The Study On Deflection Characteristics Of Sampling Needle

In the world,chronic non-communicable diseases such as malignant tumors are a serious threat to human health and impede the development of society.Due to the current medical level,malignant tumors cannot be radically cured.Early detection and prevention are very important.Percutaneous biopsy is the basis of brachytherapy and interventional therapy.It has the advantages of less trauma,less pain,and quicker recovery.It is widely used in cytological biopsy diagnosis,local tissue anesthesia,drug delivery,blood sampling,body extraction organization and so on,which is the most commonly used cancer detection and treatment method in clinical practice.For effective medical diagnosis and treatment of lesions,the puncture needle must reach the desired tissue defect.However,the biopsy puncture site is often inaccurate and the sampling rate is not high.One of the reasons is that due to the intricate complexity of the vascular mucosa inside the soft tissue,the non-uniform force between the puncture needle and the soft tissue causes the needle body to bend and deform away from the original path.In percutaneous puncture surgery,poor puncture accuracy and sampling efficiency will not only affect the doctor's diagnosis,cause unnecessary timing delays,but also increase the suffering of patients,cause huge physical and psychological harm,and ultimately lead to surgical failure.Therefore,it is of great significance to study the interaction mechanism between puncture needle and soft tissue,construct a puncture mechanics model,and analyze the flexure mechanism and puncture law of puncture needle for optimizing the sampling parameters and improving the success rate of operation.A precise puncture force bending model is the basis for studying the bending characteristics of the needle.In order to improve the accuracy of puncture,the puncture needle is designed as a cantilever fixed at the needle end.Based on the Euler-Bernoulli beam theory and the superposition theory,the quasi-static equilibrium is used to constrct the cantilever beam mechanical model on the 2D plane.The axial and radial forces of the needle were studied to study the flexural mechanism of the slant needle,and the formula for calculating the deflection was deduced.The flexural characteristics were characterized by the reaction forces and bending moments of different needle bar segments to calculate the bending deflection.The theoretical results show that the deflection of the needle is related to the reaction force and the bending moment.With the increase of the reaction force and the bending moment,the deflection increases gradually.Taking the gelatin prosthesis as the experimental object,the piezoelectric vibration system was introduced to build a vibration assisted puncture deflection measurement platform.After testing,when the frequency is the same,the amplitude of the piezoelectric ceramic vibrator increases with the input voltage and has a linear relationship;When the input voltage is the same,the amplitude of the piezoelectric ceramic vibrator decreases with increasing frequency.The effect of bionic vibration parameters and common vibration frequency on the deflection of the needle tip was studied by vibration assisted puncture gelatin prosthesis experiment.In the bionic vibration experiment,the influence of the amplitude of bionic vibration on the reaction force,the bending moment of the needle seat and the bending amount is.not obvious,but the bionic vibration frequency has the effect of reducing the deflection of the needle.In the ordinary vibration experiment,the amplitude is fixed and the frequency is increased to 200Hz.After the puncture needle is fed at the same depth,the reaction force,bending moment and deflection amount gradually decrease with increasing frequency.A new method was proposed to measure the amount of needle puncture flexion:firstly,the needle puncture flexography and the puncture-free pictures were synthesized using Corel PHOTO-PAINT X8,and then the images were converted to grayscale images using the weighted average method.Then,the image is binarized using the largest class variance method(Ostu algorithm)and edge detection is performed by the Robert operator to obtain a clear image.Finally,deflection deflection of the puncture needle is measured with Digimizer software.Gelatin prosthesis was used as the puncture target to study the effects of the dynamic and static parameters such as feed depth,puncture speed,needle diameter,needle tip curve,and tip inclination angle on the bending characteristics of the puncture needle.The experimental results show that as the penetration depth of puncture increases,the radial support reaction force of the puncture needle and the bending moment measured at the needle seat gradually increase,and the rate of increase after 70 mm is significantly accelerated,but the amount of flexion increases linearly with the depth of puncture;When the feed depth is the same,with the increase of puncture speed,the deflection of the needle tip decreases with the increase of puncture speed,but the change law of the reaction force and bending moment is not very obvious;For asymmetric monoclinic needles with the same inclination angle,as the diameter of the needle increases,the reaction force and the bending moment of the needle seat gradually increase,and the amount of deflection gradually decreases;For a puncture needle with the same diameter,the deflection of the asymmetric single bevel needle is the largest,followed by the asymmetric three bevel needle,and the deflection of the symmetrical double bevel needle is the smallest;For a single bevel needle with the same diameter,different tilt angles will change the cutting advance angle of the needle.The larger the tilt angle,the smaller the radial deflection.Gelatin prosthesis and pig liver were used as puncture targets to study the effect of gelatin mass ratio on the bending characteristics of puncture needles.It was found that as the mass ratio of gelatin increased,the reaction force,bending moment and deflection increased gradually.Orthogonal experiments were designed to study the effects of vibration frequency,puncture speed,needle diameter and gelatin mass ratio on the bending characteristics of the needle tip.The results of the experiment were verified by using the range analysis method and Minitab main effect diagram analysis.The optimal parameter combinations under the respective indexes were obtained respectively,and the degree of influence of each index was determined.The test found that when the needle diameter was taken at different levels,the needle seat had the largest difference in bending moments,which had the greatest degree of influence.The second place was the mass ratio of gelatin,followed by the vibration frequency,and the influence of the puncture speed was the least;When the needle diameter is taken at different levels,the extreme value of the branch reaction force is the largest and the impact degree is the greatest,followed by the gelatin mass ratio,followed by the puncture speed,and the influence of the vibration frequency is the smallest;When the mass ratio of gelatin was taken at different levels,the maximum deflection value was the greatest,so the change was the most obvious.The needle diameter was the second highest,followed by the vibration frequency,and the impact of the puncture speed was the smallest.The test results show that the puncture speed and vibration frequency are used as dynamic parameters to assist the needle insertion,and its influence on bending characteristics is not as good as static parameters such as needle diameter and gelatin mass ratio.