The effect of volume-of-interest misregistration on quantitative planar activity and dose estimation
The effect of volume-of-interest misregistration on quantitative planar activity and dose estimation
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DOI：
10.1088/0031-9155/55/18/014
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发表时间：
2010-09-21
影响因子：
3.5
通讯作者：
Frey, E. C.
中科院分区：
文献类型：
--
作者：
Song, N.;He, B.;Frey, E. C.
在靶向放射性核素治疗（TRT）中，剂量估算对于治疗计划和肿瘤剂量反应研究至关重要。剂量估计通常基于在给予计划剂量之后采集的患者的全身共轭视图平面或SPECT扫描的时间序列。从这些研究中量化器官中的活性是剂量估计的一个重要部分。定量平面（QPlanar）处理方法涉及通过图像形成过程的计算模型和定义待量化器官的3D感兴趣体积的组合，对图像退化因素进行精确补偿，并对器官和背景重叠进行校正。当器官VOI被准确定义时，该方法本质上补偿衰减、散射和部分体积效应，以及与其他器官和背景的重叠。然而，需要在QPlanar处理中使用的3D感兴趣器官体积（VOI）与平面图像中的真实器官投影之间进行对准。本研究的目的是研究VOI配准不良对使用QPlanar方法获得的器官活动估计的准确性和精密度的影响。在这项工作中，我们建模的残余配准不良的程度，将预期自动配准程序后，随机错位3D SPECT/CT图像，VOI信息的来源，和平面图像。基于互信息的图像配准被用于将真实的模拟3D SPECT图像与2D平面图像对准。残差图像配准不良用于模拟配准不良的真实水平，并允许研究配准不良对QPlanar方法准确度和精密度的影响。我们观察到，准确的配准对于小器官或与邻近器官相比具有低活性浓度的器官尤其重要。此外，残留的配准不良引起的精度损失的活动估计，这是精度损失的顺序，由于泊松噪声的投影数据。这些结果作为配准不良对QPlanar活性估计准确度和精密度影响的下限，并证明在评估器官剂量估计的总体精密度时必须考虑配准不良误差。
In targeted radionuclide therapy (TRT), dose estimation is essential for treatment planning and tumor dose response studies. Dose estimates are typically based on a time series of whole-body conjugate view planar or SPECT scans of the patient acquired after administration of a planning dose. Quantifying the activity in the organs from these studies is an essential part of dose estimation. The quantitative planar (QPlanar) processing method involves accurate compensation for image degrading factors and correction for organ and background overlap via the combination of computational models of the image formation process and 3D volumes of interest defining the organs to be quantified. When the organ VOIs are accurately defined, the method intrinsically compensates for attenuation, scatter and partial volume effects, as well as overlap with other organs and the background. However, alignment between the 3D organ volume of interest (VOIs) used in QPlanar processing and the true organ projections in the planar images is required. The aim of this research was to study the effects of VOI misregistration on the accuracy and precision of organ activity estimates obtained using the QPlanar method. In this work, we modeled the degree of residual misregistration that would be expected after an automated registration procedure by randomly misaligning 3D SPECT/CT images, from which the VOI information was derived, and planar images. Mutual information-based image registration was used to align the realistic simulated 3D SPECT images with the 2D planar images. The residual image misregistration was used to simulate realistic levels of misregistration and allow investigation of the effects of misregistration on the accuracy and precision of the QPlanar method. We observed that accurate registration is especially important for small organs or ones with low activity concentrations compared to neighboring organs. In addition, residual misregistration gave rise to a loss of precision in the activity estimates that was on the order of the loss of precision due to Poisson noise in the projection data. These results serve as a lower bound on the effects of misregistration on the accuracy and precision of QPlanar activity estimate and demonstrate that misregistration errors must be taken into account when assessing the overall precision of organ dose estimates.