118 results about "Positron annihilation" patented technology

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.

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.

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.

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.

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.

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 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.

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.