Maryañski M J, Zastavker Y Z, Gore J C
Department of Diagnostic Radiology, Yale University, New Haven, CT 06510, USA.
Phys Med Biol. 1996 Dec;41(12):2705-17. doi: 10.1088/0031-9155/41/12/010.
A newly developed method of radiation dosimetry makes use of the optical properties of polymer gels. The dose-response mechanism relies on the production of light-scattering polymer micro-particles in the gel at each site of radiation absorption. The scattering produces an attenuation of transmitted light intensity that is directly related to the dose and independent of dose rate. For the BANG polymer gel (bis, acrylamide, nitrogen, and gelatin) the shape of the dose-response curve depends on the fraction of the cross-linking monomer in the initial mixture and on the wavelength of light. At 500 nm the attenuation coefficient (mu) increases by approximately 0.7 mm-1 when the dose increases from 0 to 5 Gy. The refractive index of an irradiated gel shows no significant dispersion in the visible region and depends only slightly on the dose. Turbidity difference spectra are compared with theoretical spectra of efficiency factors for total scattering, derived using Mie-Debye theory, and the average sizes of the cross-linked particles produced by radiation, as a function of dose, are established. The particle sizes increase with dose and reach approximately the wavelength of red light. The dependence of the particle sizes on cross-linker fraction parallels a similar dependence of the water proton NMR transverse relaxation rate dose response.
一种新开发的辐射剂量测定方法利用了聚合物凝胶的光学特性。剂量响应机制依赖于在凝胶中每个辐射吸收位点产生光散射聚合物微粒。这种散射会导致透射光强度衰减，该衰减与剂量直接相关且与剂量率无关。对于BANG聚合物凝胶（双丙烯酰胺、氮和明胶），剂量响应曲线的形状取决于初始混合物中交联单体的比例以及光的波长。在500纳米处，当剂量从0增加到5戈瑞时，衰减系数（μ）大约增加0.7毫米⁻¹。辐照凝胶的折射率在可见光区域没有明显色散，且仅略微依赖于剂量。将浊度差光谱与使用米氏 - 德拜理论推导的总散射效率因子理论光谱进行比较，并确定作为剂量函数的辐射产生的交联颗粒的平均尺寸。颗粒尺寸随剂量增加，并达到大约红光的波长。颗粒尺寸对交联剂比例的依赖性与水质子核磁共振横向弛豫率剂量响应的类似依赖性相似。
