Abstract
Objective:To investigate the use of a quantitative diffusion-weighted imaging (DWI) tool for measuring inflammation of the sacroiliac joints (SIJs) in enthesitis-related arthritis (ERA).Methods:A retrospective study was performed with institutional review board approval. Subjects were adolescents who had undergone MRI of the SIJs since January 2010. 10 patients with a clinical diagnosis of ERA and 10 controls with a clinical diagnosis of mechanical back pain were assessed. Axial T1 weighted, short tau inversion recovery (STIR) and DWI (b-values 0, 50, 100, 300 and 600 mm2 s−1) images were acquired. Apparent diffusion coefficient (ADC) maps were generated using a monoexponential fit. On each of four slices, two to three linear regions-of-interest were placed on each joint. Normalized ADC (nADC) values were defined as joint ADC divided by a reference ADC derived from normal sacral bone. STIR images were scored using a modification of an established technique. The correlation between nADC values and STIR scores was evaluated using Spearman's rank correlation.Results:Mean nADC values were significantly higher in cases than in controls (p = 0.0015). There was a strong correlation between STIR scores and nADC values (R = 0.85).Conclusion:ADC values are significantly increased in inflamed SIJs compared with controls. There is a good correlation between this diffusion-based method and STIR scores of inflammation.Advances in knowledge:We have described and provisionally validated a method for quantifying the severity of inflammation in the SIJs in ERA using ADC measurements. This method is quick, is reproducible and could potentially be automated.
Highlights
Juvenile idiopathic arthritis is the most common form of arthritis in children and adolescents and is a significant cause of morbidity.[1]
Normalized apparent diffusion coefficientin cases and controls Mean Normalized ADC (nADC) values were significantly higher in cases than in controls (p 5 0.0015) (Figure 2)
There was a strong correlation between short tau inversion recovery (STIR) scores and nADC values (R 5 0.85, p, 0.001) (Figure 3)
Summary
Juvenile idiopathic arthritis is the most common form of arthritis in children and adolescents and is a significant cause of morbidity.[1]. Biologic therapies such as etanercept are an effective treatment for ERA but come with a risk of immunosuppression and more rarely myelitis and optic neuritis.[6,7] There is a need for objective markers of joint inflammation to inform therapeutic decision-making and to facilitate clinical trials of new therapeutic agents
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