Signal intensity changes of dentate nucleus on plain MR T1WI in nasopharyngeal carcinoma patients after radiotherapy and multiple injections of gadolinium-base contrast agent
Objective To observe changes of plain MR T1WI signal intensity of dentate nucleus in nasopharyngeal carcinoma patients after radiotherapy and multiple times of intravenous injection of gadolinium-based contrast agent(GBCA).Methods Fifty patients with pathologically confirmed nasopharyngeal carcinoma and received intensity-modulated radiotherapy were retrospectively enrolled as the nasopharyngeal carcinoma group,and 50 patients with other malignant tumors and without history of brain radiotherapy were retrospectively enrolled as the control group.All patients received yearly GBCA enhanced MR examinations for the nasopharynx or the head.T1WI signal intensities of the dentate nucleus and the pons on same plane were measured based on images in the year of confirmed diagnosis(recorded as the first year)and in the second to the fifth years.T1WI signal intensity ratio of year i(ranging from 1 to 5)was calculated with values of dentate nucleus divided by values of the pons(△SIi),while the percentage of relative changes of year j(ranging from 2 to 51 was calculated with △SIj compared to △SIi(Rchangej).The values of these two parameters were compared,and the correlation of △SI and GBCA injection year-time was evaluated within each group.Results No significant difference of gender,age nor △SI1 was found between groups(all P＞0.05).The second to the fifth year △SI and Rchange in nasopharyngeal carcinoma group were all higher than those in control group(all P＜0.05).Within both groups,△SI was positively correlated with GBCA injection year-time(both P＜0.05).Conclusion Patients with nasopharyngeal carcinoma who underwent radiotherapy and multiple times of intravenous injection of GBCA tended to be found with gradually worsening GBCA deposition in dentate nucleus,for which radiotherapy might be a risk factor.
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