Design of Fan Beam Gamma Ray Tomography Scanning System

摘要

Industrial tomography system needs a fast data acquisition, as well as high accuracy and precision scanning control which is operated in an automated manner. In this research, the data were acquired from 2 detector fan beam scanning method. This design consists of: gamma ray source from Cs-137 isotope having 30 mCi activity, scintillation detector made of NaI(Tl) crystal connected to Ludlum M2200 radiation counter, and motion system made up of source rotator and detector rotator with each motion corresponds to one motor. The scanning system was controlled by Arduino Mega as a microcontroller and LabView as a graphical user interface. Microcontroller was used to actuate motors, read encoders, and communicate serially with radiation counter and PC. Motors were able to rotate the source and detector with angle starting from 1° around the center of rotation and take time about 1 second per degree rotation. Radiation counting resulted in 1.47% statistical error for 1-second counting time and decreased to 0.99% as counting time is increased to 2 seconds. The reconstructed image from the proposed fan beam method resulted in poorer quality than from the parallel beam method with the same pixel size. However, for nearly same quality of the image, the proposed method required less scan time. Spatial resolution of both methods could identify the holes within phantom with diameters starting from 1 cm.