Measurement of localized cartilage volume and thickness of human knee joints by computer analysis of three-dimensional magnetic resonance images.

RATIONALE AND
OBJECTIVES: This work demonstrates a new method for computerized measurement of the dimensions (thickness and volume) of articular cartilage for any specified region of the human knee joint. Three-dimensional magnetic resonance (MR) images optimized for cartilage contrast have been analyzed using computerized edge-detection techniques, and the reproducibility of articular cartilage thickness and volume measurements is assessed.
METHODS: A fat-suppressed, three-dimensional SPoiled GRass MR sequence (45/7.5/30 degrees) with total scan time of approximately 12 minutes was used to acquire volume images of human knee joints at spatial resolution of 0.6 x 1.2 x 1.2 mm. Measurements were made using six repeated scans for three healthy volunteers over a period of 2 months. The subsequent semi-automated image processing to establish total cartilage volume and cartilage thickness maps for the femur required approximately 60 minutes of operator time.
RESULTS: The mean coefficient of variation for total cartilage volume for the six repeated scans for the three volunteers was 3.8%, and the average coefficient of variation for the user-selected cartilage plugs was 2.0%. The cartilage thickness maps from the repeated scans of the same knee were similar.
CONCLUSIONS: Standard resolution MR images with fat-suppressed contrast lead to an objective and reproducible measurement of spatial dimensions of articular cartilage when analyzed semi-automatically using computerized edge-detection methods.