(Saturday, 4/4/2020) [Mountain Time (GMT-6)]
Purpose: To increase the efficiency of plan quality evaluation for liver SBRT cases by computing Veff and NTCP in real-time.
Methods: Liver SBRT plans have specific dose criteria for all critical structures, but also have limits for the liver effective volume (Veff) and Normal Tissue Complication Probability (NTCP). Even if the normal dose criteria are met, the prescription (Rx) dose may have to be reduced to meet the Veff/NTCP criteria. To ease the plan optimization process, a script was written in the Eclipse 13.7 Treatment Planning System to calculate liver Veff/NTCP in real time. It uses the plan’s DVH curve to calculate the Veff and the Lyman-Kutcher-Burman model along with the volume-effect, slope-effect parameters, and liver TD50 values to compute the NTCP. When the script is run in Eclipse, the user interface prompts to select the specific plan for the patient, and if the plan is hepatocellular carcinoma or metastatic. By clicking an “Execute” button, the calculation begins and the Veff and NTCP values are displayed in the user interface.
Results: The Veff and NTCP values generated by the script were compared with the values obtained by hand calculation for 10 mixed cases (hepatocellular/metastatic, different Rx doses) in order to evaluate the accuracy of the script’s calculations. The agreement was excellent. Because the script runs quickly, the planners can use it iteratively to evaluate Veff /NTCP at various stages of plan optimization.
Conclusion: The script has proven to be useful in expediting the liver SBRT planning process. Normally, the planner must wait for a medical physicist to calculate Veff /NTCP outside of Eclipse. Using the script, the planner can assess the Veff /NTCP of a plan in real-time, providing crucial information for the plan optimization process.
ePosters
Contact Email
