Abstract：
Objective. Proton therapy currently faces challenges from clinical complications on organs-at-risk due to range uncertainties. To address this issue, positron emission tomography (PET) of the proton-induced11C and15O activity has been used to provide feedback on the proton range. However, this approach is not instantaneous due to the relatively long half-lives of these nuclides. An alternative nuclide,12N (half-life 11 ms), shows promise for real-timein vivoproton range verification. Development of12N imaging requires better knowledge of its production reaction cross section.Approach. The12C(p,n)12N reaction cross section was measured by detecting positron activity of graphite targets irradiated with 66.5, 120, and 150 MeV protons. A pulsed beam delivery with 0.7-2 × 108protons per pulse was used. The positron activity was measured during the beam-off periods using a dual-head Siemens Biograph mCT PET scanner. The12N production was determined from activity time histograms.Main results. The cross section was calculated for 11 energies, ranging from 23.5 to 147 MeV, using information on the experimental setup and beam delivery. Through a comprehensive uncertainty propagation analysis, a statistical uncertainty of 2.6%-5.8% and a systematic uncertainty of 3.3%-4.6% were achieved. Additionally, a comparison between measured and simulated scanner sensitivity showed a scaling factor of 1.25 (±3%). Despite this, there was an improvement in the precision of the cross section measurement compared to values reported by the only previous study.Significance. Short-lived12N imaging is promising for real-timein vivoverification of the proton range to reduce clinical complications in proton therapy. The verification procedure requires experimental knowledge of the12N production cross section for proton energies of clinical importance, to be incorporated in a Monte Carlo framework for12N imaging prediction. This study is the first to achieve a precise measurement of the12C(p,n)12N nuclear cross section for such proton energies.
摘要：
目的：由于范围的不确定性，质子治疗目前面临着来自危险器官的临床并发症的挑战，解剖学变化,和设置错误。为了解决这个问题，质子诱导的11C和15O活性的正电子发射断层扫描（PET）已用于提供质子范围的反馈。然而,由于这些核素的半衰期长，这种方法不是瞬时的。一种替代核素，12N(半衰期11ms),显示了质子范围的实时体内验证的希望。12N成像的发展需要更好地了解其生产反应截面。
方法：12C(p，n）通过检测用66.5、120和150MeV质子辐照的石墨靶的正电子活性来测量12N反应截面。使用每个脉冲具有0.7-2×108个质子的脉冲束递送。使用双头SiemensBiographmCTPET扫描仪在光束关闭期间测量正电子活性。从活动时间直方图确定12N的产生。
主要结果：计算了11个能量的横截面，范围从23.5到147MeV，使用有关实验设置和光束传递的信息。通过全面的不确定性传播分析，统计不确定度为2.6~5.8%,系统不确定度为3.3~4.6%.此外,校准测量显示系统校正因子为1.21(±7.5%)，对全球不确定性的贡献最大。尽管如此,与先前唯一的核反应研究报告的值相比，横截面测量的精度有所提高。为了获得连续的横截面函数，使用两个数据集进行加权样条插值。＆＃xD;意义：我们的结果被纳入RayStation蒙特卡洛（MC）引擎，用于计算治疗期间的12N正电子an灭分布，目的是开发MC模拟框架来预测12NPET成像，以进行范围验证。
