QUANTITATION OF ARTICULAR-CARTILAGE USING MAGNETIC-RESONANCE-IMAGING AND 3-DIMENSIONAL RECONSTRUCTION

A quadrature knee coil was used in conjunction with a magnetic resonan ce imaging scanner for quantitation of test phantom volumes, ex vivo b ovine cartilage thickness, and in vivo human articular cartilage volum es. Optimal magnetic resonance parameters were obtained by testing a s eries of spin-echo and gradient-echo pulse sequences to determine the sequence that provided the highest resolution of articular cartilage a nd best defined the cartilage interfaces with synovial fluid and subch ondral bone. Extensive testing revealed that two sequences were requir ed to define articular cartilage accurately: a spoiled gradient-echo s equence and a steady state free-precession sequence. Three-dimensional reconstruction and statistical analyses of test phantoms and of bovin e and human cartilage images were performed. Differences between actua l phantom volumes and three-dimensional measurements demonstrated that , as magnetic resonance slice thickness was increased, the measurement variability also increased (coefficient of variation ranging from 1.7 +/- 1.3% for 1.0 mm slice thickness to 22.7 +/- 1.9% for 3.0 mm slice thickness). When the phantom volume was greater than 1,800 mm(3), the intraobserver, interobserver and interscan accuracies were greater th an 97, 98, and 96%, respectively. This high degree of reproducibility pertained for the data on in vivo human cartilage data also. For exper ienced observers, the intraobserver and interobserver reproducibility were greater than 98 and 97%, respectively. The interscan reproducibil ity was greater than 98%. These data demonstrate that improved magneti c resonance pulse sequencing, in conjunction with three-dimensional re construction and measurement techniques, can accurately and reproducib ly measure the volume of articular cartilage. Clinical application of this approach offers the potential for early diagnosis BE osteoarthrit is and for serial, noninvasive assessment of changes in articular cart ilage volume in response to therapeutic modalities.