MRI features of the parotid gland in Sj?gren syndrome

Abstract

Objective To investigate MR imaging features of parotid gland in Sj?gren′s syndrome ( SS).Methods Twenty-seven cases of xerostomia patients were collected and divided into SS group ( n=21) and non-SS group (n=6) according to the international classification (diagnosis) criteria for SS.Ten healthy volunteers were recruited as the control group.All the subjects underwent conventional MRI of parotid gland and MR sialography ( MRS).Standard deviation of T 1 WI and T2 WI signal intensity among 3 groups was observed, meanwhile, grading was made according to parotid glands , fat signal and parotid duct expansion degree respectively.With clinical diagnosis as the gold standard , diagnostic value of conventional MRI , MRS and their combination used in SS was compared.One-way ANOVA was used in comparison of standard deviation of parotid gland′s signal intensity among 3 groups , and Chi-square test was applied in comparison of conventional MRI and MRS diagnostic value.Moreover , Kappa value was calculated to assess the consistency of two grading results in SS.Results Signal intensity of parotid glands in control group and non-SS group was homogeneous.However , bilaterally diffused and heterogeneous high signal intensity on both T1WI and T2WI was found in SS patients, which was depressed on T2WI fat suppression sequences.Forty-two parotid glands were graded by fat signal:Grade 0 (n=2 glands), Grade 1 (n=10), Grade 2 (n=10), Grade 3 (n=6) and Grade 4 (n=14).Parotid peripheral ducts of control group and non-SS group were unexpanded , while bilaterally expanded parotid peripheral ducts were shown in SS patients.The grading of 42 parotid glands by expansion degree of parotid duct , Grade 0 was rated in 12, Grade 1 in 8, Grade 2 in 10, Grade 3 in 5, and Grade 4 in 7.Standard deviation of T1WI signal intensity of parotid glands among SS group , non-SS group and control group were 124.1 ±30.0, 81.8 ±27.6, and 86.3 ±35.0 respectively;and standard deviation of T 2 WI signal intensity were 115.1 ±35.2, 69.8 ±23.5, and 80.1 ±31.4 respectively; the standard deviation of T 1 WI and T2 WI signal intensity of SS group was higher than both non-SS group and control group′s ( F value =13.780 and 13.301, respectively, P 0.05).Among 42 parotid glands with SS, conventional MRI and MRS showed parotid gland lesions in 40 and 30 respectively , and the difference was statistically significant (χ2 =13.04, P=0.013).There was no false positive result.The combination of the two methods detected all 42 lesions.The consistency of detecting parotid abnormalities with SS between conventional MRI and MRS was poor (Kappa=0.12, P=0.092).Conclusions Diffuse fatty infiltration on conventional MRI and diffuse peripheral duct dilatation on MRS in the parotid gland are characteristic features of SS , and conventional MRI could be used as the preferred technique for the SS.combination with MRS may improve diagnostic accuracy. Key words: Sj?gren′s syndrome ; Parotid gland ; Magnetic resonance imaging ; Sialography ;