Abstract
The relationships between IVIM and DCE-MRI parameters in AS are not clear. We explore the correlation between intravoxel incoherent motion (IVIM) diffusion weighted imaging (DWI) and dynamic contrast-enhanced (DCE) parameters obtained on MR images in patients with ankylosing spondylitis (AS). Forty-four patients with AS were prospectively examined using a 1.5-T MR system. IVIM DWI was performed with 11 b values (range, 0–800 s/mm2) for all patients. The correlation coefficients between IVIM and DCE-MRI parameters were analyzed using Spearman's method. Our results showed that intra- and interobserver reproducibility were excellent to relatively good (ICC = 0.804–0.981; narrow width of 95% limits of agreement). Moderate positive correlations were observed between pure molecular diffusion (Ds) and maximum enhancement (ME) and relative enhancement (RE) (r = 0.700, P < 0.001; r = 0.607, P < 0.001, resp.). Perfusion-related diffusion (Df) showed negative moderate correlation with ME (r = −0.608, P < 0.001). However, no correlation was observed between perfusion fraction (f) and any parameters of ME, RE, TTP, and BE (r = −0.093–0.213; P > 0.165). In conclusion, the IVIM parameters, especially f, might play a critical role in detecting the progression of AS, because it can provide more perfusion information compared with DCE-MRI; besides the IVIM MRI is a noninvasive method.
Highlights
The prevalence of ankylosing spondylitis (AS) is 0.1–2% of the general population
The Shapiro-Wilk test showed that all dynamic contrast-enhanced (DCE) (RE, maximum enhancement (ME), time to peak (TTP), and brevity of enhancement (BE)) and intravoxel incoherent motion (IVIM) (Ds, f, and Df) parameters had normal distributions, and the Levene test revealed that all the variances were homogeneous
There was no significant difference among three observations of parameters (RE, ME, TTP, BE, Ds, f, and Df), determined by observer 1 and 2 (P = 0.825–0.963)
Summary
The prevalence of ankylosing spondylitis (AS) is 0.1–2% of the general population. The AS is a chronic disease with active and inactive stage and it is very important to detect the active stage of AS [1]. Thanks to recent introductions of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and Diffusion weighted imaging (DWI), AS could be diagnosed early, and the active or inactive stages of AS could be detected via observation on sacroiliitis. Using pharmacokinetic models from a DCE-MRI acquisition, semiquantitative and BioMed Research International quantitative hemodynamic parameters, including relative enhancement (RE), maximum enhancement (ME), time to peak (TTP), and brevity of enhancement (BE), have been processed and modeled [4, 5]. Bane et al have reported that those parameters of the active group were significantly higher than those of the inactive group with AS and showed that DCE-MRI was valuable in assessing treatment of AS [6]. Parameters of DCE-MRI are influenced by the injection duration time, circulation time, and contrast dosage. It should be noted that the contrast agents might increase the risk of renal fibrosis [7, 8]
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