Photon counting detectors (PCDs) with energy discrimination capabilities have been developed for medical x-ray computed tomography (CT) and x-ray (XR) imaging. Using detection mechanisms that are completely different from the current energy integrating detectors and measuring the material information of the object to be imaged, these PCDs have the potential not only to improve the current CT and XR images, such as dose reduction, but also to open revolutionary novel applications such as molecular CT and XR imaging. The performance of PCDs is not flawless, however, and it seems extremely challenging to develop PCDs with close to ideal characteristics. In this paper, the authors offer our vision for the future of PCD-CT and PCD-XR with the review of the current status and the prediction of (1) detector technologies, (2) imaging technologies, (3) system technologies, and (4) potential clinical benefits with PCDs.

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Vision 20/20: Single photon counting x-ray detectors in medical imaging

A summary is presented of the present status of several compound semiconductor radiation detectors, including detectors fabricated from GaAs, HgI2, CdTe, Cd1−xZnxTe and PbI2

Room-temperature compound semiconductor radiation detectors

The development of radiation detectors capable of delivering spatial information about gamma-ray interactions was one of the key enabling technologies for nuclear medicine imaging and, eventually, single-photon emission computed tomography (SPECT). The continuous sodium iodide scintillator crystal coupled to an array of photomultiplier tubes, almost universally referred to as the Anger Camera after its inventor, has long been the dominant SPECT detector system. Nevertheless, many alternative materials and configurations have been investigated over the years. Technological advances as well as the emerging importance of specialized applications, such as cardiac and preclinical imaging, have spurred innovation such that alternatives to the Anger Camera are now part of commercial imaging systems. Increased computing power has made it practical to apply advanced signal processing and estimation schemes to make better use of the information contained in the detector signals. In this review we discuss the key performance properties of SPECT detectors and survey developments in both scintillator and semiconductor detectors and their readouts with an eye toward some of the practical issues at least in part responsible for the continuing prevalence of the Anger Camera in the clinic.

/pdf/spect-detectors-the-anger-camera-and-beyond-1crz00c7wv.pdf

SPECT detectors: the Anger Camera and beyond.

A radiological imaging apparatus of the present invention comprises an image pickup device and a medical examinee holding device that is provided with a bed. The image pickup device includes a large number of radiation detectors and radiation detector support plates. A large number of radiation detectors are mounted around the circumference of a through-hole and arranged in the axial direction of the through-hole. The radiation detectors are arranged in three layers formed radially with respect to the center of the through-hole and mounted on the lateral surfaces of the radiation detector support plates. Since the radiation detectors are not only arranged in the axial direction and circumferential direction of the through-hole but also arrayed in the radial direction, it is possible to obtain accurate information about a γ-ray arrival position in the radial direction of the through-hole (the positional information about a radiation detector from which a γ-ray image pickup signal is output). The use of accurate information about γ-ray arrival increases the tomogram accuracy. As a result, the present invention enhances the tomogram accuracy, that is, the PET examination accuracy.

Radiological imaging apparatus

The results of an effort to improve the performance at CdTe detectors by addressing starting element purity and crystallinity are described. Structural perfection was improved by alloying with ZnTe to form crystals of Cd/sub 1-x/Zn/sub x/Te. Crystals were grown by a high-pressure Bridgman method. Evidence for significant enhancements of the mu tau products resulting from these efforts is presented. Features of Cd/sub 0.8/Zn/sub 0.2/Te detectors include: energy resolutions at 122 keV >

Cd/sub 1-x/Zn/sub x/Te gamma ray detectors

Polarization has been studied in semi-insulating cadmium telluride compensated with chlorine. Several parameters have been considered including surface preparation, nature of the contact, temperature, as well as type and strength of the source. A model that assumes that the space charge region is produced by injected electrons being trapped by deep acceptors explains most of the effects observed. The possible nature of the center is discussed. Finally it is demonstrated that MIS structures are also a practical means to suppress the polarization.

Polarization in Cadmium Telluride Nuclear Radiation Detectors

Performance of halogen-doped CdTe gamma - ray detectors has been improved significantly by the development of new device fabrication methods. In particular, these detectors do not exhibit any of the previously observed polarization effects. Room temperature resolution of 7% at 122 keV has been achieved using applied fields of less than 50 V/mm for detectors up to 100 mm3 in volume.

Advances in CdTe Gamma-Ray Detectors

A new look at CdTe solar cells

A nomograph which can expedite the calculation of mobility-trapping time (μr) product from α-particle measurement of semiconductor nuclear radiation detector materials is presented. Scale ranges are selected specifically for CdTe, but the nomograph is basically unrestricted in use.

H. B. Serreze

Papers

Polarization in Cadmium Telluride Nuclear Radiation Detectors

Advances in CdTe Gamma-Ray Detectors

A new look at CdTe solar cells

Nomograph for determination of mobility-trapping time (μr) product using nuclear techniques