Spine SBRT involves the delivery of very high doses of radiation to targets adjacent to the spinal cord and is most commonly delivered in a single fraction. Highly conformal planning and accurate delivery of such plans is imperative for successful treatment without catastrophic adverse effects. 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 targets planned and delivered using four different treatment planning systems (TPSs) and delivery systems to evaluate the various capabilities of each. An anthropomorphic E2E SBRT phantom was simulated and treated on each system to evaluate agreement between measured and calculated doses. The phantom accepts ion chambers in the thoracic region and radiochromic film in the lumbar region. Four representative targets were developed within each region (thoracic and lumbar) to represent different presentations of spinal metastases and planned according to RTOG 0631 constraints. Plans were created using the TomoTherapy TPS for delivery using the Hi·Art system, the iPlan TPS for delivery using the Vero system, the Eclipse TPS for delivery using the TrueBeam system in both flattened and flattening filter free (FFF), and the MultiPlan TPS for delivery using the CyberKnife system. Delivered doses were measured using a 0.007 cm3 ion chamber in the thoracic region and EBT3 GAFCHROMIC film in the lumbar region. Films were scanned and analyzed using an Epson Expression 10000XL flatbed scanner in conjunction with FilmQAPro2013. All treatment platforms met all dose constraints required by RTOG 0631. Ion chamber measurements in the thoracic targets delivered an overall average difference of 1.5%. Specifically, measurements agreed with the TPS to within 2.2%, 3.2%, 1.4%, 3.1%, and 3.0% for all three measureable cases on TomoTherapy, Vero, TrueBeam (FFF), TrueBeam (flattened), and CyberKnife, respectively. Film measurements for the lumbar targets resulted in average global gamma index passing rates of 100% at 3%/3 mm, 96.9% at 2%/2 mm, and 61.8% at 1%/1 mm, with a 10% minimum threshold for all plans on all platforms. Local gamma analysis was also performed with similar results. While gamma passing rates were consistently accurate across all platforms through 2%/2 mm, treatment beam‐on delivery times varied greatly between each platform with TrueBeam FFF being shortest, averaging 4.4 min, TrueBeam using flattened beam at 9.5 min, TomoTherapy at 30.5 min, Vero at 19 min, and CyberKnife at 46.0 min. In spite of the complexity of the representative targets and their proximity to the spinal cord, all treatment platforms were able to create plans meeting all RTOG 0631 dose constraints and produced exceptional agreement between calculated and measured doses. However, there were differences in the plan characteristics and significant differences in the beam‐on delivery time between platforms. Thus, clinical judgment is required for each particular case to...

There are numerous commercial radiotherapy systems capable of delivering single fraction spine radiosurgery/SBRT. We aim to compare the capabilities of several of these systems to deliver this treatment when following standardized criteria from a national protocol. Four distinct target lesions representing various case presentations of spine metastases were contoured in both the thoracic and lumbar spine of an anthropomorphic SBRT phantom. Single fraction radiosurgery/SBRT plans were designed for each target with each of our treatment platforms. Plans were prescribed to 16 Gy in one fraction to cover 90% of the target volume using normal tissue and target constraints from RTOG 0631. We analyzed these plans with priority on the dose to 10% of the partial spinal cord and dose to 0.03 cc of the spinal cord. Each system was able to maintain 90% target coverage while meeting all the constraints of RTOG 0631. On average, CyberKnife was able to achieve the lowest spinal cord doses overall and also generated the sharpest dose falloff as indicated by the Paddick gradient index. Treatment times varied widely depending on the modality utilized. On average, treatment can be delivered faster with Flattening Filter Free RapidArc and Tomotherapy, compared to Vero and Cyberknife. While all systems analyzed were able to meet the dose constraints of RTOG 0631, unique characteristics of individual treatment modalities may guide modality selection. Specifically, certain modalities performed better than the others for specific target shapes and locations, and delivery time varied significantly among the different modalities. These findings could provide guidance in determining which of the available modalities would be preferable for the treatment of spine metastases based on individualized treatment goals.

Purpose: 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. Methods: 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. Results: 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. Conclusion: 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.