George C. Giakos

Medical applications of CdTe and CdZnTe detectors

Abstract This review on the medical applications of CdTe and CdZnTe semiconductors is an update on the 1992 and 1996 papers [1]. In addition, future trends in the application of these semiconductors to the medical field are presented and discussed. Several solid-state detectors, based on direct or indirect detection principles, have been proposed for digital radiography and radionucleide imaging applications, although there is no single technology of choice that addresses all the issues for optimal imaging. CdTe/CdZnTe semiconductor substrates are promising digital sensors for medical imaging applications. The widespread use of these detectors depends on the large-scale production of low-cost, large-size semiconductor substrates.

Noninvasive imaging for the new century

Noninvasive imaging technologies are expected to play a significant role in the area of medical diagnosis and industrial imaging. The engineers of the 21st century will need the appropriate skill to master the power of new technologies. To face the challenges of the new century, a strong impulse toward a multidisciplinary and diversified engineering knowledge will be essential. Some examples of noninvasive imaging (spiral CT, microwave imaging, hybrid modalities) and image enhancement techniques are presented.

Engineering Aspects of a Kinestatic Charge Detector

The engineering aspects of a nine-channel digital radiographic system developed for bioimaging research, based on high gas pressure ionography and kinestatic principles, are presented. The research imaging system uses a pulsed x-ray beam which allows one to study simultaneously the ionic signal characteristics at 10 different ionization sites along the drift axis. This research imaging detector system allows one to investigate methods to improve the detection and image quality parameters as part of the development of a large scale prototype medical imaging system.

Multispectral, multifusion, laser polarimetric imaging principles

The engineering and physical principles of a novel multispectral, multifusion, optical imaging system, based on all-active interrogation of targets surrounded by scattered media, using the Mueller matrices-based formalism, are presented. Specifically, the uniqueness of this innovative imaging system consists in the fusion of dual-energy subtraction principles, with multispectral rotating retarder, complete Mueller matrix-based polarimetric principles, implemented with other parameters. The experimental results indicate clearly that, high-contrast images can be obtained by backscattered photons from several embedded targets, in scattered media, by means of the presented principles

Key paradigms of emerging imaging sensor technologies

In this paper, key paradigms of emerging imaging technologies from different technological areas, are presented. Examples of transfer, utilization, and exchange of the imaging technology are offered and discussed. These phenomena, will create advanced solutions for potential development in different areas of science and technology. Overall, new imaging technologies will merge and are expected to play an ever-expanding role in the civilian and military applications of the next century.

Multifusion, Multispectral, Optical Polarimetric Imaging Sensing Principles

The goal of this study is to present novel, multifusion optical imaging sensing principles, based on active-multispectral polarimetric imaging of targets surrounded by scattered media. Specifically, the novelty of this study consists in the fusion of multispectral images, with polarimetric imaging principles, forming image differences. The experimental results indicate clearly that, high-contrast multispectral Mueller polarimetric image differences, as well as Degree of Linear Polarization (DOLP) images can be obtained from transmitted or backscattered photons, from targets embedded in turbid media

Rapid pulsed microwave propagation

Transit time measurements of the leading edge of pulse modulated microwaves in open space and inside a rectangular waveguide have been performed. The experimental setup used is described. Both measurements show that a part of the energy associated with the leading edge of the pulse propagates with the phase velocity. Calibration techniques and repeated measurements confirm this phenomenon.<<ETX>>

Sensitometric response of Cd/sub 1-x/Zn/sub x/Te detectors for chest radiography

The sensitometric response of Cd/sub 1-x/Zn/sub x/Te semiconductor detectors using a geometrical chest phantom, within the X-ray diagnostic energy range, has been studied with the aim of optimizing the image quality parameters of these solid state-ionization devices. In addition, the dependence of the spatial resolution of a planar Cd/sub 1-x/Zn/sub x/Te substrate on the phantom thickness has been experimentally determined. The results of this study indicate that Cd/sub 1-x/Zn/sub x/Te detectors exhibit a high signal-to-noise ratio (S/N).

Novel multifusion optical imaging sensing principles

The goal of this study is to present novel, multifusion, optical imaging sensing principles, based on laser polarimetric imaging of targets surrounded by scattered media, using the Mueller matrices based formalism. Specifically, the novelty of the imaging system consists in the fusion of dual-energy imaging principles, with polarimetric imaging principles at varying focal lengths and exposures. The experimental results indicate clearly that, high specificity images can be obtained by transmitted and scattered photons from several media, by means of the proposed technique.

Study of detection efficiency of Cd/sub 1-x/Zn/sub x/Te detectors for digital radiography

In this paper, the signal-to-noise ratio (S/N) of resistive Cd/sub 1-x/Zn/sub x/Te semiconductor detectors, at different directions of irradiation, within the X-ray diagnostic energy range, has been experimentally studied. In addition, the dependence of the spatial resolution of a planar Cd/sub 1-x/Zn/sub x/Te substrate both on the applied bias voltage and thickness has been experimentally determined. The detection efficiency of semiconductor detectors depend upon the energy absorption efficiency as well as the collection efficiency. This study suggests that high signal-to-noise ratios can be obtained by optimally choosing which polarizing electrode is directly exposed to the incident X-ray beam, as well as on both the detector thickness and applied bias voltage. In addition, the experimental results on the temporal system MTF indicate a spatial resolution of >6 cy/mm. Besides the intrinsic charge transport characteristics of the semiconductor sample, by decreasing the collector size and optimizing the X-ray digital system geometry and temporal response, the temporal system MTF can be improved significantly. The research imaging detector system allows one to investigate methods to improve the detection and imaging performance parameters as part of the development of a digital radiographic system.