Accurate Measurement of Cartilage Morphology Using a 3D Laser Scanner

We describe a method to accurately assess articular cartilage morphology using the three-dimensional laser scanning technology. Traditional methods to obtain ground truth for validating the assessment of cartilage morphology from MR images have relied on water displacement, anatomical sections obtained with a high precision band saw, stereophotogrammetry, manual segmentation, and phantoms of known geometry. However, these methods are either limited to overall measurements such as volume and area, require an extensive setup and a highly skilled operator, or are prone to artifacts due to tissue sectioning. Alternatively, 3D laser scanning is an established technology that can provide high resolution range images of cartilage and bone surfaces. We present a method to extract these surfaces from scanned range images, register them spatially, and combine them into a single surface representing the articular cartilage from which volume, area, and thickness can be computed. We validated the laser scanning approach using a knee model which was covered with a synthetic articular cartilage model and compared the computed volume against water displacement measurements. Using this method, the volume of articular cartilage in five sets of cadaver knees was compared to volume estimates obtained from segmentation of MR images.