Karlsson A, Gustavsson H, Månsson S, McAuley K B, Bäck S A J
Department of Medical Radiation Physics, Lund University, Malmö University Hospital, Sweden.
Phys Med Biol. 2007 Aug 7;52(15):4697-706. doi: 10.1088/0031-9155/52/15/021. Epub 2007 Jul 18.
Dose integration properties were investigated for normoxic polymer gels based on methacrylic acid (nMAG) and acrylamide/N, N'-methylenebisacrylamide (nPAG). The effect of sequential irradiation was studied for different fractionation schemes and varying amounts of methacrylic acid for the nMAG gels. Magnetic resonance imaging (MRI) was used for read out of the absorbed dose response. The investigated gels exhibited a dependence on the fractionation scheme. The response when the total dose was divided into fractions of 0.5 Gy was compared with the response when the total dose was delivered in a single fraction. The slope of the R2 versus the absorbed dose response decreased when the absorbed dose per fraction was increased. Also, for higher amounts of methacrylic acid in the nMAG system the difference in the response increased. For gels containing 2, 4, 6 and 8% methacrylic acid, the R2 versus the absorbed dose response increased by 35, 37, 63 and 93%, respectively. Furthermore, the effect of the fractionation was larger when a higher total absorbed dose was given. The effect was less pronounced for the investigated nPAG, containing 3% acrylamide and 3% N, N'-methylenebisacrylamide, than for the nMAG systems. Consequently, this study indicates that the nPAG system has preferable beam integration characteristics compared with the nMAG system.
研究了基于甲基丙烯酸的常氧聚合物凝胶（nMAG）和丙烯酰胺/N,N'-亚甲基双丙烯酰胺（nPAG）的剂量积分特性。针对不同的分次照射方案以及nMAG凝胶中不同量的甲基丙烯酸，研究了分次照射的效果。使用磁共振成像（MRI）读取吸收剂量响应。所研究的凝胶表现出对分次照射方案的依赖性。将总剂量分为0.5 Gy分次时的响应与总剂量单次给予时的响应进行了比较。当每分次吸收剂量增加时，R2与吸收剂量响应的斜率降低。此外，在nMAG体系中，随着甲基丙烯酸含量的增加，响应差异增大。对于含有2%、4%、6%和8%甲基丙烯酸的凝胶，R2与吸收剂量响应分别增加了35%、37%、63%和93%。此外，当给予更高的总吸收剂量时，分次照射的效果更大。对于含有3%丙烯酰胺和3% N,N'-亚甲基双丙烯酰胺的所研究的nPAG，其效果不如nMAG体系明显。因此，本研究表明，与nMAG体系相比，nPAG体系具有更好的射束积分特性。
