Knoll Peter, Rahmim Arman, Gültekin Selma, Šámal Martin, Ljungberg Michael, Mirzaei Siroos, Segars Paul, Szczupak Boguslaw
Department of Nuclear Medicine with PET Center, Wilhelminenspital, Vienna, Austria.
Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Johns Hopkins University, Baltimore, Maryland 21287, USA.
Rev Sci Instrum. 2017 Sep;88(9):094303. doi: 10.1063/1.5001024.
Quantitative nuclear medicine imaging is an increasingly important frontier. In order to achieve quantitative imaging, various interactions of photons with matter have to be modeled and compensated. Although correction for photon attenuation has been addressed by including x-ray CT scans (accurate), correction for Compton scatter remains an open issue. The inclusion of scattered photons within the energy window used for planar or SPECT data acquisition decreases the contrast of the image. While a number of methods for scatter correction have been proposed in the past, in this work, we propose and assess a novel, user-independent framework applying factor analysis (FA). Extensive Monte Carlo simulations for planar and tomographic imaging were performed using the SIMIND software. Furthermore, planar acquisition of two Petri dishes filled with Tc solutions and a Jaszczak phantom study (Data Spectrum Corporation, Durham, NC, USA) using a dual head gamma camera were performed. In order to use FA for scatter correction, we subdivided the applied energy window into a number of sub-windows, serving as input data. FA results in two factor images (photo-peak, scatter) and two corresponding factor curves (energy spectra). Planar and tomographic Jaszczak phantom gamma camera measurements were recorded. The tomographic data (simulations and measurements) were processed for each angular position resulting in a photo-peak and a scatter data set. The reconstructed transaxial slices of the Jaszczak phantom were quantified using an ImageJ plugin. The data obtained by FA showed good agreement with the energy spectra, photo-peak, and scatter images obtained in all Monte Carlo simulated data sets. For comparison, the standard dual-energy window (DEW) approach was additionally applied for scatter correction. FA in comparison with the DEW method results in significant improvements in image accuracy for both planar and tomographic data sets. FA can be used as a user-independent approach for scatter correction in nuclear medicine.
定量核医学成像是一个日益重要的前沿领域。为了实现定量成像，必须对光子与物质的各种相互作用进行建模和补偿。虽然通过纳入x射线CT扫描（准确）解决了光子衰减校正问题，但康普顿散射校正仍是一个未解决的问题。在用于平面或SPECT数据采集的能量窗内包含散射光子会降低图像的对比度。虽然过去已经提出了许多散射校正方法，但在这项工作中，我们提出并评估了一种应用因子分析（FA）的新颖、独立于用户的框架。使用SIMIND软件对平面和断层成像进行了广泛的蒙特卡罗模拟。此外，使用双头伽马相机对两个装有Tc溶液的培养皿进行了平面采集，并进行了Jaszczak体模研究（美国北卡罗来纳州达勒姆市的数据光谱公司）。为了将因子分析用于散射校正，我们将应用的能量窗细分为多个子窗，作为输入数据。因子分析产生两个因子图像（光电峰、散射）和两条相应的因子曲线（能谱）。记录了平面和断层Jaszczak体模伽马相机测量结果。对断层数据（模拟和测量）的每个角度位置进行处理，得到一个光电峰和一个散射数据集。使用ImageJ插件对Jaszczak体模的重建横断面切片进行定量分析。因子分析获得的数据与所有蒙特卡罗模拟数据集中获得的能谱、光电峰和散射图像显示出良好的一致性。为了进行比较，还额外应用了标准双能量窗（DEW）方法进行散射校正。与双能量窗方法相比，因子分析在平面和断层数据集的图像准确性方面都有显著提高。因子分析可作为核医学中一种独立于用户的散射校正方法。
