# US 9,435,901 B2 · Systems and methods for improving the quality of images in a PET scan > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,435,901 B2 - Document ID: US9435901B2 - Status: Granted - Kind: B2 - Application number: 14/319,740 - Filed: 2014-06-30 - Published: 2014-12-25 - Granted: 2016-09-06 - Earliest claimed: 2014-06-30 - Assignees: University of Manitoba - Applicants: University of Manitoba - Inventors: Stephen Pistorius; Hongyan Sun - Web page: https://patentgrep.com/patent/US9435901B2 ## CPC - G01T 1/2985: {In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis); (using external radiation sources A61B6/02)} - A61B 6/037: {Emission tomography} - G01T 1/1647: {Processing of scintigraphic data (not related to a particular imaging system G01T1/2992)} - G06T 12/10: Image preprocessing, e.g. calibration, positioning of sources or scatter correction - G01T: MEASUREMENT OF NUCLEAR OR X-RADIATION (radiation analysis of materials, mass spectrometry G01N23/00; tubes for determining the presence, intensity, density or energy of radiation or particles H01J47/00) - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL ## Abstract Systems, devices and methods of reconstructing an image from a positron emission tomography scan that may include detecting a plurality of photons selected from scattered photons and unscattered photons by a plurality of detectors, identifying a time interval for each of the plurality of photons by a processing device, matching each of the plurality of photons into a plurality of pairs of coincident photons based upon a substantially simultaneous time interval identified by the processing device, measuring an energy produced by each of the plurality of photons by the plurality of detectors, determining a scattering angle for each pair of coincident photons from an annihilation point relative to the position of the plurality of detectors by the processing device based on the energy produced and reconstructing an image using a reconstruction algorithm, wherein the reconstruction algorithm uses the scattering angle of each pair of coincident photons. ## Claims ### Claim 1 A method of reconstructing an image from a positron emission tomography scan, comprising: detecting a pair of photons by a plurality of detectors, wherein the pair of photons comprises a first photon and a second photon; measuring, by the plurality of detectors, an energy produced by each of the pair of photons; calculating, by a processing device, a first arc and a second arc between detector locations based on the energy produced by each of the pair of photons; determining, by the processing device, a first annihilation area bounded at least in part by the first arc and the second arc, wherein the first annihilation area indicates a plurality of possible locations of an annihilation point from which the pair of photons originated; and reconstructing, by the processing device, an image using a reconstruction algorithm, wherein the reconstruction algorithm uses information regarding the first annihilation area. ### Claim 2 (depends on 1) The method of claim 1, wherein the calculating further comprises: calculating the first arc based on the energy produced by the first photon of the pair of photons; and calculating the second arc based on the energy produced by the second photon of the pair of photons. ### Claim 3 (depends on 1) The method of claim 1, further comprising: identifying a plurality of possible locations of the annihilation point within the first annihilation area. ### Claim 4 (depends on 3) The method of claim 3, further comprising: using the reconstruction algorithm to identify a second plurality of possible locations of the annihilation point; matching the plurality of possible locations of the annihilation point within the first annihilation area with the second plurality of possible locations of the annihilation point identified from the reconstruction algorithm; and from the matching, determining an actual location of the annihilation point. ### Claim 5 (depends on 3) The method of claim 3, wherein the identifying a plurality of possible locations of the annihilation point within the first annihilation area decreases a sensitivity of the positron emission tomography scan to the scattered photons. ### Claim 6 (depends on 1) The method of claim 1, further comprising: identifying a second annihilation area bounded by a subject outline; and identifying the plurality of possible locations of the annihilation point within both the first annihilation area and the second annihilation area bounded by the subject outline. ### Claim 7 (depends on 1) The method of claim 1, wherein the measuring further comprises: constructing an outline of a subject; constructing one or more lines from a point of detection of an unscattered photon of the pair of photons to each intersection of the outline of the subject with the first arc or the second arc; identifying a second annihilation area bounded by three or more of the following: the one or more lines, the outline of the subject, and one of the first arc or the second arc; and identifying the plurality of possible locations of the annihilation point within the second annihilation area. ### Claim 8 (depends on 1) The method of claim 1, wherein the reconstruction algorithm comprises a Maximum-Likelihood Expectation-Maximum algorithm. ### Claim 9 (depends on 1) The method of claim 1, wherein the reconstruction algorithm comprises an ordered subset expectation maximization algorithm. ### Claim 10 (depends on 1) The method of claim 1, wherein the reconstruction algorithm comprises a maximum a posteriori expectation maximization algorithm. ### Claim 11 (depends on 1) The method of claim 1, wherein the reconstruction algorithm comprises a filtered back projection algorithm. ### Claim 12 (depends on 1) The method of