Effectiveness of Tube Voltage Selection of 70 kV in Abdominal Dual Energy CT Protocol

Recently, CT equipment has a dose modulation function that adjusts the dose to the patient. But, the dose is proportional to the tube voltage and changes with the square of the tube current. Therefore, reducing tube voltage rather than tube current has a greater effect on reducing radiation exposure. High tube voltage is used to improve image noise and contrast resolution. When high tube voltage is used, the surface dose is reduced, but the overall exposure dose is increased. So, the dose should be appropriately adjusted to the patient. Accordingly, research and attempts to obtain high-quality images with a small dose are continuously being conducted, the development of detectors and software performance are improving. Due to the improvement of CT equipment, 70 kV can be used for dual scan. In this study, the 70 kV, and 80 kV, 90 kV, 100 kV used in the conventional CT examination were compared and evaluated at the same dose. The study was conducted using ACR Phantom and KAGAKU Abdomen Phantom. CT number(HU), Noise, SNR, and CNR of each image were compared by quantitative evaluation, and CT number and noise level were evaluated by qualitative evaluation. As a result of comparison, using 70 kV obtained equivalent or better noise, CT number, SNR, and CNR than 80 kV, 90 kV, and 100 kV with the same CTDIvol. In conclusion, it is considered that diagnostically excellent image can be obtained with a small exposure dose by dual scan using 70 kV.