The feasibility study of low-dose CT scanning in chest tumor with 125I radioactive seed implantation

Objective To investigate the feasibility of reducing CT scanning dose in the process of 125I radioactive seed implantation. Methods GEMS phantom and 062 M phantom were scanned using GE Lightspeed RT large hole CT with 120 kV, 100 kV and 80 kV separately, and 150-10 mA (20 mA decreased progressively). The scanning dose, CT value and noise of the region of interest were recorded and the image quality was evaluated. Image signal-to-noise ratio (SNR) and contrast to noise ratio (CNR) values were calculated. Results With the decreasing of tube voltage and current, the SNR values were reduced accorgingly. The values had significant difference with those of standard images except the images acquired with 120 kV, 150-70 mA and 100 kV, 150-90 mA (t=-9.294-3.717, P<0.05). With the decreasing of the tube voltage and current, the CNR decreased significantly. The image quality was too low to evaluate while CNR lower than 2. The high contrast resolution of the CT images were not affected obviously with the tube voltage and current lowering. Conclusions In the process of 125I radioactive seed implantation, it is feasible to choose lower tube voltage and tube current(100 kV, 70 mA) to scan the same area repeatedly except for the first scan with standard chest scanning parameters. The patient radiation dose has fallen dramatically. Key words: Low-dose CT; 125I radioactive seed implantation; Radiation dose; Image quality