Abstract Computed Tomography Pulmonary Angiography (CTPA) examination is one of the essential imaging procedures to detect pulmonary embolism (PE). Despite its advantages, it may contribute high dose exposure to the patients if unoptimized parameters were applied. Numbers of optimization techniques have been introduced to reduce dose while preserving the diagnostic quality of the procedure. Hence, this study aimed to evaluate the effects of using iterative reconstruction (IR) algorithm with adoption of different tube potentials and establish the Figure of Merit (FOM) in the relationship between radiation exposure and image quality. Thirty adult patients (n = 30) were retrospectively recruited. Data, such as patient demography, scanning protocols and radiation dose information, were collected and analyzed. Each CT image was reconstructed with different levels of IR algorithm. A 150 mm2-wide circular region of interest (ROI) was drawn inside five consecutive areas surrounding the pulmonary artery in each reconstructed image. Diagnostic performance was evaluated based on signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Meanwhile, FOM was evaluated in four different indicators, which were SNR2/Cvol, SNR2/SSDE, CNR2/Cvol and CNR2/SSDE. Volume weighted CT Dose Index (Cvol) and Size-specific Dose Estimate (SSDE) were estimated for each subject and utilized for the denominator in calculating FOM. Cvol and SSDE increased up to 170% and 154%, respectively, with higher tube voltage. They also increased up to 33% and 16%, respectively, as the patients' effective diameter increased. SNR, CNR and FOM values were comparable with different IR levels, tube voltage and effective diameter. In conclusion, CTPA would yield better results with increasing IR levels, decreasing tube voltage and on patients with small body size.

中文翻译：

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CT肺血管造影检查中迭代重建水平对图像质量和辐射剂量的影响

摘要 计算机断层扫描肺血管造影 (CTPA) 检查是检测肺栓塞 (PE) 的重要成像程序之一。尽管有其优势，但如果应用未优化的参数，它可能会导致患者接受高剂量暴露。已经引入了许多优化技术来减少剂量，同时保持程序的诊断质量。因此，本研究旨在评估采用不同管电位的迭代重建 (IR) 算法的效果，并建立辐射暴露与图像质量之间关系的品质因数 (FOM)。回顾性招募了 30 名成年患者（n = 30）。收集并分析了诸如患者人口统计、扫描协议和辐射剂量信息等数据。每个 CT 图像都使用不同级别的 IR 算法重建。在每个重建图像中，在肺动脉周围的五个连续区域内绘制了一个 150 mm2 宽的圆形感兴趣区域 (ROI)。根据信噪比 (SNR) 和对比度噪声比 (CNR) 评估诊断性能。同时，FOM从四个不同的指标进行评估，即SNR2/Cvol、SNR2/SSDE、CNR2/Cvol和CNR2/SSDE。为每个受试者估计体积加权 CT 剂量指数 (Cvol) 和尺寸特异性剂量估计 (SSDE)，并将其用作计算 FOM 的分母。随着管电压的升高，Cvol 和 SSDE 分别增加了 170% 和 154%。随着患者有效直径的增加，它们也分别增加了 33% 和 16%。信噪比，CNR 和 FOM 值与不同的 IR 水平、管电压和有效直径相当。总之，随着 IR 水平的增加、管电压的降低和体型较小的患者，CTPA 会产生更好的结果。