Abstract：
The stopping-power ratio (SPR) of body tissues relative to water depends on the particle energy and mean excitation energy (I value) of the tissues. Effective energies to minimize the range error in proton therapy and ion beam therapy with helium, carbon, oxygen, and neon ions and elemental I values have been updated in recent studies. We investigated the effects of these updates on SPR estimation for computed tomography-based treatment planning. The updates led to an increase of up to 0.5% in the SPRs of soft tissues, whereas they led to a decrease of up to 1.9% in the SPRs of bone tissues compared with the current clinical settings. For 44 proton beams planned for 15 randomly sampled patients, the mean water-equivalent target depth change was - 0.2 mm with a standard deviation of 0.2 mm. The maximum change was - 0.6 mm, which we consider to be insignificant in clinical practice.
摘要：
身体组织相对于水的停止功率比（SPR）取决于组织的粒子能量和平均激发能量（I值）。使质子治疗和氦离子束治疗中的距离误差最小化的有效能量，碳,氧气,最近的研究更新了氖离子和元素I值。我们调查了这些更新对基于计算机断层扫描的治疗计划的SPR估计的影响。更新导致软组织的SPR增加高达0.5％，而与目前的临床设置相比，它们导致骨组织的SPR下降高达1.9%。对于计划为15名随机抽样患者提供的44个质子束，平均水当量目标深度变化为-0.2mm,标准偏差为0.2mm.最大变化为-0.6mm,我们认为在临床实践中微不足道。
