APPLICATION OF WHOLE BODY DIFFUSION WEIGHTED MR IMAGING FOR DIAGNOSIS AND STAGING OF MALIGNANT LYMPHOMA

Objective To evaluate the clinical impact of whole body diffusion weighted imaging （WB-DWI） on diagnosis and staging of malignant lymphoma. Methods Thirty-one patients with suspected lymphadenopathy were enrolled. WB-DWI was performed by using short TI inversion recovery echo-planar imaging sequence with free breathing and built-in body coil. Axial T2- weighted imaging images of the same location were used as reference. The results of WB-DWI were compared with pathological results and other imaging modalities. The mean apparent diffusion coefficient （ADC） values of different kinds of lymph nodes were compared. Results WB-DWI was positive in all 18 cases with lymphoma, 5 cases with metastatic lymph nodes and 4 of 8 eases with benign lymphadenopathy. The mean ADC value of lymphomatous, metastatic and benign lymph nodes was （0.87 ± 0.17） × 10^3, （0.98± 0.09） × 10^3 and （1.20 ± 0.10） × 10^3 mm^2/s. There was significant difference in ADC value between benign lymph nodes and other two groups （P 〈 0.01）. The sensitivity, specificity and accuracy of WB-DWI in diagnosis of lymphoma were 100% （18/18）, 30.8% （4/13） and 71.0% （22/31）. When an ADC value of 1.08 × 10^-3 mm^2/s was used as the threshold value for differentiating malignant from benign lymph nodes, the best results were obtained with sensitivity of 87.8% and specificity of 91.3%. Sixteen of eighteen cases （88.9%） of lymphoma were accurately staged in accordance with clinical staging. Conclusions WB-DWI is a sensitive, but less specific technique for diagnosis of lymphoma. It is difficult to differentiate lymphnmatous from metastatic lymph nodes using WB-DWI. However, it is a valuable imaging modality for staging of patients with malignant lymphoma.