Effects of regions of interest methods on apparent coefficient measurement of the parotid gland in early Sjögren’s syndrome at 3T MRI

Abstract

Background The apparent diffusion coefficient (ADC) has been used to assess parotid gland abnormalities in Sjögren’s syndrome (SS) patients; however, few data exist on the influence of region of interest (ROI) methods on ADC measurements. Purpose To assess the influence of ROI methods on ADC measurement, and their diagnostic ability in detecting parotid gland abnormalities in early SS patients. Material and Methods Thirteen early SS patients underwent parotid gland diffusion-weighted imaging scans at a 3.0 T MR unit. Two readers independently measured the parotid gland ADC value using three different ROIs (whole-gland [WG], single-slice [SS], and reader-based circular [RBC]). The ADC value based on three different ROIs (ADC-ROIWG, ADC-ROISS, ADC-ROIRBC) were compared between the SS group and a matched healthy control (HC) group (n = 19). Receiver operating characteristic (ROC) curves and intra-class correlation coefficients (ICC) were used to determine the diagnostic ability and reproducibility of the parameters. Results The ADC-ROIWG, ADC-ROISS, and ADC-ROIRBC in the SS group were all significantly higher than those in HC group (all P < 0.05). The ADC-ROIWG showed better diagnostic ability than did ADC-ROIRBC ( P = 0.0200), while no significant difference was found between ADC-ROIWG and ADC-ROISS ( P = 0.4636). The ROIWG method showed the best inter- and intra-reader agreement (ICC, 0.902 and 0.928, respectively), followed by ROISS and ROIRBC. Conclusion The ROI methods can influence the parotid gland ADC measurements and their diagnostic ability. Considering our results, we suggest using in clinical practice single-slice ROIs to measure the ADC of the parotid gland.