The influence of the resolution and contrast on measuring the articular cartilage volume in magnetic resonance images

The progression of OA in patients may be followed by measuring the volume o f articular cartilage from MR images. We attempted to determine the reprodu cibility of volume measurements of articular cartilage made from magnetic r esonance images of the knees and the dependence of the reproducibility on i mage resolution and contrast-to-noise. A fat-suppressed 3D technique was us ed to generate four image sets with different image resolution. Each patien t was imaged twice to obtain image pairs at each resolution. To assess the dependence of reproducibility on noise we generated six image sets for each patient by adding noise to the original images and repeating the compariso n. On each image set, the femoral, tibial, and patellar cartilage were outl ined by a combination of computer and manual methods, and the images were u sed to calculate the volume of each cartilage plate. Comparing the coeffici ent of variance between the volume measurements made from the two visits, t he volume measurements made from images with the highest resolution (0.275 x 0.275 x 1.0 mm) had the highest reproducibility. The high resolution imag es of the tibia and femur had the least partial-volume averaging and, as a result, better defined the boundaries between cartilage and adjacent tissue s. A different trend was evident for the patella. For studies of osteoarthr itis therapies, we recommend using MR images with the highest possible in-p lane spatial resolution to provide the most reproducible volume measurement s of knee cartilage. (C) 2000 Elsevier Science Inc. All rights reserved.