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Implementation of Respiratory and Cardiac Double-Gating to Passive Scattered Proton Delivery

H Lee*, KW Jee , R Brett , YL Chen , J Pursley , J Flanz , HM Lu , Massachusetts General Hospital, Boston, MA


(Thursday, 8/2/2018) 7:30 AM - 9:30 AM

Room: Karl Dean Ballroom A1

Purpose: Cardiac-induced motion mitigation methods have not been well studied nor implemented. When a target is in or near the heart, the contractile motion contributes to a targeting uncertainty. Cardiac motion mitigation is challenging not only due to its shorter period, but also due to the correlated movement of respiratory and cardiac motions. The purpose of this work is to explore a respiratory and cardiac double gated system for range-modulated proton treatment.

Methods: At our Proton Center, We use a respiratory gating system to compensate for respiration-induced target motion. A pulse generator is used to generate a pulse train that closely simulates the signal from ECG based gating, corresponding to a reference cardiac duration. An electronic circuit was built to combine the cardiac gating signal, respiration gating signal, and the beam control signal for range modulation, and send an electronic pulse to the ion source when all signals are in phase, generating the proton beam. We measured and analyzed the number of range-modulation cycles to achieve a spread-out Bragg peak (SOBP) for resting heart beats between 60 and 100 bpm with varying duty cycles and modulation widths.

Results: We measured the dose distribution as the beam was on when all the related signals were in phase with the respiratory and cardiac double gating system. The distribution showed SOBP within a designed modulation. The times required to obtain a SOBP distribution with acceptable dose characteristics depended on the motion periods, gating duty cycles, and modulation width, but were all less than one minute.

Conclusion: This work demonstrates operation of a double gating system able to account both respiratory and cardiac induced organ motion. Measurements were made to estimate the delivery dose rate and time for clinical use. The overall quality of SOBP for normal resting heart beats was also evaluated.


Not Applicable / None Entered.


TH- External Beam- Particle therapy: Proton therapy - motion management(intrafraction)

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