CT机型与管电压对图像质量影响的体模研究

目的:使用体模评价两种CT机型两组管电压下的图像质量。方法:采用西门子SOMATOM Force CT和飞利浦IQon Spectral CT分别扫描Catphan500图像质量控制体模的CTP 528和CTP 515组件。对比研究两台机器4组图像，分别为Force_120kVp，Force_140kVp，IQon_120kvp以及IQon_140kvp图像；4组图像均为20 mGy剂量。评价指标包括高对比度分辨率CTP 528最佳线对（1～2 lp/cm）]、低对比度分辨率CTP 515 1％ 浓度下最小孔径（直径2～15 mm）]、图像噪声、对比噪声比（CNR）和信噪比（SNR）。结果:Force_120kVp和IQon_120kvp两组图像的高对比度分辨率最高（均为6 lp/cm）。4组图像低对比度分辨率相同（最小孔径均为5 mm）。Force_120kVp图像噪声最小（2.500±0.000），且SNR最高（30.806±1.398）；噪声和SNR在4组图像间差异具有统计学意义。IQon_140kvp图像的CNR最高（3.325±0.300），各组图像间差异无统计学意义。结论:不同机型不同管电压下的图像质量存在差异；两台机器120 kVp图像的对比度分辨率略好于140 kVp图像；Force CT的120 kVp图像相比140 kVp图像的图像噪声更小，而IQon Spectral CT的两组图像噪声参数无显著差别。 

Phantom Study on the Influence of CT Model and Tube Voltage on Image Quality

Objective: To compare the image quality between two CT scanners under two different tube voltages using a dedicated phantom. Materials and Methods: Siemens SOMATOM Force CT and Phillips Spectral IQon CT were used for scanning and the dedicated Assurance Quality Phantom Catphan 500 was applied. Module CTP 528 and CTP 515 were performed for evaluation of high resolution and low-contrast sensitivity, respectively. Four sets of images of two scanners were acquired, including group A to D whic represented force 120 kVp, force 140 kVp, IQon 120 kVp and IQon 140 kVp. The dosage of all four set of images was 20mGy.Evaluation of high resolution was carried out by two radiologists via the smallest line pair one could distinguish and low-contrast sensitivity was measured by the smallest diameter under 1% contrast. Mean noise, signal-to -oise ratio (SNR) and contrast-to-noise ratio (CNR) were also evaluated for each group. Results: Group A and C had the highest high resolution with a line pair of 6 lp/cm; the same low-contrast sensitivity was observed by all the groups (diameter of 5 mm). Group A showed the smallest noise (2.500±0.000) and highest SNR (30.806±1.398). Noise and SNR were both significantly different among four groups. The highest CNR (3.325±0.300) was observed in Group D, but no statistical difference was found among the four groups. Conclusion: Image quality varied under different CT scanners and tube voltages. Images with 120 kVp showed better contrast compared with those with 140 kVp. 120 kVp with force CT showed improved image noise than that of 140 kVp images; while for IQon spectral CT, no obvious difference in noise parameters was found between the two tube voltages.