Room: Exhibit Hall
Purpose: Quality assurance procedures in radiotherapy require image guided verification of patient position. Often 3D -CBCT is used. Every imaging procedure based on X-rays provides/delivers a dose to the patient body. Rarely this dose is taken into account in the treatment plans. The aim of the study is to configure kV beam data in Eclipse treatment planning system (Varian Medical Systems) to simulate dose distribution from 100kV CBCT imaging and incorporate imaging dose in total dose distribution
Methods: The new accelerator with 100 kV photon beam was defined in Eclipse v. 13.6. To configure Anisotropic Analytical Algorithm (AAA) v. 13.6 a percentage depth dose and dose profiles were defined with the use of literature data. Secondly, dose distribution in test patient was estimated. Treatment plan for 1cm brain tumor in proximity to chiasm, with 60Gy total dose in 30 fraction was the case study. To predict the dose from the imaging procedure an arc technique with 20cm x20cm field size was planned. Two CBCTs for each fraction were assumed. Total radiation dose from the treatment and imaging was estimated. The influence of low energy beam on biological effects was not taken into account.
Results: Dose from CBCT in this specific plan has been predicted. Hypothetical double daily imaging caused an increase in the maximum dose to critical organs of 15%.
Conclusion: Implementation of imaging dose calculation into treatment planning systems is possible, however further work is required to introduce the appropriate dose of CBCT and different energy beam configuration. Moreover, It is expected that using other fractionation e.g. stereotaxis, other dose from imaging will be obtained. It is necessary to extend the study with the calculation of the kV and MV radiation biological effects.
Funding Support, Disclosures, and Conflict of Interest: K. Slosarek - Scentific Consultant at Varian Poland
Not Applicable / None Entered.