Wave propagation and group velocity

Over the last decade, cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) wide band gap semiconductors have attracted increasing interest as X-ray and gamma ray detectors. Among the traditional high performance spectrometers based on silicon (Si) and germanium (Ge), CdTe and CdZnTe detectors show high detection efficiency and good room temperature performance and are well suited for the development of compact and reliable detection systems. In this paper, we review the current status of research in the development of CdTe and CdZnTe detectors by a comprehensive survey on the material properties, the device characteristics, the different techniques for improving the overall detector performance and some major applications. Astrophysical and medical applications are discussed, pointing out the ongoing Italian research activities on the development of these detectors.

https://www.mdpi.com/1424-8220/9/5/3491/pdf?view=inline

Progress in the Development of CdTe and CdZnTe Semiconductor Radiation Detectors for Astrophysical and Medical Applications

Vision in scattering media is important but challenging. Images suffer from poor visibility due to backscattering and attenuation. Most prior methods for scene recovery use active illumination scanners (structured and gated), which can be slow and cumbersome, while natural illumination is inapplicable to dark environments. The current paper addresses the need for a non-scanning recovery method, that uses active scene irradiance. We study the formation of images under widefield artificial illumination. Based on the formation model, the paper presents an approach for recovering the object signal. It also yields rough information about the 3D scene structure. The approach can work with compact, simple hardware, having active widefield, polychromatic polarized illumination. The camera is fitted with a polarization analyzer. Two frames of the scene are taken, with different states of the analyzer or polarizer. A recovery algorithm follows the acquisition. It allows both the backscatter and the object reflection to be partially polarized. It thus unifies and generalizes prior polarization-based methods, which had assumed exclusive polarization of either of these components. The approach is limited to an effective range, due to image noise and illumination falloff. Thus, the limits and noise sensitivity are analyzed. We demonstrate the approach in underwater field experiments.

/pdf/active-polarization-descattering-1hvlq0m273.pdf

Active Polarization Descattering

Methods for differential image quality enhancement for a detection system including multiple electromagnetic radiation detectors which include obtaining an image from a chemical band electromagnetic radiation detector and an image from a reference band electromagnetic radiation detector. Each of the images includes a plurality of pixels, each pixel having an associated intensity value. One or more intensity values of a plurality of pixels from the reference band image are adjusted based on one or more intensity value parameters of the chemical band image.

Methods for differential image quality enhancement for a multiple detector system, systems and use thereof

A review of electronic portal imaging devices (EPIDs) used in external beam, megavoltage radiation therapy is presented. The review consists of a brief introduction to the definition, role and clinical significance of portal imaging, along with a discussion of radiotherapy film systems and the motivations for EPIDs. This is followed by a summary of the challenges and constraints inherent to portal imaging along with a concise, historical review of the technologies that have been explored and developed. The paper then examines, in greater depth, the two first-generation technologies that have found widespread clinical use starting from the late 1980s. This is followed by a broad overview of the physics, operation, properties and advantages of active matrix, flat-panel, megavoltage imagers, presently being commercially introduced to clinical environments or expected to be introduced in the future. Finally, a survey of contemporary research efforts focused on improving portal imaging performance by addressing various weaknesses in existing commercial systems is presented.

/pdf/electronic-portal-imaging-devices-a-review-and-historical-32u0ia4a2l.pdf

Electronic portal imaging devices: a review and historical perspective of contemporary technologies and research

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.

Medical applications of CdTe and CdZnTe detectors

The present invention relates to a multi-energy system that generates and/or forms images of targets/structures by applying Mueller matrix imaging principles and/or Stokes polarimetric parameter imaging principles to data obtained by the multi-energy system. In one embodiment, the present invention utilizes at least one energy or light source to generate two or more Mueller matrix and/or Stokes polarization parameters images of a target/structure, and evaluates the Mueller matrix/Stokes polarization parameters multi-spectral difference(s) between the two or more images of the target/structure. As a result, high contrast, high specificity images can be obtained. Additional information can be obtained by and/or from the present invention through the application of image, Mueller matrix decomposition, and/or image reconstruction techniques that operate directly on the Mueller matrix and/or Stokes polarization parameters.

Multi-wavelength imaging system

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.

Noninvasive imaging for the new century

The application of gas-detection principles on both dual-energy detection, such as for chest radiography and mammography, and quantitative autoradiography enhances dramatically the image quality of the digital dual-energy detector with great implications in general-purpose digital radiography, computer assisted tomography (CT), microtomography and x-ray microscopy, and offers notable advantages over film autoradiography with a higher sensitivity, much lower exposure times, as well as imaging access at the cellular level. A gas microstrip detector (20) receives incident radiation (44) through a subject (45) to generate an image. The detector (20) includes a substrate (26) having on a first surface a plurality of alternating anodes (22) and cathodes (24), a detector cathode (30) spaced apart from and opposing the substrate, and a zone for dispensing a gaseous medium (34) between the substrate and the detector cathode and for receiving incident radiation imparted through the subject.

Multimedia detectors for medical imaging

The objective of this paper is to present novel detection principles based on all active multispectral polarimetric subtraction imaging principles of targets embedded in scattering media. The novelty of this contribution consists in the formation of multispectral Stokes' parameter image differences, degree of linear polarization image differences, and Mueller-matrix image differences. As a result, high-contrast high-specificity images can be obtained by removing the background from the target. Further contrast enhancement of the target with light beam steering capabilities can be obtained by doping the background surrounding the target or the target itself with high-index-of-refraction polar molecules/nanoparticles. The presented optical principles can be successfully applied to a variety of applications, such as cancer detection and treatment, molecular imaging, and development of photonics and nanophotonic devices, for a widespread group of applications, such as defense and advanced medical diagnostic and analytical devices

George C. Giakos

Papers

Medical applications of CdTe and CdZnTe detectors

Multi-wavelength imaging system

Noninvasive imaging for the new century

Multimedia detectors for medical imaging

Multifusion Multispectral Lightwave Polarimetric Detection Principles and Systems