Research And Implementation Of Automatic Exposure Algorithm For X-Ray Machine

Automatic exposure system is an important part of modern digital X-ray machine.The traditional way of manual exposure not only increases the workload of doctors but also produces a phenomenon of being overexposed or underexposed due to some unskilled operators,as a result of which increased the probability of radiation damage brought to medical staff and patients.The X-ray machine with automatic exposure system can adjust the appropriate exposure parameters according to the human body,so as to avoid the above situation and reduce radiation damage.It is a focal issue in the field of imaging equipment,which is of great significance to medical imaging technology.However,most of the X-rays machine with automatic exposure system in the market base on the principle of ionization chamber and photomultiplier tube,which are very expensive.Furthermore,maintenance of the equipment is relatively complicated,and it has an influence on image quality.In order to design an automatic exposure system with low cost,good image quality and low exposure dose,this paper designs an automatic exposure method which combines double exposure and image enhancement.It can reduce the exposure dose as well as ensuring image quality.In addition,the double exposure method doesn't require additional installation of large equipment,and that greatly reduce equipment cost.The main features of this paper are as follows:(1)The main methods of automatic exposure at home and abroad are studied,and a reasonable analysis to double exposure is given.A comparison of several existing automatic exposure method is studied,this paper chooses double exposure as a method of automatic exposure on the basis of considering equipment costs and imaging quality,also analyses the principle its algorithm in detail.It is proved that there is a linear relationship between the contrast of image and the size of KV,average gray value of image also has a linear relationship to the size of mAs,thereby the rationality of double exposure method is verified.Based on the above analysis,an automatic exposure scheme is designed in this paper which combines double exposure method and image enhancement technique.(2)A medical image enhancement algorithm basing on image pyramid isproposed.This paper first puts a global multi-scale enhancement on the details of image,and then differentiates between image details and edges by using the deviation between Gaussian Pyramid and Laplacian Pyramid,finally adopt edge aware algorithm on the basis of Laplacian Pyramid to process details and edges of image respectively.Experiments show that this algorithm can realize details enhancement while preserving the edge.(3)The existing computation formula of KV and mAs in double exposure method is optimized and unites image enhancement technology in this paper.A method is proposed which adopts contrast of bone area to calculate KV value and the average gray value of bone and tissue regions to calculate mAs value after a detailed analysis of the existing methods.At last,this paper uses image enhancement technology to enhance and optimize double exposure algorithm.Experiments show that automatic exposure method proposed in this paper can not only reduce exposure dose,but also obtain image quality reaching the requirements of diagnosing.