Polymer gel dosimetry aims to provide three-dimensional images of radiation therapy dose distributions in irradiated aqueous gels. The first gels required manufacture in an oxygen-free environment, but later the MAGIC formulation was introduced, which could be made in normal atmospheric conditions. Here we report our studies of the effects of variations in the composition of the MAGIC gel performed in order to optimize its performance over the useful dose range of 0 to 20 Gy. A new formulation (termed 'MAGIC-2') is comprised of 87% water, 4% methacrylic acid, 9% gelatin, 17.38 x 10(-6) M Cu(2+) and a molar ratio of ascorbic acid to [Cu(2+)] of 1000:1. MAGIC-2 has a dose-response slope-to-intercept ratio that is 78% greater than the original formulation and other more favorable properties.