Russell M T, Fink J R, Rebeles F, Kanal K, Ramos M, Anzai Y
Department of Radiology, University of Washington, Seattle, WA 98195-7115, USA.
AJNR Am J Neuroradiol. 2008 Apr;29(4):727-31. doi: 10.3174/ajnr.A0891. Epub 2008 Jan 25.
The advancement of multidetector CT technology has resulted in improved image quality as well as an increase in ionizing radiation dose to patient. The purpose of this study was to assess radiation dose and overall image quality of CT examination of the neck between fixed-tube current and automatic tube current modulation (ATCM) at 2 separate noise index levels.
A total of 84 patients underwent neck CT with use of a 64-section multidetector row CT (MDCT) scanner. Patients were divided into 3 groups: fixed-tube current (n = 28), ATCM with a noise index of 11.4 (n = 28), and ATCM with a noise index of 20.2 (n = 28). All other scan parameters remained constant. Scan coverage length and transclavicular distance were measured. Two radiologists blinded to the scanning parameters assessed overall image quality, noise level, and streak artifacts using a 5-point grading scale. The radiation dose in dose-length product (DLP) and CT dose index (CTDI) was recorded.
Compared with a fixed-tube current technique, ATCM with a noise index of 11.4 reduced CTDI by 20% (P < .01 x 10(-6)), and ATCM with a noise index of 20.2 reduced CTDI by 34% (P < .01 x 10(-12)). Although the difference in image quality between the fixed-tube current technique and the noise index reached statistical significance (P < .05), the magnitude of the difference was small, with average scores of 3.79 (+/-0.59) and 3.57 (+/-0.53), respectively.
Compared with the fixed-tube current technique, ATCM resulted in significant reduction of radiation dose without substantially reducing the image quality of the CT of the neck. Judicious monitoring of radiation dose to patients has to be balanced with diagnostic image quality.
多排探测器CT技术的进步提高了图像质量，但患者所接受的电离辐射剂量也随之增加。本研究旨在评估在两个不同噪声指数水平下，颈部CT检查采用固定管电流与自动管电流调制（ATCM）时的辐射剂量及整体图像质量。
84例患者使用64排多排探测器CT（MDCT）扫描仪进行颈部CT检查。患者分为3组：固定管电流组（n = 28）、噪声指数为11.4的ATCM组（n = 28）和噪声指数为20.2的ATCM组（n = 28）。所有其他扫描参数保持不变。测量扫描覆盖长度和经锁骨距离。两名对扫描参数不知情的放射科医生使用5分制评分量表评估整体图像质量、噪声水平和条纹伪影。记录剂量长度乘积（DLP）和CT剂量指数（CTDI）中的辐射剂量。
与固定管电流技术相比，噪声指数为11.4的ATCM使CTDI降低了20%（P <.01×10⁻⁶），噪声指数为20.2的ATCM使CTDI降低了34%（P <.01×10⁻¹²）。尽管固定管电流技术与噪声指数之间的图像质量差异具有统计学意义（P <.05），但差异幅度较小，平均得分分别为3.79（±0.59）和3.57（±0.53）。
与固定管电流技术相比，ATCM可显著降低辐射剂量，且不会大幅降低颈部CT的图像质量。对患者辐射剂量的审慎监测必须与诊断图像质量相平衡。
