NON-RESONANT ELECTRON SPIN RESONANT PROBE AND ASSOCIATED HARDWARE
20200003909 ยท 2020-01-02
Assignee
Inventors
- Jason Campbell (Washington, DC, US)
- Jason Ryan (Washington, DC, US)
- Kin Cheung (Washington, DC, US)
- Marc Desrosiers (Washington, DC, US)
- Robert Gougelet (Washington, DC, US)
- Pragya Shrestha (Washington, DC, US)
Cpc classification
International classification
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.
Claims
1. An operational physical dosimetry system deployable as a retrospective public health counter measure comprising: (a) individual personal surrogate devices for humans and service animals, or other objects to be protected, of identification card (or the like) form factor carried on persons, or such objects routinely or close in proximity i.e. purse, lanyard and easily accessed by a radiation status instrument, (b) a radiation variable material with immediate and stable preservation of a radiation exposure effect incorporated into or on said device wherein the radiation variable material responsive to incident radiation exposure in one or more bands of the electromagnetic spectrum undergoes a shift in characteristics as a result of an initial of such exposure and retains such shift after the event, (c) a radiation status instrument detecting predictable electron spin changes as a result of ionizing radiation specifically and optimally gamma radiation, and (d) means for enabling a read-out of said radiation variable material by the detector instrument and transfer to a local or distant recorder or display, (e) wherein the instrument is an ESR detector instrument with permanent magnet poles and configured with a transmission line microwave probe for extraction and detection operation and comprising coils to sweep and modulate magnetic fields to establish and record a valid resonance peak, with accuracy and speed enhanced by incorporation of perforations or fissures into the transmission line conducting surfaces to improve magnetic field modulation at higher frequencies thereby allowing faster scans and the use of rapid scanning detection artifacts, both increasing speed and accuracy of measurements, the combination enabling low cost, effective widespread distribution in large populations required for rapid and widespread present or retrospective detection of radiation exposure and allowing maintenance of structural integrity by not requiring destruction of the personal surrogate device which can have continued intended use and thereby allow multiple cumulative exposure measurements.
2. (canceled)
3. (canceled)
4. The system of claim 1 wherein the ESR detector instrument is an electron spin resonance spectroscopic instrument configured to operate in a single ESR spectrum mode, the system further comprising: (f) a transmission line associated with the carrier and its radiation sensitive compartment and constructed and arranged for excitation and detection of radiation status of the radiation sensitive material of the carrier.
5. The system of claim 1 wherein the variable characteristic is paramagnetic free radicals content optimally comprising L-alanine.
6. The system of any of claims 1, 4 or 5 with reliability exceeding 99% at clinically significant level of 2 Gy+/0.5 Gy, enabled by use of a stable crystalline structure immediately and permanently responsive in a linear response to ionizing radiation due to purity and reproducibility of material, and optimal placement for reflection at higher frequency and therefore shorter scan times, and higher accuracy reading.
7. A personal surrogate radiation detection device of identification card (or the like) form factor with a radiation sensitive material therein or coated thereon.
8. The device of claim 7 constructed and arranged to operate without full or partial destruction that can be read multiple times and with cumulative reading of both neutron and gamma radiation, optimally gamma, and including a sensor dosimetry material with stable physical characteristics not impacted by sunlight and further contained in laminate, chamber, film pack, or other containment system of the device resistant to humidity, incidental spills, or additional environmental factors and included in the device in a manner which does not interfere with the structural integrity, durability, security features, near field communications, barcode, and does not require a transparent layer for measurement allowing for graphic overlays, holograms, bar codes, pictures, fingerprints, antennas, and demographic information necessary related to dosimetry and/or information unrelated to dosimetry for day to day uses of the device.
