Application Research On High-Volt Generator Of Mobile Intraoperative Radiotherapy Therapy System

Brachytherapy is a highly effective treatment for patients with cancer.With a remarkable difference from external radiotherapy,brachytherapy is characterized by source's high dose which is sharply attenuated away from the target.In brachytherapy,the radioactive source is placed near or into brain tumor,which allows accurate high dose to be delivered over the well-defined tumor volume with minimal exposure to surrounding normal structures.Intraoperative Radiotherapy Therapy(IORT) is an effectively procedure which is composed of the irradiation during surgical operation,and the source are directly placed in the local tumour or a surgically exposed tumour bed to be irradiated.By its contribution to the increase of locally delivered dose,better local control and reduction of current complication rate due to irradiation can be expected.The mobile intraoperative radiotherapy therapy system which it is a miniature therapeutic device to deliver radiation during surgical procedure,inaugurates a new way to brachytherapy using x-ray.It consists of four components-a novel needle-based miniature x-ray generating source,control units,x-ray irradiation dosage monitor and stereotactic frame.And the miniature x-ray source plays an crucial role in this system,because it produces a radiation field similar to that of a low-energy brachytherapy source but with a delivery speed typical of external-beam radiotherapy.This miniature and flexible system has several improvements:it can be located directly over the target volume to have a brachytherapy;background radiation exposure is minimal with no special shielding for patients;the supply source is easy to handle without accelerator's bulkfactor.This paper aims at developing a low-cost,portable,safety x-ray generator,and along with the accessories,this miniature x-ray source enables IORT devices to become miniaturized,thereby it can be highly effective on intraoperative radiotherapy therapy.This paper begins with a brief introduction about the theory and the equipment components of PRS,and then emphatically describes how to design a miniature x-ray source and experimental verification.Based on recent technical advance and preliminary researches,this paper concentrates on a target how to design and develop a high-volt generator for mobile radiation therapy system's x-ray tube.By comparison with various convertor modes of power circuits,we have to try and adopt some techniques such as generating high-volt by high-frequency switch circuit and CW voltage doubling rectifying circuit,and steadying voltage by close-loop control circuit with pulse amplitude modulation,all of which are supplied with a 12V storage battery.The main circuit of our design has been tested with simulation software,and the test result is satisfactory given by the experimental graphes that most of the parameters meet the original design requirements.By the way,the experimental results also show that the circuit is simple,reliable and small-sized. However,how to make high-volt circuit work together with other circuits remains a big problem,and it's worth to discuss and study further.At the end of the paper,several remaining issues on the research were discussed, as well as further vision and outlook about the design of mobile intraoperative radiotherapy instruments were made.At the same time,further tumor model testing will be important to determine the ultimate efficacy of local x-ray radiation energy. In sum,we hope that this paper will give a reference to the interested designers.