Abstract:

BACKGROUND: Image noise level is closely related with the image quality in the CT images, it directly affects and limits of CT resolution of low-contrast material.
OBJECTIVE: To evaluate the correlation of estimated noise with the noise of different tissues and to analyze characteristic of different tissues noise on low dose chest scan by adding noise on raw data to simulate low dose scan.
METHODS: The noise was artificially introduced to the images of 20 volunteers using an image space noise addition tool to simulate nine groups of low dose scans with tube current of 10, 30, 50, 80, 100, 120, 150, 180 and 240 mA. The estimated noise of images was recorded. The noise of aorta, tissue of chest wall, vertebra, lung and air on levels of aortic arch, heart and liver were measured.
RESULTS AND CONCLUSION: There was significant statistical difference between the estimated noise and the measured noise in the index of aortic artery and other tissues estimated noise (P < 0.05), which had linear correlation. The noise of different tissues increased significant in groups of 10-50 mA, and decreased gradually with the increase of current in groups of 80-240 mA. There was no statistical difference of the estimated noise value between the noise of 120 and 180 mA groups (P < 0.05). The estimated noise of noise addition tool can be used to evaluate the image noise of different tissues. The tube current of 120 mA to 180 mA in low dose chest CT scan can reduce radiation dose and keep the image quality of different tissues.