Computer-aided Quantitative Assessment of Knee Articular Cartilage Using Musculoskeletal Ultrasound

Knee osteoarthritis is the most common type of arthritis in the elderly, which causes knee pain, swelling, joint movement restriction to patients. Cartilage abnormalities are primary features of osteoarthritis. Although X-ray is the most common radiological examination for diagnosis of knee osteoarthritis, the radiographic diagnosis has limitations and few information of cartilage condition. Musculoskeletal ultrasound (US) is a useful technique to quantify the cartilage thickness and detect inflammation in the knee joint by evaluating the cartilage periarticular soft tissue, and inflammation was considered contribute to the progression of knee osteoarthritis. In this study, we proposed an automatic computer-aided quantitative assessment system for thickness measurement of knee cartilage in the US image. In the proposed system, cartilage area segmentation was presented to extract the cartilage area, and the boundary delineation was used to automatically detect and refine the upper and lower boundaries of knee cartilage. Then, thickness measurement was performed to measure the distance between the upper and lower boundaries of the cartilage area. In the experiment, the proposed assessment system was tested with a dataset of 67 cases, and the overall accuracy of thickness measurement achieved 83.69%. Also, the target position located by the proposed system had the overall mean difference of 0.842 mm by comparing to the ground truth measured by orthopedist. In conclusion, based on the experiment result, our system has ability to provide a confident and reliable thickness measurement of knee cartilage in musculoskeletal US, and to overcome the limitations of X-ray and ultrasound.