121 results about "Positron annihilation" patented technology

An imaging system comprises: a ring of positron emission tomography (PET) detectors; a PET housing at least partially surrounding the ring of PET detectors and defining a patient aperture of at least 80 cm; a coincidence detection processor or circuitry configured to identify substantially simultaneous 511 keV radiation detection events corresponding to electron-positron annihilation events; and a PET reconstruction processor configured to reconstruct into a PET image the identified substantially simultaneous 511 keV radiation detection events based on lines of response defined by the substantially simultaneous 511 keV radiation detection events. Radiation planning utilizing such an imaging system comprises: acquiring PET imaging data for a human subject arranged in a radiation therapy position requiring a patient aperture of at least about 80 cm; reconstructing said imaging data into a PET image encompassing an anatomical region to undergo radiation therapy; and generating a radiation therapy plan based on at least the PET image.

The present invention provides a new scintillator, cerium bromide (CeBr3), for gamma ray spectroscopy. Crystals of this scintillator have been grown using the Bridgman process. In CeBr3, Ce3+ is an intrinsic constituent as well as a luminescence center for the scintillation process. The crystals have high light output (˜68,000 photons / MeV) and fast decay constant (˜17 ns). Furthermore, it shows excellent energy resolution for γ-ray detection. For example, energy resolution of <4% (FWHM) has been achieved using this scintillator for 662 keV photons (137Cs source) at room temperature. High timing resolution (<200 ps-FWHM) has been recorded with CeBr3-PMT and BaF2-PMT detectors operating in coincidence using 511 keV positron annihilation γ-ray pairs.

An apparatus comprising a radiation source, coincident positron emission detectors configured to detect coincident positron annihilation emissions originating within a coordinate system, and a controller coupled to the radiation source and the coincident positron emission detectors, the controller configured to identify coincident positron annihilation emission paths intersecting one or more volumes in the coordinate system and align the radiation source along an identified coincident positron annihilation emission path.

An apparatus comprising a radiation source, coincident positron emission detectors configured to detect coincident positron annihilation emissions originating within a coordinate system, and a controller coupled to the radiation source and the coincident positron emission detectors, the controller configured to identify coincident positron annihilation emission paths intersecting one or more volumes in the coordinate system and align the radiation source along an identified coincident positron annihilation emission path.

A cellulose ester film exhibiting: a free volume radius of 0.25 to 0.31 nm and a half-width of 0.04 to 0.1 nm, the free volume radius and the half-width being determined by positron annihilation lifetime spectroscopy; and Ro of 0 to 10 nm and Rt of −30 to ⇄20 nm, Ro and Rt being defined by the following equations: Equation (a): Ro=(nx−ny)×d; Equation (b): Rt=((nx+ny) / 2−nz)×d (Ro: in-plane retardation, Rt: retardation in the thickness direction of the film, nx: in-plane refractive index in slow axis direction, ny: in-plane refractive index in fast axis direction, nz: refractive index in the thickness direction of the film (refractive indexes being measured at wavelength of 590 nm), d: thickness of the film (nm)).

Methods and systems for imaging by using a filter for Time-Of-Flight Positron Emission Tomography (TOF PET) are described. The described methods of imaging a patient by using a positron emission tomography (PET) system includes acquiring a plurality of frames of sinogram data, filtering the acquired sinogram data and back-projecting the filtered sinogram data to form an output image of the patient. The acquired sinogram data defines a line of response (LOR) and a time-of-flight (TOF) measurement that localizes positron annihilation within the patient. The filtering of the acquired sinogram data is performed using the TOF measurement.

A method, process and apparatus for compensating for changes to the gain of photo detectors in a nuclear imaging apparatus is disclosed. Specifically, embodiments detect positron annihilation event pulses using photo detectors. Changes to the gain of the photo detectors are compensated for by determining the relationship of a detected event pulse peak with a target event pulse peak. Based on the difference between these two peaks, a corrected gain is determined in a closed-loop control system. The corrected gain can be used to compensate for temperature changes that can affect the gain of the photo detectors.

