Abstract
There are many treatment options for cancer, with the primary ones including surgery, chemotherapy, radiation therapy, etc. In this study, we pay great attention to radiation therapy, which is a kind of particle therapy. Some quality assurance instruments, such as ionizing chamber associated with measuring instruments, are used for radiation measurement use. With the measurement of the weak current output from the ionizing chamber, the radiation dose can be estimated. The central architecture in the measuring instrument is current integrator. While current integrators are usually expansive and slow, in this thesis, a low-cost real-time current measuring system for ionizing chamber using trans-impedance amplifier as central architecture is proposed. The proposed system includes a trans-impedance amplifier (TIA), a MSP430 board, and a PC. TIA detects and converts the received ionized electrons in the ionizing chamber generated by radiation beam into voltage signal. Then, the analog to digital converter (ADC) on the MSP430 board converts the analog voltage signal into digital form. In the end, the digital voltage signal is transmitted to the PC via RS-232 to USB interface. A control program is developed for MSP430 to control the data acquisition task while a Labview-based DAQ/GUI program is developed on PC, which displays real-time waveform and detects temperature. The proposed system is tested and justified with the discrepancy smaller than 1%. The experimental result show that our system has achieved the anticipated goal and can run in a practical situation.