Direct Response to Proton Beam Linear Energy Transfer (LET) in a Novel Polymer Gel Dosimeter Formulation

MD Anderson Cancer Center Orlando, 1400 South Orange Avenue, Orlando, FL 32806. .
Technology in cancer research & treatment (Impact Factor: 1.73). 05/2012; 11(5):441-5. DOI: 10.7785/tcrt.2012.500263
Source: PubMed


Linear energy transfer (LET) of clinical proton beams is an important parameter influencing the biological effects of radiation. This work demonstrates LET-induced response enhance_ment in novel formulations of polymer gel dosimeters, potentially useful for LET mapping of clinical proton beams. A series of four polymer gel dosimeters (labeled A through D), prepared based on the BANG3-Pro2 formulation, but with varying concentrations of polymerization modifiers, were irradiated by a clinical proton beam with a spread out Bragg peak modulation (SOBP) and read out using the OCTOPUS-IQ optical CT scanner. The evaluation of optical density profiles in the SOBP (constant physical dose) revealed response deviations at the distal end consistent with variations in gel composition. Maximum response deviations were as follows: 23% (under-response) for gel A, and over-response of 2%, 12%, and 17% for gels B, C, and D, respectively, relative to the mean dose in the center of the SOBP. This enhancement in optical response was correlated to LET by analytical calculations. Gels A and B showed no measurable dependence on LET. Gel C responded linearly in the limited range from 1.5 to 3.5 keV/μm. LET response of gel D was linear up to at least 5.5 keV/μm, with the threshold at about 1.3 keV/μm. These results suggest that it may be possible to develop a polymer gel system with direct optical response to LET for mapping of LET distributions for particle therapy beams.

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    • "Polymer gel dosimeters have been proposed to verify various photon delivery techniques, such as intensity-modulated radiation therapy (IMRT) [2], [3], RapidArc radiation therapy [4], stereotactic radiosurgery (SRS) [5], [6], and brachytherapy [7], [8]. In addition, the potential applications of polymer gels for the proton therapy [9], [10], boron-neutron capture therapy (BNCT) [11], [12], and targeted radionuclide therapy [13] are promising because of the tissue-equivalent characteristics regarding the effective atomic number, electron density, and stopping power ratio of gel to water. A dose conversion system for the irradiated gels should offer high accuracy and reliability for the demanding applications. "
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    PLoS ONE 07/2013; 8(7):e67281. DOI:10.1371/journal.pone.0067281 · 3.23 Impact Factor
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    Physics in Medicine and Biology 07/2014; 59(15):4295. DOI:10.1088/0031-9155/59/15/4295 · 2.76 Impact Factor
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