Method and system for high-speed, 3D imaging of optically-invisible radiation and detector and array of such detectors for use therein

Abstract

A high-speed, three-dimensional, gamma-ray imaging method and system as well as a detector and array of such detectors for use therein are provided which characterize radioactivity distributions in nuclear and radioactive waste and materials facilities by superimposing radiation images on a view of the environment using see-through display screens or shields to provide a stereoscopic view of the radiation. The method and system provide real-time visual feedback about the locations and relative strengths of radioactive sources. The method and system dynamically provide continuous updates to the displayed image illustrating changes, such as source movement. A pair of spaced gamma-ray cameras of a detector subsystem function like “gamma eyes”. A pair of CCD cameras may be coupled to the detector subsystem to obtain information about the physical architecture of the environment. A motion tracking subsystem is used to generate information on the user's position and head orientation to determine what a user “sees”. The invention exploits the human brain's ability to naturally reconstruct a 3D, stereoscopic image from 2D images generated by two “imagers” separated by a known angle(s) without the need for 3D mathematical image reconstruction. The method and system are not only tools for minimizing human exposure to radiation thus assisting in ALARA (As Low As Reasonably Achievable) planning, but also are helpful for identifying contamination in, for example, laboratory or industrial settings. Other optically-invisible radiation such as infrared radiation caused by smoldering fires may also be imaged. Detectors are manufactured or configured in curvilinear geometries (such as hemispheres, spheres, circles, arcs, or other arrangements) to enable sampling of the ionizing radiation field for determination of positional activity (absolute or relative amounts of ionizing radiation) or spectroscopy (energy distributions of photons). More than one detector system may be used to obtain three-dimensional information. The detector systems are specifically suitable for direct visualization of radiation fields.

Description

TECHNICAL FIELD This invention relates to methods and systems for high-speed, 3D imaging of optically-invisible radiation and detectors and arrays of such detectors for use therein. BACKGROUND ART One of the fundamental problems involving work with radioactive materials is that radiation is invisible to the human eye and thus poses an invisible hazard. The hazard is compounded when one considers that these materials can be present in an environment when not expected such as with radioactive contamination or leaking radioactive waste storage tanks. To make the concern even more valid, these sources of radiation can be moving, as can be the case with airborne contamination. Thus, it is clear that there is a need for a way to localize radioactive sources, preferably in real-time. Much work has been done on ways to image various forms of radiation to provide the user with a “picture” of the radiation present in an environment. Currently available gamma-ray cameras are capable of prov...

AI Technical Summary

Benefits of technology

The method and system of the present invention have several unique benefits for potential users. In general, the invention has its strongest applications in dose minimization since it allows the user to see the radiation in the environment she is working in. For example, there are many instances when one desires to locate radioactive contamination in an environment. These environments can be quite complex thus requiring more sophisticated images than the standard 2D images. Contamination searches are presently conducted by a radiation worker with a survey meter who spends a great deal of time inspecting the environment by hand. The invention would allow the user to obtain rapid 3D radiation maps in real-time. Should the source by moving or changing, this would be able to be monitored. Thus, the clean up of the contamination would be significantly faster, reducing the worker's exposure to the radiation. This application would be extremely useful to any industrial or laboratory setting which uses gamma-ray radiation.

Another example involves the survey of waste drums or casks such as those stored at Hanford National Laboratory (HNL), a facility run by the Department of Energy. Such containers require constant monitoring to determine if they are leaking. This monitoring could be quickly and easily achieved by the invention which would minimize worker time and possible exposures to unnecessary amounts of radiation.

Problems solved by technology

One of the fundamental problems involving work with radioactive materials is that radiation is invisible to the human eye and thus poses an invisible hazard.

The hazard is compounded when one considers that these materials can be present in an environment when not expected such as with radioactive contamination or leaking radioactive waste storage tanks.

However, these cameras are not independently capable of providing information to locate the source in three dimensions.

However, based on current designs, the performance of some tasks in radiation environments precludes simultaneous monitoring of the radiation field by the individual worker, possibly resulting in increased radiation exposures.

Also, these methods rely on complex mathematical reconstruction making them cumbersome and time-consuming.

A new problem arises if one considers the complex environments that these sources can exist in since even when radiation images are blended with light images three-dimensionality is lost, real-time manipulation of the images becomes complex, and difficulties arise with time-varying source distributions.

Unfortunately, the value of ρh for most compound semiconductors is generally much lower than the value of ρe Largely differing values of ρ for electrons and holes are not conducive to high resolution gamma-ray energy spectroscopy when using simple planar semiconductor detector designs (Day, Dearnaley and Palms, 1967; Knoll and McGregor, 1993).

Images