The iQID camera: An ionizing-radiation quantum imaging detector

https://doi.org/10.1016/j.nima.2014.05.070Get rights and content

Abstract

We have developed and tested a novel, ionizing-radiation Quantum Imaging Detector (iQID). This scintillation-based detector was originally developed as a high-resolution gamma-ray imager, called BazookaSPECT, for use in single-photon emission computed tomography (SPECT). Recently, we have investigated the detector׳s response and imaging potential with other forms of ionizing radiation including alpha, neutron, beta, and fission fragment particles. The confirmed response to this broad range of ionizing radiation has prompted its new title. The principle operation of the iQID camera involves coupling a scintillator to an image intensifier. The scintillation light generated by particle interactions is optically amplified by the intensifier and then re-imaged onto a CCD/CMOS camera sensor. The intensifier provides sufficient optical gain that practically any CCD/CMOS camera can be used to image ionizing radiation. The spatial location and energy of individual particles are estimated on an event-by-event basis in real time using image analysis algorithms on high-performance graphics processing hardware. Distinguishing features of the iQID camera include portability, large active areas, excellent detection efficiency for charged particles, and high spatial resolution (tens of microns). Although modest, iQID has energy resolution that is sufficient to discriminate between particles. Additionally, spatial features of individual events can be used for particle discrimination. An important iQID imaging application that has recently been developed is real-time, single-particle digital autoradiography. We present the latest results and discuss potential applications.

Introduction

Single-event imaging detectors that are sensitive to photons (gamma/X rays) and particles (alphas, betas, neutrons, fission fragments, auger electrons, etc.) are important in a number of applications. Examples of medical imaging applications include single-photon emission computed tomography (SPECT), gamma-ray scintigraphy, digital radiography, SPECT/CT, and autoradiography. Both scintillation and semiconductor technologies exist, each with trade-offs in terms of cost, counting-rate capability, spatial resolution, energy resolution, and active area.

One such detector developed at the Center for Gamma-Ray Imaging is BazookaSPECT [1], [2], [3]. It is a scintillation detector that combines image intensifiers and CCD/CMOS cameras for high-resolution gamma-ray imaging applications. Our latest objective has been to explore the detector׳s response and imaging potential with other forms of ionizing radiation including alpha, neutron, beta, and fission fragment particles. We present an overview of the technology and discuss recent results demonstrating the camera׳s sensitivity to a broad range of ionizing radiation, which has prompted its new title: iQID (ionizing-radiation Quantum Imaging Detector).

Section snippets

iQID imaging system

iQID operates on the principle of using electro-optical gain to amplify scintillation light from an event before imaging onto a CCD or CMOS camera sensor. This optical gain is provided by an image intensifier, which amplifies scintillation light while also preserving spatial information. iQID typically uses microchannel plate (MCP) image intensifiers, which have luminous gains ranging from 104to106 or higher, depending on the number of MCPs used. With intensifiers having two or more MCPs, even

Particle detection

Images of the iQID camera׳s response to alpha particles and fragments from spontaneous fission are shown in Fig. 5, with magnified regions of a selected alpha particle and fission fragment. The pixel colorbar scale of the top magnified images shows the amplitude difference while the bottom shows the spatial extent of the light distribution between particles. The light generated from fission fragments and alphas particles is high enough that the intensifier is operated at the minimum gain

Discussion and conclusion

We have successfully developed a high-resolution imaging detector that is sensitive to a broad range of ionizing radiation including gamma rays, alpha, beta, neutron, and fission fragment particles. An important feature of the iQID camera is a real-time dynamic imaging capability. It is highly portable and does not require cooling and can be operated using a laptop computer, potentially even with a smartphone in the near future. iQID provides fine sampling of scintillation-event light

Acknowledgments

This work is supported by the Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory, a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy. B.W. Miller is grateful for the support of a Linus Pauling Distinguished Postdoctoral Fellowship at PNNL. iQID camera development is in collaboration with the Center for Gamma-Ray Imaging, NIH Grant P41EB002035.

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