# US 11,029,418 B2 · Micro-dose calibrator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,029,418 B2 - Document ID: US11029418B2 - Status: Granted - Kind: B2 - Application number: 16/644,441 - Filed: 2018-09-04 - Published: 2020-07-23 - Granted: 2021-06-08 - Earliest claimed: 2017-09-06 - Assignees: The United States of America, as represented by the Secretary, Department of Health and Human Services - Applicants: THE UNITED STATES OF AMERICA, as represented by THE SECRETARY, DEPARTMENT OF HEALTH AND HUMAN SERVICES - Inventors: Stephen S. Adler - Web page: https://patentgrep.com/patent/US11029418B2 ## CPC - G01T 1/167: Measuring radioactive content of objects, e.g. contamination (whole body counters G01T1/163) - G01T 1/2006: {using a combination of a scintillator and photodetector which measures the means radiation intensity} - G01T 1/202: the detector being a crystal - G01T 1/2023: {Selection of materials} - G01T 1/40: Stabilisation of spectrometers - G01T 7/005: {calibration techniques (stabilization of spectrometer G01T1/40)} - 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) ## Abstract Methods and apparatus for calibrating radioactive sources are described. An array of scintillation detectors forms a receptacle within which a sample or sample container can be retained by a holder. The scintillation detectors are coupled via light transducers such as photomultiplier tubes (PMTs) to independent electronic counters. Coincidence processing of time-tagged events yields a correlated event rate. One or more corrections can be applied as needed, for background counts, deadtime, or random coincidences. Voltage tuning of PMTs yields improved reproducibility. Accuracy of 1% has been demonstrated over a range of 10 kBq-3 MBq. ## Claims ### Claim 1 An apparatus for calibration of a radioactive micro-dose sample, the apparatus comprising: a receptacle containing a sample chamber and configured to retain the radioactive micro-dose sample; an array of at least three scintillation detectors disposed around the sample chamber; an array of light transducers, each light transducer optically coupled to a respective one of the scintillation detectors; and a plurality of electronic counters comprising an electronic counter for each respective scintillation detector; wherein each light transducer is electrically coupled to a respective one of the electronic counters for independently counting radioactive decay events of the micro-dose sample detected by the respective scintillation detector. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein each of the electronic counters is configured to time-tag digital packets of the radioactive decay events of the micro-dose sample corresponding to particles detected by the respective scintillation detector. ### Claim 3 (depends on 1) The apparatus of claim 1, further comprising one or more hardware processors configured to: receive time-tagged events from the electronic counters; compare time stamps of the time-tagged events; detect multiple events of the time-tagged events as a coincidence for a case where the time stamps of the multiple events are within a coincidence window; determine a correlated event rate by counting the time-tagged events from the electronic counters with the multiple events collectively counted as one event; and determine a calibrated micro-dose strength of the radioactive micro-dose sample by application of one or more calibrations or corrections to the correlated event rate. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein the multiple events are three or more events. ### Claim 5 (depends on 3) The apparatus of claim 3, wherein the determining the correlated event rate comprises determining an intermediate rate for each of the scintillation detectors, the intermediate rate being a rate of events detected by the each scintillation detector that are not in coincidence with any of the events detected by any other of the scintillation detectors. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the array of scintillation detectors is arranged as a ring of 4 to 100 contiguous scintillation detectors having shapes that conform to adjacent scintillation detectors. ### Claim 7 (depends on 6) The apparatus of claim 6, wherein gaps between neighboring detectors of the ring of contiguous scintillation detectors have a maximum width in a range 0.001-5 mm. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the scintillation detectors are contiguously disposed over at least a hemisphere about a center of the sample chamber. ### Claim 9 (depends on 1) The apparatus of claim 1, further comprising an adjustable stage operable to position the micro-dose at a central location of the array of scintillation detectors. ### Claim 10 (depends on 1) The apparatus of claim 1, further comprising a holder configured to be reproducibly positioned within the sample chamber, and further configured to retain a sample container storing the radioactive micro-dose sample, wherein the sample container is a syringe, a vial, or a test tube. ### Claim 11 (depends on 1) The apparatus of claim 1, wherein the apparatus is operable to calibrate the radioactive micro-dose sample to 1% accuracy for radioactive micro-dose samples having any gamma or x-ray radioactivity in the range of 10 nanocuries to 10 microcuries. ### Claim 12 (depends on 1) The apparatus of claim 1, further comprising one or more synchronization cables connecting the electronic counters. ### Claim 13 (depends on 1) The apparatus of claim 1, wherein each electronic counter comprises: a signal input connected to a light transducer; a discriminator; a time-tagger; a packetizer; and an accumulator. ### Claim 14 (depends on 1) The apparatus of claim 1, further comprising a computer system having one or more processors, memory coupled thereto, and computer-readable media storing instructions which, when executed by the one or more processors, cause implementation of: an interactive user interface configured to receive input for commencing a calibration procedure on the radioactive micro-dose sample, and to present a calibrated micro-dose strength of the radioactive micro-dose sample subsequent to the calibration procedure. ### Claim 15 One or more computer-readable media storing instructions which, when executed by one or more hardware processors, cause the one or more hardware processors to perform operations comprising: synchronizing respective counting electronics for an array of at least three scintillation detectors; and time-tagging and counting digital packets of micro-dose decay events independently for each of the scintillation detectors. ### Claim 16 (depends on 15) The one or more computer-readable media of claim 15, wherein the operations further comprise: performing coincidence processing on the time-tagged events to determine a correlated event rate; and determining the radioactivity level of the micro-dose based on the correlated event rate. ### Claim 17 (depends on 16) The method of claim 16, wherein the determined radioactivity level is within a range of 10 nanocuries to 100 microcuries and has an error less than or equal to 1%. ### Claim 18 A method for calibrating a radioactive micro-dose, comprising: providing a ring of scintillation detectors coupled by photodetectors to respective counting electronics; tuning high-voltage power supplies coupled to the photodetectors so that photopeaks of particles emitted by a radioactive calibration source appear at aligned energy channels at the respective counting electronics; positioning a sample container containing a radioactive micro-dose at a central location of the ring of scintillation detectors; synchronizing the counting electronics; time-tagging decay events detected at the scintillation detectors, independently for each scintillation detector; detecting coincidences among the time-tagged decay events from two or more of the scintillation detectors; aggregating time-tagged decay events from the scintillation detectors, with coincidences being singly counted, to obtain a correlated event rate; determining a micro-dose radioactivity level by applying at least a basic calibration factor to the correlated event rate; and reporting the determined micro-dose radioactivity level. ### Claim 19 (depends on 18) The method of claim 18, wherein the correlated event rate is a first correlated event rate, and the method further comprises: determining second correlated event rates by measuring decay events detected by the ring of scintillation detectors during decay of a calibration source; performing a parameterized fit of the determined second correlated event rates as a function of strength of the calibration source to determine deadtime model parameters; and evaluating the deadtime model at the first correlated event rate to determine a deadtime correction; wherein the determining the micro-dose radioactivity level further comprises applying the deadtime correction. ### Claim 20 (depends on 19) The method of claim 19, wherein the parameterized fit is a segmented fit over a fixed first region associated with a first range of correlated event rates, a second region associated with a second range of correlated event rates, and a third region associated with a third range correlated event rates, wherein the third range is a transition range between the first range and the second range.