A dual modality gamma camera using lanthanum chloride(cerium) scintillators

Portable gamma-ray imaging devices capable of responding to a broad energy range while providing reasonable angular resolution and efficiency are useful in a number of applications, including environmental remediation and industrial surveys. Due to this, a dual radiation imaging system that combines the advantages of a multi-aperture mechanical collimator with electronic-collimation has been designed, built, and tested. The combination of these two disparate imaging modalities offers both efficiency and good angular resolution, and is unique since a single gamma ray can contribute information to both modalities simultaneously. The mechanically collimated camera is most effective for imaging lower energy photons while electronic collimation uncouples spatial resolution from efficiency for higher energies. The Dual Modality Gamma Camera (DMGC) combines a high-resolution URA coded aperture with a Compton scatter camera to provide a broader range of energy response suitable for a wider range of industrial applications (50keV-2MeV). The LaCl3(Ce) in the first detector module has 22x22 voxels, each voxel having a dimension of 2x2x5mm 3. The LaCl3(Ce) in the second detector module has 6x6 voxels having dimensions of 4x4x 10mm3. Both scintillators are coupled to PSPMTs. For the front-end circuit of the first detector, a VaTa chip from IDEAS and a custom circuit are utilized and we compared images from both. Point and ring radiation sources (140, 364, 662 and 1275 keV) are simulated. The results show that the DMGC can cover a broad energy range of radiation and the combined dual collimation image, using the maximum likelihood method for image reconstruction, yields better images than either a mechanical or an electronic collimation image at intermediate energies. Experimental results at the intermediate energies confirm that dual collimation image outperforms a mechanical or an electronic collimation image.