Study On Enhancement Method For High Dynamic Range Medical Images

Medical imaging is one of the most widely used techniques for diagnosis and monitoring of disease associated with underlying tissues in the human body.Digital imaging and communications in medicine(DICOM),a standard format for medical image storage and communication,is widely used in the field of medical diagnostic.Due to the special imaging principle and method of medical images,medical images always have the properties of non-uniform distribution of pixel gray values and low contrast,which always affects medical diagnosis and disease analysis,and even leads to misdiagnosis in practical applications.Medical image enhancement is a very practical and promising means to improve image quality and can increase the accuracy and efficiency in real medical applications.Aiming at the phenomenon of non-uniform distribution of pixel gray values and low contrast,this paper proposes a MRI image enhancement method based on improved bilateral filtering(DRC&DE),which overcomes the shortcomings of image gray adjustment methods which based on histogram equalization,such as the reduction of the pixel value and the disappearance of some details.The main contributions of the DRC&DE include two aspects: the dynamic range compression(DRC)is used to adjust the high dynamic range pixel values to the appropriate range on the premise of protecting the details,and the details enhancement(DE)adopts the improved bilateral filtering combined with Laplacian pyramid to remove the noise and enhance the details.This method can effectively enhance the MRI images.In order to obtain a generally applicable enhancement method for DICOM format medical images,a new contrast and detail enhancement method based on luminance-level modulation and gradient modulation(LM&GM)is proposed.The main contributions of the LM&GM include two aspects: first,the luminance-level modulation(LM)operation adjusts the dynamic range of luminance levels while preserving the difference between pixels.This operation not only can set the degree of luminance-level modulation discretionarily,but also can choose the starting point of the luminance-level modulation,in order to achieve more effective protection of details.Second,the gradient modulation(GM)operation is used to enhance the details and textures of the images further on the basis of the result of LM.This operation adopts improved fast local Laplacian filter(FLLF)with a modified remapping function,which makes the proposed method more suitable for the special pixel value distribution characteristics of medical images.The method can effectively enhance X-ray images,CT images and MRI images,and has commendable universality and stability in medical image processing.Experiments show that MRI image enhancement method based on improved bilateral filtering(DRC&DE)is superior to the traditional medical image enhancement methods in term of simple structure,high operation speed and effective enhancement results for MRI image.A new contrast and detail enhancement method based on luminance-level modulation and gradient modulation(LM&GM)has attractive effects in X-ray images,CT images and MRI images enhancement processing,meanwhile can effectively avoid the halo and staircase artifacts.The above two methods have a good application prospect in medical image enhancement processing.