9. The process of utilizing one or more of crystalline materials with optimal radiation sensitive characteristics selected from the group consisting of alanine, hydroxyapatite, and lithium format and included filler/binding material in a device of card form factor that maintains structural integrity during manufacturing process and lifespan of the host card form factor device, without requiring a stabilizing material, in physical dosimetry of radiation in an ESR instrument configured to operate in single ESR spectrum mode, with a transmission line microwave probe for extraction and detection operation and comprising coils to sweep and modulate magnetic fields to establish and record a valid resonance peak.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0057] The following descriptions explain how the product functions, referencing the drawings, but does not indicate possible limitations of usage;
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DETAILED DESCRIPTION OF EMBODIMENTS
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[0069] The volume of the encased RSM will depend on the composition of the chosen RSM and final ID Card dimensions. ESR-derived dosimetry is a transfer dosimetry measurement. Thereby an ESR measurement of the total number of stable free radicals generated in the RSM is related to a calibrated total absorbed dose. Thus, the volume of RSM is dependent on the required dose sensitivity needed to assess personal dose. Higher doses of radiation generate larger numbers of ESR-visible free radicals and require smaller volumes of RSM to arrive at a calibrated dose. Lower doses of radiation generate comparatively smaller numbers of ESR-visible free radicals and require larger volumes of RSM. This volume ratio assumes a fixed ESR measurement time. If the ESR measurement times can be extended, then similar volumes of RSM can be used for both higher and lower dose assessments.
[0070] The placement of the RSM within the thickness of the ID card is somewhat inconsequential. The ESR measurement is sensitive to the volume of RSM throughout the ID card. The pocket of RSM could be offset to either the top or bottom faces, with very little consequence to the dose assessment, area placement is subject to detector instrument probe alignment.
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[0077] Besides being transmitted lo local oscillator arm 32, some of the power of the excitation frequency from splitter 11 is transmitted to the non-resonant probe 4,5 through the high frequency coaxial connectors 6 via attenuator 12 and pick-off tee 13 before being split by splitter 17 and simultaneously transmitted through reference arm 16 and sample arm 31. This energy is transmitted through the resonant probe to combiner 20.
[0078] Concurrently, reference arm 16 communicates the excitation frequency from excitation source 9 through attenuator 18 and phase shifter 19 so that the excitation frequency from sample arm 31 and reference arm 16 are coincident at combiner 20 and can destructively combine. Due to destructive combination of the excitation frequency combined at combiner 20 from reference arm 16 (the excitation frequency) and sample arm 31 (the excitation frequency transmitted through the non-resonant probe, 4,5 and high frequency coaxial connectors 6 in the absence of absorption by a sample) are either in phase and constructively combine or are out of phase and destructively combine. The resulting superposition of the combination of the excitation frequencies from reference arm 16 and sample arm 31 can be made to have zero amplitude (or approximately zero amplitude) by adjusting phase shifter 19 so that bridge 24 is balanced and produces the combined frequency having zero amplitude or a very low amplitude.
[0079] When the excitation frequency from reference arm 16 and sample arm 31 are present at combiner 20, reference arm 16 and sample arm 31 are balanced and the combined frequency that is output from combiner 20 has a low amplitude, perhaps zero. However, when the RSM absorbs the excitation frequency, and the signal frequency is present at combiner 20, reference arm 16 and sample arm 31 are unbalanced. For the unbalanced case, the combined frequency output from combiner 20 is proportional to the number of unpaired electrons present in an excitation volume non-resonant probe 4,5 that absorbs power from the excitation frequency. As mentioned, combiner 20 transmits the combined frequency to radiofrequency input 34 of mixer 23. Pick-off tee 21 can be interposed between combiner 20 and amplifier 22 to allow monitoring of the combined frequency.
[0080] Mixer 23 mixes the combined frequency at radiofrequency input 34 and the excitation frequency at local oscillator input 33 and produces a detection frequency (e.g., an intermediate frequency) at output port 35 of mixer 23. The detection frequency is transmitted subsequently to phase sensitive detector 25, which is locked to a phase and frequency of reference oscillator 26. In this arrangement, use of phase sensitive detector 25 to monitor the detection frequency at a frequency and phase of the reference frequency accomplishes heterodyne detection of the resonant absorption of the excitation frequency by RSM as a function of the excitation frequency and magnetic field strength. Therefore, in an embodiment, the electron spin resonance spectrometer includes the bridge that bas the local oscillator arm, which includes the mixer, such that the bridge is configured to produce the detection frequency and transmit the detection frequency to the detector.
