Isotopes for New Modalities of PET/SPECT Imaging: Experimentation and Evaluation

通过PET和SPECT的常规医学成像依赖于反投影技术，并且其具有由于伽马射线的散射和吸收而导致的伪影的缺点，从而导致假阴性和/或假阳性诊断。已经建议使用单独的同位素的双能量成像作为改善图像质量的可能手段。他们总是涉及额外的设备，更高的剂量和更长的曝光等，我们尝试了一种新的方法相结合的PET/SPECT成像与单一的同位素发射正电子和伽马射线在不到几纳秒的时间滞后。实现后，可以采用核物理和粒子物理实验中的标准三维顶点重建技术. 除了增强对比度之外，该方法还提供了基于不同软件切割的多个图像以及传统的反投影，以严格评估图像伪影并最大限度地减少错误诊断。在确定候选同位素时，我们关注同位素对人体的生物相容性、衰减校正的双重能量要求、经济可行性和易于生产、材料的稳定性等。候选同位素是43-Sc、73-Se、123-Sc、85-Y、77-Kr和75-Br，其中的元素已经在医学上使用和摄入。 我是一个国际合作的主要研究者，成员来自加拿大，日本，韩国，印度和越南。我们将在大坂大学日本，TRIUMF实验室在UBC校园和萨斯喀彻温大学的回旋加速器实验室进行质子和α束的实验，以确定最佳的束能量和照射时间，以最大限度地生产所选的同位素，同时将干扰活动保持在最低限度。 这项研究的下一阶段是放射化学分离程序，以开发临床可用的同位素生产和分离方法，并将这些知识传递给卫生组织的最终用户。 某些同位素将在足够低的能量下制造，使得几MeV质子束的高强度的小型回旋加速器，这将避免巨大的真实的地产或长距离运输。 组合PET/SPECT的模态可以被改装为现有PET 对成像硬件/软件进行微小更改的机器。我们将在实验室环境中使用原型探测器组件进行成像测试。 该项目完成后，将巩固加拿大作为核医学成像研究和开发领导者的地位。加拿大社会将受益，因为患者将获得更少的辐射剂量和更少的模糊性改善成像。放射科医生将有多个人体器官的图像，所有这些图像都是在一个环境中用一种同位素获得的，并且能够对它们进行严格的评估，并对患者的病情进行更好的评估。

The conventional medical imaging by PET and SPECT relies on back projection techniques and it has drawbacks of artifacts due to scattering and absorption of gamma rays, contributing to false negative and/or false positive diagnostics. Dual energy imaging with separate isotopes has been suggested as possible means of improving the image qualities. They invariably involve additional equipment, higher doses and longer exposures etc. We attempt a novel approach of combining PET/SPECT imaging with single isotopes which emit positrons and gamma rays within less than a few nano second time lags. When implemented, we can employ standard 3D- vertex reconstruction technique of nuclear and particle physics experiments. In addition to enhanced contrast, this method provides multiple images based on different software cuts with conventional back projection to evaluate the image artifacts critically and minimize false diagnostics. In identifying candidate isotopes, we focussed on biological compatibility of isotopes to humans, dual energy requirement for attenuation corrections, economic viability and ease of production, stability of materials etc. The candidate isotopes are 43-Sc, 73-Se, 123-Xe, 85-Y, 77-Kr and 75-Br, the elements of which are already in medical use and ingestion. I am the principal investigator of an international collaboration with members from Canada, Japan, Korea, India and Vietnam. We will perform experiments at Osaka university-Japan, TRIUMF- laboratory on UBC campus and at the cyclotron laboratory of the University of Saskatchewan with proton and alpha beams to determine the optimum beam energies and irradiation times to maximize the production of isotope of choice, while keeping the interfering activities to a minimum. The next phase of this research is radiochemical separation procedures to develop clinically usable isotope production and separation methods and pass on this knowledge to the end users in health organizations. Some of the isotopes are to be made at sufficiently low energies such that small cyclotrons of several MeV proton beams of high intensities, which will avoid huge real estate or long distance transportations. The modality of combined PET/SPECT can be retrofitted to existing PET machines with minor changes of hardware/software of imaging. We will perform imaging tests with a prototype detector assembly in laboratory setting. This project, when completed, will consolidate the position of Canada as a leader of nuclear medial imaging research and development. Canadian society will benefit as the patients will get improved imaging with less radiation doses and less ambiguities. Radiologists will have multiple images of human organs, all obtained in one setting with a single isotope and be able to critically evaluate them and make better assessment of a patient condition.