Methods and systems for imaging by using a filter for Time-Of-Flight Positron Emission Tomography (TOF PET) are described. The described methods of imaging a patient by using a positron emission tomography (PET) system includes acquiring a plurality of frames of sinogram data, filtering the acquired sinogram data and back-projecting the filtered sinogram data to form an output image of the patient. The acquired sinogram data defines a line of response (LOR) and a time-of-flight (TOF) measurement that localizes positron annihilation within the patient. The filtering of the acquired sinogram data is performed using the TOF measurement.

A focus ring is shaped by cutting off a silicon carbide body formed by a sintering method or a CVD method. The shaped focus ring is exposed to a plasma generated from at least one of a carbon tetra fluoride gas and an oxygen gas for producing impurities, and the impurities are introduced to void-like defects existing in the vicinity of a surface of the focus ring. Subsequently, positrons are injected in the vicinity of the surface of the focus ring into which the impurities are introduced, and the defect density in the vicinity of the surface of the focus ring is detected by the positron annihilation method.

The invention provides a detector for positron emission imaging equipment, and positron emission imaging equipment. The detector includes a scintillation crystal and at least one photoelectric sensor array, wherein the scintillation crystal is an integrated scintillation crystal, and is provided with a through hole; the through hole is used for accommodating an object waiting for imaging; the photoelectric sensor array is coupled with the scintillation crystal, and is used for detecting a visible photon which is generated when a gamma photon and the scintillation crystal react; and the gamma photon is generated through positron annihilation effect which occurs in the object waiting for imaging. The detector for positron emission imaging equipment enables the positron emission imaging equipment using the detector to be high in positioning accuracy of the gamma photon, to be high in sensitivity, to be weak in edge effect and to be low in mechanical design difficulty.

Provided are new methods for enhancing the selection of true (T) annihilation events relative to the inclusion of true scattered (TS) and random (R) annihilation events in PET tomographs and thereby improving the sensitivity and / or resolution of PET scanners. The methods include reconstruction of Compton scattering interactions in the γ-ray detectors for determining the angles of incidence of the γ-rays received at the detectors and may utilize γ-ray polarization effects and electron recoil data associated with positron annihilation and Compton scattering. The use of the γ-ray polarization effects provides an improved ability for selecting data corresponding to T events while simultaneously suppressing data corresponding to TS and R events during PET applications.

In positron emission tomography, a nuclear medicine scanner is utilized to detect γ-ray events resulting from positron annihilation events. Molecules with known behaviors are tagged with radioactive isotopes which decay into γ-ray pairs which are detected coincidentally, i.e. in a near-simultaneous fashion, by radiation detectors. A temporal recorder and a subject support monitor indicate the time and position of the subject when the coincident γ-rays were detected. A storage buffer collects γ-ray detection times and locations along with support positions. Every 1 / 100th- 1 / 10th second, a batch of data collected in the buffer is reconstructed into overlapping portions of an image memory as the support moves continuously through the scanner.

The invention provides a reaction position positioning method and apparatus. The method includes receiving the energy information of the visible photon coupled to a scintillation crystal, detected by at least one photoelectric sensor array, and generated by the reaction of the gamma photon with the scintillation crystal, wherein the scintillation crystal is an integrated scintillation crystal and has a through hole for receiving an object to be imaged, and the gamma photon is generated by the positron annihilation effect in the object to be imaged; and determining the reaction position of the gamma photon in the scintillation crystal according to the received energy information, wherein the reaction position is represented by a cylindrical coordinate system. According to the invention, by providing a way for positioning the reaction position of the gamma photon for a positron emission imaging apparatus with the integrated scintillation crystal, the problem that a conventional position calculation method is not suitable for the improved positron emission imaging apparatus can be solved.

