The Diagnostic Value Of Dynamic Contrast-Enhanced MRI In Nasopharyngeal Carcinoma And Its Changes After Radiotherapy

Objective:To investigate the diagnostic value of dynamic contrast-enhanced MRI (DCE-MRI) in nasopharyngeal carcinoma(NPC) and its changes after radiotherapy.Material and methods:A prospective study were performed in fifty-seven consecutive patients with NPC proven histopathologically,who received DCE-MRI at our institution using a 1.5 T MR system from November 2004 to December 2008.The patients were divided into three groups according to their clinical history:a group of 33 patients with NPC without any treatments after histopathologically proven,a group of 18 patients with nasopharyngeal fibrosis after radiotherapy for NPC,and a group of 6 patients with recurrence nasopharyngeal carcinoma (RNPC) after radiotherapy.MR findings were reviewed and perfusion parameters(time to peak(TTP),the maximum slope(Slope_max),and area under the signal intensity—time(SI-T) curve(AUC)) were calculated by using Perfusion GUI,which based on the software of Matrix Laboratory(MATLAB).Results:TTP,Slope_max and AUC are statistically significant differences in cases of three groups,the mean of the three parameters are compared each other in statistically significant difference in pre-treatment group and RF group,but only the mean of Slope_max are compared each other in statistically significant difference in RNPC group and RF group.In the pre-treatment group,SI-T curves manifest as up speed-up slow type in 9 cases,up speed—the platform type in 10 cases and up speed-down slow type in 14 cases.All patients' SI-T curves appear as up slow type in RF group,while there are 5 cases up speed-up slow type curves and 1 case up speed-down slow type curves in RNPC group.3.According to the forms of SI-T curve showed that a maximum enhancement difference RF group and RNPC group(or pre-treatment group) could be obtained at 42.5 to 45 seconds after the injection of contrast agent. Pseudo-color images of the three parameters can visually display the situations of blood supply in tumor or fibro tissue after radiotherapy by different colors.Conclusion:The Perfusion GUI software which based on MATLAB can be used successfully in visually displaying the situations of blood supply which before and after therapy in NPC by pseudo-color images of TTP,Slope_max and AUC.Not only the types of dynamic contrast-enhanced SI-T curves but also the maximum slope of SI-T curves can distinguish the fibro tissue from recurrent nasopharyngeal carcinoma.Scanning at the first 42.5 to 45 seconds after the injection of contrast agent is recommended to maximize enhancement difference between fibro tissue and recurrent nasopharyngeal carcinoma.