NMR RELAXATION ENHANCEMENT IN GELS POLYMERIZED AND CROSS-LINKED BY IONIZING-RADIATION - A NEW APPROACH TO 3D DOSIMETRY BY MRI
NMR RELAXATION ENHANCEMENT IN GELS POLYMERIZED AND CROSS-LINKED BY IONIZING-RADIATION - A NEW APPROACH TO 3D DOSIMETRY BY MRI
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DOI：
10.1016/0730-725x(93)90030-h
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发表时间：
1993-01-01
影响因子：
2.5
通讯作者：
SCHULZ, RJ
中科院分区：
文献类型：
--
作者：
MARYANSKI, MJ;GORE, JC;SCHULZ, RJ
提出了一种用于电离辐射剂量分布磁共振成像的新型组织等效介质。琼脂糖凝胶注入丙烯酰胺和N， N'-亚甲基-双丙烯酰胺（Bis）共聚体，这些共聚体很容易在脱气水溶液中被自由基引发剂聚合。水辐射解的自由基产物局部诱导的聚合和交联逐渐增加了水质子自旋弛豫的速率，直至约15 Gy的剂量。R1和R2在64 MHz时的剂量响应曲线斜率分别为0.015和0.28 s-1 Gy-1。琼脂糖基质以及每总单体交联剂（Bis）的高（重量50%）相对浓度限制了聚合的扩散，因此辐射剂量的空间分布忠实地反映在松弛速率的空间分布中。该凝胶可以用传统的磁共振成像设备成像，具有较高的空间分辨率和精度。此外，由于高度交联的丙烯酰胺的不溶性团聚体的沉淀作用，凝胶的光学浊度随着吸收剂量的增加而逐渐增加。这可以提供一种在三维上显示剂量分布的附加方法。丙烯酰胺-双琼脂糖凝胶与依赖于离子化学剂量计的凝胶（例如，fricke注入凝胶）相比的主要优势在于，在辐照之后或与辐照同时发生的辐射引起的化学变化没有扩散。
A new type of tissue-equivalent medium for magnetic resonance imaging of the dose distributions produced by ionizing radiation has been developed. Agarose gel is infused with acrylamide and N, N'-methylene-bis-acrylamide (Bis) comonomers, which are readily polymerized by free radical initiators in de-aerated aqueous solutions. Polymerization and cross-linking induced locally by free radical products of water radiolysis increase the rate of water proton spin relaxation gradually up to doses of about 15 Gy. The slopes of the dose-response curves at 64 MHz are 0.015 and 0.28 s-1 Gy-1 for R1 and R2, respectively. The agarose matrix as well as the high (50% by weight) relative concentration of the cross-linker (Bis) per total comonomer limit the spread of polymerization so that the spatial distribution of the radiation dose is faithfully represented in the resultant spatial distribution of relaxation rates. The gel can be imaged with conventional magnetic resonance imaging devices with high spatial resolution and accuracy. In addition, due to the well established effect of the precipitation of insoluble agglomerates of highly cross-linked acrylamide, the optical turbidity of the gel increases gradually with the absorbed dose. This may provide an additional means of visualizing the dose distribution in three dimensions. The major advantage of the acryl-amide-Bis-agarose gels over those that depend on ionic chemical dosimeters, for example, Fricke-infused gels, lies in the lack of diffusion of radiation-induced chemical changes subsequent to or concurrent with irradiation.