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Develop An Accurate Model of Spot-Scanning Treatment Delivery Time for a Compact Superconducting Synchrocyclotron Proton System

G Liu1*, L Zhao1, W Zheng1, A Qin1, D Yan1, G Janssens2, J Shen3,C Stevens1, P Kabolizadeh1, X Ding1, (1) Beaumont Health, ,,(2) Ion Beam Application,,,(3) Mayo Clinic

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose:
An accurate treatment beam delivery time(BDT) model help assess the interplay effect and estimate patient throughput for a proton center. Due to the high instantaneous dose rate per pulse, the compact superconducting synchrocyclotron proton system delivers an accurate dose to each spot using blind golfer algorithm which repaints each energy layer into three bursts. Such phenomena result in a new beam parameter: Burst Switching Time(BST). This study is to develop an accurate treatment delivery sequence and time model for such a new compact superconducting synchrocyclotron proton system.

Methods:
Several square fields with different MU per spot(range:0.01 to 100MU/Spot), number of spots(#:121~6561) and energy layers(range:70~220 MeV) were created to test this new beam parameter. Besides, a series of spot-scanning deliver plan and delivery sequence proposed by Sheng et al in 2015[1] were used to derive the other standard beam parameter and delivery sequence such as magnet preparation time (MPT), spot scanning speed and energy layer switch time (ELST), and spot dwell time (SDT). All the test fields were delivered using a clinical compact superconducting synchrocyclotron proton system, IBA ProteusONE. The machine log files were retrospectively analyzed to quantitatively model the treatment BDT. The accuracy of the BDT model was retrospectively evaluated using ten clinical IMPT plans.

Results:

The BST was found proportional to the total number of pulses or the size of the logfile recorded in each burst. The average ELST in the descending order was 0.72s. The average scanning speeds were 4.16m/s in x-direction and 1.82m/s in y-direction. SDT is determined by the number of pulses(1ms per pulse). The average MPT was 0.99ms. The average total BDT of ten patients were within 5% difference from the machine log file.

Conclusion:
An accurate model of spot-scanning BDT prediction for a clinical compact superconducting synchrocyclotron proton therapy system was achieved experimentally.

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Funding Support, Disclosures, and Conflict of Interest: Research funding from Ion Beam Application

Keywords

Not Applicable / None Entered.

Taxonomy

TH- External Beam- Particle/high LET therapy: Proton therapy – Development (new technology and techniques)

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