A Study of Computer Tomography with Accelerated Proton Beam

提出并研究了一种质子计算机断层扫描（CT）。12UD串联加速器用于加速质子粒子。质子的能量是24MeV。虽然质子CT的原理与x射线CT相似，但由于质子在材料中的相互作用机制与x射线的相互作用机制有很大的不同，需要用新的思路来实现。提出了一种新的方法——剩余能量法，并进行了试验。根据这个想法，层析图是由质子在吸收材料的每个部分的电子停止功率制成的。与x线CT相比，我们可以预期质子CT有几个优势。在此，总结其优点。1)由于对辐照的所有质子粒子进行了测量，因此可以在较少的质子辐照下获得非常高质量的层析成像。然后，预期某一特定剂量的放射性物质会减少。2)与x射线相反，由于质子粒子是带电粒子，而不是像x射线那样的静电波，所以用几种电磁光学装置可以将质子粒子聚焦在被照射材料的很小一部分上。因此，更容易获得具有很高比分辨率的层析成像。质子CT已经用鬼影试过了。质子束直径控制在0.1mm以内。层析成像观察成功。空间分辨率为0.25mm，足以用于医疗用途。这些试验仍在调查中。

A proton computer tomography (CT) has been proposed and investigated. A 12UD tandem accelerator is used to accelerate proton particles. The energy of the proton is 24MeV.Though the principal of the proton CT is similar to that of a X-ray CT,a new idea is requested to realize it because the interaction mechanism of the proton in the material strongly different from that of the X-ray. A new idea, which is named Residual Energy Method, is proposed and is gotten a tryout. According to the idea, a tomogram is made from the electronic stopping power of the proton at the each part of an absorption material. As comparison with the X-ray CT,we can expect several advantages in the proton CT.Here, the strong points are summarized. 1) A very high quality tomogram can be get with less proton irradiation to a person because of measurement of all proton particles which are irradiated. Then, it is expected the decrease of a specific dose of radioactivity. 2) In contradiction to the X-ray, the proton particle can be focused on a very small portion of the irradiated material with several kind of electromagnetic optical devices because it is charged particle, not electrostatic wave like X-ray. Consequently, it becomes easier to get the tomogram with very high specific resolution.The proton CT has been tried with a haunt. The diameter of the proton beam is controlled to be less than 0.1mm. The tomogram has been observed successfully. The space resolution is 0.25mm which is sufficient for medical usage. The trials are still under investigation.