Quantitative Assessment of Condylar Bone Changes in Osteoarthritis Patients Using Single-photon emission computed tomography/computed tomography and Magnetic resonance imaging

Objectives This retrospective study aimed to investigate and evaluate the signal intensity ratio (SIR) on magnetic resonance imaging (MRI) and maximum Standard Uptake Value (SUVmax) and Hounsfield Unit (HU) values on Single-photon emission computed tomography/computed tomography (SPECT/CT) in relation to the diagnosis of Temporomandibular joint osteoarthritis (TMJ OA). Methods Ninety-six TMJ from 63 patients who took SPECT/CT and MRI between January 2017 and September 2023were included. SUVmax and HUmedulla of TMJ were measured. SIR was measured and calculated based on the ratio of magnetic signal intensity of the condyle and cerebral cortex on proton density weight image (PDWI) and T2-weighted image (WI). Results The TMJ OA group showed high SUV max (7.98 ± 4.09; median: 6.5), compared to the normal (3.21 ± 0.76; median: 3.1) with significant difference (p < 0.001). A significant difference was also observed in the HU, with the TMJ OA (457.14 ± 247.48) versus normal (296.91 ± 117.51) (p = 0.001). Both SIR measured by PDWI and T2-WI were lower in the TMJ OA (0.89 ± 0.28; median: 0.9 and 1.19 ± 0.26; median: 1.2) compared to the normal (1.23 ± 0.23; median: 1.2 and 1.00 ± 0.23; median: 1.0) with significant difference (p < 0.001). Conclusions This study can provide the basis that SIR can be helpful in diagnosis in patients clinically suspected of having OA. Advances in knowledge This study is the first to quantitatively evaluate condylar bone changes in TMJ OA by combining SUVmax from SPECT/CT, HU from CT, and SIR from MRI within the same cohort. This integrated imaging approach may contribute to more objective and reliable diagnosis of TMJ osteoarthritis.