Halo artifacts from urinary catheters can occur due to inaccurate scatter correction, and the artifacts affect the tumor visibility in 18F-FDG PET/CT images. We investigated the incidence rate and the mechanisms of halo-artifact generation and explored several scatter correction techniques to prevent artifacts. We conducted patient and phantom studies. (1) We retrospectively reviewed the cases of patients who had undergone 18F-FDG PET/CT scans. To determine the frequency of halo-artifact generation, we used the patients’ PET images with a standard scatter correction based on a tail-fitted single-scatter simulation (TF-SSS) using 4-mm voxel μ-maps (TFS 4-mm). (2) We performed phantom studies to evaluate the effects of a urine catheter and two scatter correction techniques, i.e., TF-SSS with 2-mm voxel μ-maps (TFS 2-mm) and a Monte Carlo-based single-scatter simulation (MC-SSS) using 4-mm voxel μ-maps (MCS 4-mm). The average standardized uptake values (SUVs) were measured for axial PET images. (3) Using the patients’ data, we investigated whether TFS 2-mm and MCS 4-mm can eliminate the artifacts in the clinical images. (1) There were 61 patients with urinary catheters; in five (8.2%), halo artifacts were observed in the TFS 4-mm PET images. (2) The phantom study clearly reproduced the halo artifacts in the TFS 4-mm PET images. The halo artifacts were generated when urine moved in the interval between the CT and PET imaging, and when the urinary catheter was placed in a circular shape. The SUVs for the TFS 4-mm and TFS-2mm PET images were underestimated at the halo-artifact regions, whereas the SUVs for the MCS 4-mm PET images were close to the true values. (3) The halo artifacts disappeared in the TFS 2-mm PET images in 4/5 patients but not 1/5 patient, whereas the halo artifacts were completely absent in the MCS 4-mm PET images in 5/5 patients. These data suggest that halo artifacts are caused if the PET images do not correspond to the physical material in the μ-maps, which induces the scatter correction error. With the MC-SSS, it was possible to accurately estimate the scatter without generating halo artifacts.

中文翻译：

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在¹⁸ F-FDG PET / CT成像中通过不正确的散射校正实现留置导尿管的晕圈伪影：发生率，机理和解决方案

归因于不正确的散射校正，可能会出现导尿管产生的光晕伪影，并且这些伪影会影响18F-FDG PET / CT图像中的肿瘤可见度。我们调查了发生率和产生光晕伪像的机制，并探索了几种散射校正技术来防止伪像。我们进行了耐心和幻像研究。（1）我们回顾性地回顾了接受18F-FDG PET / CT扫描的患者病例。为了确定产生光晕伪像的频率，我们使用患者的PET图像进行了标准散点校正，该散点校正基于使用4毫米体素μ-图（TFS 4毫米）的尾部拟合单散点模拟（TF-SSS） ）。（2）我们进行了幻像研究，以评估尿导管和两种散射校正技术的效果，即 带有2毫米体素μ贴图的TF-SSS（TFS 2毫米）和使用4毫米体素μ贴图（MCS的4毫米）的基于蒙特卡洛的单散射模拟（MC-SSS）。测量轴向PET图像的平均标准化摄取值（SUV）。（3）使用患者的数据，我们研究了TFS 2-mm和MCS 4-mm是否可以消除临床图像中的伪影。（1）有导尿管的患者61例；在五分之二（8.2％）中，在TFS 4-mm PET图像中观察到了光晕伪影。（2）幻像研究清楚地再现了TFS 4毫米PET图像中的光晕伪像。当尿液在CT和PET成像之间的间隔内移动，以及将导尿管放置成圆形时，会产生光晕伪影。用于TFS 4-mm和TFS-2mm PET图像的SUV在光晕区域内被低估了，而用于MCS 4毫米PET图像的SUV接近真实值。（3）4/5的患者在TFS 2-mm PET图像中没有出现光晕伪影，而1/5的患者中没有，而5/5的MCS 4-mm PET图像中完全没有光晕伪影。这些数据表明，如果PET图像与μ-map中的物理材料不对应，则会引起光晕伪像，从而导致散射校正误差。使用MC-SSS，可以在不产生光晕伪影的情况下准确估计散射。这些数据表明，如果PET图像与μ-map中的物理材料不对应，则会引起光晕伪像，从而导致散射校正误差。使用MC-SSS，可以在不产生光晕伪影的情况下准确估计散射。这些数据表明，如果PET图像与μ-map中的物理材料不对应，则会引起光晕伪像，从而导致散射校正误差。使用MC-SSS，可以在不产生光晕伪影的情况下准确估计散射。