Factors Effect on the Measurement of CT Value and Its Countermove / 实用放射学杂志

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.