Positron emission tomography (PET) is a powerful tool because we can acquire functional information of tissue from the images with high sensitivity and relatively high spatial resolution. However, high-spatial-resolution PET imaging for high-energy positron emitters is difficult because the positrons have a long range and annihilation radiations are emitted at the endpoints of the positrons’ trajectories. Along the trajectories, Cerenkov light (CL) is also emitted in advance of the emission of annihilation radiations. Hence, CL can be used for the imaging of high-energy positron emitters. Bremsstrahlung X-rays are also emitted along the trajectories of positrons, and imaging is possible. However, the differences in the spatial distributions of these three types of radiations are not obvious. Because CL and bremsstrahlung X-rays are produced before the endpoint of the positron, high-spatial-resolution imaging may be possible for high-energy positrons. In this study, to clarify this point, we simulated the spatial distribution of CL, bremsstrahlung X-rays, and annihilation radiations using Monte Carlo simulation and compared the distributions. The distributions of the bremsstrahlung X-rays and CL were smaller than those of the annihilation radiations in case of high energy positrons, and we found that the distributions of bremsstrahlung X-rays nearly matched those of CL for high-energy positron emitters. We concluded that CL and bremsstrahlung X-ray imaging have higher spatial resolution than annihilation radiation imaging for MeV ordered positron emitters, and thus they are promising for high-spatial-resolution imaging of high-energy positron emitters such as O-15 for ion therapy and Ga-68 for PET imaging.

正电子发射断层扫描 (PET) 是一种强大的工具，因为我们可以从具有高灵敏度和相对较高空间分辨率的图像中获取组织的功能信息。然而，高能正电子发射体的高空间分辨率PET成像很困难，因为正电子的射程很长，而且在正电子轨迹的端点处会发射湮没辐射。沿着轨迹，切伦科夫光 (CL) 也先于湮灭辐射的发射而发射。因此，CL 可用于高能正电子发射体的成像。Bremsstrahlung X 射线也沿着正电子的轨迹发射，并且成像是可能的。但是，这三种辐射的空间分布差异并不明显。由于 CL 和轫致辐射 X 射线是在正电子的终点之前产生的，因此高能正电子的高空间分辨率成像可能是可能的。在这项研究中，为了澄清这一点，我们使用蒙特卡罗模拟模拟了 CL、轫致辐射 X 射线和湮灭辐射的空间分布，并比较了这些分布。在高能正电子的情况下，轫致辐射 X 射线和 CL 的分布小于湮没辐射的分布，我们发现，对于高能正电子发射体，轫致辐射 X 射线的分布几乎与 CL 的分布相匹配。我们得出结论，对于 MeV 有序正电子发射体，CL 和轫致辐射 X 射线成像具有比湮没辐射成像更高的空间分辨率，