A Monte Carlo and physical phantom evaluation of quantitative In-111SPECT
A Monte Carlo and physical phantom evaluation of quantitative In-111SPECT
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DOI：
10.1088/0031-9155/50/17/018
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发表时间：
2005-09-07
影响因子：
3.5
通讯作者：
Frey, EC
中科院分区：
文献类型：
--
作者：
He, B;Du, Y;Frey, EC
在靶向放射性核素治疗（TRT）中，准确估计三维体内放射性分布对于剂量估计是非常重要的。尽管SPECT可以潜在地提供这样的估计，但是没有补偿图像退化因素的SPECT在定量上是不准确的。在这项工作中，我们评估了定量SPECT（QSPECT）重建方法，包括补偿各种物理效应。使用GE VH/豪克耶系统和RSD躯干体模获得实验投影数据。将已知活性的In-111氯化物置于肺、肝、心脏、背景和内径分别为22 mm和34 mm的两个球形隔室中。基于临床来源的In-111替伊莫单抗数据的具有器官活性的3D NCAT体模用于Monte Carlo（MC）模拟研究。使用先前验证的MC模拟方法模拟低噪声投影数据。生成了50组具有现实计数水平的噪声投影。使用OS-EM算法进行重建，具有衰减（A）、散射（S）、几何响应（G）、准直器-探测器响应（D）和部分体积补偿（PVC）的各种组合。从每个器官总活性估计的准确性和精确度方面评估了来自各种补偿组合的QSPECT图像。对于实验数据，除了较小的球体（-11.9%）外，ADS和PVC补偿的器官活动误差小于6.5%。对于有噪声的模拟数据，除肺（20.9%）和血管（15.2%）外，ADS补偿的器官活动误差小于5.5%。其他补偿组合的误差显著（A，AS）或稍大（AGS）。随着PVC的增加，器官活动的误差略有改善，但肺（11.5%）和血管（3.6%）的改善更为显著。标准差/平均值比值均小于1.5%。我们的结论是，QSPECT方法与适当的补偿提供了准确的In-111器官活动的估计。对于所使用的准直器，AGS几乎与ADS一样好，并且由于减少了重建时间而可能是优选的。PVC对于肿瘤等小结构或靠近高活性区域的器官很重要。从QSPECT方法的定量准确性的提高有可能改善TRT中的器官剂量估计。
Accurate estimation of the 3D in vivo activity distribution is important for dose estimation in targeted radionuclide therapy (TRT). Although SPECT can potentially provide such estimates, SPECT without compensation for image degrading factors is not quantitatively accurate. In this work, we evaluated quantitative SPECT (QSPECT) reconstruction methods that include compensation for various physical effects. Experimental projection data were obtained using a GE VH/Hawkeye system and an RSD torso phantom. Known activities of In-111 chloride were placed in the lungs, liver, heart, background and two spherical compartments with inner diameters of 22 mm and 34 mm. The 3D NCAT phantom with organ activities based on clinically derived In-111 ibritumomab tiuxetan data was used for the Monte Carlo (MC) simulation studies. Low-noise projection data were simulated using previously validated MC simulation methods. Fifty sets of noisy projections with realistic count levels were generated. Reconstructions were performed using the OS-EM algorithm with various combinations of attenuation (A), scatter (S), geometric response (G), collimator-detector response (D) and partial volume compensation (PVC). The QSPECT images from the various combinations of compensations were evaluated in terms of the accuracy and precision of the estimates of the total activity in each organ. For experimental data, the errors in organ activities for ADS and PVC compensation were less than 6.5% except the smaller sphere (-11.9%). For the noisy simulated data, the errors in organ activity for ADS compensation were less than 5.5% except the lungs (20.9%) and blood vessels (15.2%). Errors for other combinations of compensations were significantly (A, AS) or somewhat (AGS) larger. With added PVC, the error in the organ activities improved slightly except for the lungs (11.5%) and blood vessels (3.6%) where the improvement was more substantial. The standard deviation/mean ratios were all less than 1.5%. We conclude that QSPECT methods with appropriate compensations provided accurate In-111 organ activity estimates. For the collimator used, AGS was almost as good as ADS and may be preferable due to the reduced reconstruction time. PVC was important for small structures such as tumours or for organs in close proximity to regions with high activity. The improved quantitative accuracy from QSPECT methods has the potential for improving organ dose estimations in TRT.