Faculty Bibliography

PURPOSE: To determine the accuracy of T1-weighted fat-suppressed (FS) three-dimensional (3D) fast low-angle shot (FLASH) magnetic resonance (MR) imaging for the detection of articular cartilage abnormalities of the patellofemoral joint. MATERIALS AND METHODS: Forty-one patients with suspected internal derangement of the knee were examined with a T1-weighted FS 3D FLASH sequence and subsequently underwent arthroscopy. The patellofemoral articular cartilage was graded blindly on both the MR and arthroscopic images with a modification of the Noyes classification scheme. RESULTS: For the detection of abnormal articular cartilage of the patellofemoral joint with the FS 3D FLASH sequence, sensitivity was 81%, specificity was 97%, and accuracy was 97%. Of the lesions detected on MR images, 77% were graded identically on MR and arthroscopic images. For the remaining 23%, MR imaging and arthroscopic ratings were within one grade of each other. CONCLUSION: T1-weighted FS 3D FLASH imaging is accurate for the detection and grading of articular cartilage abnormalities of the patellofemoral joint

This is an unusual case of an adamantinoma in an early phase of evolution. It was much smaller than adamantinomas typically seen at presentation, although it was located in the usual anterior tibial cortical region. Slow growth and a prolonged period of symptoms are common with adamantinoma and were also observed in this patient. The multifocal presentation within the same bone is unusual. This case illustrated the need to consider adamantinoma in the differential diagnosis of any pre-tibial cortical lesion despite the small size, benign presentation, or the longevity of symptoms

OBJECTIVE. A localized form of anterior arthrofibrosis, the so-called cyclops lesion, has recently been reported to be a significant cause of loss of knee extension after reconstruction of the anterior cruciate ligament (ACL) of the knee. The purpose of this study was to characterize the MR appearance of this lesion. SUBJECTS AND METHODS. Five patients who had arthroscopic verification of a focal nodule of fibrous tissue in the intercondylar notch anterior to the reconstructed ACL (the cyclops lesion) and who had an MR examination after ACL reconstruction but before repeat arthroscopy and excision of the cyclops lesion were included in this study. The MR images were evaluated for the presence of soft tissue in the intercondylar notch anterior to the reconstructed ACL. If present, this tissue was graded as 1, 2, or 3, depending on its anterior extent along the femoral condyle. RESULTS. MR images of all five patients showed abnormal soft tissue with signal characteristics consistent with fibrous tissue anterior to the reconstructed ACL in the intercondylar notch. The abnormal tissue was grade 2 or 3 in all patients. CONCLUSION. MR imaging shows soft tissue with signal characteristics consistent with fibrous tissue anterior to the reconstructed ACL in the intercondylar notch in patients with localized anterior arthrofibrosis. Although the sensitivity and specificity of MR imaging for the cyclops lesion are yet to be determined, visualization of such fibrous tissue on MR images in a patient with clinical symptoms suggestive of localized anterior arthrofibrosis may be helpful in confirming the diagnosis

OBJECTIVE: Denervation hypertrophy is an entity well recognized in the neurology literature, but with little mention in the radiology literature. Denervation hypertrophy occurs when a muscle paradoxically enlarges rather than atrophies in response to loss of innervation. The purpose of this report is to describe the MR appearance of true hypertrophy and pseudohypertrophy of muscle following denervation. MATERIALS AND METHODS: The clinical data and MRI findings in three patients with muscle enlargement due to denervation hypertrophy are reviewed retrospectively. Two women and one man aged 19-80 years were included. Denervation resulted from spinal stenosis in one patient, a herniated thoracic disc in another, and spina bifida with a tethered cord in the third. RESULTS: True hypertrophy of a single muscle was seen in one patient and pseudohypertrophy of two muscles was present in one patient. One patient had one muscle with true hypertrophy and one muscle with pseudohypertrophy. Electromyographic examination was performed and was consistent with denervation in two patients. Biopsy confirmation of denervation was obtained in two patients. All five abnormal muscles exhibited increased volume, well defined margins, and normal contour. In true hypertrophy the enlarged muscle was isointense with normal muscle on all MRI sequences. In pseudohypertrophy the MRI appearance was consistent with an excessive amount of fat interspersed throughout normal muscle. CONCLUSION: Magnetic resonance in these cases established muscle hypertrophy rather than neoplasm as the cause of a palpable mass. If muscle hypertrophy or pseudohypertrophy is seen on an MR examination of an enlarged extremity, the possibility of an underlying neurologic process should be considered

We describe a case of massive dystrophic subcutaneous calcification in the anterior thighs of a long-term insulin-dependent diabetic

Recent advances in the treatment of articular cartilage abnormalities have created a need for an accurate noninvasive imaging method for the evaluation of articular cartilage. Although its role remains undefined in this regard, magnetic resonance imaging (MRI) appears to be the most promising method. We review the current status and possible future directions of MRI of articular cartilage

Intra-articular ganglion cysts arising from the cruciate ligaments are unusual lesions, there being only nine previously reported cases. We report 16 cases and describe their MR appearance. Nine ganglia originated from the posterior cruciate ligament, most often appearing as well-defined multilocular lesions. The seven ganglia arising from the anterior cruciate ligament most often appeared as fusiform cystic lesions extending along and interspersed within the fibers of the ligament. Although uncommon, intra-articular ganglion cysts arising from the knee appear to have a distinctive MR appearance which should allow their correct diagnosis

Advances in surgical and pharmacologic techniques for treating and preventing chondral abnormalities are creating a demand for an accurate, noninvasive imaging method to evaluate articular cartilage. The most promising technique is MR imaging, but its exact role in this evaluation remains undefined. This article reviews the MR appearance of normal and abnormal articular cartilage and the various pulse sequences that can be used to evaluate chondral lesions. It also briefly discusses possible future directions for MR imaging of articular cartilage

In previous papers relative signal intensity increase was used as a quantitative assessment parameter for contrast uptake in contrast-enhanced MRI. However, relative signal intensity increase does not only reflect contrast uptake but depends also on tissue parameters (native T1 relaxation time) and sequence parameters (repetition time and flip angle); thus, the contrast uptake cannot be assessed accurately using relative signal intensity increase. Based on an analysis of the contrast behavior of spoiled gradient echo sequences, a method is described in this paper that overcomes the limitations of relative signal intensity increase measurement. A parameter, called 'enhancement factor' (EF) is introduced that approximates differential T1 relaxation rate. The enhancement factor scales linearly with contrast uptake and is independent of tissue and sequence parameters. The additional measurement time involved in determining the enhancement factor is less than 1 min and computation is straightforward. The practicality of the new method was confirmed by phantom measurements using T1-weighted and proton density-weighted spoiled gradient echo sequences (FLASH-2D). Enhancing tissues were simulated by water phantoms doped with increasing concentrations of Gd-DTPA