【摘要】 目的探讨影响CT值测量的因素及对策。方法通过固定扫描条件对机器自带水模进行扫描,然后在其它条件不变的情况下,改变其中1个扫描条件(层厚、曝光量、重建函数、仟伏、FOV、机器)再对水模各扫描1次,测量CT图像一定兴趣区(ROI)的CT值(x±SD)与固定扫描条件的图像相对应ROI的CT值(x±SD)进行比较。结果相对应ROI的平均CT值:层厚为5mm及曝光量为150mAs与10mm、300mAs比较接近;重建函数为Fc80较Fc10略低;仟伏为130kV(因很少用未作校正)较120kV有明显的增加。相对应ROI的SD(噪声):层厚为5mm和曝光量为150mAs比较接近,较10mm、300mAs有明显增加;重建函数为Fc80较Fc10增加更明显;仟伏为130kV较120kV略有降低。在单纯小场水模的小场和中场CT图像中,相对应ROI的平均CT值和噪声:小场都大于中场。在单纯检测不同机器水模的CT图像中,相对应ROI的平均CT值及噪声:东芝旧CT机均高于GE新CT机。结论CT值不是恒定的,在诊断中只能作为参考,而不能作为诊断的依据。更多还原

【Abstract】 Objective To study the factors effect on the measurement of CT value.Methods CT water phantom was scanned using the regular condition of scaning first,then changed one of scaning conditions (thick slice, exposure capacity, reconstruction of function, kV, FOV and CT-scanner) to scan the water phantom again. The CT value (mean±SD) of image region of interest (ROI) was compared in two conditions. Results The mean CT value in the opposite ROI in thick slice 5mm and exposure capacity 150 mAs was similar to that in thick slice 10mm and exposure capacity 300mAs, the reconstruction of function Fc80 was lower Fc10 , the 130kV was distinct higher 120Kv in mean of CT value respectively.The SD(noise) in thick slice 5mm was near to the exposure capacity 150mAs, while in contrast to the thick slice 10mm and the exposure capacity 300mAs was obvious increased , but the reconstruction of function Fc80 was distinct higher Fc10, the 130kV was slightly lower 120Kv in SD(noise) respectively . All of mean CT value and the noise in the small field were higher in the middle field ,when CT imaging in the water phantom of the single small field .This result was also received when the old Toshiba CT-scanner was compared with the new GE CT-scanner in the differ water plantom.Conclusion The CT value is not constant and can’t act as a diagnostic standred.更多还原