Adam L E, Bellemann M E, Brix G, Lorenz W J
PET Research Group, German Cancer Research Center, Heidelberg, Germany.
J Nucl Med. 1996 Dec;37(12):2024-9.
This study quantifies the different scatter components in PET and examines how the different components degrade reconstructed PET images.
We simulated the measurement of various phantoms using Monte Carlo (MC) calculations and compared the MC-generated projections and images with the corresponding experimental data. The coincidences were subdivided in four classes: primaries, object scatter (scattered in the object only), gantry scatter (scattered in the scanner only) and mixed scatter (scattered both in the object and the scanner).
In the projections of the line sources, the gantry scatter was closely located around the source position, whereas the object scatter was smeared over the whole field of view and could be parameterized well by a monoexponential function. The mixed scatter had nearly the same distribution as the object scatter, but with a smaller amplitude. The calculations and experimental data were in excellent agreement; i.e., led to the same parameterization of the scatter distribution functions and to a similar localization of the scatter components in the reconstructed images.
The spatial distribution of the scatter components justifies the widely-used assumption that it is sufficient to restrict experimental scatter correction techniques to the object scatter. Furthermore, it is possible to derive the parameters for the scatter kernels, which are needed for the convolution-subtraction algorithm, by MC simulations.
本研究对正电子发射断层扫描（PET）中的不同散射成分进行了量化，并研究了不同成分如何降低重建的PET图像质量。
我们使用蒙特卡罗（MC）计算模拟了各种体模的测量，并将MC生成的投影和图像与相应的实验数据进行了比较。符合事件被细分为四类：原发射线、物体散射（仅在物体中散射）、机架散射（仅在扫描仪中散射）和混合散射（在物体和扫描仪中均有散射）。
在线源的投影中，机架散射紧密位于源位置周围，而物体散射则散布在整个视野中，并且可以用单指数函数很好地参数化。混合散射的分布与物体散射几乎相同，但幅度较小。计算结果与实验数据高度吻合；即，导致散射分布函数的参数化相同，并且在重建图像中散射成分的定位相似。
散射成分的空间分布证明了广泛使用的假设是合理的，即仅对物体散射进行实验散射校正技术就足够了。此外，通过MC模拟可以得出卷积减法算法所需的散射核参数。
