Study Of A Measurement System Based On PXI And Virtual Instrumentation

CT is one revolutionary outcome of modern medical techniques, which has been applied a lot in clinical uses, with DAS as one of its greatest important sub-systems. The raw data from DAS is the basis for CT image reconstruction and its accuracy and reliability have direct influence on image quality. To accurately evaluate the precision of CT system and effectively enhance system performance, the analysis of DAS'performance has become to be a premise and must. Based on the measurement techniques'status, the thesis tried to apply PXI structure and Virtual Instrumentation in the performance measurement of CT DAS, which has great importance in practice and theoretical study.On the basis of thorough study to the operation mechanism and interface definition of CT DAS, a PXI based measurement system scheme is put forward, which provides interface signals to activate DAS A/D conversion. The system goes on with acquisition, data processing and analysis checking DAS performance to meet its specification.The system is comprised of a high precision DC source, a digital millimeter, two interface boards and a PXI platform. The interface boards are designed with Cadence PSD15.2, mainly including power supply circuit, multi-channel input signal generation circuit, and interface circuits with DAS and PXI cards.A measurement software is built up with LabVIEW 8.20, which has the functions of controlling a DC source and a digital millimeter via GPIB, CAN communication with DAS, generation of timing sequence signals and control signal, status monitoring, data acquisition and processing, and also exception handling.Experimental results show that the system could measure DAS'critical to quality characteristics efficiently and effectively. In practical product measurement, the system is easy for further extension with module design and proved to be with friendly interface, long stability and reliability. In addition, the means to analyze and measure CT DAS could also act as a reference to performance evaluation of other electric and electronic devices.