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The effect of magnetic field on positron range and spatial resolution in an integrated whole-body time-of-flight PET/MRI system

机译:集成的全身飞行时间PET / MRI系统中磁场对正电子范围和空间分辨率的影响

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Simultaneous imaging systems combining positron emission tomography (PET) and magnetic resonance imaging (MRI) have been actively investigated. A PET/MR imaging system (GE Healthcare) comprised of a time-of-flight (TOF) PET system utilizing silicon photomultipliers (SiPMs) and 3-tesla (3T) MRI was recently installed at our institution. The small-ring (60 cm diameter) TOF PET subsystem of this PET/MRI system can generate images with higher spatial resolution compared with conventional PET systems. We have examined theoretically and experimentally the effect of uniform magnetic fields on the spatial resolution for high-energy positron emitters. Positron emitters including 18F, 124I, and 68Ga were simulated in water using the Geant4 Monte Carlo toolkit in the presence of a uniform magnetic field (0, 3, and 7 Tesla). The positron annihilation position was tracked to determine the 3D spatial distribution of the 511-keV gammy ray emission. The full-width at tenth maximum (FWTM) of the positron point spread function (PSF) was determined. Experimentally, 18F and 68Ga line source phantoms in air and water were imaged with an investigational PET/MRI system and a PET/CT system to investigate the effect of magnetic field on the spatial resolution of PET. The full-width half maximum (FWHM) of the line spread function (LSF) from the line source was determined as the system spatial resolution. Simulations and experimental results show that the in-plane spatial resolution was slightly improved at field strength as low as 3 Tesla, especially when resolving signal from high-energy positron emitters in the air-tissue boundary.
机译:积极研究了结合正电子发射断层扫描(PET)和磁共振成像(MRI)的同时成像系统。最近在我们的机构中​​安装了一个PET / MR成像系统(GE Healthcare),该系统由飞行时间(TOF)PET系统组成,该系统使用硅光电倍增管(SiPM)和3-特斯拉(3T)MRI。与常规PET系统相比,此PET / MRI系统的小环(直径60厘米)TOF PET子系统可以生成具有更高空间分辨率的图像。我们已经从理论和实验上检查了均匀磁场对高能正电子发射器空间分辨率的影响。在均匀磁场(0、3和7 Tesla)存在的情况下,使用Geant4 Monte Carlo工具套件在水中模拟了包括18F,124I和68Ga的正电子发射体。跟踪正电子an灭位置,以确定511-keV伽玛射线发射的3D空间分布。确定了正电子点扩展函数(PSF)的第十个最大值的全角(FWTM)。实验上,使用研究性PET / MRI系统和PET / CT系统对空气和水中的18F和68Ga线源体模进行成像,以研究磁场对PET空间分辨率的影响。来自线源的线扩展函数(LSF)的全角半峰(FWHM)被确定为系统空间分辨率。仿真和实验结果表明,在低至3 Tesla的场强下,平面内空间分辨率略有提高,尤其是在分辨空气组织边界中来自高能正电子发射器的信号时。

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