探讨符合线路SPECT配置针孔准直器进行小动物高能成像的可行性

Discussion on the Feasibility of Small Animal High-Energy Imaging Using Coincidence SPECT with a Pinhole Collimator

目的探讨符合线路SPECT配置针孔准直器进行小动物高能成像的可行性。方法 1点源试验。将14.8 MBq的99Tcm、131I和18F三种核素的点源分别置于针孔准直器表面中心轴线不同距离处,采集点源图像并计算分辨率;2小鼠成像。首先采集小鼠的99Tcm和18F-FDG平面图像,次日采集小鼠的18F-FDG符合线路断层融合影像。结果 99Tcm的点源图像清晰、无伪影;131I和18F点源周围均存在少量透射和散射伪影,图像边缘有较明显的环形透射伪影。三种核素点源分辨率均随距离增加而下降,在距离探头30 mm位置,99Tcm、131I和18F的点源分辨率FWHM分别为4.3、5.2、7.4 mm,分辨率FWTM分别为7.1、10.1、14.5 mm。其中,18F分辨率FWHM为7.2 mm,优于SPECT的系统分辨率10 mm。经过模拟放大2.5倍后,小鼠的高、低能影像均较清晰,环形伪影位于有效视野之外。小鼠符合线路18F-FDG的影像不清晰。结论在对分辨率要求不高的场合,符合线路SPECT配置低能针孔准直器进行小动物高能成像是可行的。

Objective This study was aimed to explore the feasibility of small animal high-energy imaging using coincidence SPECT（Single-Photon Emission Computerized Tomography） with a pinhole collimator.Methods First,the point sources of 14.8MBq＇s three radionuclides（99Tcm,131 I and 18F） were placed at different distances from the central axis of the pinhole collimator respectively.Images of point sources were acquired to calculate their resolutions.Then,99 Tcm and 18F-FDG images of mice were acquired respectively.The coincidence images of the mouse were acquired on the second day.Results The images of 99 Tcm point source were clear without artifacts; however,there were minor penetration and scattered artifacts in 131 I and 18 F images.Additionally,both images had significant circular penetration artifacts in their edges.Resolutions of 99 Tcm,131 I and 18 F were declined with the distance increased.At the distance of 30 mm from the pinhole collimator,their FWHM（Full-Widths-at-Half-Maximum） and FWTM（Full-Widths-at-Tenth-Maximum） resolutions were 4.3,5.2,7.4 mm and 7.1,10.1,14.5 mm respectively.The FWHM resolution of 18 F showed advantages over the resolution of the images acquired by SPECT.After being zoomed in 2.5 times,both the high-energy and low-energy mice images were clear with the ring artifacts outside the effective field of view.Coincidence 18F-FDG images of the mouse were not clear.Conclusion The coincidence SPECT with the lowenergy pinhole collimator can be used for small animal high-energy imaging if there was no restriction on the resolution of images.