Study On Technology Of Ultrasound-Guided Intra-Operative Radiation Therapy

Background and Objectives:Intra-Operative Radiation Therapy(IORT)refers to the application of therapeutic levels of radiation to the tumor or tumor bed while the target area is exposed during surgery,which has been widely used for cancer treatment.For lack of information of three dimensional(3D)image and dose distribution in IORT,it is not safe and reasonable enough to setup treatment parameters only by observation and personal experience.In addition,due to lack of calculation of the 3D dose distribution combining intraoperative with postoperative radiotherapy,the accuracy of postoperative radiotherapy may be affected.This study mainly focused on:(A)simulation method for ultrasound(US)-guided IORT;(B)planning method and system for IORT;(C)a Monte Carlo simulation design and test of a spherical applicator for IORT with a linear accelerator.This research is related to the second one and is its one application.The first and second ones were used to establish a method for US-guided IORT,and the third one was to enable the intra-operative electron beam to deliver a spherical dose distribution.Materials and Methods:We firstly established the simulation method for US-guided IORT and planning method for IORT according to the clinical requirements and the devices available,and designed the hardware(US phantom,multi-function applicator and its accessories)and software(Monte Carlo simulation IORT treatment system);then,fabricated the hardware,and developed and evaluated the IORT planning system(using the gamma analysis),which were used to test the simulation method and planning method;finally,designed a spherical applicator for IORT with a linear accelerator using the developed Monte Carlo simulation algorithm,and established the method to evaluate the spherical dose distributions quantitatively as well as fabricated and tested the applicator.Results:The US image was acquired by using the developed devices(multi-function applicator,US phantom and its accessories),and the simulation method for US-guided IORT and planning method for IORT were established and validated with phantom.One Monte Carlo simulation IORT planning system was developed,and the difference in percentage depth dose between simulation and measurement could pass the gamma criteria 2%/2mm as well as the off axis rate at the depth of maximum dose.A complete technique of US-guided IORT was established.The spherical applicators(with a 5-cm diameter sphere and a 2-cm diameter collimator cone)for the beams of energies 4,6,9 and 12 MeV were designed by using the developed Monte Carlo simulation method,the roundness introduced to evaluate the spherical dose distributions quantitatively was 0.01?0.12 cm in the coronal plane while 0.05?1.38 cm in the axial plane,and fabricated and evaluated the spherical applicator for the 9 MeV electron beam preliminary which should be improved in the axial plane.Conclusions:This work established and validated the method of US-guided IORT.Moreover,a method for delivering a spherical dose distribution with a linear electron beam was proposed.The method of US-guided IORT introduced in this study was easy and feasible,which not only provided accurate dose data for IORT,but also for post-operative radiation therapy that would resulted in improving the safety and effectiveness of radiation therapy.