[0081] Magnet poles 8 are disposed proximate to probe 4,5 of electron spin resonance spectrometer, and modulation coil 30 is disposed on a surface of magnet 8. Electron spin resonance spectrometer is configured to receive RSM in an ID card form factor proximate to the non-resonant probe 4,5, modulation coil 30, and magnet 8. Magnet 8 applies a magnetic field to the RSM, and modulation coil 30 modifies the strength of the magnetic field applied to the RSM. When the RSM includes an unpaired electron, the applied magnetic field from magnet 8 or modulation coil 30 perturbs the energy levels associated with the magnetic spin quantum number according to the Zeeman effect. As a result, the energy levels associated with the unpaired electron, are split as a function of the magnetic field strength, and a transition between spin states (m, =) of the electron occurs when the excitation frequency is resonant with the energy difference between two magnetic spin states of the unpaired electron. Here, a single unpaired electron is discussed, but the RSM may contain a plurality of unpaired electrons that potentially are perturbed by the magnetic field. Thus, an electron spin resonance transition (i.e. a transition between electron magnetic spin states given by the magnetic quantum number m) occurs for the RSM present in the applied magnetic field from magnet 8 (or as modified by modulation coil 30) when the excitation frequency subjected to the RSM through the non-resonant probe 4,5 matches the frequency separation between the magnetic sublevels of the unpaired electron. In this manner, sample the RSM absorbs some power from the excitation frequency from the non-resonant probe 4,5. As a result, the amount of power of the excitation frequency that is transmitted through the non-resonant probe 4,5 is less than the power of the excitation frequency in the absence of the RSM undergoing an electron spin resonance transition. As discussed below, when an electron spin resonance transition occurs, the transmitted excitation frequency is referred to as a signal frequency because it includes information about the reference frequency applied to the RSM from modulation coil 30. Moreover, when the RSM is absent or does not absorb power from the excitation frequency (because the excitation frequency is not resonant with the Zeeman splitting of the energy levels of the unpaired electron), the excitation frequency is transmitted to combiner 20 so that bridge 24 remains balanced.
[0082] When the RSM absorbs power from the excitation frequency, the signal frequency is transmitted to combiner 20. However, bridge 24 was balanced with respect to the excitation frequency transmitted to the non-resonant probe 4,5 and not the signal frequency transmitted through the non-resonant probe 4,5 In the presence of the signal frequency at combiner 20, bridge 24 is unbalanced such that a combined frequency output from combiner 20 has an amplitude that is proportional to the signal frequency (i.e. an amount of power of the excitation frequency that is absorbed by the RSM).
[0083] Reference oscillator 26 produces and transmits the reference frequency to phase sensitive detector 25 as well as modulation coil 30 interposed between magnet poles 8 and the non-resonant probe 4,5. Bias tee 28 receives the reference frequency from amplifier 27 and a bias voltage from power source 29 (e.g., a sweep generator) and transmits (as an output to modulation coil 30) the reference frequency biased at the level of the bias voltage. Hence, modulation coil 30 receives the reference frequency biased at a level of the bias voltage so that modulation coil 30 modulates the magnetic field strength from magnet 8 that is applied to the non-resonant probe 4,5. It is contemplated that modulation coil 30 is configured to receive the bias voltage, the reference frequency, or a combination thereof. In this manner, the signal frequency transmitted through the non-resonant probe 4,5 is modulated at the reference frequency of reference oscillator 26 corresponding to modulated absorption of the RSM in the applied magnetic field. In this arrangement, phase sensitive detector 25 is part of a homodyne detection system wherein an absorption of the excitation frequency by the RSM is modulated at the frequency of the reference frequency, and the amplitude of the absorption is proportional to the number of unpaired electrons (or a defect density) in the RSM that are within the excitation volume of the non-resonant probe 4,5. Furthermore, absorption by the RSM occurs at the frequency of the excitation frequency that is resonant with the separation of the electron magnetic spin states due to the strength of the magnetic field from a combination of magnet 8 and modulation coil 30.
