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Initial Evaluation of the Clinical Reliability of a New Treatment Delivery System Design

JDP Hoisak*, G Kim , K Moore , T Pawlicki , UC San Diego, La Jolla, CA


(Monday, 7/30/2018) 1:15 PM - 1:45 PM

Room: Exhibit Hall | Forum 7

Purpose: Our institution recently introduced a Varian Halcyon into routine clinical use. The design goals of this novel linac configuration included improved reliability and throughput for resource-limited environments. Our intent was to assess the clinical operation of Halcyon focusing on machine faults and up-time.

Methods: The technical support demands of Halcyon were compared with three conventional linacs (two TrueBeams, one 21EX) in the same clinic over the period when Halcyon was introduced into clinical use (September 2017-March 2018). We queried our institution’s online machine fault reporting system for the following parameters related to reported technical events: machine type, number of events, number of machine-down events, event description and estimated downtime. A machine-down event was defined as a fault with the linac that interrupted or prevented patient treatments and required cancellations or adjustments to the schedule. The reported downtime per event was estimated by clinical staff from the time of the initial report to return to service. The record and verify system was queried for the number of fractions delivered over this period to estimate machine usage.

Results: Over 119 clinical days, 404 events were reported, including 23 machine-down events. Halcyon accounted for 15.6% of the reported events, and 21.7% of the machine-down events. Halcyon delivered fewer fractions over this time period, but per number of fractions, exhibited fewer technical faults, machine down events and less downtime than the other linacs. The TrueBeams reported over twice as many events as Halcyon, including more imaging and MLC-related faults. Halcyon experienced fewer beam generation/steering, accessory and cooling-related faults than the other linacs but reported more computer and network issues.

Conclusion: Preliminary results suggest that despite being a new design, Halcyon is at least as reliable as current conventional linacs, and is possibly more reliable in some critical sub-systems. Longer term evaluation is required.


Linear Accelerator, Quality Control, Quality Assurance


TH- External beam- photons: Quality Assurance - Linear accelerator

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