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 60.8–913.9 cc for HCC and 2.4–22.9 cc for the cervix tumour. In HCC, the average at DTV volume increased to 124.98 ± 29.02, whereas the average  increased to 105.36% ± 2.66% for the Planning Target Volume-crop (PTV-crop). For cervix tumour cases, the highest dose on DTV volume reached 138.49%, and the average  at DTV volume increased to 116.80% ± 13.19%. In addition, the average  increased to 101.89% ± 5.58% 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 106.93% ± 5.57%, and OAR-cervix is 101.18% ± 1.87%.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.