Abstract
Recently, it has been proposed that a mixed helium/carbon beam could be used for online monitoring in carbon ion beam therapy. Fully stripped, the two ion species exhibit approximately the same mass/charge ratio and hence could potentially be accelerated simultaneously in a synchrotron to the same energy per nucleon. At the same energy per nucleon, helium ions have about three times the range of carbon ions, which could allow for simultaneous use of the carbon ion beam for treatment and the helium ion beam for imaging. In this work, measurements and simulations of PMMA phantoms as well as anthropomorphic phantoms irradiated sequentially with a helium ion and a carbon ion beam at equal energy per nucleon are presented. The range of the primary helium ion beam and the fragment tail of the carbon ion beam exiting the phantoms were detected using a novel range telescope made of thin plastic scintillator sheets read out by a flat-panel CMOS sensor. A 10:1 carbon to helium mixing ratio is used, generating a helium signal well above the carbon fragment background while adding little to the dose delivered to the patient. The range modulation of a narrow air gap of 1 mm thickness in the PMMA phantom that affects less than a quarter of the particles in a pencil beam were detected, demonstrating the achievable relative sensitivity of the presented method. Using two anthropomorphic pelvis phantoms it is shown that small rotations of the phantom as well as simulated bowel gas movements cause detectable changes in the helium/carbon beam exiting the phantom. The future prospects and limitations of the helium/carbon mixing as well as its technical feasibility are discussed.
Highlights
Introduction pteAc ce cri pt us et al 2018, Mazzucconi et al 2018)
Graeff et al (2018) have shown the potential of using a mixed helium/carbon beam as a range probe for carbon ion treatment investigating lung patient cases using based on 4D treatment planning
Assuming a fixed helium contamination in the primary carbon ion beam during the plan optimisation, they showed that the additional RBE dose stemming from a 10 %
Summary
Introduction pteAc ce cri pt us et al 2018, Mazzucconi et al 2018). The approximately equal mass/charge ratio of fully stripped helium and carbon ions (relative difference ≈ 0.065 %), could enable their simultaneous acceleration in a synchrotron accelerator to the same velocity (same energy per nucleon). Due to the helium ions’ ∼3 times larger range compared to that of carbon ions at the same velocity, treatment with a carbon ion beam and simultaneous treatment monitoring with helium ions could be possible. The similarity in accelerator settings for the delivery of a mixed helium/carbon beam (12 C 4+ with 3 He+ ) has been reported already in Kanai et al (1997) for a cyclotron facility for the purpose of treatment with beams of mixed relative biological effectiveness (RBE) but without consideration for online treatment monitoring. Graeff et al (2018) have shown the potential of using a mixed helium/carbon beam as a range probe for carbon ion treatment investigating lung patient cases using based on 4D treatment planning. Assuming a fixed helium contamination in the primary carbon ion beam during the plan optimisation, they showed that the additional RBE dose stemming from a 10 %
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
