Varma M N, Baum J W, Kuehner A V
Phys Med Biol. 1980 Jul;25(4):651-6. doi: 10.1088/0031-9155/25/4/003.
Linear energy transfer restricted in radius (LETr) and total linear energy transfer (LET infinity) were determined for 42 MeV bromine ions in tissue-equivalent gas. A variable pressure cylindrical ionisation chamber was used. Dose as a function of distance from the ion's path was also determined using a mesh wall ionisation chamber placed inside the cylindrical chamber. The range of distances studied was from 5 to 710 A in simulated tissue of unit density. Experimentally obtained values of radial dose were compared with calculations made using Paretzke's program. Stopping power for these ions in tissue-equivalent gas was extrapolated from proton stopping power in constituent gases. In this calculation the effective charge of the ions was obtained from the formula given by Dimitriev and Nikolaev. This calculated value was 6.3 x 10(4) MeV g-1 cm2. The experimentally determined value was 7.3 x 10(4) MeV g-1 cm2. The discrepancy between calculated and experimental values may be due to uncertainty in the determination of the effective charge of the incident ions. Uncertainty on the experimental value of LET infinity was estimated to be +/- 5% (one standard deviation).
测定了42兆电子伏溴离子在组织等效气体中的受限半径线性能量转移（LETr）和总线性能量转移（LET∞）。使用了可变压力圆柱形电离室。还使用置于圆柱形室内的网状壁电离室测定了剂量随离离子路径距离的变化。研究的距离范围在单位密度模拟组织中为5至710埃。将实验获得的径向剂量值与使用帕雷茨克程序进行的计算结果进行了比较。这些离子在组织等效气体中的阻止本领是从质子在组成气体中的阻止本领外推得到的。在该计算中，离子的有效电荷是根据季米特里耶夫和尼古拉耶夫给出的公式获得的。该计算值为6.3×10⁴兆电子伏·克⁻¹·厘米²。实验测定值为7.3×10⁴兆电子伏·克⁻¹·厘米²。计算值与实验值之间的差异可能是由于入射离子有效电荷测定的不确定性所致。LET∞实验值的不确定性估计为±5%（一个标准偏差）。
