(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: Gamma Knife treatments include high doses in single or hypofractionation schemes, delivered with sub-millimeter accuracy and very sharp dose gradients. These characteristics make accurate independent dose verification critical. Prior works have shown verification methodologies, but accuracy falls short in situations where the target is shallow in depth or when the patient is positioned with a gamma angle other than 90 degrees. This is likely due to the use of discrete cranial radii measurements used for skull rendering employed in the secondary calculation algorithm. In this work, we compare a commercially available secondary dose calculation software to a new secondary calculation software, which utilizes an innovative image threshold method to render the skull for dose calculation.
Methods: Using the new secondary calculation software with image threshold skull rendering, six hundred sixty-six treated plans (corresponding to a year of treatments with various patient and target geometries) were imported from our treatment planning system (GammaPlan 11.0.3) and a secondary dose calculation was conducted. The agreement between the new calculations and the TPS were compared to the original secondary dose calculation agreement with the TPS using various descriptive statistics and a Wilcoxon Signed Rank Test.
Results: The mean absolute percent differences between the TPS and both the commercially available and new secondary dose calculation was 1.15% and 0.7%, respectively. The largest absolute difference was 10.25% and 3.33%, respectively. The Wilcoxon Signed Rank Test indicates a significant difference in the agreement between the two secondary calculations and the TPS, with a p-value <0.0001.
Conclusion: The new secondary dose calculation software has better agreement with the TPS than the commercially available secondary calculation software over a range of diverse treatment geometries. This indicates that the image threshold method of skull rendering is a robust technique for modeling the skull in Gamma Knife secondary dose calculation.
Funding Support, Disclosures, and Conflict of Interest: Washington University School of Medicine has a service agreement with Lifeline
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