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首页> 外文期刊>Physics in medicine and biology. >Production of clinically useful positron emitter beams during carbon ion deceleration.
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Production of clinically useful positron emitter beams during carbon ion deceleration.

机译：在碳离子减速过程中产生临床上有用的正电子发射束。

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In external beam radiation therapy, radioactive beams offer the best clinical solution to simultaneously treat and in vivo monitor the dose delivery and tumor response using PET or PET-CT imaging. However, difficulties mainly linked to the low production efficiency have so far limited their use. This study is devoted to the analysis of the production of high energy (11)C fragments, preferably by projectile fragmentation of a stable monodirectional and monoenergetic primary (12)C beam in different absorbing materials (decelerators) in order to identify the optimal elemental composition. The study was performed using the Monte Carlo code SHIELD-HIT07. The track length and fluence of generated secondary particles were scored in a uniform absorber of 300 cm length and 10 cm radius, divided into slices of 1 cm thickness. The (11)C fluence build-up and mean energy variation with increasing decelerator depth are presented. Furthermore, the fluence of the secondary (11)C beam was studied as a function of its mean energy and the corresponding remaining range in water. It is shown that the maximum (11)C fluence build-up is high in compounds where the fraction by weight of hydrogen is high, being the highest in liquid hydrogen. Furthermore, a cost effective alternative solution to the single medium initially envisaged is presented: a two-media decelerator that comprises a first liquid hydrogen section followed by a second decelerating section made of a hydrogen-rich material, such as polyethylene (C(2)H(4)). The purpose of the first section is to achieve a fast initial (11)C fluence build-up, while the second section is primarily designed to modulate the mean energy of the generated (11)C beam in order to reach the tumor depth. Finally, it was demonstrated that, if the intensity of the primary (12)C beam can be increased by an order of magnitude, a sufficient intensity of the secondary (11)C beam is achieved for therapy and subsequent therapeutic PET imaging sessions. Such an increase in the intensity might be easily achieved with a superconducting cyclotron.
机译：在外部束放射治疗中，放射性束提供了最佳的临床解决方案，可同时使用PET或PET-CT成像同时治疗和体内监测剂量输送和肿瘤反应。然而，迄今为止，主要与生产效率低有关的困难限制了它们的使用。这项研究致力于分析高能（11）C碎片的产生，最好是通过在不同吸收材料（减速器）中稳定单向和单能初级（12）C光束的射弹碎裂来确定最佳元素组成。该研究使用蒙特卡罗代码SHIELD-HIT07进行。在长度为300 cm，半径为10 cm的均匀吸收器中对轨道长度和产生的次级粒子的通量进行评分，并分为1 cm厚的切片。提出了随着减速器深度的增加，（11）C能量密度的建立和平均能量的变化。此外，研究了次级（11）C束的注量，它是其平均能量和水中相应剩余范围的函数。结果表明，在氢的重量分数较高的化合物中，最大的（11）C通量积累很高，在液态氢中最高。此外，提出了一种针对最初设想的单一介质的具有成本效益的替代解决方案：一种双介质减速器，该减速器包括一个第一液态氢部分，然后是一个由富含氢的材料（例如聚乙烯）制成的第二减速部分（C（2） H（4））。第一部分的目的是实现快速的初始（11）C能量密度建立，而第二部分的主要目的是调制所产生的（11）C光束的平均能量，以达到肿瘤深度。最后，证明了，如果可以将主（12）C束的强度增加一个数量级，则可以达到足够的第二（11）C束强度用于治疗和后续的治疗性PET成像。用超导回旋加速器可以容易地实现强度的这种增加。

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