# US 8,585,286 B2 · Spectral detector calibration > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,585,286 B2 - Document ID: US8585286B2 - Status: Granted - Kind: B2 - Application number: 12/934,661 - Filed: 2009-03-20 - Published: 2011-01-20 - Granted: 2013-11-19 - Earliest claimed: 2008-04-01 - Assignees: Koninklijke Philips N.V. - Applicants: Amir Livne; Naor Wainer; Jens-Peter Schlomka; Ewald Roessl; Roland Proksa - Inventors: Amir Livne; Naor Wainer; Jens-Peter Schlomka; Ewald Roessl; Roland Proksa - Web page: https://patentgrep.com/patent/US8585286B2 ## CPC - G01T 7/005: {calibration techniques (stabilization of spectrometer G01T1/40)} - A61B 6/032: {Transmission computed tomography [CT]} - A61B 6/4042: {K-edge filters} - A61B 6/482: {involving multiple energy imaging} - A61B 6/585: {Calibration of detector units} - G01T 1/1647: {Processing of scintigraphic data (not related to a particular imaging system G01T1/2992)} - A61B 6/4035: {the source being combined with a filter or grating} - A61B 6/4441: {the rigid structure being a C-arm or U-arm} - G01N 2223/3037: standards (constitution) - 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) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract A method includes detecting radiation that traverses a material having a known spectral characteristic with a radiation sensitive detector pixel that outputs a signal indicative of the detected radiation and determining a mapping between the output signal and the spectral characteristic. The method further includes determining an energy of a photon detected by the radiation sensitive detector pixel based on a corresponding output of the radiation sensitive detector pixel and the mapping. ## Claims ### Claim 1 A method, comprising: detecting generated radiation that traverses a material having a known spectral attenuation or fluorescence characteristic with a radiation sensitive detector pixel that outputs a signal indicative of the detected radiation, wherein the radiation is generated by an imaging system, the material is located in a filter tray of the imaging system, and the filter tray is movable to selectively move the material into and out of the generated radiation; counting a number of times a peak amplitude of the output signal exceeds each of a plurality of different thresholds corresponding to an output range of the detector pixel; and determining a mapping between the output signal of the pixel and the known spectral characteristic, wherein the mapping is based on a distribution of the counts over the output range. ### Claim 2 (depends on 1) The method of claim 1, further including determining an energy of a photon detected by the radiation sensitive detector pixel based on a corresponding output of the radiation sensitive detector pixel and the mapping. ### Claim 3 (depends on 1) The method of claim 1, further including locating the spectral characteristic in the distribution based on an accumulation of the counts over the output range. ### Claim 4 (depends on 1) The method of claim 1, further including differentiating the distribution one or more times to identify a peak in the differentiated distribution that corresponds to the spectral characteristic. ### Claim 5 (depends on 1) The method of claim 1, further including: comparing a peak amplitude of the output signal with a plurality of different thresholds that represent an output range of the detector pixel; counting a number of times the peak amplitude exceeds each of the thresholds; and mapping the output signal of the pixel and the known spectral characteristic based on a distribution of an accumulation of the counts over the output range. ### Claim 6 (depends on 1) The method of claim 1, wherein the signal is indicative of an energy of a detected photon. ### Claim 7 (depends on 1) The method of claim 1, wherein the spectral characteristic is a k-absorption edge of the material. ### Claim 8 (depends on 1) The method of claim 1, wherein the material includes one of silver, tin, gadolinium, antimony, iodine, barium, lutetium, gold, lead, bismuth, or uranium. ### Claim 9 An imaging system, comprising: a radiation source that emits radiation that traverses an examination region; a tray located near the radiation source, wherein the tray includes a material with known spectral characteristics, and the tray is movable to selectively position the material in a path of the emitted radiation; a spectral detector that detects radiation that traverses the material and the examination region; a calibration component that calibrates the spectral detector based on the detected radiation; a count accumulator that accumulates counts representing a number of times a peak value of the output signal exceeds each of a plurality of different threshold values; and a mapper that maps a peak value of the accumulated counts to a k-edge energy of the material, wherein the calibration component generates a calibration for the spectral detector based on the mapping. ### Claim 10 (depends on 9) The imaging system of claim 9, wherein the material has a known k-edge, and the detector outputs a signal indicative of the energy of detected radiation, and wherein the calibration component generates a calibration based on the k-edge of the material and the output value of the spectral detector. ### Claim 11 (depends on 9) The imaging system of claim 9, wherein the calibration component further includes: a peak enhancer that enhances the peak value of the accumulated counts prior to the mapping. ### Claim 12 (depends on 11) The imaging system of claim 11, wherein the peak enhancer differentiates the accumulated counts to enhance the peak value of the accumulated counts. ### Claim 13 (depends on 9) The imaging system of claim 9, further including: an energy discriminator that energy discriminates the output signal based the thresholds; and a counter that counts a number