To investigate the sensitivity of chemoradiotherapy on nasopharyngeal carcinoma using intravoxel incoherent motion MRI

Objective: To investigate the application value of intravoxel incoherent motion (IVIM) MRI for evaluating the sensitivity of chemoradiotherapy on nasopharyngeal carcinoma (NPC). Methods: Sixty eight consecutive patients newly diagnosed with NPC in the stage of T3 (30 patients) or T4 (38 patients) were retrospectively enrolled. They were divided into effective group (45 patients) and poor-effective group (23 patients) clinically after a standard chemoradiotherapy according to the RECIST criteria. IVIM with 13 b-values (range, 0 to 800 s/mm²) and general MRI were performed at 3.0 T MR scanner before and after chemoradiotherapy. Two radiologists major in MRI diagnose analyzed all images independently and placed regions of interest (ROIs). Intraclass correlation coefficient (ICC) was used to evaluate intra-observer and inter-observer agreement. And Mann-Whitney test was used to assess the differences between the two groups. Results: The reproducibility between intra-observer and inter-observer was relatively good. Statistically, D [(0.69 ± 0.06) × 10^-3 mm²/s vs. (0.52 ± 0.10) × 10^-3 mm²/s; U = 51.5, P < 0.01)] and D^* [(161.33 ± 11.50) × 10^-3 mm²/s vs. (126.96 ± 10.27) × 10^-3 mm²/s; U = 18.0, P < 0.01] were significantly higher in effective group than those in poor-effective group, whereas the difference of f (16.68 ± 1.94% vs. 16.40 ± 1.11%, U = 434.5, P = 0.282) and ADC (1.23 ± 0.11) × 10^-3 mm²/s vs. (1.25 ± 0.10) × 10^-3 mm²/s, U = 427.0, P = 0.240) could not reach statistical significance between the 2 groups (P > 0.05). Conclusions: IVIM may be potentially useful in assessing the chemoradiotherapy on NPC. The higher D value combined with higher D^* value might indicate the chemoradiotherapy on NPC is more sensitive, and the higher D^* value might reflect increased blood vessel generation and parenchymal perfusion in NPC. (authors)