HYALINE CARTILAGE - TRUNCATION ARTIFACT AS A CAUSE OF TRILAMINAR APPEARANCE WITH FAT-SUPPRESSED 3-DIMENSIONAL SPOILED GRADIENT-RECALLED SEQUENCES

PURPOSE: To investigate the cause of the trilaminar appearance within hyaline cartilage observed on magnetic resonance (MR) images obtained with a fat-suppressed three-dimensional spoiled gradient-recalled sequ ence. MATERIALS AND METHODS: The knees of three asymptomatic volunteer s were imaged with a fat-suppressed, three-dimensional, spoiled gradie nt-recalled sequence. The field of view, number of phase-encoding step s, and phase-encoding direction were varied. On each image, the thickn ess of the patellar and trochlear cartilage was measured in millimeter s and divided by the pixel dimension, which effectively expressed the thickness as the number of pixels. Finally, the number of pixels was c ompared with the number of alternating hyperintense and hypointense li nes depicted. RESULTS: The number of truncation lines increased as pix el dimension was reduced by either decreasing the field of view or inc reasing the number of phase-encoding steps. The accuracy for predictin g more that three lines with use of an anteroposterior phase-encoding direction varied between 83% and 92%. The appearance of the cartilage was altered when phase- and frequency-encoding directions were exchang ed, but truncation lines were still evident. CONCLUSION: The trilamina r appearance depicted within hyaline cartilage on MR images obtained w ith this sequence is predominantly attributable to truncation artifact rather than to histologic zonal anatomy.