A method of PET image reconstruction is provided that includes obtaining intra-patient tissue activity distribution and photon attenuation map data using a PET / MRI scanner, and implementing a Maximum Likelihood Expectation Maximization (MLEM) method in conjunction with a specific set of latent random variables, using an appropriately programmed computer and graphics processing unit, wherein the set of latent random variables comprises the numbers of photon pairs emitted from an electron-positron annihilation inside a voxel that arrive into two given voxels along a Line of Response (LOR), where the set of latent random variables results in a separable joint emission activity and a photon attenuation distribution likelihood function.

The invention discloses a novel positron annihilation life time spectrometer. The positron annihilation life time spectrometer comprises a scintillation detector unit, wherein the scintillation detector unit is used for receiving gamma rays generated by disintegration of a radioactive source and positron annihilation and generating scintillation light; after being transmitted and modulated, the scintillation light enters a photocathode through a slit to generate photoelectrons; after being accelerated by a grid net, the photoelectrons enter a deflection plate and are deflected under the action of a high-frequency high-voltage electric field generated by a pulse signal source; after being multiplied and amplified by a micro channel plate, the deflected photoelectrons are imaged on a fluorescent screen; and an image acquisition and data analysis unit is used for reading the image on the fluorescent screen and carrying out on-line fitting on a single pulse signal according to position information to accurately obtain energy and generation time of the gamma rays. According to the positron annihilation life time spectrometer, the time resolution of the positron annihilation life time spectrometer can be effectively improved, the signal processing requirement of a system is reduced and the performance of the positron annihilation life time spectrometer is improved.

The embodiment of the invention relates to a novel positron annihilation spectrometer and a measurement method thereof. The novel positron annihilation spectrometer comprises a radioactive source, a collimator, a detector module and an image obtaining and processing unit, wherein the radioactive source generates positive electron, and the collimator is arranged at the front end of the detector module; the detector module comprises a scintillator, an optical module and a streak tube unit; and the image obtaining and processing unit reads space information recorded by the streak tube unit, obtains the position and amplitude information of gamma rays incident to the detector module according to the space information, respectively obtains the position and amplitude information of gamma rays of a start signal and two termination signals, and further obtains the annihilation life information of positron generated by the radioactive source and the energy information of the gamma rays. The positron annihilation spectrometer can realize the coincidence measurement of high momentum resolution and high time resolution positron annihilation information at the same time and is significantly increased on aspects of momentum resolution, time resolution, testing speed and the like.

A monitor is provided for measuring the presence of a small concentration of at least one hazardous material within a vessel. A positron source emits positrons into an annihilation region of the vessel. A plurality of species of positronium are formed from the positrons as they interact with a sample of the ambient environment disposed within the vessel. At least one gamma ray detector is located externally of the vessel for detecting gamma rays generated primarily by the absorption of the species of positronium within the annihilation region. A method is also provided where a source of positrons is arranged to direct positrons into a vessel containing a specimen of gas and a contaminant to form species of positronium. The timing of the application of positrons is sensed along with the annihilation of each of the plurality of species of positronium. The time delay between the time of application of each positron and the annihilation of the of positronium is measured to obtain a decay rate characteristic of the specimen of gas.

A method for evaluating a material specimen comprises: Mounting a neutron source and a detector adjacent the material specimen; bombarding the material specimen with neutrons from the neutron source to create prompt gamma rays within the material specimen, some of the prompt gamma rays being emitted from the material specimen, some of the prompt gamma rays resulting in the formation of positrons within the material specimen by pair production; collecting positron annihilation data by detecting with the detector at least one emitted annihilation gamma ray resulting from the annihilation of a positron; storing the positron annihilation data on a data storage system for later retrieval and processing; and continuing to collect and store positron annihilation data, the continued collected and stored positron annihilation data being indicative of an accumulation of lattice damage over time.

