Experimental investigation of factors affecting the absolute recovery coefficients in iodine-124 PET lesion imaging
Experimental investigation of factors affecting the absolute recovery coefficients in iodine-124 PET lesion imaging
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DOI：
10.1088/0031-9155/55/8/016
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发表时间：
2010-04-21
影响因子：
3.5
通讯作者：
Jentzen, Walter
中科院分区：
文献类型：
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作者：
Jentzen, Walter
在I-124 PET病变成像中使用恢复系数（RC）是一种简单的方法，主要针对部分容积效应校正成像的放射性浓度（AC），并在一定程度上校正瞬发γ符合效应。本体模研究的目的是通过实验研究影响I-124 RC的各种因素。考虑了三种基于RC的校正方法。这些方法在绘制的感兴趣体积（VOI）方面不同，其确定成像AC和RC：包含最大值（最大RC）的单体素VOI、具有扫描仪分辨率（分辨率RC）的直径的球形VOI和等于物理对象体积（等体积RC）的VOI。主要使用独立PET扫描仪（EXACT HR+）和最新一代PET/CT扫描仪（BIOGRAPH mCT）进行测量。使用包含球体或旋转椭球体的圆柱体模确定RC，并从使用参考采集协议采集的图像中获得RC。对于每种类型的RC，评估了以下因素对RC的影响：对象形状、背景活动溢出和迭代图像重建参数。为了评估基于RC的校正方法的鲁棒性，从使用不同AC方案的临床采集协议采集的图像确定RC校正的AC与真实AC之间的百分比偏差。的形状和溢出效应的观察结果进行了比较与来自卷积为基础的模型的模拟数据。研究表明，形状效应可以忽略不计，因此，与理论预期一致。与模拟结果相反，观察到的溢出效应出乎意料地小。为避免重建参数变化导致RC测定的变化，建议使用像素长度约为扫描仪分辨率的三分之一或更少的图像重建和OSEM 1 x 32算法或有效迭代次数略高的算法。使用临床采集协议，体模研究表明，基于分辨率或等体积的恢复校正方法似乎更适合从患者数据中恢复AC;然而，将三种基于RC的校正方法应用于包含低AC的小病变尤其与大幅低估相关。体模研究有几个局限性，详细讨论了这些局限性。
The use of recovery coefficients (RCs) in I-124 PET lesion imaging is a simple method to correct the imaged activity concentration (AC) primarily for the partial-volume effect and, to aminor extent, for the prompt gamma coincidence effect. The aim of this phantom study was to experimentally investigate a number of various factors affecting the I-124 RCs. Three RC-based correction approaches were considered. These approaches differ with respect to the volume of interest (VOI) drawn, which determines the imaged AC and the RCs: a single voxel VOI containing the maximum value (maximum RC), a spherical VOI with a diameter of the scanner resolution (resolution RC) and a VOI equaling the physical object volume (isovolume RC). Measurements were performed using mainly a stand-alone PET scanner (EXACT HR+) and a latest-generation PET/CT scanner (BIOGRAPH mCT). The RCs were determined using a cylindrical phantom containing spheres or rotational ellipsoids and were derived from images acquired with a reference acquisition protocol. For each type of RC, the influence of the following factors on the RC was assessed: object shape, background activity spill in and iterative image reconstruction parameters. To evaluate the robustness of the RC-based correction approaches, the percentage deviation between RC-corrected and true ACs was determined from images acquired with a clinical acquisition protocol of different AC regimes. The observed results of the shape and spill-in effects were compared with simulation data derived from a convolution-based model. The study demonstrated that the shape effect was negligible and, therefore, was in agreement with theoretical expectations. In contradiction to the simulation results, the observed spill-in effect was unexpectedly small. To avoid variations in the determination of RCs due to reconstruction parameter changes, image reconstruction with a pixel length of about one-third or less of the scanner resolution and an OSEM 1 x 32 algorithm or one with somewhat higher number of effective iterations are recommended. Using the clinical acquisition protocol, the phantom study indicated that the resolution- or isovolume-based recovery-correction approaches appeared to be more appropriate to recover the ACs from patient data; however, the application of the three RC-based correction approaches to small lesions containing low ACs was, in particular, associated with large underestimations. The phantom study had several limitations, which were discussed in detail.