To predict the radiosensitivity of nasopharyngeal carcinoma using intravoxel incoherent motion MRI at 3.0 T

Purpose: To investigate intravoxel incoherent motion (IVIM) MRI for evaluating the sensitivity of radiotherapy on nasopharyngeal carcinoma (NPC). Results: The reproducibility between intra-observer and inter-observer was relatively good. D (0.72x10(-3) mm(2)/s +/- 0.14 vs. 0.54x10(-3) mm(2)/s +/- 0.23; P < 0.001) and D* (157.92x10(-3) mm(2)/s +/- 15.21 vs. 120.36x10(-3) mm(2)/s +/- 10.22; P < 0.0001) were significantly higher in effective group than poor-effective group, whereas the difference of f (18.79%+/- 2.51 vs. 16.47%+/- 1.51) and ADC (1.21x10(-3) mm(2)/s +/- 0.11 vs. 1.33x10(-3) mm(2)/s +/- 0.23) could not reach statistical significant between the 2 groups (P > 0.05). Conclusions: IVIM may be potentially useful in assessing the radiosensitivity of NPC. The higher D value combining with higher D* value might indicate the more radiosensitive of NPC, and increased D* might reflect increased blood vessel generation and parenchymal perfusion in NPC. Materials and Methods: Sixty consecutive patients (20 female, range, 27-83 years, mean age, 52 years) newly diagnosed NPC in the stage of T3 or T4 were enrolled. Forty-two of them were divided into effective group clinically after a standard radiotherapy according to the RECIST criteria. IVIM with 13 b-values (range, 0-800 s/mm(2)) and general MRI were performed at 3.0T MR scanner before and after radiotherapy. The parameters of IVIM including perfusion fraction (f), perfusion-related diffusion (D*), pure molecular diffusion (D) and apparent diffusion coefficient (ADC) were calculated. Two radiologists major in MRI diagnose analyzed all images independently and placed regions of interest (ROIs). Intra-class correlation coefficient (ICC) was used to evaluate intra-observer and inter-observer agreement. And MannWhitney test was used to assess the differences between the two groups.