Development of a prototype Compton scattering camera using three-dimensional position sensitive CZT detectors.

摘要

The first prototype Compton scattering camera using two 1 cm3 three-dimensional position sensitive CZT detectors has been built and tested. The energy resolution is around 6 keV, 7 keV and 12 keV for 59.5 keV, 122 keV and 662 keV respectively for both detectors. The position resolution is about 1 mm in 3-dimensions. The optimal offset angle &thetas; _c between the two detectors is 50° and the center to center distance between them is 5 cm. The field of view (FOV) for the camera is ±30° around the axis of the first detector corresponding to 20°∼80° scatter angles. The list mode maximum likelihood algorithm is implemented for the image reconstruction. The imaging capability of the system has been demonstrated both for a point source and a line source. The measured angular resolution FWHM at 662 keV is about 5° for the Cs-137 point source and the line source. The intrinsic camera efficiency for the point Cs-137 source is 1.53 × 10−5. Comparing with other previously built Compton cameras, this system is very compact and can operate at room temperature. The CZT detectors with 3-D position sensing capability with the current energy resolution can be used for Compton scatter imaging for gamma ray energy above 500 keV, and are particularly well-suited for portable imaging devices.