EVALUATION ABOUT INFLUENCE OF INTRAVENOUS CONTRAST ON DOSE DISTRIBUTION AND MONITOR UNIT USING CT IN TREATMENT PLANNING FOR LUNG AND CERVICAL CANCERS

Purpose/Object: The purpose of this study was to evaluate the difference in dose and the monitor units (MUs) between the two plan groups on two CT images with contrast and non-contrast. Then, it is proposed to use CT images with intravenous contrast as the basic sequence of images to plan cancer treatment for patients. Materials/Methods: A total of 20 contrasted and non-contrasted patients with lung and cervical cancers were included. Prowess 5.1 software was used to do the treatment planning. Results: There was no significant difference in dose distribution and monitor unit of both intravenous and non-intravenous contrast had the mean difference in the dose of 1.17% and on MU was 1.42% with plan groups of lung cancer and 0.45% and 0.32% with plan groups of cervical cancer. Some cases had big differences; for example, the difference was 4.14% of the volume of PTV received maximum dose. The main cause of this discrepancy was that the patients were unable to control their breathing, resulting in their bodies moving differently during CT before and after contrast injection. Conclusions: The use of contrast agents doesn’t significantly influence dose and monitor unit at some cases of lung and cervical cancer but it can influence dose accuracy for other cancer sites such as head and neck, prostate or rectum.