Study On Simulation Of Cone-beam CT Dynamic Bowtie

After the birth of CT,CT has rapidly become a core technology in diagnostic imaging application because of its advantage of nondestructive testing.With the popularity of CT,the radiation dose has become a hot topic and a global health issue.In order to reduce the radiation dose of CT scanning,some effective technical methods and equipment,which has been used in modern CT system,have been developed.Bowtie filter,as a beam shaping attenuator placed between X-ray source and scanned object in computed tomography system,can effectively reduce radiation dose.In addition,bowtie filter can equalize the photon flux reaching different detector channels.In the scanning process,the filtering requirement is changing because the scanning profile of scanned object keep changing.However,the traditional bowtie is designed to target only a fixed species.For all scanned object models,it produces an invariable attenuation profile in each scan.Therefore,we propose a dynamic bowtie filter design,which is called cone-beam CT dynamic bowtie,to modulate the X-ray dynamically in real time.Compared with other dynamic bowtie designs,cone-beam CT dynamic bowtie has a significant advantage.It is able to meet the requirement of cone-beam CT system,which can achieve the leap from two-dimensional to three-dimensional.As a result,cone-beam CT dynamic bowtie has a higher practical value.In this paper,we use Monte Carlo simulation technology to analyze and study the performance of cone-beam CT dynamic bowtie.In this simulation experiment,we determined the surface parameters of high attenuation bowtie filter(HB)successfully.The main contents of this paper include:(1)Matlab program is used to simulate the scanning process of X-ray with a cone beam CT dynamic bowtie.The experimental results show that cone-beam CT dynamic bowtie can follow the variation of projections in different X-ray path dynamically.The experiment results show that detector reading of photon flux has been modulated so detector performance has been improved.(2)With Monte Carlo simulation technique,X-ray energy spectrum,photon flux and attenuation material of cone beam CT bowtie was studied.Base on the experimental data,surface parameters of high attenuation module was determined.Using a HB filter,the ratio between the minimum value and max value of photon flux data increase up 46%.Simulation experimental results show that detector reading of Photon flux has been uniformed effectively benefiting from the filtering effect of HB.(3)Radiation dose simulation experiment of cone beam CT dynamic bowtie was studied with flux-dose conversion coefficient method.Considering the practical application environment of CT,a human body model was established in the MCNP program.The simulation results show that,under the image quality remaining unchanged,the cone-beam CT dynamic bowtie can not only reduce the overall radiation dose of the scanned object,but also effectively reduce the radiation dose in the non-interest region.In the cone angle field,the dose distribution of different sections can be effectively modulated,which indicates that the cone-beam CT dynamic bowtie can meet the filtering requirement of the cone-beam CT.(4)Particle scattering simulation experiment of cone-beam CT dynamic bowtie show that the dynamic bowtie filter can reduce the influence of scattered photons on the region of interest.As a result,the useful information of the image is enhanced.Therefore,more image information and more details can be obtained,and the image quality has been improved after the filtering of a cone-beam CT dynamic bowtie.