Research On Speed Of Sound Reconstruction And 3D Ultrasound Imaging

Ultrasound imaging is one of the most important technique in the field of modern medical imaging.In the recent thirty years,the technique of ultrasound imaging has been widely applied in medical science.In the procedure of medical diagnosis,ultrasound imaging is used for detecting tissue structure inside human body,such as muscle,blood vessel and organs.The purpose of medical imaging is to locate the focus of disease in human body by an outside equipment.As a low-cost,radiation-free approach,ultrasound will cause no damage to patients both in body and finance.Thus,ultrasound imaging is generally used in both diagnosis and cure of human disease.Ultrasound has been used as a supplement to x-ray mammography for diagnosis of breast cancer in recent years.Ultrasound image can depict small,node-negative breast cancers not seen on x-ray mammography or DBT,par ticularly for dense breast.However,the ultrasound technique regularly used today is 2D ultrasound scanning.2D ultrasound imaging has its intrinsic disadvantages.For example,2D sonography cannot provide information from multiple directions,nor structure information of tissues.In the procedure of medical diagnosis,radiologists will construct the 3D structure in their mind from the 2D images seen on the sonography screen.Therefore,the accuarcy and reliability of 2D ultrasound scanning heavily depends on the professional skills and mental condition of the operator.Besides,the most commonly used Bmode scanning can only provide qualitative information of the scanned area instead of quantitate information.Accordingly,we present the method of speed of sound(SOS)reconstruction and 3D ultrasound reconstruction in this paper.In this paper,we have two main themes.The first one is introducing three methods of speed of sound reconstruction,including full wave inversion,computed ultrasound tomography in echo mode and dual-side SOS reconstruction.Among these three methods,SOS reconstruction using dual-side transducers can generate SOS images with acceptable quality and fast speed.Thus,we first use k-wave acoustic simulation tools to prove the validation of SOS reconstruction in dual-side mode.Then,we perform this method in an ultrasound phantom by using a dual-side ultrasound imaging system.The result shows that the SOS contrast region has clear boundary in the reconstructed image.The second theme is 3D ultrasound reconstruction.We present two 3D ultrasound scanning mode in this paper.The first one is horizontal scanning with an ultrasound scanner in a fixed orientation controlled by a motor.The second one is free-hand ultrasound scanning.We use a 4K camera to track the position and orientation of the ultrasound transducer.By correlating the position and orientation information in 3D space and 2D images,we can reconstruct 3D ultrasound image from 2D image stack.In addition,we can perform image fusion between the 3D image produced by two scanning modes and generate an image of higher quality.In experiments,we perform this 3D ultrasound scanning method to one phantom with copper stick in the midde and another phantom with carrots as inclusions.Both results show that image fusion between two modes will generate a high quality 3D ultrasound image.