Diagnostic Value Of Acoustic Radiation Force Impulse And Diffusion Tensor Imaging In Parotid Tumors

ObjectiveTo investigate the diagnostic and differential diagnostic value of Acoustic Radiation Force Impulse(ARFI) and diffusion tensor imaging (DTI) in parotid tumors.Materials and MethodsTwenty-nine cases of patients with parotid tumors were examined with routine ultrasound (US), routine MR imaging, ARFI and DTI technique. All patients were proved with surgery and pathology.(1) For each lesion, routine US and ARFI images were obtained. To observe their location, size, shape, border, internal echo and vascularity with routine US.Then we examined with ARFI technique, recording shear wave velocities (SWE) of the solid part of tumors and normal gland at the same depth.(2) All cases were examined with routine MRI and DTI. T1-weighted imaging (T1WI), T2-weighted imaging(T2WI) and T2WI fat saturation sequences were used in MR. To observe the location, margin, signal intensity and adjacent condition. The b values of DTI were Os/mm2and800s/mm2. We reconstructed the Apparent Diffusion Coefficient (ADC) map and fractional anisotropy(FA)map with special software. The ADC and FA values of the tumors were measured with three regions of interest (ROI) covering the solid part of tumors.(3) The findings were compared with pathologic diagnoses. We presented pathology as the gold standard, using Medcalc11.0statistical software to analyze. The cut-off of benign or malignant lesions were affirmed with receiver operating characteristic curve (ROC), area under ROC, sensitivity and specificity were calculated as well.ResultsTwenty-nine cases of patients with parotid tumors included22benign tumors,(10pleomorphic adenomas,9Warthin tumors,1basal cell adenoma,1 schwannoma,1vascular tumor); and7malignants (2acinic cell carcinomas,2mucoepidermoid carcinomas,1pleomorphic adenoma malignant,1duct carcinoma,1basal cell carcinoma).(1) The mean SWV values of benign and malignant parotid lesions were (2.02±0.53)m/s and (2.80±0.53)m/s. There was significant difference in the SWV value between them (P<0.01). The mean SWV values of pleomorphic adenomas and Warthin tumors were (2.41±0.26)m/s and (1.58±0.51) m/s. Significant differences were found in the mean SWV values between them, as well as between Warthin tumors and malignant tumors,(P<0.01). However, pleomorphic adenomas and malignant tumors had no statistical differences. If the cut-off of2.62m/s were diagnosed as malignancies, the sensitivity and specificity for diagnosing malignant lesions in the parotid were71.4%and90.9%.(2) The mean ADC values of benign and malignant parotid lesions were (1.26±0.37x10-3mm2/s) and (0.94±0.17x10-3mm2/s). There was a significant difference in the ADC value between them. We found no statistical differences in mean FA values between benign and malignant lesions, which were0.21±0.06、0.22±0.08. The mean ADC values of pleomorphic adenomas and Warthin tumors were (1.43±0.19×10-3mm2/s) and (0.89±0.11×10-3mm2/s). There were significant differences in the SWV and FA values between pleomorphic adenomas and malignant tumors (P<0.01), however, Warthin tumors and malignant tumors had no statistical differences. The cut-off of1.17×10-3mm2/s was diagnosed as malignancies, the sensitivity and specificity were100%and54.5%.Conclusion(1) ARFI technology can display elasticity of parotid tumors, it is a valid examination in the evaluation of the parotid tumors stiffness, which can be used in the evaluation of the parotid pathology, but there is a big overlap between pleomorphic adenoma and malignant tumor, it is difficult to differentiate.(2) DTI can delineate the microstructure of the normal and pathological parotid, and provide quantitative diagnostic information. Therefore, DTI can be used in the differential diagnosis of parotid tumors, but there is somewhat difficulty to distinguish Warthin tumors from malignancy.(3) The combination of ARFI technique and DTI can improve the qualitative diagnosis of benign and malignant tumors.