Non-resonant electron spin resonant probe and associated hardware
Inventors
Campbell, Jason • Ryan, Jason • Cheung, Kin • Desrosiers, Marc • Gougelet, Robert • Shrestha, Pragya
Assignees
United States Department of Commerce
Publication Number
US-11294075-B2
Publication Date
2022-04-05
Expiration Date
2038-03-02
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Abstract
A non-resonant ESR instrument/probe that can easily accept an identification card (or the like) form factor device incorporating a radiation sensitive material providing reliable and calibrated dose measurement stably and permanently stored into the device and deployed to individual, persons, animals, or objects, to act as a personal-surrogate dosimeter primarily in radiation mass events with radiation dose derived from a measure of the radiation induced changes in paramagnetic density obtained via transmission mode electron spin resonance measurements.
Core Innovation
The invention provides a non-resonant electron spin resonance (ESR) instrument and dosimeter system that integrates a radiation-sensitive material into identification card (ID card) form factor devices. This system enables reliable and calibrated dose measurement of ionizing radiation exposure, stably and permanently stored within the device. The ID card embedded with the radiation-sensitive material acts as a personal-surrogate dosimeter, which, in combination with a novel ESR instrument using transmission mode measurement, is deployed to individuals, animals, or objects for rapid, accurate radiation dose assessment, particularly in mass casualty radiation events.
The problem addressed by the invention is the inadequacy of prior retrospective physical dosimetry technologies for deployment in massive nuclear or radiological mass casualty events. Existing methods such as thermal and optical luminescent devices, conventional ESR systems requiring resonance chambers and electromagnets, biological markers, and tooth or fingernail dosimetry have significant limitations including size, weight, complexity, scan time, stability, accuracy, field deployability, cost, environmental variability, and limited clinical utility. There is a need for a practical, widely deployable, accurate, and stable dosimetry system that can rapidly sort and triage individuals exposed to radiation doses indicative of acute radiation syndrome (ARS).
The invention overcomes these problems by providing a system comprising a personal dosimeter embedded in an ID card with a radiation-sensitive material such as L-alanine, and an optimized high definition magnetic resonance (HDMR) ESR instrument configured to operate in a non-resonant transmission mode. The instrument uses a microwave micro-strip transmission line structure that excites and detects radiation-induced free radical resonances in the radiation-sensitive material between a signal line and ground plane, all while a large quasi-DC magnetic field is applied via permanent magnets or electromagnets. This configuration drastically reduces the size, weight, complexity, power requirements, and staffing needs compared to conventional ESR systems, allowing for rapid dose measurement (e.g., reliably detecting 2±0.5 Gy in less than 2 minutes). The system supports high-throughput, tiered radiation dose assessment applicable pre-, during, or post-mass casualty events, enabling self-assessment and public health countermeasures.
Claims Coverage
The patent includes two independent claims covering an operational physical dosimetry system and a method for large scale radiation exposure measurement deployment. These claims broadly cover the inventive features of the dosimeter devices and ESR measuring instrument operating in non-resonant transmission mode.
Identification card form factor dosimeter devices with radiation responsive variable characteristic material
Devices of identification card form factor are carried by or associated with persons, animals, or objects. Each device contains or is combined with a radiation responsive material that immediately and stably preserves radiation exposure effects. This material undergoes measurable characteristic shifts proportional to cumulative radiation exposure, enabling accurate dose retention and measurement.
Non-resonant ESR instrument configured for single spectrum mode detection with transmission line microwave probe
The radiation status measuring instrument is an ESR spectrometer configured to operate in a non-resonant mode using opposing magnet poles to apply a magnetic field to the device under test. It incorporates a transmission line microwave probe with conducting surfaces for excitation and detection of electron spin resonance transitions. The instrument includes coils to sweep and modulate magnetic fields across the radiation sensitive material to establish and record the resonance spectrum.
Incorporation of perforations or fissures to improve magnetic field modulation
The transmission line conducting surfaces can include perforations or fissures to enhance magnetic field modulation at higher frequencies, thereby improving measurement sensitivity and speed.
Use of paramagnetic free radicals as the radiation sensitive variable characteristic
The radiation sensitive material is characterized by its content of paramagnetic free radicals generated in response to radiation exposure, which serve as the measurable variable indicating dose.
Utilization of L-alanine as the radiation sensitive material
L-alanine is specified as the preferred radiation sensitive material due to its stable crystalline structure that linearly responds to ionizing radiation exposure, enabling accurate dose measurement.
Achievement of high reliability and clinical accuracy at 2 Gy±0.5 Gy
The system is constructed and arranged to provide reliability exceeding 99% at a clinically significant dose of about 2 Gy with a tolerance of ±0.5 Gy, facilitated by the stable crystalline radiation sensitive material and the instrument design.
Use of permanent magnets in ESR instrument to reduce size and complexity
The ESR instrument employs a permanent magnet to generate the required quasi-static magnetic field, contributing to a compact, low power design suitable for field deployment.
The independent claims cover a deployable dosimetry system consisting of identification card form factor devices embedding stable radiation sensitive materials and a compact, non-resonant ESR instrument employing a transmission line microwave probe and permanent magnets. Collectively, these features enable rapid, reliable, and high-throughput radiation dose measurement suitable for mass casualty triage and public health countermeasures.
Stated Advantages
The system enables rapid, accurate, and reliable radiation dose measurement in less than two minutes without requiring operational expertise, allowing for self-assessment.
The non-resonant ESR probe substantially reduces the size, weight, complexity, and power consumption of traditional ESR devices, facilitating field deployment.
The identification card form factor allows widespread distribution and use as a personal-surrogate dosimeter, promoting mass casualty response efficiency.
The system supports tiered response protocols enabling rapid patient sorting, timely administration of medical countermeasures, and efficient utilization of limited medical resources.
Documented Applications
Use in radiation mass events to act as personal-surrogate dosimeters for humans, animals, and objects for rapid retrospective dose measurement.
Deployment as a public health countermeasure for sorting and triage of individuals potentially exposed to acute radiation syndrome doses following nuclear or radiological incidents.
Pre-event distribution to first responders, healthcare workers, and military personnel for operational readiness and post-event exposure assessment.
Use for cumulative dose monitoring in at-risk civilian populations and occupational exposures to support long-term health surveillance.
Potential application in non-radiation mass casualty events including chemical, biological, toxic releases, and infectious disease outbreaks by detecting stable free radicals or biomarkers in the dosimeter or associated samples.
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