ABSTRACT
Objective To investigate the impacts of the CT value-electron density transformation curves on radiotherapy dosage for different scanning sites.Methods The CT value-electron density transformation curves under head,chest and abdomen modes were obtained with CIRS062 nonuniform equivalent phantom,a CT simulator and the same scanning parameters.Totally 8 patients with glioma,lung cancer or gastric cancer had the radiotherapy dosages calculated with Pinnacle 9.8 TPS and CT value-electron density transformation curve under the three modes,so as to analyze the dosage deviation involving in hop value as well as the dose volume histogram (DVH) for the target area and organs at risk (OAR).Results With the scanning parameters kept the same,the head area had no significant differences in the CT value-electron density transformation curve and exposure dosage with the abdomen area (P＞0.05),while the head and abdomen areas had statistical differences in the CT value-electron density transformation curve with the chest area (P＜0.05).CT values varied greatly at the high-density tissue,while the dosage deviations at the target area and OAR were both less than 2％.Conclusion CT value-electron density transformation curve for different scanning sites has influences on radiotherapy dosage,and head and chest tumors should have the dosage calculation based on the CT value-electron density transformation curve with corresponding scanning modes to ensure dosage computation precision during treatment planning.