Influence of low tube voltage in combination with simultaneous iterative reconstruction algorithm on image quality and radiation dose in thoracic CT angiography: a chest phantom study

Objective To study the effect of low-tube voltage combined with the iterative algorithm(IR) on image quality and radiation dose in thoracic CT angiography. Methods A simulated blood vessel of chest was constructed using an ATOM 701-D adult male chest phantom and iodine-water mixture contrast medium. A 320-row volume CT was used to scan the chest at tube voltages of 80, 100 and 120 kV in combination with off, mild, standard and strong IR levels (12 protocols in total), respectively. Tube currents and other parameters were not changed during scanning. The radiation doses were recorded. CT value of the transverse infusion tube and its corresponding noise, CT value of mediastinal soft tissues, signal-to-noise ratio(SNR) and contrast-to-noise ratio (CNR) were obtained. Influence of different tube voltages and simultaneous iterative reconstruction levels on image quality was investigated. Results The CTDIvol, DLP and E were 12.50 mGy, 453 mGy·cm, and 6.35 mSv, at 120 kV; 7.60 mGy, 276.50 mGy·cm and 3.87 mSv at 100 kV; 3.80 mGy, 138.70 mGy·cm and 1.94 mSv at 80 kV, respectively. Radiation dose significantly decreased as the tube voltage decreased. The tube voltage had significant influence on the CT values and its standard deviation(SD), SNR and CNR(F=1 029.24, 8.56, 3.44, 4.09, P 0.05). There were no significant differences between the influences of tube voltages and reconstruction algorithms on the CT values of mediastinal soft tissues (P>0.05). Conclusions Using a protocol of 80 kV with a standard IR algorithm could result in reduction of the effective dose and high-quality thoracic CT angiogram. Key words: Tomography, X-ray computed; Tube voltage; Iterative reconstruction; Radiation dose; Thoracic CT angiography