PRESAGE和PAGAT聚合物剂量计的放射学特性。

Radiological properties of the PRESAGE and PAGAT polymer dosimeters.

作者信息

Brown S, Venning A, De Deene Y, Vial P, Oliver L, Adamovics J, Baldock C

机构信息

Institute of Medical Physics, School of Physics, University of Sydney, NSW, Australia.

出版信息

Appl Radiat Isot. 2008 Dec;66(12):1970-4. doi: 10.1016/j.apradiso.2008.06.005. Epub 2008 Jun 11.

DOI:10.1016/j.apradiso.2008.06.005

PMID:18693028

Abstract

The radiological properties of the PRESAGE and PAGAT polymer dosimeters have been investigated and their water equivalence determined for use in radiotherapy dosimetry. The radiological water equivalence of each of the polymer dosimeters was determined by comparing the photon and electron interaction cross-sections over the 10 keV-20 MeV energy range and by Monte Carlo modelling the depth dose from a linear accelerator using the BEAMnrc software package. PRESAGE was found to have an effective Z-value and mass density (kgm(-3)) approximately 17% and 10% higher than water, respectively. A maximum difference of 85% was discovered in the photoelectric interaction probability curve of PRESAGE when compared to water over the energy range 10-100 keV, partially due to the Z(3) dependence of the photoelectric effect. The mass radiative stopping power ratios and mass scattering power ratios were both found to have less than 9% difference from water. The depth dose for PRESAGE from a 6MV photon beam had an absolute percentage difference to water of less than 2% and a relative percentage difference of less than 8%. The mass density of PAGAT was found to be 2.6% higher than water due to its high gelatine and monomer concentration. The cross-sectional attenuation and absorption coefficient ratios were found to be within 5% for energies between 10 and 100 keV and within 1% for energies between 100 keV and 20 MeV. The mass collisional stopping power, mass radiative stopping power and mass scattering power ratios were all less than 1% over the energy range studied. The depth dose had an absolute percentage difference to water of less than 1% and a relative percentage difference of less than 2.5%. These results indicate that the PAGAT polymer gel formulation is more radiological water equivalent than the PRESAGE formulation. However, the PRESAGE dosimeter offers some advantages in terms of ease of use and its lack of water equivalence may be overcome with dosimetric correction factors.

摘要

已对PRESAGE和PAGAT聚合物剂量计的放射特性进行了研究，并确定了它们的水等效性，以用于放射治疗剂量测定。通过比较10 keV至20 MeV能量范围内的光子和电子相互作用截面，并使用BEAMnrc软件包对直线加速器的深度剂量进行蒙特卡罗建模，确定了每种聚合物剂量计的放射水等效性。发现PRESAGE的有效Z值和质量密度（kgm(-3)）分别比水高约17%和10%。在10-100 keV能量范围内，与水相比，PRESAGE的光电相互作用概率曲线中发现最大差异为85%，部分原因是光电效应的Z(3)依赖性。质量辐射阻止本领比和质量散射本领比与水的差异均小于9%。来自6MV光子束的PRESAGE深度剂量与水的绝对百分比差异小于2%，相对百分比差异小于8%。由于其高明胶和单体浓度，发现PAGAT的质量密度比水高2.6%。在10至100 keV能量之间，横截面衰减和吸收系数比在5%以内，在100 keV至20 MeV能量之间在1%以内。在所研究的能量范围内，质量碰撞阻止本领、质量辐射阻止本领和质量散射本领比均小于1%。深度剂量与水的绝对百分比差异小于1%，相对百分比差异小于2.5%。这些结果表明，PAGAT聚合物凝胶配方比PRESAGE配方具有更高的放射水等效性。然而，PRESAGE剂量计在易用性方面具有一些优势，其缺乏水等效性可通过剂量校正因子来克服。