The basic magnetic resonance (MR) imaging pattern of normal and degenerated hyaline articular cartilage was studied in vitro in 40 fresh bovine patellae. With the use of an ample spectrum of strongly T1- to T2-weighted sequences, two zones of cartilage with different signal intensities were observed in all specimens. A superficial cartilaginous layer in the MR image with higher water content and longer T1 and T2 correlated with the tangential and transitional zones of normal articular cartilage, whereas a second MR imaging zone with shorter T1 and T2 was identified in the depth of the articular cartilage. Different functional properties in pressure resistance were observed in the two layers. In early cartilage degeneration without thinning, there was increased hydration of the superficial cartilage layer. This study suggests that strongly T1- and T2-weighted images are indispensable for evaluating details in articular cartilage degeneration.

The authors report a case of renal cell carcinoma in which computed tomography (CT) revealed fatty tissue and calcification within a solid renal mass. The detection of a mass with negative CT numbers at CT and increased echogenicity at ultrasound led to the incorrect diagnosis of angiomyolipoma (renal hamartoma). The presence of intratumoral calcification should have prompted further evaluation because angiomyolipomas usually do not calcify. The authors do not believe that the nonsurgical approach to angiomyolipomas should be abandoned.

The low-field MR-system offers low-cost MR examinations of peripheral joints with good image quality and reliable diagnostic information.

Selective digital subtraction arteriographic investigations of the arteries of the femoral head in 31 patients with traumatic and 34 patients with nontraumatic femoral head necrosis (FHN) were compared with investigations in a control group of 35 patients without hip disease. In the control group and in patients with nontraumatic FHN atypical arteriographic findings were found only in one third of cases. In traumatic FHN, however, vascular alterations could be detected in 97% of cases. This evidence suggests that damage to the femoral head vessels is a major etiological factor in traumatic, but not in nontraumatic, FHN. In late arterial phases of DSA a perinecrotic hypervascularization was the common feature in all nontraumatic necroses and could be observed in 71% of traumatic necroses. Its pathophysiological mechanism is discussed.

Magnetic resonance tomography (MR) was used to examine the femoral heads of 20 normals and of 56 patients with diseases of the femoral head, including Perthe's disease (four cases), adult necrosis of the femoral head (39 cases) and pain of unknown cause (13 cases). Femoral head necrosis and Perthe's disease regularly produce reduced signal intensity. The localisation of the areas of necrosis can be determined accurately in the coronary and sagittal plane. In 11 femoral heads, necrosis could be demonstrated unequivocally by MR in the presence of normal radiographic findings. Follow-up of nine patients with negative MR findings and indefinite symptoms confirmed the absence of necrosis.