Quantifying motion artifacts using a rotating Phantom: insights towards dynamic musculoskeletal applications

Abstract

Dynamic Computed Tomography is a promising tool to investigate affections, predominantly of vascular and perivascular origin. Advances in CT technology are opening up the possibility to also evaluate musculoskeletal diseases using dynamic CT. Wide beam CT scanners have the potential to acquire images from the same anatomic area over lengths up to 16 cm. As such, detailed analysis of joint morphology and dynamic phenomena can be investigated. Based on image processing techniques, kinematics can then be obtained from these images. Motion artifacts are however a major concern in dynamic CT for musculoskeletal applications. Such artifacts are influenced by the acquisition protocol and the speed of motion. In this study, we designed a phantom that could rotate in the gantry of the CT in an attempt to quantify motion artifacts. Dynamic scans were obtained while the phantom was rotating at 720/s in the wide beam CT scanner. Visual inspection revealed two main types of artifacts: high intensity artifacts and blurring or distortion of the holes in the phantom. Two quantitative metrics were defined to assess the degree of motion artifacts induced by the rotation of the phantom. These metrics were used to compare two different dynamic CT acquisition protocols; cine and cardiac. Results showed that the cardiac protocol significantly preserved the original shape of the holes by as much as 75%+/- 8 while that of cine was 62% +/- 4. However, the cardiac protocol showed 2 times more pixels with high intensity spots than the cine protocol and that difference was significant.