Quantitative Comparison of Varian Halcyon to Varian Truebeam for Cardiac Radioablation Treatment Planning
Abstract
Purpose
Cardiac radioablation is one of the most demanding applications in radiation oncology, requiring high-dose conformity and steep dose gradients. Conventional C-arm systems, such as Varian TrueBeam (Varian – a Siemens Healthineers Company, Palo Alto, CA), reliably achieve these requirements. While Varian Halcyon offers a non-traditional, high-throughput alternative, its intrinsic planning capability for cardiac radioablation has not been benchmarked quantitatively. This study determines whether Halcyon provides a treatment planning performance comparable to TrueBeam for cardiac radioablation.
Methods
Five cardiac targets were contoured on a single CT dataset. Plans were created in the Eclipse treatment planning system for each target using four standardized coplanar beam arc geometries on each platform. Plans were normalized to D95% = 95% of the prescription dose (25 Gy) to the planning target volume. Plans were compared to one another using the conformity index (100% isodose volume divided by target volume), the R50 (50% isodose volume divided by target volume), the maximum dose 2cm from the target, the monitor unit ratio (MU ratio, total MUs divided by 2500 MUs), and beam-on time. Significance was measured using paired, two-tailed t-tests.
Results
Halcyon plans show no significant differences from TrueBeam plans in conformity, maximum dose 2cm from the target, and MU ratio in most cases. For select targets and beam geometries, Halcyon demonstrates higher R50 values. Beam-on times are an average of 3.5 minutes longer for Halcyon plans. All plans meet organ-at-risk constraints.
Conclusion
Although Halcyon demonstrates comparable performance to TrueBeam for conformity, MU ratio, maximum dose 2cm from the target, and organ-at-risk compliance, TrueBeam has superior low-dose wash in select cases and is able to achieve shorter treatment times. To the best of our knowledge, these results are the first to support the evidence-based consideration of Halcyon for cardiac radioablation while highlighting platform-specific trade-offs relevant to clinical implementation.