A linear CdZnTe pad detector array with approximately 1 mm2 pad area has been developed. The detector has a wide energy range from about 20 to 200 keV. A fast, low-noise monolithic mixed signal ASIC chip has been developed to read out these detector F a y s . A prototype x-ray imaging system consisting of the CdZnTe detector array and the monolithic ASIC chip has been fabricated and tested. In this system, the detectors are abutted against each other to form an approximately 1 m long linear array. The system has been used to take preliminary scanned images of complex objects at various energies. New results obtained from this system is discussed.
Recently, much has appeared in the literature concerning methods to improve the resolution and photopeak efficiency of CdZnTe radiation detectors operating at or around ambient temperature. These methods generally involve either the use of modified electrode structures (e.g. coplanar grids, three-terminal devices) or pulse processing techniques, both of which add complexity, and hence cost, to the production and operation of such devices. In this paper, we will report on results obtained with a simpler, modified two-terminal device.The detector structure combines a planar anode with an extended surface cathode, and relies on a standard, single channel preamplifier/shaping amplifier system. The results obtained demonstrate that the charge collection efficiency of the device, as shown by the Peak-to-Valley (P/V) ratio, is significantly improved when compared to the standard planar geometry, especially at higher (>200 keV) photon energies.
Cadmium Zinc Telluride, or CZT, cameras offer dual-isotope imaging capabilities impossible to duplicate using any other preclinical molecular imaging system. This new technology will enable the investigation of multiple biological processes in parallel and open new areas in research and drug development. The dual-isotope capability is due to the improved energy resolution of CZT (4.5% for 99m Tc), which is 2-3 times better than in existing systems. This improved energy resolution allows for the rejection of more scattered photons, yielding higher contrast images. In addition, CZT provides increased sensitivity compared to traditional pixellated NaI(Tl) systems due to the absence of any escape peaks. These properties combine to give a higher sensitivity detector with significantly improved contrast. The present work demonstrates the use of CZT in dual-isotope imaging of mice using two radiopharmaceuticals with very close energy peaks. These included 99m Tc-labelled MDP (bone agent) and 123 I (thyroid) and a mouse bone ( 99m Tc-MDP) image with a 57 Co fiducial marker. The results show the first ever simultaneous 99m Tc / 123 I mouse images. The individual isotope peaks showed significant separation and yielded an image with the thyroid (2-3 mm) clearly distinguished from the bone structure. GM-I's new FLEX Triumph™ Pre-clinical system is the first in the field to offer CZT SPECT detectors.
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