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

PET 和 SPECT 的传统医学成像依赖于反投影技术，并且由于伽马射线的散射和吸收而存在伪影的缺点，导致假阴性和/或假阳性诊断。已建议使用单独同位素的双能量成像作为提高图像质量的可能方法。它们总是涉及额外的设备、更高的剂量和更长的曝光时间等。我们尝试了一种将 PET/SPECT 成像与单一同位素相结合的新方法，该同位素在不到几纳秒的时滞内发射正电子和伽马射线。实施后，我们可以采用核物理和粒子物理实验的标准 3D 顶点重建技术。 除了增强对比度之外，该方法还通过传统的反投影提供基于不同软件切割的多个图像，以批判性地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，我们重点关注同位素对人体的生物相容性、衰减校正的双能量需求、经济可行性和生产的简易性、材料的稳定性等。候选同位素是 43-Sc、73-Se、123-Xe、85-Y、77-Kr 和 75-Br，其元素已用于医疗用途和摄入。 ***我是一项国际合作的首席研究员，成员来自加拿大、日本、韩国、印度和越南。我们将在日本大阪大学、UBC 校园的 TRIUMF 实验室和萨斯喀彻温大学的回旋加速器实验室用质子和 α 束进行实验，以确定最佳束能量和照射时间，以最大限度地提高所选同位素的产量，同时将干扰活动保持在最低限度。 该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。 ***一些同位素将以足够低的能量制造，以便小型回旋加速器具有高强度的几个 MeV 质子束，这将避免巨大的空间或长距离运输。 组合 PET/SPECT 的模式可以对现有 PET*** 机器进行改造，只需对成像硬件/软件进行微小的更改。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。加拿大社会将从中受益，因为患者将获得更好的成像效果，辐射剂量更少，模糊性更少。放射科医生将拥有人体器官的多幅图像，所有这些图像都是在一种环境下使用单一同位素获得的，并且能够批判性地评估它们并更好地评估患者的状况。 ******

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. ******