Early assessment of radiation-induced parotid damage with T2 ? mapping / 实用放射学杂志

ABSTRACT

Objective To monitor the dynamic changes of radiation-induced parotid damage using T2 ? mapping.Methods Thirty-four patients with nasopharyngeal carcinoma (NPC)were enrolled.All patients underwent T1 WI,T2 WI and T2 ? mapping for bilateral parotid glands at pre-RT (2 weeks before radiotherapy),mid-RT (5 weeks after the beginning of radiotherapy)and post-RT (4 weeks after the completion of radiotherapy).Parotid MR parameters,mean radiation dose and xerostomia degrees of the patients at different time points were recorded.Furthermore,nine healthy volunteers were enrolled,who undergone T2 ? mapping twice with an interval of 4 weeks in order to analyze the reproducibility of T2 ? value.Results From pre-RT to mid-RT and post-RT,parotid volume decreased [atrophy rates,(25.34±11.33)％ and (25.74±9.93)％,respectively]and T2 ? values decreased [change rates,(-5.63±8.86)％ and (-4.81±10.67)％, respectively]significantly (all P < 0.01 ).Parotid normalized T1 signal intensity decreased significantly from pre-RT to post-RT [change rate,(-7.43±10.61)％,P =0.007],and the change rate was correlated inversely with mean radiation dose significantly (r =-0.646, P <0.001).Parotid volume and T2 ? value changed correspondingly with xerostomia degrees of the patients during radiotherapy.Parotid MR parameters showed excellent reproducibility (intraclass correlation coefficient,0.843 -0.993).Conclusion The dynamic changes of radiation-induced parotid damage in patients with NPC can be noninvasively evaluated by routine MRI and T2 ? mapping.