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Hyaline cartilage plays an essential role in the maintenance of normal synovial joint function by reducing friction and distributing loads. Histologic analysis of hyaline cartilage reveals zonal variation in cellular morphology, proteoglycan concentration, and collagen fiber size and orientation. High-resolution magnetic resonance (MR) imaging reveals an analogous laminar anatomy that is often visible on clinical images obtained with proper attention to technique. In vitro and in vivo pulse sequences show three distinct laminae: a hypointense superficial lamina, a hyperintense intermediate lamina, and a heterogeneous deep lamina that consists of alternating hyperintense and hypointense bands perpendicular to the subchondral bone. Imaging pitfalls include magic angle effects, truncation artifact, partial volume effect, regional anatomic variation, chemical shift, and magnetic susceptibility effects. Pathologic conditions that affect articular cartilage include chondromalacia patellae, osteoarthritis, and localized traumatic lesions. Although detection of early cartilage disease remains elusive, MR imaging can demonstrate intermediate and advanced lesions.

The design of a piezoelectric-controlled trimmer capacitor and its use as a tuning element of an MRI surface coil at 63.8 MHz are described. It is found that image quality does not depend strongly on match of the coil to the transmission line but that tuning can be a significant factor. The work is intended to lead eventually to an automatic frequency control circuit in which the capacitor serves as the active element in holding the resonant frequency of the nuclei and the resonant frequency of the coil in coincidence.