Towards two-dimensional brachytherapy dosimetry using plastic scintillator: New highly efficient water equivalent plastic scintillator materials

Abstract

Plastic scintillator (PS) has been proposed for both one- and two-dimensional (1D and 2D) dose measurements for radiation therapy applications. For low-energy photon modalities (e.g., brachytherapy), an efficient water equivalent scintillator is needed. To perform 2D measurements, a high localization of the scintillation process is required. Guided by comparison of the mass energy absorption coefficients as a function of energy and of the dose distribution as a function of distance from the radioactive source, as modeled by Monte Carlo photon transport simulation, a small quantity of medium atomic number (Z) atoms (4% Cl) was incorporated in a polyvinyl toluene (PVT) based PS to approximate closely (within 10%) the radiological properties of water in the 20-662 keV energy range. However, the scintillation efficiency of commercial PS mixtures drops as much as 70% when loaded with high atomic number additives. We developed experimental techniques to assess the scintillation efficiency and locality of 15 new PS mixtures. These mixtures differ by the type of the scintillation dyes and the type of compound containing the medium Z atoms (chlorine). To achieve higher material stability, 4-chlorostyrene was used as a loading compound to ensure polymerization with the PVT base. Two of the new PS materials exhibited scintillation efficiencies within 30% of one of the most efficient commercially available products (BC-400), which is not water equivalent at such low energies. These new scintillator materials are promising candidates for the development of an accurate and efficient radiation dosimetry method not only for brachytherapy, but also for superficial and diagnostic applications.

New water equivalent liquid scintillation solutions for 3D dosimetry

“…4͒. A more detailed description of the experimental setup and the measurement procedure can be found in Kirov et al 9 This type of measurement allows us to account for the wavelength dependence of the PMT sensitivity and to compare the scintillation efficiency of cocktails with different emission spectra. The comparison of the intensities of the primary and secondary peaks in the spectra is a sensitive indicator of the localization of scintillation photon emission.…”

“…Silicon satisfies the above requirements better than chlorine (Zϭ17), which was used in a similar study for obtaining water equivalent plastic scintillator material. 9 As a Si loading compound we investigated two compounds ͑Aldrich Chemical Company, Inc., Milwaukee, WI 53233͒ ͓Figs. 2͑a͒ and 2͑b͔͒: poly͑dimethylsiloxane͒: (-Si͑CH 3 ͒ 2 O-) n , known also as optical grease, and poly͑m-ethylphenylsiloxane͒ (-Si͑CH 3 ͒͑C 6 H 5 ͒O-) n .…”

“…In recent years was initiated the development of a two-dimensional dose measurement method. [7][8][9] A CCD ͑charged-coupled device͒ sensor was used to record the scintillation light image from a similar PS sheet. Pseudo-3D measurements with such a system can be achieved by smoothly changing the position of the PS sheet with respect to the brachytherapy source.…”

Measurements of Relative Depth Doses Using Fiber-Optic Radiation Sensor and EBT Film for Brachytherapy Dosimetry

“…Generally, the sensing size of a fiber-optic dosimeter is much smaller than that of conventional dosimeters used in brachytherapy dosimetry such as diamond detector, in vivo diode and ionization chamber, and the high resolution dose-measurements are possible with a FORS. In addition, a typical organic scintillator, which is based on polystyrene (PS), does not show significant aging for absorbed doses up to 1.0 kGy and can be used in an implantable dosimeter due to its chemically inert characteristics [5]- [11].…”

Rotational Dynamics of Nonpolar and Dipolar Molecules in Polar and Binary Solvent Mixtures

“…E428 has been used to generate circularly polarized light in glassy liquid crystal films (Chen et al, 1999). Exalites are mixed with plastic scintillators (PS) to form new scintillaors, which are for superficial and diagnostic applications (Kirov et al, 1999).…”