of times the peak value of the output signal exceeds a threshold, for each of the thresholds. ### Claim 14 A method for calibrating a detector array of an imaging system, comprising: detecting fluorescence radiation having a known spectral characteristic with a radiation sensitive detector pixel of the detector array, which outputs a signal indicative of an energy of the detected fluorescence radiation; determining a mapping between the output signal and the known spectral characteristic; wherein the mapping is based on a distribution of counts over an output range of a detector pixel detecting the radiation; and determining a calibration for the detector array of the imaging system based on the mapping. ### Claim 15 (depends on 14) The method of claim 14, further including: generating the fluorescence radiation by irradiating a material having the known spectral characteristic with x-radiation, wherein the material emits the fluorescence radiation. ### Claim 16 (depends on 15) The method of claim 15, further including: employing the calibration to set at least one energy threshold of a photon energy-discriminator of the system. ### Claim 17 (depends on 14) The method of claim 14, further including: determining a feature of the output signal, wherein the feature is indicative of the energy of the detected fluorescence radiation; and mapping the feature to the known spectral characteristic. ### Claim 18 (depends on 17) The method of claim 17, wherein the feature includes at least one of a peak amplitude of an emission distribution of the detected fluorescence radiation, an amplitude increase in the distribution greater than a first threshold, or an amplitude decrease in the distribution greater than a second threshold. ### Claim 19 (depends on 14) The method of claim 14, further including generating the fluorescence radiation by alternatively illuminating at least one high energy emitter with radiation produced by an x-ray tube of the imaging system and at least one low energy emitter with radiation produced by an x-ray tube of the imaging system. ### Claim 20 (depends on 19) The method of claim 19, further including: generating a calibration curve based on a first mapping using a first output signal of the detector array corresponding to the at least one low energy emitter and on a second mapping using a second output signal of the detector array corresponding to the at least one high energy emitter. ### Claim 21 An imaging system, comprising: a radiation source that emits first radiation that traverses an examination region; a detector array that detects the first radiation and generates a signal indicative thereof; a detector calibration apparatus; including: a radiation block that blocks the first radiation from illuminating the detector array; and at least one target that receives the first radiation and generates second radiation that includes a known spectral characteristic and that illuminates the detector array; and a calibration component that generates a calibration for the detector array based on an identified known spectral characteristic of the second radiation and a pre-determined spectral characteristic of the target. ### Claim 22 (depends on 21) The system of claim 21, further including: a feature identifier that identifies the known spectral characteristic in the second radiation. ### Claim 23 (depends on 21) The system of claim 21, wherein the calibration correlates the identified spectral characteristic and the pre-determined spectral characteristic. ### Claim 24 (depends on 21) The system of claim 21, wherein the identified spectral characteristic includes at least one of a peak amplitude of an emission distribution corresponding to the second radiation, an amplitude increase in the distribution greater than a first threshold, or an amplitude decrease in the distribution greater than a second threshold. ### Claim 25 (depends on 21) The system of claim 21, wherein the radiation block is selectively moveable between a first position at which it blocks the transmission radiation and at least a second position at which it does not block the transmission radiation. ### Claim 26 (depends on 21) The system of claim 21, wherein the target includes at least two materials, each having a different spectral characteristic. ### Claim 27 (depends on 26) The system of claim 26, wherein the at least two materials are alternately positioned in a path of the first radiation, and a first spectral characteristic is identified for one of the at least two materials and a second spectral characteristic is identified for another of the at least two materials, and the calibration component generates the calibration based on the first and second spectral characteristics. ### Claim 28 A system, comprising: a detector calibration apparatus; including: a radiation block that blocks first radiation from illuminating a detector array, wherein the first radiation is emitted by a radiation source and traverses an examination region and the detector array detects the first radiation and generates a signal indicative thereof; and at least one target that receives the first radiation and generates second radiation that includes a known spectral characteristic and that illuminates the detector array; and a calibration component that generates a calibration for the detector array based on an identified known spectral characteristic of the second radiation and a pre-determined spectral characteristic of the target. ### Claim 29 (depends on 28) The apparatus of claim 28, wherein the radiation block and/or the target is removably mounted to the system when calibrating the detector array and removed from the system when scanning an object or subject. ### Claim 30 (depends on 28) The apparatus of claim 28, wherein the target includes at least two materials that emit radiation having a different known spectral characteristics.