Gadoteridol dose dependence in MR imaging of a liver abscess model.

A necrotic liver abscess model was studied with magnetic resonance (MR) imaging at 1.5 T before and after intravenous administration of gadoteridol at doses of 0.1, 0.25, and 0.5 mmol/kg in 24 rabbits. Enhancement characteristics and lesion delineation were assessed with both breath-hold and non-breath-hold imaging techniques. Lesion delineation, as assessed both by signal intensity measurements and evaluations by two image readers blinded to imaging technique, was greatest on high-dose (0.5 mmol/kg) breath-hold images. Lesion rim enhancement was seen consistently only on postcontrast images obtained at a dose of 0.5 mmol/kg and progressed with time after injection of contrast material.

Glenoid labrum: evaluation with MR imaging.

Fifteen patients with shoulder instability and nine asymptomatic volunteers were studied with magnetic resonance (MR) imaging. The shoulder joint was visualized by means of arthroscopy or surgery in all patients. Ten patients had abnormalities of the glenoid labrum. Two musculoskeletal radiologists interpreted the MR images of the patients and volunteers without knowledge of the clinical history or surgical results. The surgical and arthroscopic results were used as the standard of reference in symptomatic patients. Observer A achieved a sensitivity of 44.4% and a specificity of 66.7%; observer B had a sensitivity of 77.8% and a specificity of 66.7%. In addition to the poor sensitivities and specificities, there was substantial intra- and interobserver variability. Assuming that the shoulders of the asymptomatic volunteers were normal, the specificities were 100.0% and 88.9% for observers A and B respectively. In this small study, axial MR imaging was relatively insensitive and nonspecific in the evaluation of labral lesions. Further study will be necessary to determine the utility and limits of MR imaging in this regard.

Clinical and radiologic features of malignant neoplasms in organ transplant recipients: cyclosporine-treated vs untreated patients.

The radiologic and clinical features of 37 posttransplantation malignant tumors occurring in 33 organ transplant recipients were reviewed to determine the characteristics of the tumors, particularly in relation to previous treatment (or nontreatment) with cyclosporine. The 37 malignant tumors included lymphomas (eight in patients receiving cyclosporine and four in patients not given cyclosporine) and carcinomas of the skin and lips (11), head and neck (five), colon and rectum (three), uterus (two), vulva (two), lung (one), and urinary bladder (one). The neoplasms of the internal viscera and head and neck were relatively advanced when detected. The neoplasms of the skin, vulva, uterine cervix, and urinary bladder were low-grade malignant tumors. Most of the cyclosporine-induced malignant lesions were lymphomas. The lymphomas in cyclosporine-treated recipients were characterized by early appearance after transplantation; more extensive organ involvement; multiple, homogeneous solid lesions without central low density on CT and sonography; and regression after reduction of cyclosporine dose. We conclude that malignant tumors occurring after transplantation are often advanced and that lymphoma induced by cyclosporine has characteristic features.

Knee menisci. Correlation between microstructure and biomechanics.

Light and scanning electron microscopy techniques were used to define the microstructure of human knee menisci. Two structurally different regions were shown: a mesial part that included the innermost two thirds and a peripheral part formed by the remaining outer one third. The organization of collagen bundles of the mesial part demonstrated a radial pattern. Those of the peripheral part were larger and circumferential. The articular surfaces of the mesial part were lined by thinner bundles parallel to the surface, while the outer portion was covered by synovium. This structural organization suggested specific biomechanical functions: mainly compression mesially with tension peripherally and a direct translation of forces from the inner wedge-shaped part to the outermost region. The covering layer is well suited for surface to surface motion. Outward displacement of the menisci by the femoral condyles is resisted by solid anchorage of the peripheral circumferential fibers to the intercondylar bone. The resistance to such displacement would force the femoral condyles inwards. Such an organization of menisci has implications in knee joint stability and in the pathology of meniscal injuries.

[A study of the menisci of the knee by scanning electron microscopy (author's transl)]. / Les ménisques du genou. Etude en microscopie électronique à balayage et corrélation biomécanique.

Sixty menisci have been studied by scanning electron microscopy. In the frontal plane of the middle third of the meniscus, two distinct parts can be discerned - a central part corresponding to the medial two thirds and a peripheral part corresponding to the lateral third. Collagen fibres can be arranged in four different ways; radial fibres in the central portion; a marginal area underlying each surface of the meniscus made up of mixed collagen fibres; circumferential fibres in the peripheral part and a fascicular layer of fibres made up of loose connective tissue arising from the articular capsule and penetrating into the circumferential fibrous layer. The authors consider that the radial fibres are best adapted to pressure, whilst circumferential fibres are submitted to traction forces; the marginal areas are best adapted to gliding forces. Both menisci comprise a single functional unit.