Institute of Biomedical Engineering (IBT), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.
Mannheim Institute for Intelligent Systems in Medicine (MIISM), Heidelberg University, Mannheim, Germany.
Phys Med Biol. 2024 Jul 30;69(16). doi: 10.1088/1361-6560/ad6370.
3D-localization of gamma sources has the potential to improve the outcome of radio-guided surgery. The goal of this paper is to analyze the localization accuracy for point-like sources with a single coded aperture camera.We both simulated and measured a point-like241Am source at 17 positions distributed within the field of view of an experimental gamma camera. The setup includes a0.11mmthick Tungsten sheet with a MURA mask of rank 31 and pinholes of0.08mmin diameter and a detector based on the photon counting readout circuit Timepix3. Two methods, namely an iterative search including either a symmetric Gaussian fitting or an exponentially modified Gaussian fitting (EMG) and a center of mass method were compared to estimate the 3D source position.Considering the decreasing axial resolution with source-to-mask distance, the EMG improved the results by a factor of 4 compared to the Gaussian fitting based on the simulated data. Overall, we obtained a mean localization error of0.77mmon the simulated and2.64mmon the experimental data in the imaging range of20-100mm.This paper shows that despite the low axial resolution, point-like sources in the nearfield can be localized as well as with more sophisticated imaging devices such as stereo cameras. The influence of the source size and the photon count on the imaging and localization accuracy remains an important issue for further research.
γ源的 3D 定位有可能改善放射性引导手术的效果。本文的目的是分析使用单个编码孔径相机对点状源进行定位的准确性。我们分别对一个位于实验伽马相机视场内的 241Am 点状源的 17 个位置进行了模拟和测量。该设置包括一个 0.11mm 厚的钨片，上面有一个秩为 31 的 MURA 掩模和直径为 0.08mm 的针孔，以及一个基于光子计数读出电路 Timepix3 的探测器。我们比较了两种方法，即包括对称高斯拟合或指数修正高斯拟合（EMG）的迭代搜索和质心法，以估计 3D 源位置。考虑到随着源到掩模距离的增加轴向分辨率降低，与基于模拟数据的高斯拟合相比，EMG 将结果提高了 4 倍。总的来说，在 20-100mm 的成像范围内，我们在模拟数据上获得了 0.77mm 的平均定位误差，在实验数据上获得了 2.64mm 的平均定位误差。本文表明，尽管轴向分辨率较低，但近场中的点状源也可以像立体相机等更复杂的成像设备一样进行定位。源尺寸和光子计数对成像和定位精度的影响仍然是进一步研究的重要问题。
