Quantitative Research Of Radiation Dose And Image Quality In Dedicated Breast CT

The dedicated breast computed tomography (DBCT) is a new method for breast cancer detection proposed in recent years,which combining the cone-beam CT scanning technology and the flat-panel detector technology to scan the breasts in three dimensions, so the DBCT avoids the tissue overlaying shortcoming of two-dimensional imaging and has a good resolution for calcification and small tumors in the meantime. Quantitative researches about radiation dose measurement and image quality evaluation methods of the DBCT has been done in this paper on the base of the dedicated breast CT system developed by the nuclear technology application research center in institute of high energy physics, Chinese academy of sciences.On one hand, The DBCT radiation dose is a problem we should pay close attention to because it affects the safety of the equipment. Therefore, a relatively complete and simple measurement method that apply to dedicated breast CT dose evaluation has been developed in this paper with reference to the concept of CTDIw(weighted CT Dose Index) in the standard conventional CT dose evaluation. The method use a pen-shaped ionization chamber in combination with the cylindrical breast phantoms can obtain the average glandular dose quickly and accurately. The impacts of phantoms’ material and size on the dose measurements were also calculated and correction factors were given for different phantoms.Comparisons between the CTDIw results and the results of Monte Carlo simulations and other experimental measurements methods have proved the effectiveness of CTDIw. In addition, we also improved the dose distribution method using TLDs to make it can obtain the dose inside breasts more detailed and accurate. On the other hand, to obtain the best possible image quality under the safe radiation dose is the aim that we have been pursued in the research and development of the DBCT. The factors may influence the image quality of DBCT were analyzed quantificationally using the simulation software GATE (GEANT4 Application for Tomographic Emission), including tube voltage, additional filter material and thickness, bow-tie filter and so on. And eventually the relative best running condition of DBCT was given, which is aimed at achieving the best match of high image quality and low radiation dose so that the ability to detect the microcalcifications clusters and tumors.