Kawamoto Keishin, Sato Hideyuki, Kogure Yosuke
From the Department of Radiological Technology, Juntendo University Hospital, Tokyo, Japan.
J Comput Assist Tomogr. 2024;48(2):236-243. doi: 10.1097/RCT.0000000000001538. Epub 2023 Aug 31.
This study aimed to evaluate the effect of a silver (Ag) additional filter on dose characteristics and image quality in low-dose chest computed tomography (CT).
A dose evaluation phantom, physical evaluation phantom, and chest phantom were scanned with and without an Ag additional filter. The doses were adjusted so that the displayed the volume CT dose indexes (CTDI vol ) were from 0.3 to 1.6 mGy. For dose characteristics, the spectrum of photon energies and the measured CTDI vol were calculated for each scanning condition. For task-based image quality analysis, task transfer function, noise power spectrum, and system performance were evaluated. Streak artifacts, image noise, and contrast-to-noise ratio were quantified using a chest phantom.
With the Ag additional filter, mean energy was 22% higher and the CTDI vol was approximately 30% lower than those without the Ag additional filter. The task transfer function and noise power spectrum with the Ag additional filter were lower than those without the Ag additional filter. The system performance with the Ag additional filter was similar to that without the Ag additional filter. The Ag additional filter reduced streak artifact near the lung apex and image noise in the lung fields. The contrast-to-noise ratio was slightly higher with the Ag additional filter than that without the Ag additional filter.
The output dose and spatial resolution with the Ag additional filter were lower than those without the Ag additional filter. However, this filter helped reduce the radiation dose, image noise, and streak artifacts, particularly when scanning at ultralow doses.
本研究旨在评估银（Ag）附加滤过器对低剂量胸部计算机断层扫描（CT）剂量特性和图像质量的影响。
使用和不使用Ag附加滤过器对剂量评估体模、物理评估体模和胸部体模进行扫描。调整剂量，使显示的容积CT剂量指数（CTDIvol）为0.3至1.6 mGy。对于剂量特性，计算每种扫描条件下的光子能量谱和测量的CTDIvol。对于基于任务的图像质量分析，评估任务传递函数、噪声功率谱和系统性能。使用胸部体模对条纹伪影、图像噪声和对比噪声比进行量化。
使用Ag附加滤过器时，平均能量比不使用Ag附加滤过器时高22%，CTDIvol约低30%。使用Ag附加滤过器时的任务传递函数和噪声功率谱低于不使用Ag附加滤过器时。使用Ag附加滤过器时的系统性能与不使用Ag附加滤过器时相似。Ag附加滤过器减少了肺尖附近的条纹伪影和肺野中的图像噪声。使用Ag附加滤过器时的对比噪声比略高于不使用Ag附加滤过器时。
使用Ag附加滤过器时的输出剂量和空间分辨率低于不使用Ag附加滤过器时。然而，这种滤过器有助于降低辐射剂量图像噪声和条纹伪影，特别是在超低剂量扫描时。
