双源CT不同扫描条件下颞骨图像质量与剂量的定量研究

Quantitative study on image quality and dosage of dual-source CT for temporal bone under different scanning conditions

目的:应用定量参数评估第三代双源CT不同扫描条件下颞骨图像的质量及剂量,为临床应用提供参考。方法:采用CT成像性能检测模体及仿真头模,将管电压分别设置为100 kV、110 kV、120 kV、130 kV和140 kV;管电流时间乘积分别设置为100 mAs、130 mAs、160 mAs、180 mAs和220 mAs,共得到25种扫描组合条件;记录辐射剂量,以噪声、低对比分辨力、高对比分辨力及颞骨信噪比等指标评估颞骨图像质量。结果:当扫描管电压≥120 kV,管电流时间乘积≥160 mAs时,颞骨高分辨CT图像Z轴高对比分辨力可达9.62 LP/cm,横断面图像高对比分辨力可达>11.36 LP/cm,低对比分辨率可低于2.71 mm。当图像的辐射剂量增高时,图像的噪声降低,信噪比随之增高。结论:在颞骨扫描时,扫描管电压≥120 kV、管电流时间乘积≥160 mAs时,可得到稳定的高质量图像,在临床应用中,应结合需求选择适合的扫描条件。

Objective: To assess the image quality and dosage of dual-source computed tomography(CT) of third generation for temporal bone under different scanning conditions by using quantitative parameter so as to provide references for clinical application. Methods: The detection phantom and simulated head phantom of CT imaging performance were adopted for testing. And the tube voltages were set to 100 kV, 110 kV, 120 kV, 130 kV and 140 kV respectively. The products of tube currents and time were set to 100 mAs, 130 mAs, 160 mAs, 180 mAs and 220 mAs, and a total of 25 kinds of composition conditions of scanning were obtained. The radiation dose was recorded, and then the image quality of temporal bone was assessed by series of indicators of noise, low contrast resolution, high contrast resolution and temporal bone signal-to-noise ratio(SNR) and so on. Results: When the scanning voltage was greater than or equal to 120 kV and the product of tube current and time was greater than or equal to 160 mAs, the high contrast resolution of Z-axis in the high resolution CT image of temporal bone could reach 9.62 LP/cm, and the high contrast resolution of the cross-sectional image could reach higher than 11.36 LP/cm, and the low contrast resolution could be less than 2.71 mm. When the radiation dose of image increased, the noise of image decreased but the SNR increased. Conclusion: In scanning temporal bone, when tube voltage of scan is greater than or equal to 120 kV and the product of tube current and time is greater than or equal to 160 mAs, the stable high quality images can be obtained. In clinical application, the suitable scanning conditions should be selected according to the requirements.