Study of MRI Diffusion-weighted Imaging in the Diagnosis of Lymphadenopathy and Evaluation after Radiotherapy
|Course||Medical Imaging and Nuclear Medicine|
|Keywords||MRI diffusion-weighted imaging lymphadenopathy diagnosis radiotherapy|
Objective:1、To evaluate the value of ADC values and relative ADC values in the differentiation of inflammatory and malignant lymph nodes with MRI diffusion-weighted imaging in animal models.2、To collect ADC values of metastatic lymph node in patients before and after irradiation, and verify the value of DWI in the assessment of radiation effect.Methods:PartⅠExperimental Study of Diffusion-weighted MRI for discrimination of inflammatory and metastatic lymph nodesTwo groups of animal models, including metastatic lymph node and inflammatory lymph nodes, were established. Some morphological indicators of lymph nodes were measured in conventional MRI, including shortest diameter, border (smooth, lobulated or indistinct), and necrosis. ADC values of lymph nodes were also measured in MRI DWI. The contralateral quadriceps femoris was selected as the reference site for rADC values. The rADC was calculated by ADCiesion/ADCreference site-The benefit of rADC over ADC was validated for identifying metastatic lymph nodes. The diagnostic value of ADC was analyzed by ROC curves.PartⅡMR diffusion-weighted imaging for evaluation of therapeutic responds in neck metastastic lymph nodesBy following-up of nasopharyngeal carcinoma, according to the size of lymph nodes, all patients were divided into an effective group and an ineffective group. All patients were examined with MRI and diffusion-weighted imaging. The ADC values of cervical metastastic lymph nodes were measured before treatment and at the 7th and 14th days after treatment. Repeated measures analysis were used to evaluate the ADC values at different time points, and to explore the possibility of the application of diffusion-weighted imaging in predicting therapeutic effect.Results:PartⅠThe average ADC value of inflammatory and metastatic nodes was (0.859±0.037)×10-3mm2/s and (1.089±0.244)×10-3mm2/s. There was statistical difference between them (P<0.05). The area under the ROC curves was 0.791. Threshold value to distinguish benign and malignant lesions were 0.889×10-3mm2/s. The sensitivity, specificity were 80% and 75% respectively.PartⅡSeventy-five lymph nodes were found in 24 patients before radiotherapy. There were significant difference between the effective group and the ineffective group before and after radiotherapy in lymph node sizes. There was no significant difference of ADC values between the effective group and the ineffective group before treatment(t=0.582, P=0.562), however the 7th and 14th days after treatment,significant difference was observe(t=-2.219, P=0.03; t=-2.597, P=0.011).Conclusion:1、DWI is an useful tool for the discrimination of inflammatory and metastatic lymph nodes in VX2 rabbits. DWI with high b value can better distinguish between benign and malignant lymph nodes than a lower b values. The ADC values and rADC values of malignant lymph nodes were significantly higher than benign lymph nodes. The rADC value can better distinguish the benign and malignant lymph nodes than the ADC value.2、After the treatment in nasopharyngeal carcinoma metastatic cervical lymph nodes, diffusion-weighter imaging can reflect the differences between effective and ineffective group at different time points of early response. And it is useful to monitor the treatment responds.