The comprehensive goal of this project is to develop novel weight-bearing computed tomography (CT) imaging to support an imaging biomarker <93>stress test<94> of the knee joint. This test will then reveal abnormal tissue biomechanics and kinematics that put a knee at high risk for OA, by measuring the articular cartilage deformation between different weight-bearing conditions.

The standard application area for C-arm CT is in the interventional suite, where it usually acquires images using a vertical trajectory around the patient. For this project we opted for a C-arm device that can be almost arbitrarily positioned in space. This allows for a horizontal trajectory which is necessary to acquire images whilst the patient is standing upright or in squatting position.

From a medical image reconstruction point of view, there exist two main challenges. First, the limited detector size of C-arm CTs leads to difficulties in acquiring images from two adjoining knees in their natural position. Therefore, one goal is to explore so called large volume techniques which extend the field of view by adjusting the imaging trajectory to the objects shape. Another goal of this project will be to investigate methods for motion correction, as the standing position results in increased patient motion during image acquisition and therefore to increased motion artefacts. Multiple methods are conceivable that give additional information about patient motion. For example metallic markers that encode the object's position in the different detector images. Also external range imaging cameras could be used to keep track of the motion during a scan. Both methods would then allow the registration of different detector images, to allow for a correct reconstruction of the volume of interest.

This volume is then used to compute the necessary metrics of the knee joint, which can be interpreted as a biomarker for evaluating the risk of osteoarthritis.