Scientists: David Holdsworth, PhD, Rob Bartha, PhD & Terry Peters, PhD, FCCPM
Musculoskeletal diseases represent a leading cause of pain, physical disability, and health-care utilization in Canada. For example, approximately 1 in 6 individuals in Canada over the age of 15 are affected by osteoarthritis (OA). Musculoskeletal imaging is emerging as a research area of great importance, fueled by recent advances in pharmacological and surgical therapies for arthritis. The Arthritis Imaging program at Robarts involves all aspects of bone and joint imaging, from animal studies (using micro-computed tomography and micro-MRI in rodent models), to clinical imaging of early joint disease and monitoring of patients following total joint replacement. This program is strengthened by collaborations with leading biologists, engineers, and physicians at the University of Western Ontario and associated hospitals.
Radiographic Assessment of Joint Replacements
Total joint replacement (TJR) is a cost-effective method of alleviating joint pain and restoring function; however, many of them must be revised before the expected maximum lifetime of the patient. Many studies have revealed that the long-term clinical stability of TJR can be predicted by careful measurements of small motions between the implant and surrounding bone. It is important to make these measurements with great care, because the amount of motion needed to be detected over one year may be equivalent to the thickness of a sheet of paper! The group is fortunate to have one of North America’s only dedicated stereo digital x-ray imaging systems for assessing implant stability in patients, following joint replacement surgery. With support from the CIHR, the group is now working to extend these techniques to include dynamic imaging, which will allow observation of the function of replacement components in the hip and knee, eventually leading to the development of improved joint replacements.
Bone and Joint Imaging in Research Animals
Arthritis causes degenerative changes in the bone and cartilage of affected individuals, and there is a strong incentive to develop new drug therapies to slow or prevent that damage. To develop new drug treatments for arthritis, animal models are used to mimic the disease patterns in humans. Part of the research program involves the development of new imaging techniques that can be used to monitor bone and cartilage in live animals, allowing the team to follow the development of arthritis and the response to new therapies. Working with colleagues in Skeletal Biology, they have developed a rat model of arthritis and optimized micro-CT and micro-MRI imaging techniques to observe changes to the joint over a few months. Robarts provides access to state-of-the-art MR imaging (at 9.4-Tesla) and high-resolution computed tomography. This program is now being extended to include nuclear medicine imaging, using one of Canada’s only micro-SPECT imaging systems, which provides sub-millimeter imaging of bone metabolic activity in rodents.
High-field MRI of Bone and Cartilage
Conventional radiographic techniques (x-ray radiography and trans-axial CT) do not provide sufficient sensitivity and specificity to detect OA at its earliest stages, or to monitor cartilage response to therapy. The need for improved non-invasive imaging will increase in the next decade, as the population ages and new pharmacological therapies become available. As part of the Arthritis Imaging Program, the team is developing new techniques to image cartilage and bone in patients, using high-field (3-Tesla) MRI. The state-of-the-art facilities at Robarts provide access to 3-Tesla MRI systems from two major vendors (GE and Siemens), allowing the team to develop new imaging techniques that can be implemented at many other sites. The MRI facilities are also integrated with the digital x-ray system, allowing comparison of x-ray and MRI results.
The development of new arthritis imaging techniques has taken on renewed priority in recent years, due to the development of new drugs and surgical techniques that promise to reduce the impact of arthritis. The musculoskeletal imaging research team is developing the next generation of x-ray, CT, and MRI techniques for use in animal studies and clinical trials. Over the next decade, imaging will play a pivotal role in the development of effective new treatments for arthritis.