claim 1, wherein the reconstruction algorithm comprises a conjugate gradient algorithm. ### Claim 13 (depends on 1) The method of claim 1, wherein the reconstruction algorithm comprises a coincidence-list-ordered sets expectation-maximization algorithm. ### Claim 14 (depends on 1) The method of claim 1, further comprising: based on the energy produced, determining a scattering angle for the pair of photons from the annihilation point relative to the position of the plurality of detectors; and determining the first arc and the second arc based on the scattering angle, and wherein the first arc and the second arc are circular arcs. ### Claim 15 (depends on 1) The method of claim 1, wherein the detector locations comprises a first detector location at which the first photon of the pair of photons was detected and a second detector location at which the second photon of the pair of photons was detected. ### Claim 16 A system for use in reconstructing an image from a positron emission tomography scan, wherein the system comprises: a processing device; and a non-transitory computer-readable storage medium in communication with the processing device, wherein the computer-readable storage medium contains one or more programming instructions that, when executed, cause the processing device to: measure an energy produced by a first photon and a second photon of a pair of photons; calculate a first arc and a second arc between detector locations based on the energy produced by each of the pair of photons; determine a first annihilation area bounded at least in part by the first arc and the second arc, wherein the first annihilation area indicates a plurality of possible locations of an annihilation point from which the pair of photons originated; and reconstruct an image using a reconstruction algorithm, wherein the reconstruction algorithm uses information regarding the first annihilation area. ### Claim 17 (depends on 16) The system of claim 16, wherein the computer-readable storage medium contains one or more programming instructions that, when executed, further causes the processing device to: calculate a first arc based on the energy produced by the first photon of the pair of photons; calculate a second arc based on the energy produced by the second photon of the pair of photons; identify a plurality of possible locations of the annihilation point within the first annihilation area. ### Claim 18 (depends on 17) The system of claim 17, further comprising a plurality of detectors configured to detect photons, wherein the plurality of detectors further comprises a plurality of energy sensitive detectors. ### Claim 19 (depends on 18) The system of claim 18, wherein the computer-readable storage medium contains one or more programming instructions that, when executed, further causes the processing device to: direct the plurality of energy sensitive detectors to measure the energy produced by a plurality of scattered photons from an annihilation event. ### Claim 20 (depends on 17) The system of claim 17, wherein the computer-readable storage medium contains one or more programming instructions that, when executed, further causes the processing device to: use the reconstruction algorithm to identify a second plurality of possible locations of the annihilation point; match the plurality of possible locations of the annihilation point within the first annihilation area with the second plurality of possible locations of the annihilation point identified from the reconstruction algorithm; and from the matching, determine an actual location of the annihilation point. ### Claim 21 (depends on 16) The system of claim 16, wherein the computer-readable storage medium contains one or more programming instructions that, when executed, further causes the processing device to: identify a second annihilation area bounded by a subject outline; and identify a second plurality of possible locations of the annihilation point within the second annihilation area. ### Claim 22 (depends on 16) The system of claim 16, wherein the computer-readable storage medium contains one or more programming instructions that, when executed, further causes the processing device to: construct an outline of a subject; construct one or more lines from a point of detection of an unscattered photon of the pair of photons to each intersection of the outline of the subject with the first arc or the second arc; identify a second annihilation area bounded by the first arc, the second arc, and at least one of the one or more lines and the outline of the subject; and identify the plurality of possible locations of the annihilation point within the second annihilation area. ### Claim 23 (depends on 16) The system of claim 16, wherein the identifying a plurality of possible locations of the annihilation point within the first annihilation area decreases a sensitivity of the positron emission tomography scan to the scattered photons. ### Claim 24 (depends on 16) The system of claim 16, wherein the reconstruction algorithm comprises a Maximum-Likelihood Expectation-Maximum algorithm. ### Claim 25 (depends on 16) The system of claim 16, wherein the reconstruction algorithm comprises an ordered subset expectation maximization algorithm. ### Claim 26 (depends on 16) The system of claim 16, wherein the reconstruction algorithm comprises a maximum a posteriori expectation maximization algorithm. ### Claim 27 (depends on 16) The system of claim 16, wherein the reconstruction algorithm comprises a filtered back projection algorithm. ### Claim 28 (depends on 16) The system of claim 16, wherein the reconstruction algorithm comprises a conjugate gradient algorithm. ### Claim 29 (depends on 16) The system of claim 16, wherein the reconstruction algorithm comprises a coincidence-list-ordered sets expectation-maximization algorithm.