Application value of three-dimensional heavily T2 weighted turbo spin echo imaging technique in differential diagnosis of malignant and benign parotid tumors

Abstract

Objective To investigate the application value of three-dimensional(3D) heavily T2 weighted turbo spin echo(T2-SPACE) imaging technique in differential diagnosis of malignant and benign parotid tumors. Methods A total of 51 patients with parotid tumors were prospectively recruited from June 2015 to December 2017 in Ningbo No.2 Hospital. There were 23 males and 28 females, aged from 16 to 74 years. All the patients were scanned by routine MRI sequences and heavily T2-SPACE sequence. Imaging data were post-processed with 3D multiplane reformation, and facial nerve and parotid gland were reformatted with curved planar reformation. Tumor location, morphology, margin, cystic necrosis and signal characteristics were observed on heavily T2-SPACE imaging. By analyzing the position relationship between tumor and parotid gland or facial nerve on routine MRI and heavily T2-SPACE sequences, benign parotid tumors were distinguished from malignant tumors. The accuracy rate was also compared to pathological findings, which is regarded as golden standard. Results Heavily T2-SPACE images shows 55 lesions were included in 51 patients. Twenty-five lesions were located in the superficial lobe, 16 lesions in the deep lobe, 14 lesions across the crack. The image findings of the 55 lesions included: regular shape and well-defined margin in 34 lesions, irregular shape and indistinct margin in 21 lesions, heterogeneous intensity with cystic necrosis in 31 lesions. The number of facial nerve displayed on routine MRI T1, T2 sequence and heavily T2-SPACE sequence was 39, 41, 53 sides, respectively, and parotid gland was 32, 45, 54 sides, which illustrated that heavily T2-SPACE sequence was able to find more facial nerve and parotid gland and showed clearer image. Among the 55 lesions, 34 lesions were diagnosed benign and 21 lesions were diagnosed malignant on routine MRI sequence, whereas 35 lesions were diagnosed benign and 20 lesions diagnosed malignant on heavily T2-SPACE sequence. According to pathological result (36 lesions benign, 19 lesions malignant), the accuracy rate of benign and malignant on routine MRI was 75.0%(27/36), 12/19, and the total accuracy was 70.9%(39/55), meanwhile the accuracy rate of heavily T2-SPACE sequence was 88.9%(32/36), 16/19 and 87.3%(48/55), respectively. Diagnostic accuracy was improved by using heavily T2-SPACE sequence with statistical difference (χ2=7.111, P<0.05) . Conclusions Tumor location, margin, internal signal and position relations between parotid and facial nerve or parotid duct are better demonstrated on heavily T2-SPACE images, meanwhile, certain value is found in differential diagnosis of malignant and benign tumors, operation strategy, protection of facial nerve and prognosis judgement by using heavily T2-SPACE sequence, which is worthy to be widely applied in MR examination of parotid gland. Key words: Parotid neoplasms; Magnetic resonance imaging; Turbo spin echo sequences; Facial nerve; Parotid duct