Osteoarthritis Imaging in Low-Field MRI (0.55T)

MR imaging of the knee has long been established in a plethora of conditions as well as research settings. It is the most robust and non-invasive imaging modality enabling evaluation of all tissue components, including cartilage, ligaments and tendons, bone, and synovium. T2 relaxation properties of cartilage compartments have been established as one of the most robust biomarkers for early OA diagnosis. So far, most of the clinical utilities have been demonstrated on mid-field MRI systems, especially on 1.5T and 3.0T, considering the superior image quality, signal-to-noise ratio (SNR), and conventional availability. In recent years, low-field (0.55T) MRI scanners have experienced a renaissance with novel technical developments ensuring high-quality image acquisition with improved resolution, SNR, and accelerated scan time. Moreover, the 0.55T scanner offers additional advantages such as allowing safer image acquisition due to much lowered specific absorption rates (SAR) and providing higher flexibility to be installed at a broader geography due to lower weight and transportation requirements, with no quench pipe and minimal helium involved. Potential uses of 0.55T scanners have been demonstrated for brain, pulmonary, cardiac, and musculoskeletal imaging domains. Still in its early days, quantitative biomarker estimation and associated reliability have not been explored in-depth for the musculoskeletal system, particularly for knee OA. In this study, we present one of the first exploratory results of evaluating T2 properties (healthy knee cartilages and knee cartilages of hip-OA subjects) at 0.55T estimated by Radial TSE and MR fingerprinting. The average percentage increase of T2 values at 0.55T enables a wider range to detect smaller changes in the cartilage areas. The initial findings reported in this study can be utilized further for comparing healthy cartilages vs. early-to-moderate OA. Eventually, OA research findings at 3.0T could be potentially translated at low-field scanners, much more accessible from economic and installation-cost point-of-view.