A defect distribution in the vicinity of a surface of a glass substrate is inspected by a positron annihilation gamma ray measurement. A buffer layer including a brittle layer and / or a coating layer is created on the surface of the glass substrate. The brittle layer is formed by irradiating a gas cluster ion on the surface to deteriorate the glass. The coating layer is formed by coating the surface with a soft substance. Next, a thickness of the created buffer layer is measured by a positron annihilation gamma ray measurement. The surface of the glass substrate is then cleaned. To create a slurry, abrasive particles for the slurry are uniformly scattered on a polishing implement for polishing the glass substrate and a liquid component for the slurry is added thereto. The glass substrate is then chemically mechanically polished from the buffer layer with the slurry.

Provided are new methods for enhancing the selection of true (T) annihilation events relative to the inclusion of true scattered (TS) and random (R) annihilation events in PET tomographs and thereby improving the sensitivity and / or resolution of PET scanners. The methods include reconstruction of Compton scattering interactions in the γ-ray detectors for determining the angles of incidence of the γ-rays received at the detectors and may utilize γ-ray polarization effects and electron recoil data associated with positron annihilation and Compton scattering. The use of the γ-ray polarization effects provides an improved ability for selecting data corresponding to T events while simultaneously suppressing data corresponding to TS and R events during PET applications.

The invention discloses a positron annihilation lifetime spectrometer based on a silicon photomultiplier (SiPM), and the lifetime spectrometer comprises a SiPM detector module, an analog signal processing module, a timing and discrimination circuit module, a digital acquisition circuit module, a matching unit and a low voltage power supply module, wherein the SiPM detector receives gamma photons and generates scintillation light, which is converted into a photoelectric signal by the SiPM; the photoelectric signal is processed into a pulse signal through further amplification, noise reduction and the like by the analog signal processing module; the pulse signal is timed and discriminated by the timing and discrimination circuit module to obtain position information, energy information and time information of the gamma photons; the information is acquired by the digital acquisition circuit module and filtered by the matching unit to a meeting event; and all the modules are powered by thelow voltage power supply module. The positron annihilation lifetime spectrometer can improve measurement accuracy, reduce measurement time, greatly reduce cost, reduce power supply requirements and simplify the spectrometer structure.

A composite semipermeable membrane, which comprises a separating functional layer comprising polyamide formed on a porous substrate film, wherein the separating functional layer comprising polyamide has a mean pore radius of 0.25 nm to 0.35 nm and a vacancy content of 0.2 nm3% to 0.3 nm3%, measured by positron annihilation lifetime spectroscopy.

A structure for detection of radiation emitted by positron annihilation comprising a thin wall tube the inner surface of which is covered with an electrically conductive coating which is encompassed and enclosed by a spaced apart thin layer of lead, bismuth or an alloy thereof, an electrically conductive wire element coaxially positioned within said tube and an electrically insulative and pressure retaining element closing each tube end to contain there within from 0.1 to 10 bar of a gaseous atmosphere comprising argon together with a quench gas component or another suitable counting gas; and a PET imaging camera having closely packed arrays of a plurality of such tube structures.

An improved gamma ray detector and method for discriminating between “true” pairs of gamma rays produced by a single positron annihilation event and those randomly occurring “pairs” of gamma rays that may fall within the conventional acceptance criteria for “true” pairs. The gamma ray detector incorporates an additional array of “veto” detectors arranged adjacent or around a primary detector array. The array of “veto” detectors is configured to detect gamma rays that escape detection in the primary detector array. The detection data from both the primary detector array and the veto detector array are used as inputs into a discrimination circuit for “vetoing” those pairs of gamma rays detected by the primary detector array that are likely to be the result of two or more unrelated positron annihilation events. By increasing the proportion of “true” events used in image reconstruction, the apparatus and method may improve the quality of the resulting image, reduce the image processing time and / or reduce the need for subsequent data collection and / or manipulation.

This invention relates to one positron annihilation life spectrum detector, which comprises initial detector and terminal detector and is different to the regular detector by adopting the different terminal channel detector to the initial channel and locating one round well in the center of the flash of the terminal detector and putting specimen and 22Na positron emission power.

