Value of diffusion-weighted magnetic resonance imaging on the follow-up of nasopharyngeal carcinoma after radiotherapy

Purpose: To explore the value of diffusion-weighted imaging (DWI) and magnetic resonance imaging (MRI) on the follow-up of nasopharyngeal carcinoma (NPC) after radiotherapy.

Material and methods: Eighty-three NPC patients after radiotherapy were divided into two groups: 4 cases of residual tumor and 33 cases of non-residual within 6 months, the cases of recurrent and non-recurrent were 5 and 41 over 6 months, respectively. MRI and DWI imaging of these cases were closely analyzed, and the apparent diffusion coefficient (ADC) of the nasopharyngeal residual mass and nasopharyngeal wall thickening, skull base destruction and lateral pterygoid muscle were measured.

Results: The ADC of the lateral pterygoid muscle was (1.501 ± 0.069) × 10<formula>^{ - 3}</formula> mm<formula>^{2}</formula>/s in 83 cases. The ADCs of the non-residual group, residual group, non-recurrent group and recurrent group were (1.843 ± 0.133.4) × 10<formula>^{ - 3}</formula> mm<formula>^{2}</formula>/s, (1.097 ± 0.183) × 10<formula>^{ - 3}</formula> mm<formula>^{2}</formula>/s, (1.884 ± 0.134) × 10<formula>^{ - 3}</formula> mm<formula>^{2}</formula>/s and (0.787 ± 0.067) × 10<formula>^{ - 3}</formula> mm<formula>^{2}</formula>/s respectively.The ADCs of the residual group and recurrent group were lower than that of the lateral pterygoid muscle, while the ADCs of the non-residual group and non-recurrent group were higher than that of the lateral pterygoid muscle.The differences were statistically significant (P < 0.05).

Conclusion: DWI can provide qualitative and quantitative information about the tumor cellular level; it can also identify residual, local fibrosis and recurrence after NPC radiotherapy sensitively and accurately by measuring the ADC of the region of interest.