ACR Accreditation Evaluation of a Novel High Speed Ring-Gantry Linac kV CBCT System
PD-0902
Abstract
ACR Accreditation Evaluation of a Novel High Speed Ring-Gantry Linac kV CBCT System
Authors: Allison Haertter1, Michael Salerno1, Brandon Koger1, Christopher Kennedy1, Boon-Keng Kevin Teo1, Michelle Alonso-Basanta1, Lei Dong1, Taoran Li1
1University of Pennsylvania, Department of Radiation Oncology, Philadelphia, USA
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Purpose or Objective
The newly introduced Varian HyperSight™ imaging system features improved imaging hardware, reconstruction algorithm, and imaging speed. To assess the feasibility of using HyperSight CBCT for treatment planning and target/organ delineation, we evaluated its imaging performance using American College of Radiology (ACR) Program accreditation tests for diagnostic CTs, and compared it with existing CBCT systems such as a Varian TrueBeam™, Varian Halcyon™ version 2.0, and a diagnostic CT scanner (Siemens Somatom Edge).
Material and Methods
Image quality performance of several CBCT image protocols produced by the Varian HyperSight was assessed and compared to existing imaging modalities using an ACR Head CT phantom. Image quality assessments included contrast-to-noise ratio (CNR), spatial resolution, HU accuracy, and image scaling analyses. All image quality assessments were made following the recommendations and passing criteria provided by the ACR (see Figure 1).
Results
The Varian HyperSight imaging system produces excellent image quality, with many imaging protocols capable of passing all ACR CT accreditation standards (see Figure 2 (a)). The Head, H&N, pediatric head, abdomen, and pelvis protocols passed all ACR criteria, and the abdomen large and pelvis large protocols are able to pass all ACR criteria except for water HU accuracy. The pediatric abdomen protocol passed all ACR criteria except CNR and spatial resolution; however, we speculate optimization of the mAs could improve the CNR to a passing level. When compared to other standard imaging modalities, both the head and pelvis imaging protocols of the HyperSight system matched the passing criteria for Somatom CT scanner and substantially surpassed those of for Halcyon 2.0 and TrueBeam systems (see Figure 2 (b)).
Conclusion
When subject to ACR accreditation standards for diagnostic CTs, the Varian HyperSight imaging system was able to pass the majority of tests, with quality similar to those produced by diagnostic CT scanners and substantially superior to existing linac-based CBCT imaging systems. Further protocol optimization is being conducted on this new imaging system, which has the potential to perform CT simulations and dose calculations similar to conventional CT simulators.