A 3D CdZnTe detector can provide 3D position information as well as energy information of each individual interaction when a gamma ray is scattered or absorbed in the detector. This unique feature provides the 3D CdZnTe detector the capability to do Compton imaging with a single detector. After detector calibration, real-time data acquisition and imaging are implemented with a single detector system. Because the detector has a finite size and any point in the detector can be the first scattering position, 3D gamma-ray imaging in near field is possible. In this work we will show the result of the 4π Compton imaging with a single 15mm × 15mm × 10mm CdZnTe detector. Different algorithms for sequence and imaging reconstruction will be addressed and compared. The angular uncertainty is estimated and the most recent results from measurements are presented.

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The performance of gamma-ray spectrometers at high energies (several MeV) can be greatly improved through intelligent spectroscopic analysis if spatial information is obtained for each energy deposition. In position-sensitive detectors, the energy and three-dimensional (3-D) position of each interaction in the detector are determined. Recognizing the signatures of multiple interactions in the detector can help to reconstruct the energies of the initial gamma-rays even when the full energies are not deposited. Experimental work by our research group has demonstrated the feasibility of carrying out spatially resolved measurements of individual gamma-ray interactions throughout the volume of a CdZnTe spectrometer. We present the results of a simulation study for gamma-rays incident upon a 6-cm 3 CdZnTe detector using two reconstruction methods: high-efficiency intelligent spectroscopy (HEIS) in which the peak-to-total ratio is greatly improved relative to traditional spectroscopy while maintaining almost the same intrinsic peak efficiency; and peak-only intelligent spectroscopy (POIS) in which the peak-to-total ratio can approach 0.9, assuming realistic values for energy resolution. Although POIS reduces the intrinsic peak efficiency, it will significantly improve the signal-to-noise ratio for many measurements. The predicted performance is unprecedented for a detector of such small volume and illustrates the gains that can be expected by exploiting 3-D information.

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We present position sensitivity measurements obtained with one of the 32-fold segmented HPGe detectors from Michigan State University. These measurements were performed with a collimated beam of 137Cs gamma rays scattered by 90 degrees. This deposits 374 keV at a given location inside the crystal. A position resulution can be determined over many events by examining the digitally recorded pulse shapes on the 32 electrical contacts. If position resolution is adequate, gamma ray Compton camera imaging may be possible.