Real-Time Tracking of Implanted Markers During Radiation Treatment by Use of Simultaneous kV and MV Imaging

Abstract

Abstract : In the presence of organ motion, geometric target uncertainty can hamper the benefits of highly conformal dose techniques such as IMRT. A critical step in dealing with intra-fraction prostate tumor motion is the real-time monitoring of the tumor position. The aim of this investigation is the first time demonstration of a real-time 3D internal fiducial tracking system based on onboard kV diagnostic imaging together with a MV electronic portal-imaging device (EPID). A Varian radiotherapy system equipped with both kV and MV imaging systems was used in this work. An in house built marker detection tool using prior CT based knowledge was created to locate gold cylindrical markers in the kV/MV frames. The geometric tracking capabilities of the system were evaluated using a pelvic phantom with embedded fiducials placed on a 3D moveable stage to mimic actual prostate motion. The maximum 3D tracking speed of the kV-MV system is approximately 9 Hz. The geometric accuracy of the system is found to be on the order of less than 1 mm in all three spatial dimensions. This investigation has demonstrated the use of a real-time 3D fiducial tracking system using combined kV and MV imaging for the first time.