Study Of DSC-PWI In Differential Diagnosis Of Lymph Node Lesions And Evaluation After Radiotherapy In Animal Models

Objective: To explore the differences of perfusion parameters with dynamic susceptibility contrast (DSC)-perfusion weighted imaging (PWI) between metastatic and benign lymph nodes, and to evaluate the early response of metastatic lymph node after radiotherapy in animal models.Methods: Twenty rabbits are divided randomly into two groups, the benign group(Group B)and malignant groups(Group M1 and M2). In Group B and M1, two readers draw regions of interest. In Group M2, the right limbs of rabbits received single-dose radiotherapy of 10 Gy locally, DSC-PWI was performed a day prior to as well as 1 day, 3 days and 7 days after radiotherapy respectively; one reader draws regions of interest including lymph nodes or muscle of another limbs respectively. The time-intensity curve (TIC) was derivatized into perfusion parameters, such as the time to peak (TTP), the maximal slope descending (MSD%) and the peak heighted (PH%). To compare the results between two readers, the intraclass correlation coefficient(ICC) was used; two sample t test was used to analyze the outcomes between two groups; the difference which was induced by radiotherapy was compared, and the results were analyzed with the one-way ANOVA. HE staining was examined.Results: Lymph nodes of Group M1 are bigger than Group B (P<0.01). 9 cases (90%) in Group M1 and 8 cases (80%) in Group B show the same shape of TIC, including obvious steep down slope, upslope and a long plateau. Between two readers, the intraclass correlation coefficient of every semi-parameters are equal or bigger than 0.800. The TTP, MSD% and PH% between two groups(Group B and M1) are different (P<0.05). At seventh day after therapy in Group M2, the TTP values increase, and MSD% values decrease, which reveal significantly difference (P<0.05). The muscle of heterolateral limbs show no statistic different changes before and after the time of treatment in the models (P>0.05). Lymphatic sinus in Group B expand, intercellular substance swell where neutrophilic granulocyte infiltrating. But in Group M1 and M2, normal structure in lymph node damaged and was replaced by tumor cells before treatment. In Group M2, some nucleus stained and cells swell at the first day after irradiation; some tumour cells degenerate at third day; necrosis scatter in lymph nodes at seventh day.Conclusion: Based on the TIC, the semi-parameters can differentiate the hemodynamic characteristics of malignant lymph nodes from benign, and also can be used to observe early response of malignant lymph nodes after radiotherapy to some extent.