To discuss the value of incoherent motion diffusion-weighted imaging (IVIM-DWI)-magnetic resonance imaging (MRI) in the evaluation of sacroiliac joint activity in ankylosing spondylitis (AS).

The 128 patients with AS in our hospital from March 2018 to March 2021 were selected as the AS group, which were divided into active group (n=42) and stable group (n=86) according to the Basdai disease activity index (BASDAI), and the 50 healthy persons were selected as the healthy group during the same period. The pure water molecular diffusion coefficient (D), perfusion-related pseudo diffusion coefficient (D*) and perfusion-related fraction (F) were detected by IVIM-DWI-MRI, and the D, D* and F of the each groups were compared, the evaluation value of IVIM-DWI-MRI on the sacroiliac joint disease activity of AS were analyzed.

The D, D* and F in AS group were higher than those in healthy group, the difference was statistically significant (P<0.05). The D, D* and F in the activity group were higher than those in the stable group, the difference was statistically significant (P<0.05). The ROC curve shows that, in the sensitivity, specificity, and area under the curve for assessing the sacroiliac joint activity of AS, the D were 76.19%, 79.07% and 0.817; the D* were 66.67%, 72.09%, 0.765; the F were 71.43%, 74.42% and 0.803; The combined values of D, D* and F were 95.24%, 93.02% and 0.905, the combined values of D, D* and F were higher than those of D, D* and F alone, the difference was statistically significant (P<0.05).

The D, D*, F and other indexes in IVIM-DWI-MRI are related to the changes of the sacroiliac joint lesion activity, which can be used AS evaluation indexes, and the combined evaluation value of D, D*, F is higher.