Quantitative DCE-MRI: an efficient diagnostic technique for evaluating early micro-environment permeability changes in ankylosing spondylitis

Abstract

Background: In the management of early inflammatory joint of ankylosing spondylitis (AS), there is a need for reliable noninvasive quantitative monitoring biomarker to closely assess status of synovitis progression. Cognizant to this,studies geared on improving techniques for quantitative evaluation of micro-environment permeability of the joint space are necessary. Such improved techniques may provide tissue perfusion as important biological parameters and can further help in understanding the origin of early changes associated with AS. The purpose of this study was to prospectively evaluate the diagnostic performance and determine longitudinal relationships of early micro-environment active in the joint space of the sacroiliac joint (SIJ) with a rat model by using quantitative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).

Methods: Thirty wistar male rats were randomly assigned to the model (n = 15) or control (n = 15) group. All rats underwent DCE-MRI of SIJ region at fixed time points (12, 17 and 22 weeks),between September 2018 and October 2019. Differences in permeability parameters between the two groups at the same time point were compared by using an independent samples t test. Spearman correlations of DCE-MRI parameters with different time points in model group were analyzed. All statistical analyses were performed with software.

Results: At 12 weeks,the K^trans,K_ep and V_e values in the model group were slightly lower than those in control group,but all the differences were not statistically significant (p > 0.05). Compared with control group,the transfer constant (K^trans) values increased significantly at 17 weeks and 22 weeks in model group,while the rate constant (K_ep) and volume of extravascular extracellular space (V_e) significantly increased only at 22 weeks(p < 0.05). The K^trans,K_ep and V_e were positively correlated with increasing time points (r = 0.946, P<0.01 for K^trans; r = 0.945, P<0.01 for K_ep; and r = 0.832, P<0.01 for V_e).

Conclusion: Quantitative DCE-MRI parameters are valuable for evaluating the early longitudinal relationship of micro-environment permeability changes in the joint space of SIJ.

Keywords: Animal model; Ankylosing spondylitis; Dynamic contrast-enhanced magnetic resonance imaging; Quantitatively micro-environment; Sacroiliac joint.

Fig. 1

Representative images of ROIs outlined. a Image shows that ROIs have been manually drawn on magnified DCE-MRI image,and that the colour parametric maps of (b) K^trans (min^− 1), (c) K_ep (min^− 1) and (d) V_e are automatically generated

Fig. 2

Bland-Altman plots show interobserver reliability for measurement of DCE-MRI parameters (a-c). SD = standard deviation

Fig. 3

Graphs show longitudinal DCE-MRI parameters in the model and control groups of wistar rats. At 12 weeks,all the differences of K^trans (min^− 1),K_ep (min^− 1) and V_e values were not statistically significant between the model and control groups. Compared with control group, (a) the K^trans (min^− 1) was significantly increased at 17 weeks and 22 weeks in model group,while(b) K_ep (min^− 1) and (c) V_e were significantly increased only at 22 weeks