Zhao Yongxia, Wu Yanmin, Zuo Ziwei, Suo Hongna, Zhao Sisi, Zhang Haisong
The Affiliated Hospital of Hebei University, Baoding, China.
Medicine School of Hebei University, Baoding, China.
J Xray Sci Technol. 2017;25(1):79-91. doi: 10.3233/XST-160608.
To investigate the differences in imaging quality and radiation dose in CT pulmonary angiography (CTPA) by using fast-kV switching dual energy CT imaging and 3D Smart mA modulation at different body mass indices (BMIs) and at different noise index (NI) values with an adaptive statistical iterative reconstruction (ASIR) algorithm.
Four hundred patients who underwent CTPA were equally divided into two groups: A (18.5 kg/m2 ≦ BMI <24.9 kg/m2) and B (24.9 kg/m2 ≦ BMI ≦ 4.9 kg/m2). The groups were randomly subdivided into four subgroups (n = 50): A1-A4 and B1-B4. The patients in subgroups A1 and B1 underwent fast-kV switching dual energy CT imaging. The other patients underwent 3D Smart mA modulation with the ASIR algorithm at NI values 26, 36, and 46 for A2/B2, A3/B3, and A4/B4, respectively. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all images were calculated after CTPA. Images were then subjectively evaluated using a 5-point scale. The volume CT dose index and dose-length product (DLP) were recorded and their means calculated. The DLP was converted to the effective dose (ED).
In group A, the SNR, CNR, and subjective image scores showed no statistical differences (P > 0.05). The ED in subgroup A4 was 67.12% and 31.53% lower than that in A1 and A2, respectively. In group B, the variables showed no significant differences between the subgroups B3, B1, and B2 (P > 0.05). The ED in subgroup B3 was 50.12% and 35.95% lower than that in B1 and B2, respectively.
Setting different NI values according to BMIs and applying the ASIR algorithm can more effectively reduce the radiation dose in CTPA than in fast-kV switching dual energy CT, while maintaining image quality. Imaging may be performed at NI = 46 in patients with lower BMI (group A) and at NI = 36 in patients with higher BMI (group B).
采用快速千伏切换双能量CT成像和3D智能毫安调制技术，在不同体重指数（BMI）和不同噪声指数（NI）值下，利用自适应统计迭代重建（ASIR）算法，研究CT肺血管造影（CTPA）的成像质量和辐射剂量差异。
400例行CTPA的患者平均分为两组：A组（18.5kg/m²≤BMI＜24.9kg/m²）和B组（24.9kg/m²≤BMI≤44.9kg/m²）。两组再随机细分为四个亚组（n = 50）：A1 - A4和B1 - B4。A1和B1亚组的患者接受快速千伏切换双能量CT成像。其他患者分别在NI值为26、36和46时，对A2/B2、A3/B3和A4/B4组采用ASIR算法进行3D智能毫安调制。CTPA后计算所有图像的信噪比（SNR）和对比噪声比（CNR）。然后用5分制对图像进行主观评估。记录容积CT剂量指数和剂量长度乘积（DLP）并计算其均值。将DLP转换为有效剂量（ED）。
在A组中，SNR、CNR和主观图像评分无统计学差异（P＞0.05）。A4亚组的ED分别比A1和A2亚组低67.12%和31.53%。在B组中，B3、B1和B2亚组之间的变量无显著差异（P＞0.05）。B3亚组的ED分别比B1和B2亚组低50.12%和35.95%。
根据BMI设置不同的NI值并应用ASIR算法，与快速千伏切换双能量CT相比，能在保持图像质量的同时更有效地降低CTPA的辐射剂量。BMI较低的患者（A组）可在NI = 46时进行成像，BMI较高的患者（B组）可在NI = 36时进行成像。
