Computed diffusion-weighted imaging for differentiating synovial proliferation from joint effusion in hand arthritis

The objective of this study is to investigate computed DWI (cDWI) as an alternative method to contrast-enhanced MRI in comparison with directory measured DWI (mDWI) and apparent diffusion coefficient (ADC) for differentiating synovial proliferation from joint effusion. Nine patients suspected with RA (5 women) were included in this study. A radiologist identified region of interest (ROI) based on STIR, and evaluated using a 5-point grading scale of 0 (fluid) to 4 (synovial proliferation) according to the degree of contrast enhancement within the ROI. cDWI was synthesized for b values from 1000 to 2000 at 200 s/mm² intervals using the combination of b values at mDWI. In addition to ADC values, contrast ratios were calculated using signal intensity for each ROI on the mDWI and cDWI. Visual assessment by a radiologist was conducted between pairs of STIR image and mDWI or cDWI. ROI grades were most significantly correlated with cDWI₂₀₀₀ based on b values of 400-1000 s/mm² (r_s = 0.405, p < 0.01). The area under the curve of cDWI₂₀₀₀ based on b values of 400-1000 s/mm² (0.762) was larger than that of ADC values (0.570-0.608) when comparing low versus high contrast enhancement grades. Both cDWI₁₈₀₀ (200-1000) and cDWI₂₀₀₀ (400-1000) demonstrated high sensitivity and specificity in visual assessment (84.6% and 66.7%, respectively). The cDWI₂₀₀₀ based on b values of 400-1000 s/mm² may be useful for noninvasive differentiation of synovial proliferation from joint effusion in hand arthritis.