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[0087] The forms of effective RSM can be varied from the pellet described above including, e.g. (a) reduction of pellet size from the 15 mm4 mm0.6 mm used above to smaller sizes e.g. 5 mm4.5 mm0.6 mm (about 15 mg) yielding an increase of yield of say 1 kilogram of material (from about 100,000 pellets at 15 mm4 mm0.6 mm to about 300,000 at 5 mm5 mm0.6 mm), (b) round, square, elliptical, rectangular pellets or dishes or other, tetrahedral, spherical, rod or oblate solid forms, (c) as gels or (d) in fluid forms including slurries and emulsions. The fluid forms can be present at the compartment for interfacing the spectrometer magnetic field or contained elsewhere and fed to the components at the time of measurement microfluidic channels leading to the compartment under various forms of drive including peristaltic rolls, finger pressure, electrostatic, electromagnetic or otherwise. Alternatively, various RMS locations of the RSM content of the card can be presented to the component field sequentially and the readings summed.
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[0089] L-alanine was chosen for these measurements, as it has a known stable radiation-induced free radical. However, the present inventions need not be limited to L-alanine, though it is presently preferred, as there are a variety of other radiation-sensitive material (RSM) candidates suitable for this application, e.g. dense hydroxyapatite [Ca.sub.10(PO.sub.4).sub.6(OH).sub.2]; lithium or calcium formate. The measurements were also taken at B.sub.0 values of approximately 300 mT and microwave frequencies of approximately 9 GHz. These resonance conditions were chosen for compatibility with conventional room-temperature ESR measurements and do not represent limitations on operation conditions. In principle, as long as the resonance condition is met, both B.sub.0 and the microwave frequencies can scale to meet the application's needs.
[0090] The general public would employ this design of the ESR-based dosimetry system as follows. An individual would insert the ID card into the ESR sensor, after which the system returns a received dose value and instructions for further action. Using the non-resonant transmission line structure also allows for a downsizing of much of the ancillary infrastructural equipment. The complete system drastically reduces the physical weight and foot print of the ESR spectrometer, and facilitates use of personal dosimeters and detector instrumentation, in highly deployable packages suitable for delivery during or soon after (preferably before) the mass-casualty radiation event.
[0091] The devices and methods can be used to measure radiation dose in close proximity to humans, animals, plants and objects after radiation that requires rapid mitigation steps, or to confirm none or non-significant injury, and eliminate subjects to allow effective mitigation activities. The device and system as a whole (i.e., with devices analogous to the card form factor dosimeters described above) can also be used for rapid, widespread analysis of large populations, to deal with other mass casualty conditions (actual or supposed) other than radiation energy spectrum events such as chemical toxic biological releases, or infection spreads/pandemics via various vectors.
[0092] The identification-card form factor can also carry related information about the projected subject who carries it (or may have it affixed or embedded), for example: card identification/association, affiliations, medical conditions or history, emergency contact information, special needs, and/or exposure monitoring (presently or retrospectively).
[0093] While one or more embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation. Embodiments herein can be used independently or can be combined.
[0094] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. The ranges are continuous and thus contain every value and subset thereof in the range. Unless otherwise stated or contextually inapplicable, all percentages, when expressing a quantity, are weight percentages. The suffix (s) as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including at least one of that term (e.g., the colorant(s) includes at least one colorants). Optional or optionally means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event occurs and instances where it does not. As used herein, combination is inclusive of blends, mixtures, alloys, reaction products, and the like.
[0095] As used herein, a combination thereof refers to a combination comprising at least one of the named constituents, components, compounds, or elements, optionally together with one or more of the same class of constituents, components, compounds, or elements.
[0096] All references referred to herein by citation or description without citation are incorporated herein by reference and without prejudice to contrasting prior art or other significant relevance to patentability. The use of the terms a and an and the and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Or means and/or. It should further be noted that the terms first, second, primary, secondary, and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier about used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). The conjunction or is used to link objects of a list or alternatives and is not disjunctive; rather the elements can be used separately or can be combined together under appropriate circumstances.