A positron annihilation characteristics measurement system 10 comprises a positron source; radiation detection means 14 for detecting radiation emitted when a positron generated by the positron source is annihilated; and a positron detector 40 that detects a positron that is not injected into a measured sample S after being generated by the positron source. The positron source is disposed between the measured sample S and the positron detector. An arithmetic device 50 calculates the annihilation characteristics of the positron in the measured sample S after eliminating the radiation that is detected by the radiation detection means 14 and is expected to be emitted when the positron detected by the positron detector 40 is annihilated.

A simplified digital corresponding Doppler broadening spectrum machine is used for setting a digital Doppler broadening spectrum analysis drawing system in a computer. A high-pressure power source outputs high pressure of a high-purity germanium photoelectric detector. The high-purity germanium photoelectric detector receives positron annihilation radiation gamma photons and is used for converting optical energy into electric energy, outputting pulses which are in direct proportion to gamma light energy and then outputting the pulses to a digital acquisition card. The digital collection card is used for sampling the pulses, converting the pulses into digital signals and inputting the digital signals to the computer. After the pulses are analyzed and processed through a digital corresponding Doppler broadening spectrum analysis drawing system, corresponding Doppler broadening spectrum is drawn. The simplified digital corresponding Doppler broadening spectrum machine is little in parts, convenient to transport and very easy to assemble and use. Compared with a traditional corresponding Doppler broadening spectrum, the simplified digital Doppler corresponding broadening spectrum machine has better energy resolution and a counting rate and has lower total price, and therefore the simplified digital corresponding Doppler broadening spectrum machine has higher cost performance.

An optical fiber which reduces transmission loss increase even in a high humidity environment or under water is provided. To solve the above issue, an optical fiber according to the present invention comprises a glass optical fiber coated with at least two coating layers, soft and hard layers. The optical fiber is further coated by a colored resin to make a colored optical fiber. The hard layer and the color layer of the colored optical fiber have a free volume radius of at least 0.290 nm according to positron annihilation lifetime spectroscopy.

A side amino polysiloxane-modified polyurethane coating agent is disclosed. Side aminopolysiloxane (SAPDMS), polytetrahydrofuran glycol and polyethylene glycol as mixed soft segments, dimethylol propionic acid as a hydrophilic chain extender, and 1,4-butanediol as a hard segment regulator are reacted with isophorone diisocyanate to synthesize a waterborne silicone modified polyurethane (WSSPU), and the waterproof and moisture-permeable fabric coating agent is prepared based on the WSSPU. The composition and microstructure of a WSSPU film can be characterized by an infrared spectroscopy, a differential scanning calorimeter, a dynamic mechanical analyzer, a positron annihilation lifetime spectroscopy, and the like. The mechanical properties of the WSSPU film and the waterproof and moisture-permeable properties of a coated fabric are investigated. Results show that a stable emulsion can be obtained when the dosage of the side aminopolysiloxane (mass ratio) is less than 15%. After polysiloxane modification, the internal micro-phase separation structure of the film is more obvious, the free volume cavity becomes larger, and the moisture-permeable properties are improved.

The invention relates to a method for positron annihilation lifetime spectrum measurement, a system for positron annihilation lifetime spectrum measurement, and a scintillation detector. The method for positron annihilation lifetime spectrum measurement includes the following steps that: a time point when a positron pulse bunch arrives at a sample to be measured is recorded as a first time point; a plurality of gamma photon signals generated by the annihilation of the positron pulse bunch in the sample to be measured are distinguished according to positions, and the plurality of gamma photon signals are collected, time points when the plurality of gamma photon signals are collected are recoded as a plurality of second time points; the plurality of second time points are processed, so that a plurality of first time differences can be obtained; and the plurality of first time differences are put into statistics, so that a positron annihilation lifetime spectrum can be obtained. With the method of the invention adopted, the time distribution of gamma photons generated by the annihilation of a plurality of positrons can be measured simultaneously, and therefore, measurement efficiency can be improved.