Correction for collimator-detector response in SPECT using point spread function template.
Correction for collimator-detector response in SPECT using point spread function template.
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DOI：
10.1109/tmi.2012.2225441
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发表时间：
2013-02
影响因子：
10.6
通讯作者：
Dewaraja YK
中科院分区：
文献类型：
--
作者：
Chun SY;Fessler JA;Dewaraja YK
对SPECT中准直-检测器响应（CDR）的补偿对于精确定量是非常重要的。CDR既有几何响应，也有间隔穿透和准直散射响应。几何响应可以解析建模，如果几何响应占主导地位，则通常用于整个CDR的建模。然而，对于发射中等或高能光子的放射性核素，如I-131，间隔穿透和准直散射响应是重要的，其在CDR校正中的建模对于准确量化非常重要。有两种主要的基于深度的CDR建模方法，既包括几何响应，也包括间隔穿透和准直散射响应。一种方法是拟合高斯加指数函数，该函数在几个源-探测器距离上对被测点源响应具有旋转不变性。然而，旋转不变的指数函数不能详细地表示星形间隔穿透尾。另一种方法是执行蒙特卡罗（MC）模拟，以生成所有必要距离的深度相关点扩展函数（psf）。然而，MC模拟需要对SPECT检测器组件进行仔细的建模，这可能具有挑战性，并且可能无法对诊所中所有不同的SPECT扫描仪获得准确的结果。在本文中，我们提出了一种CDR建模的替代方法。我们使用高斯函数加上二维b样条PSF模板，并将模型拟合到几个距离上的I-131点源的测量值。所提出的基于psf模板的方法几乎是非参数的，捕获间隔穿透尾的特征，并最小化拟合和测量CDR在感兴趣距离上的差异。新模型应用于I-131 SPECT重建实验幻体测量，患者研究和MC患者模拟研究使用XCAT幻体。与传统高斯模型和高斯加指数模型相比，该模型的回收率分别提高了16.5%和10.8%。
Compensating for the collimator-detector response (CDR) in SPECT is important for accurate quantification. The CDR consists of both a geometric response and a septal penetration and collimator scatter response. The geometric response can be modeled analytically and is often used for modeling the whole CDR if the geometric response dominates. However, for radionuclides that emit medium or high-energy photons such as I-131, the septal penetration and collimator scatter response is significant and its modeling in the CDR correction is important for accurate quantification. There are two main methods for modeling the depth-dependent CDR so as to include both the geometric response and the septal penetration and collimator scatter response. One is to fit a Gaussian plus exponential function that is rotationally invariant to the measured point source response at several source-detector distances. However, a rotationally-invariant exponential function cannot represent the star-shaped septal penetration tails in detail. Another is to perform Monte-Carlo (MC) simulations to generate the depth-dependent point spread functions (PSFs) for all necessary distances. However, MC simulations, which require careful modeling of the SPECT detector components, can be challenging and accurate results may not be available for all of the different SPECT scanners in clinics. In this paper, we propose an alternative approach to CDR modeling. We use a Gaussian function plus a 2-D B-spline PSF template and fit the model to measurements of an I-131 point source at several distances. The proposed PSF-template-based approach is nearly non-parametric, captures the characteristics of the septal penetration tails, and minimizes the difference between the fitted and measured CDR at the distances of interest. The new model is applied to I-131 SPECT reconstructions of experimental phantom measurements, a patient study, and a MC patient simulation study employing the XCAT phantom. The proposed model yields up to a 16.5 and 10.8% higher recovery coefficient compared to the results with the conventional Gaussian model and the Gaussian plus exponential model, respectively.