The Key Technologies Research Of Radiofrequency Ablation Surgery Planning For Barin Tumors

As a minimally invasive tumor physical therapy, radiofrequency ablation hasbeen widely used in the treatment of a variety of solid tumors and brain neuro disease.However, recently the heating power and time of radiofrequency ablation in the clinictherapy are mainly determined by the experience of the doctor. The purpose of thispaper is making a surgical planning with computer, to determine the treatmentparameters such as, the power and heating time of radiofrequency ablation, and designan optimal therapy program auxiliary before the surgery.By processing the sequence of brain MRI scan image, we reconstructed the braintumor tissue and built the visualization model. By establishing the brain tissue heattransfer model during the radiofrequency ablation, we simulated the temperaturedistribution during the radiofrequency ablation by using the finite element method. Bythe comparision between the brain tumor model and simulated thermal fieldconformally according to model matching algorithm, we determined the optimaltherapy programs. Finally, we developed a computer-assisted surgery planning systemfor radiofrequency ablation. The research points were as following:(1) Based on the status of segmenting the brain tumors in the clinical manually,this paper proposed an interactive segment method based on the graph theory. Firstly，using the coherent filter instead of gaussian filter to preprocess the image. As thecoherent filter could enhance the edge of image when filter the noise, making it moreconductive to extract the tumr contour. Secondly, based on the problems that it wasdifficult to obtain the appropriate segmentation parameters when the gray differenceinto the tumor was too large, reducing the image resolution to ignore the influencecaused by the large grey difference, then restoring the original resolution according tothe linear interpolation techniques after the completion of graph segment.Using themarching cubes algorithm method of three-dimensional surface rendering toreconstruct the brain tumor model.(2) Based on the problems that RF ablation parameters were set mainly dependenton the doctors’ experience rather than quantitative data, we did some experimentresearch on the thermal field of the radiofrequency ablation with two RF generators,RFA-II generator and FYJS85-IV generator. Then we established the correspondingfinite element model according to the parameters in the experiment by using the ANSYS software, simulating the temperature distribution during the RF ablation. Bythe comparison of the ablation zone and the temperature rising curve during the RFablation between the experiments and simulation, verifing the feasibility of theestablished finite element model. Get the different ablation model under a different setof parameters by using the FEM, and established the database storing the RF ablationtemperature field model.(3) To assist the clinicians do the RF surgery better, we established a brain tumorradiofrequency ablation surgery planning system. This system consisted of braintumor three-dimensional visualization module, RF ablation thermal field databasemanagement module, and model matching module. The system could segment thebrain tumor interactively and reconstruct the brain model; thermal database modulecould store the ablation region models in the different parameters setting which couldbe scanned by the doctors before the surgery, and provided physicians with the queryinterface, finding the proper ablaion zone model based on the size of tumor model andthe certain safe margin; model matching module could calculate the error between thequeried ablation zone model and tumor model, providing doctors with optimalablation region model and quantization reference, to achieve the aim of tumorconformal treatment.