3 months after cessation of ultrasound therapy revealed resolution of the bone lesions. Symptoms resolved in all patients. CONCLUSION This study demonstrated that ultrasound diathermy may produce an osseous injury. The abnormality itself was usually mild and transient, with apparent full recovery after termination of therapy.