Key Technology Research For Intraosseous Ultrasound Navigation Based On Micro Ultrasonic Probe

Ultrasound has the advantages of no ionizing radiation,no electromagnetic interference,low cost and easy to carry;but at first,it was considered that it was not suitable for bone tissue because its resolution was lower than CT and its resolution was inversely proportional to the penetration.In the 1980s-1990 s,ultrasound probe technology has made great progress.The emergence of dual power Doppler and color flow imaging,as well as the successful development and application of intracavitary ultrasound probe,have significantly improved the spatial resolution of ultrasound imaging,greatly expanded the scope of clinical application,provided the possibility of using ultrasound to solve the problem of intraosseous navigation,and reduced screw errors in spinal pedicle surgery.It is of great significance to improve the rate of implantation and the risk of operation.In order to further verify the feasibility of ultrasound in bone navigation and improve the imaging quality of ultrasound in bone environment,three key technologies were studied in this paper,including the development of ultrasonic in vitro experimental medium preparation system,ultrasonic identification of bone limit aperture and improvement of transducer performance.In order to reduce the thickness of the backing layer and reduce the volume of the transducer,the problem of space directivity caused by the back and side echo is existed in the transducer operation,and the method of wrapping the transducer with high acoustic impedance material is proposed.First,the ultrasonic penetration tests of four kinds of common high impedance materials,nickel,tantalum,tungsten and nickel foam,were carried out to verify the feasibility of the solution.Secondly,the inhibition effect of the four kinds of high acoustic impedance materials on the back and side echo of the energy exchanger is tested.The final coating material is tungsten foil.Finally,a new clamp which can complete the pressing and wrapping process of transducer is designed at one time,which is convenient for engineering production and popularization,ensuring the consistency of products,and testing whether the tungsten foil will affect the other properties of the transducer.The limit resolution and the recognizable limit aperture size of ultrasound in orthopedic field are not clear;The imaging effect is poor in the very close range;The aperture recognition depends on the artificial experience to judge and so on.Firstly,the study of the limit aperture of bone plate which can be identified by ultrasonic is carried out to obtain the original image.Secondly,the original image is processed by using ringing signal elimination,high pass filtering,Hilbert transform and gray mapping.Through the analysis of the results,the 2mm diameter hole is the limit of ultrasonic recognition in orthopedics,which further verifies the feasibility of ultrasound in solving the problem of bone navigation.Finally,the image fusion segmentation technology(watershed algorithm,clustering algorithm,threshold segmentation method)and boundary extraction method(Robert operator,Sobel operator,Kanni operator and other edge detection operators)are combined with wavelet image fusion technology to outline the aperture boundary of bone plate,assist artificial judgment and provide early warning signal.In order to meet the requirements of the quality monitoring in the in vitro ultrasonic testing and the subsequent mass production of the micro ultrasonic transducer,a three-dimensional multi angle dual pulse emission micro ultrasonic probe test system is developed.The micro ultrasonic probe testing system consists of three parts,and is studied separately.Firstly,the test collimation system is developed.The three-dimensional rotary control platform is used to realize the rapid and accurate alignment between the hydrophone and the probe.Then,the high frequency pulse transmitter and receiver are developed,and the high frequency broadband pulse transmitter is designed and developed,and the special hydrophone is purchased and customized.Finally,the preparation system of deionized degassing water is carried out,which can meet the demand of ultrasonic testing for deionized degassing water;The control system is built to meet the requirements of integration and automation design,and saves the time cost in the experiment;And by setting up the backwash system,the daily maintenance cost of the equipment is reduced.