Quantitative Research Of Image Quality And Dose In A Dedicated Breast CT System

The breast cancer is the frequent malignant tumor in women, and it is the first high risk tumor in the female, which seriously threaten their health and life. The research shows that the breast cancer mortality decreased by 30%-40% through the breast screening in Europe and the United States. However, the data is less than 20% in our country. It is very important that the breast cancer was found and treatment in the early time. At present, the breast mammography is very effective to diagnose the breast cancer with two-dimensional digital radiography images. The images information can’t achieved clearly and that is not favorable to the detection of smaller lesions. The dedicated breast CT is different from the conventional CT, it is three-dimensional (3D) images which improve the quality of images.The image quality and the radiation dose are important performances indicator of dedicated breast CT.In this paper.the factors of tube voltage and filter were studied by Monte Carlo simulation method which have effect on the image quality and radiation dose. First, the pluripotent spectrum of photon flux is simulated by SPEKTR, the phantom of breast which is implanted with calcified points and tumor is simulated by the Geant4 application for emission tomography,the FBP algorithm is used in the image reconstruction and the dose distribution of the breast phantom is achieved by Matlab. The radiation dose and SNR of image are calculated. The quality factor M and dose efficiency are defined to describe the relationship between image quality and radiation dose. The voltage which is simulated under 20kV to 150kV at intervals of 1 OkV and the dose that are calculated to achieve the better voltage which used for the study of filter.In this paper,the author designed two kinds of flat filter and two kinds of special-shaped filter to contrast image effect that under the different condition of filter to suitable for 110 mm diameter breast mode shape of the filterResearch results show favorable dose efficiency can be gained if reasonable voltage values are selected and that optimization of filter shape can reduce dosage which human body absorbs. Therefore, rational setting of parameters can decrease radiation dose and provide significant reference for clinical application of dedicated breast CT while guaranteeing image quality as far as possible.