The visible signal responsible for proton therapy dosimetry using bare optical fibers is not Čerenkov radiation. Issue 11 (14th October 2016)

• Record Type: Journal Article
• Authors: Darafsheh, Arash; Taleei, Reza; Kassaee, Alireza; Finlay, Jarod C.
• Is Part Of: Medical physics. Volume 43:Issue 11(2016)
• Page Start: 5973
• Page End: 5980
• Publication Date: 2016-10-14
• Subjects: dosimetry -- fluorescence -- Monte Carlo methods -- optical fibres -- phantoms -- radiation therapy; Dosimetry/exposure assessment -- Therapeutic applications, including brachytherapy -- Monte Carlo simulations -- Dosimetry/exposure assessment -- Therapeutic applications -- Distribution theory and Monte Carlo studies; Radiation therapy -- Scintigraphy; Čerenkov radiation -- dosimetry -- proton therapy -- fiber optics -- luminescence -- spectroscopy -- ionization quenching; Protons -- Dosimetry -- Proton therapy -- Optical fiber testing -- Visible spectra -- Ionizing radiation -- Optical fibers -- Energy transfer -- Monte Carlo methods; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4964453
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: Proton beam dosimetry using bare plastic optical fibers has emerged as a simple approach to proton beam dosimetry. The source of the signal in this method has been attributed to Čerenkov radiation. The aim of this work was a phenomenological study of the nature of the visible light responsible for the signal in bare fiber optic dosimetry of proton therapy beams. Methods: Plastic fiber optic probes embedded in solid water phantoms were irradiated with proton beams of energies 100, 180, and 225 MeV produced by a proton therapy cyclotron. Luminescence spectroscopy was performed by a CCD‐coupled spectrometer. The spectra were acquired at various depths in phantom to measure the percentage depth dose (PDD) for each beam energy. For comparison, the PDD curves were acquired using a standard multilayer ion chamber device. In order to further analyze the contribution of the Čerenkov radiation in the spectra, Monte Carlo simulation was performed usingfluka Monte Carlo code to stochastically simulate radiation transport, ionizing radiation dose deposition, and optical emission of Čerenkov radiation. Results: The measured depth doses using the bare fiber are in agreement with measurements performed by the multilayer ion chamber device, indicating the feasibility of using bare fiber probes for proton beam dosimetry. The spectroscopic study of proton‐irradiated fibers showed a continuous spectrum with a shape different from that of Čerenkov radiation. The Monte Carlo simulations confirmed that the amount of the generated Čerenkov light does not follow the radiation absorbed dose in a medium. Conclusions: The source of the optical signal responsible for the proton dose measurement using bare optical fibers is not Čerenkov radiation. It is fluorescence of the plastic material of the fiber.