Detection of Active Plaques in Multiple Sclerosis Using 3 and 12 Directional Diffusion-weighted Imaging: Comparison with Gadolinium-enhanced MR Imaging

Background: Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS) characterized by exacerbations of neurological dysfunction due to inflammatory demyelination. MRI is the most sensitive method to make adiagnosis of multiple sclerosis. contrast-enhanced T1-weighted imaging (CE T1WI) is used as a gold standard to distinguish active and inactive MS lesions. However, Gadolinium based contrast agents (GBCAs) have some contraindications. Diffusion-weighted imaging (DWI) can detect diffusion alterations in active inflammatory lesions. The purpose of this study is to investigate whether common DWI (3 directional) and 12 directional DWI which is used in Diffusion tensor imaging can be an alternative to CE T1WI so as to demonstrat active (enhanced) MS lesions. Methods: In this cross sectional study, at two different hospitals, 138 patients who presented with CNS symptoms suggestive of demyelinating disease were examined. CE T1WI using 0.1 mmol/kg gadolinium as well as 3 & 12 directional DWI was done for all patients. To determine the reliability and accuracy of 3 & 12 directional DWI for delineating the enhancement of demyelinating lesions on CET1W, Intraclass correlation coefficient (ICC) and the plot of sensitivity versus specifity is called receiver operating characteristic (ROC) curve and the area under the curve (AUC) were calculated. Results: 114 patients (82.6%)revealed  contrast enhancement in CE T1WI, 117 (84.7%) and 107 (77.5%) patients demonstrated hyper intense lesions on DWI 12 & DWI 3 respectively. The intraclass correlation coefficient (ICC) for DWI 12 was higher than 0.92; however, for DWI 3 was less than 0.64. The DWI 12 data generated a sensitivity and specificity of 94.7% and 62.5%, combined with an AUC of 84%. Besides the sensitivity, specificity and AUC for DWI 3 CE were 86%, 62.5 and 79%, respectively. Conclusion: Among 2 different DWI sequences, 12 directional DWI images have higher reliability and accuracy. Therefore, despite lower sensitivity compared to CE T1WI, it can be a practical diagnostic sequence in discriminating enhancing lesions from non-enhancing lesions when performing CE-MRI is a concern for the patient. concerning the cons and pros of CE T1WI and DWI 12, these two sequences can be used in combination in order to reach higher sensitivities, leading to earlier diagnosis and more cost effective treatment.