Single Fraction Spine SBRT End to End Testing On TomoTherapy and Vero Treatment Platforms Using a Novel Anthropomorphic Phantom
J Gallo1*, I Kaufman2, T Bossenberger3, R Powell4,E Ramirez5, R Reynolds6, T Solberg7, J Burmeister8, (1) Wayne State University, Detroit, MI, (2) Wayne State University School of Medicine, Detroit, MI, (3) Karmanos Cancer Institute, Detroit, MI, (4) Wayne State University, Detroit, MI, (5) UT Southwestern Medical Center, Dallas, TX, (6) UT Southwestern Medical Center, Dallas, TX, (7) UT Southwestern Medical Center, Dallas, TX, (8) Wayne State Univ School of Medicine, Detroit, MIMO-F-108-9 Monday 4:30PM - 6:00PM Room: 108
Single fraction spine SBRT involves very high doses delivered to targets adjacent to the spinal cord. Highly conformal planning and accurate delivery of such plans is imperative for successful treatment without catastrophic adverse affects. End to end testing is an important practice for evaluating the entire treatment process from simulation through treatment delivery. We performed end-to-end testing for a set of representative spine SBRT targets planned and delivered using different treatment planning systems (TPSs) and delivery systems.
An anthropomorphic E2E SBRT phantom (IMT, Troy,NY) accepting ion chambers in the thoracic region and film in the lumbar region was simulated and treated to evaluate agreement between measured and calculated doses. Four representative targets were developed within each region (thoracic and lumbar) to represent different presentations of spine metastases and planned according to RTOG 0631 constraints. Plans were created using the TomoTherapy TPS for delivery using the Hi-ART system (Accuray, Sunnyvale,CA) and the iPlan TPS for delivery using the Vero system (BrainLAB, Feldkirchen,Germany). Delivered doses were measured using 0.007cc ion chambers (Standard Imaging, Middleton,WI) in the thoracic region and EBT3 Gafchromic film (Ashland, Wayne,NJ) in the lumbar region.
Both treatment platforms met all dose constraints required by RTOG 0631. Ion chamber measurements in the 4 thoracic targets delivered on TomoTherapy all agreed within 2.2%, with an average difference of 0.8%. Similar measurements on the Vero system agreed within 3.3%. Film measurements for the 4 lumbar targets resulted in gamma index passing rates over 99.7% at 3%/3mm, 99.2% at 2%/2mm, and 90% at 1%/1mm for all plans on both platforms.
In spite of the complexity of the representative targets and their proximity to the spinal cord, both treatment platforms were able to create plans meeting all RTOG dose constraints and produced exceptional agreement between calculated and measured doses.