The diagnostic potential of low-field MRI in problematic total knee arthroplasties - a feasibility study

Abstract

Purpose: Low-field MRI, allowing imaging in supine and weight-bearing position, may be utilized as a non-invasive and affordable tool to differentiate between causes of dissatisfaction after TKA ('problematic TKA'). However, it remains unclear whether low-field MRI results in sufficient image quality with limited metal artefacts. Therefore, this feasibility study explored the diagnostic value of low-field MRI concerning pathologies associated with problematic TKA's' by comparing low-field MRI findings with CT and surgical findings. Secondly, differences in patellofemoral parameters between supine and weight-bearing low-field MRI were evaluated. Methods: Eight patients with a problematic TKA were scanned using low-field MRI in weight-bearing and supine conditions. Six of these patients underwent revision surgery. Scans were analysed by a radiologist for pathologies associated with a problematic TKA. Additional patellofemoral and alignment parameters were measured by an imaging expert. MRI observations were compared to those obtained with CT, the diagnosis based on the clinical work-up, and findings during revision surgery. Results: MRI observations of rotational malalignment, component loosening and patellofemoral arthrosis were comparable with the clinical diagnosis (six out of eight) and were confirmed during surgery (four out of six). All MRI observations were in line with CT findings (seven out of seven). Clinical diagnosis and surgical findings of collateral excessive laxity could not be confirmed with MRI (two out of eight). Conclusion: Low-field MRI shows comparable diagnostic value as CT and might be a future low cost and ionizing radiation free alternative. Differences between supine and weight-bearing MRI did not yield clinically relevant information. The study was approved by the Medical Research Ethics Committees of Twente (Netherlands Trial Register: Trial NL7009 (NTR7207). Registered 5 March 2018, https://www.trialregister.nl/trial/7009).

Magnetic Resonance Imaging Versus Computed Tomography for Three‐Dimensional Bone Imaging of Musculoskeletal Pathologies: A Review

“…Low‐field MRI (<0.5 T) in particular could be acquired to diagnose pathologies associated with orthopedic hardware, 115 given the assumption that low‐field MRI is not overly impacted by susceptibility artifacts and is able to image soft tissues in the vicinity of the implant. Other advantages of low‐field MRI include its low cost (purchase and maintenance), and, when considering musculoskeletal radiology, the ability to scan in weight‐bearing position 115 . This, however, comes at the expanse of SNR and resolution.…”

“… 66 In addition, although 3 T acquisitions are usually equivalent or better than 1.5 T acquisitions for bone visualization and segmentation, 43 , 114 lower field acquisitions should be favored when inhomogeneity artifacts are expected. 36 , 61 Low‐field MRI (<0.5 T) in particular could be acquired to diagnose pathologies associated with orthopedic hardware, 115 given the assumption that low‐field MRI is not overly impacted by susceptibility artifacts and is able to image soft tissues in the vicinity of the implant. Other advantages of low‐field MRI include its low cost (purchase and maintenance), and, when considering musculoskeletal radiology, the ability to scan in weight‐bearing position.…”

“…Other advantages of low‐field MRI include its low cost (purchase and maintenance), and, when considering musculoskeletal radiology, the ability to scan in weight‐bearing position. 115 This, however, comes at the expanse of SNR and resolution.…”

Magnetic Resonance Imaging Around Metal at 1.5 Tesla

“…The trade-off using a low field system (1.0 T or below) is a lower SNR and a lower image resolution. 50,51 Sequence Fast spin-echo or TSE sequences are preferred over simple spin-echo imaging: their short echo spacing and repeated refocusing of magnetization up to the echo time and beyond, result in a reduced peri-implant signal loss and in a more robust, and improved image quality close to the metal. 7,12,52,53 As a rule of thumb, gradient-echo pulse sequences should be avoided, as the rapid intravoxel dephasing of spins with gradient-echo sequences (T2* as opposed to T2 decay) results in significant signal loss and increased artifacts.…”

Medical 3D technology

“…[66] In addition, although 3 T acquisitions are usually equivalent or better than 1.5 T acquisitions for bone visualization and segmentation, [43,114] lower field acquisitions should be favored when inhomogeneity artifacts are expected. [36,61] Low-field MRI (<0.5 T) in particular could be acquired to diagnose pathologies associated with orthopedic hardware, [115] given the assumption that low-field MRI is not overly impacted by susceptibility artifacts and is able to image soft tissues in the vicinity of the implant. Other advantages of low-field MRI include its low cost (purchase and maintenance), and, when considering musculoskeletal radiology, the ability to scan in weight-bearing position.…”