Euromedim 2006 :1st European Conference on Molecular Imaging Technology

New trends in Gamma-Ray Imaging with CdZnTe/CdTe

10 May 2006, 11:30

15m

Palais du Pharo, Marseille

oral S1-S2 Small animal imaging

Speaker

Dr LOICK VERGER (CEA-LETI)

Description

Increasing interest in room temperature solid state detectors like CdTe/CdZnTe for gamma-ray imaging has marked the last ten years with progress in crystal growth, device technology, integrated electronics and signal processing. The purpose of this paper is to present recent technological advances and potential applications in gamma-ray imaging. A new method to grow very large dimension CZT up to 300 mm in diameter is presented. Metal-Semiconductor contact process control allows design of very small electrodes (up to 100µm pitch) with good long-term stability. The development of low-noise front-end integrated electronics and new interconnects technologies have made “pixel detectors” feasible. Significant effort has been focused on reaching high-energy resolution as well as high detection efficiency. The combination of signal processing such as bi-parametric (BP) approaches and electrode design presents an interest in charge loss compensation, tailing reduction due to geometric effect and depth of interaction information. Regarding improvement in CZT performance, molecular imaging (SPECT and PET) is the most promising field of gamma-ray application and several developments of CdTe/CZT based solid state gamma camera have emerged with the expectation that such new technology would outperform conventional scintillator detectors like NaI(Tl) or LSO crystals. In this framework, CEA-Leti is being working on CZT technology and system approach for gamma-ray imaging that may still improve image quality either for low or high energy applications. An energy resolution of about 1.6 % at 122 keV with a detection efficiency of 75% has been obtained with pixelated 10x10x5 mm3 CZT detectors that allows both multi- isotopes identification and scatter event rejection. Such new CZT performance (high energy resolution, high intrinsic spatial resolution, depth of Interaction information and high count rate capabilities) may open up both new vistas for innovative system architecture of detector / collimator to overcome the sensitivity- spatial resolution trade off of the conventional Anger gamma camera and new image processing with multi-energy approach. New system architecture and image processing that take the benefit of CZT performance will lead to a technical breakthrough with the standard procedure used today in nuclear medicine either for clinical (SPECT) or small animal imaging (µSPECT). To address the spatial resolution homogeneity issue associated with small animal µPET systems, we have also jointly developed a specific three-dimensional CZT detector with orthogonal strip geometry for a transverse irradiation and a preamplifier stage: an encouraging CZT-BaF2 coincidence time of 2.6ns FWHM at 511 keV has been achieved and a good homogeneity of the spatial resolution across the Field Of View (<1 mm FWTM up to 44 mm off the FOV center) is expected. This new 3D CZT detector geometry may open up new vistas for innovative architecture in µPET system, particularly regarding the sensitivity improvement.