Production of clinically useful positron emitter beams during carbon ion deceleration
Production of clinically useful positron emitter beams during carbon ion deceleration
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DOI：
10.1088/0031-9155/56/6/005
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发表时间：
2011-02
影响因子：
3.5
通讯作者：
M. Lazzeroni;Anders Brahme
中科院分区：
文献类型：
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作者：
M. Lazzeroni;Anders Brahme
在体外放射治疗中，放射性束提供了最佳的临床解决方案，可使用 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，主要与生产效率低有关的困难迄今为止限制了它们的使用。本研究致力于分析高能 11C 碎片的产生，优选通过不同吸收材料（减速器）中稳定的单向和单能初级 12C 光束的射弹破碎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 厘米、半径为 10 厘米的均匀吸收器中对产生的二次粒子的径迹长度和注量进行评分，并将吸收器分成 1 厘米厚的切片。给出了 11C 注量累积和平均能量随着减速器深度的增加而变化。此外，还研究了次级 11C 光束的注量与其平均能量和水中相应剩余射程的函数关系。结果表明，在氢重量分数较高的化合物中，最大 11C 注量累积较高，在液态氢中最高。此外，提出了最初设想的单一介质的成本有效的替代解决方案：双介质减速器，包括第一液氢部分和随后由富氢材料（例如聚乙烯（C2H4））制成的第二减速部分。第一部分的目的是实现快速的初始 11C 注量积累，而第二部分主要设计用于调制所生成的 11C 光束的平均能量以到达肿瘤深度。最后，事实证明，如果初级 12C 光束的强度可以增加一个数量级，则次级 11C 光束的强度足以用于治疗和随后的治疗性 PET 成像过程。使用超导回旋加速器可以轻松实现这种强度的增加。
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 11C fragments, preferably by projectile fragmentation of a stable monodirectional and monoenergetic primary 12C 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 11C fluence build-up and mean energy variation with increasing decelerator depth are presented. Furthermore, the fluence of the secondary 11C beam was studied as a function of its mean energy and the corresponding remaining range in water. It is shown that the maximum 11C 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 (C2H4). The purpose of the first section is to achieve a fast initial 11C fluence build-up, while the second section is primarily designed to modulate the mean energy of the generated 11C beam in order to reach the tumor depth. Finally, it was demonstrated that, if the intensity of the primary 12C beam can be increased by an order of magnitude, a sufficient intensity of the secondary 11C 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.