Abstract
The practice of using the direct ionization radiation (electrons, protons, antiprotons, pions, ions, etc) or of the indirect ionization radiation (photons, neutrons, etc) in economy and social life has led to the introduction of the absorbed dose magnitude (ICRU 1953) defined as the energy absorbed per mass unit of the irradiated substance. This is a fundamental magnitude valid for any type of ionizing radiation, any irradiated material and any radiation energy. In case of clinical hadron beams generated by conventional accelerators or those controlled by lasers, IAEA TRS 398 recommends the absorbed dose to water. This may be determined employing the calorimeter method with water or graphite, chemical method, fluence based measurements as Faraday cups or activation measurements, and the ionization chamber method. In this paper the selected method was the thimble air filled ionization chamber method for determination of absorbed dose to water.
Highlights
The ionization method for determining the absorbed dose in air and in any irradiated substance by means of Bragg-Gray theory, was used by the Institute of Atomic Physics (IFA) in Bucharest located on Magurele Platform, with the first 30 MeV Betatron Accelerator built and commissioned in 1960 [1]
Taking into account the above and the experience gained in international hadron-based therapy centers with protons and carbon ions, the reference dosimetry techniques for clinical beams of hadrons-calorimetric dosimetry, chemical dosimetry, ionization dosimetry with Faraday cup and ionization chamber dosimetry-this paper presents how to measure the absorbed dose to water in clinical hadron beams employing the ionization chamber dosimetry
Main dosimetric quantities measured or determined by the ionization method with the associated device, except the correction factors, are: exposure X only for photon only in air, air kerma Kair (≡Ka) the average amount of energy transferred in a small volume from the indirect ionizing radiation to direct ionizing radiation, the absorbed dose in air Dair (≡Da) and the absorbed dose to water Dw, defined as a mean energy imparted by ionizing radiation to a matter in a finite volume V
Summary
It is worth mentioning that an APOLLON laser system of 10 PW (150 J, 15 fs) [13], under construction on Magurele Platform near Bucharest, induced the idea of using it to generate the therapeutic hadrons beams (protons and carbon ions) with energies of 50 to 250 MeV and 100 to 450 MeV/u, respectively In this way it is possible to skip the stage of conventional accelerators (isochronous cyclotron, synchrocyclotron, synchrotron and linac types) which include compact accelerators in the design phase (FFAG, DWA and cyclinac) and directly pass to the alternative of using the laser-driven carbon ion/proton therapy beams [14]. This condition requires that the product between the conversion efficiency η of the laser pulse energy into hadrons kinetic energy and laser pulse energy εL should be greater or equal to the absorbed dose in the tumor εT divided by the product between the laser pulse repetition frequency fR and the irradiation time tT established by the doctor overseeing therapy
Sign-in/Register to view highlights & summary 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.
