Study On Diagnostic Value Of Diffusion Weighted MRI On Local Recurrence Of Nasopharyngeal Carcinoma

Objective To analyze the difference of ADC value between recurrentnasopharyngeal neoplasm and non-recurrent lesions after radiotherapy; to investigatethe diagnostic value of Diffusion Weighted imaging (DWI) on nasopharyngealneoplasm recurrence and to study its ADC diagnostic threshold.Methods The groups that meet the inclusion criteria--local recurrence afterradiotherapy(recurrence) group39cases and fibrosis after radiotherapy(non-recurrent)group51cases, underwent routine MR scan, enhance and DWI sequence scan (b=0,800s/mm2); analyze the routine MRI findings of recurrence lesions andnon-recurrent lesions. ADC values of recurrence and non-recurrent lesions weremeasured and compared using two independent samples t-test. Two groups of data were analyzed, and diagnostic sensitivity, specificity of routine MRI, MR DWI werecalculated. Receiver operating curve (ROC) were plotted to determine ADCdiagnostic threshold of recurrent nasopharyngeal neoplasm.Results ADC values difference between recurrence group and non-recurrentgroups were statistically significant (t=-9.118; P＜0.05). Take0.887×10-3mm2/sas diagnosis threshold of MR DWI diagnosis of recurrence neoplasm, the diagnosticsensitivity and specificity were87.18%（34/39），94.12%（48/51）respectively. Thearea under ROC curve was0.968. For routine MRI diagnosis of tumor recurrence, thesensitivity and specificity were71.79%(28/39) and74.51%(38/51) respectively. Thearea under the ROC curve was0.732. The difference between both areas under theROC curve were significant statistically (Z=4.583, P＜0.0001).Conclusion DWI has a great value in detection and diagnosis of recurrentnasopharyngeal neoplasm and has a higher diagnostic efficiency than routine MRI.