Multi-point Optical-fiber X-ray Sensors Based On The Optical Switch

Radiation therapy has become one of the main methods for treating cancer.In order to achieve true "precision radiotherapy",various precision radiotherapy technologies have been developed in the field of radiotherapy,especially small field radiotherapy.In order to ensure the quality of radiotherapy,it is necessary to conduct a detailed analysis of the dose distribution of the radiation field.Traditional radiation detection devices have low spatial resolution and are difficult to meet the detection needs of non-uniform radiation fields under small field irradiation.In order to meet the quality inspection requirements of radiotherapy equipment and the requirements of small field radiotherapy dose measurement,this paper proposes a multi-point fiber optic X-ray sensor based on optical switches.The system mainly consists of multiple fiber optic X-ray sensors with different layouts,signal transmission fibers,signal switching optical switches,photoelectric conversion,and signal acquisition systems.Based on the PMMA fiber parameters used,1 × 8 fiber optic switches enable the multiplexing of 8 sensing fibers into one detector.Fiber optic X-ray sensors convert X-ray radiation into visible light.The signals of different fiber optic X-ray sensors are selected through optical switches,and then transmitted to the photoelectric conversion and signal acquisition system.The signals are then analyzed and processed by a computer to obtain the X-ray intensity at the corresponding positions of different fiber optic X-ray sensors.To test the feasibility and application effect of the sensor,a fiber optic radiation morning detector was first developed to detect the off axis ratio curve of the beam field of a linear accelerator.Analysis of the measurement results shows that the trend of the off axis ratio normalization curve obtained by the fiber optic X-ray sensor and the ionization chamber is basically consistent,with a difference of no more than 2% in the normalization of symmetrical positions in the left and right directions.Then,the system is used to further detect the symmetry and flatness of the linear accelerator field,and the measurement results are analyzed.It shows good consistency in the measurement of field flatness,and the maximum difference after normalization of each symmetric position does not exceed 3%.Finally,a small field high spatial resolution radiation sensor array was developed to measure the dose distribution at different positions of different small fields.The experimental results show that the fiber bundle sensor presents different signal response intensity distribution in the small radiation field,and the difference between the signal response intensity at the center and the edge of the radiation field is up to one order of magnitude,which provides a new solution to the measurement problem of the small radiation field.Compared to other dose detection devices,this system has the advantages of small size,fast response,real-time dose monitoring,and high dose resolution.In a word,the multipoint optical fiber X-ray sensor based on optical switch can measure the X-ray intensity of multiple positions simultaneously with a photoelectric conversion and signal acquisition system,and can build a measurement system for the intensity distribution of X-ray radiation field,especially for the high spatial resolution measurement of small radiation field.It can be seen that the research of this system in the field of radiotherapy has important significance and commercial value.