Preparations for the implementation of Cyberknife Lung SBRT

Abstract

Lung cancer is the fourth most common cancer in Ireland with over 2000 people diagnosed each year. Cyberknife Lung treatments allow for a high dose per fraction while greatly reducing normal tissue toxicity and treatment times. This is achieved using over one hundred non coplanar beams allowing for high dose conformality coupled with a steep dose falloff away from the tumour. With these properties Cyberknife allows for dose escalation and smaller margins to be used when compared to gantry based systems. The Synchrony Respiratory Motion tracking System correlated with live KV X-ray tumour tracking allows the Cyberknife to track the tumour in real-time. There are 2 primary methods for tumour tracking with this system (1) Fiducial based tumour tracking (2) algorithm based Soft tissue tracking. In this study we look at both methods and use E2E (End to End) tests and EBT3 Gafchromic films to quantify the error in both tumour tracking systems. A further enhancement of soft tissue tumour tracking known as LOT(Lung optimised treatment)is also evaluated in this study with a view towards deciding on appropriate clinical margins in situations where the tumour is visible in zero, one or both Cyberknife KV imagers. This preliminary study will focus on the tumour tracking and delivery accuracy of Lung SBRT treatments using Cyberknife. The equipment used for this study: Cyberknife VSI, Synchrony phantom, CIRS 4D phantom, Synchrony LED Vest, Fiducials, Mulitplan v4.6.1, CT scanner, and GafChromic films (EBT3).