Du Yong, Frey Eric C
Department of Radiology, Division of Medical Imaging Physics, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287, USA.
Med Phys. 2009 Jun;36(6):2021-33. doi: 10.1118/1.3120411.
A model-based method has been previously developed to estimate and compensate for the crosstalk and downscatter contamination in simultaneous 123I/99mTc dual-isotope SPECT imaging. In this method, photon scatter in the object is modeled using the effective source scatter estimate technique. Photon interactions with the collimator-detector are estimated using precalculated Monte Carlo simulated point response functions. Two different approaches, simultaneous and alternating model-based compensations, have been proposed for iterative reconstruction-based crosstalk and downscatter contamination compensation. In this work, both model-based approaches were evaluated in the context of quantitative accuracy when imaging the dopaminergic system using both Monte Carlo simulated and experimentally acquired data. Results indicate that mddel-based estimates of the crosstalk and downscatter contamination in both energy windows were in good agreement with the truth for the simulated data. The effects of the contamination reduced image contrast and overestimated absolute activity in all structures by up to 66%. Compensation using both model-based approaches improved image contrast. Errors in absolute activity quantitation were also reduced to less than +/-5% for most brain structures. The accuracy of striatal specific binding potentials, calculated as the ratio of activity in various striatal structures to the background, was also greatly improved after model-based compensation. In conclusion, model-based compensation of simultaneously acquired images of 99mTc and 123I labeled brain imaging agents provided image quality and quantitative accuracy that were comparable to the image without crosstalk. Both proposed compensation approaches can potentially be applied clinically, but when reconstruction time is a limiting factor, the alternating model-based compensation may be preferable.
先前已开发出一种基于模型的方法，用于估计和补偿同时进行的¹²³I/⁹⁹ᵐTc双同位素单光子发射计算机断层显像（SPECT）成像中的串扰和向下散射污染。在该方法中，使用有效源散射估计技术对物体中的光子散射进行建模。利用预先计算的蒙特卡洛模拟点响应函数来估计光子与准直器 - 探测器的相互作用。针对基于迭代重建的串扰和向下散射污染补偿，已提出了两种不同的方法，即基于模型的同时补偿和交替补偿。在这项工作中，当使用蒙特卡洛模拟数据和实验获取的数据对多巴胺能系统进行成像时，在定量准确性的背景下对这两种基于模型的方法进行了评估。结果表明，对于模拟数据，两个能量窗中基于模型的串扰和向下散射污染估计与真实情况高度吻合。污染的影响降低了图像对比度，并使所有结构中的绝对活度高估高达66%。使用这两种基于模型的方法进行补偿可改善图像对比度。对于大多数脑结构，绝对活度定量的误差也降低到小于±5%。基于模型的补偿后，纹状体特异性结合电位（计算为各种纹状体结构中的活度与背景活度之比）的准确性也有了很大提高。总之，基于模型的⁹⁹ᵐTc和¹²³I标记脑显像剂同时采集图像的补偿提供了与无串扰图像相当的图像质量和定量准确性。所提出的两种补偿方法都有可能应用于临床，但当重建时间是一个限制因素时，基于模型的交替补偿可能更可取。
