FIRST ASSESSMENT OF A NOVEL IGRT DEVICE FOR STEREOTACTIC BODY RADIATION THERAPY

摘要

Introduction: A new device has been developed for image-guided Stereotactic Body Radiation Therapy (SBRT). TheVero SBRT System (known as "TM2000"in Japan), a joint product of MHI (Mitsubishi Heavy Industries Ltd., Tokyo, Japan) and Brain LAB (BrainLAB AG, Feldkir-chen, Germany) utilizes a rotating, rigid ring structure to integrate a beam delivery platform and image guidance systems. An inline 6 MV C-band LINAC with MLC is mounted on orthogonal gimbals that are in turn built into the ring structure. An electronic portal imaging device (EPID) and two kV imaging devices are also integrated in the ring. Opening commissioning measurements and stereotactic "hidden target" tests were performed to assess dosimetric and targeting characteristics as well as clinical capabilities of this SBRT dedicated device.Materials and Methods: Percent depth dose curves and beam profiles were measured in a water phantom and subsequently analyzed in accordance with industry standards. Additional characteristics including dose and dose rate linearity, relative output with varying field size, and output constancy with gantry angle were also evaluated. A commercial stereotactic phantom (LucyTM, Standard Imaging, Middleton, WI) was used to assess end-to-end localization accuracy of the image guidance system (through a "hidden-target" test) and for a comparison of absolute and relative dose against treatment planning calculations.Results: The essential characteristics of the Vero are commensurate with modern stereotactic requirements. Dosimetric characteristics are similar to other dedicated SRS/SBRT units, and end-to-end localization tests indicate sub-millimeter targeting accuracy.Conclusion: We have conducted preliminary commissioning and assessment of a novel device for image guided SBRT. Additionally, the integration of a gimbaled treatment beam, 2D and 3D imaging, tracking capabilities and real-time feedback provide unique opportunity to develop and implement advanced SBRT delivery techniques.