Comparison of Dose Distribution in Clinical Planning and Dose Plan Using the Concept of Definite Target Volume in Stereotactic Radiotherapy Techniques

Introduction: To implement the newly introduced concept volume of Definite Target Volume (DTV) and compare the distribution and dose-escalation in the DTV and clinical plans.Material and Methods: We used seven samples of hepatocellular carcinoma (HCC) and three cervix tumour plans. DTV is determined through occupancy probability and margin contraction. This margin reduces the Clinical Target Volume (CTV) to obtain the DTV volume. DTV optimisation was achieved by giving the maximum dose to the target volume and limiting the organ at risk (OAR) by constraint.Results: The DTV volume is obtained with a range of ۶۰.۸–۹۱۳.۹ cc for HCC and ۲.۴–۲۲.۹ cc for the cervix tumour. In HCC, the average at DTV volume increased to ۱۲۴.۹۸ ± ۲۹.۰۲, whereas the average  increased to ۱۰۵.۳۶% ± ۲.۶۶% for the Planning Target Volume-crop (PTV-crop). For cervix tumour cases, the highest dose on DTV volume reached ۱۳۸.۴۹%, and the average  at DTV volume increased to ۱۱۶.۸۰% ± ۱۳.۱۹%. In addition, the average  increased to ۱۰۱.۸۹% ± ۵.۵۸% for the PTV-crop. A larger dose delivered at the DTV will be associated with an increase in OAR. The dose increase of OAR-HCC is ۱۰۶.۹۳% ± ۵.۵۷%, and OAR-cervix is ۱۰۱.۱۸% ± ۱.۸۷%.Conclusion: The larger margins generate smaller DTV volumes or vice versa. The dose to target DTV has increased considerably, but dose increases to PTV-crop and OAR are still within clinically acceptable levels.