Beckman Instruments, Inc.

Donald L Horrocks

Richard S Kampf

Clement P Aime

Samuel H Luitwieler

Paul R Klein

A method and apparatus for indicating quench associated with a liquid scintillation solution wherein the solution includes a sample, a solvent and a solute. The method includes exposing the solution to flashes of light, detecting a pulse height spectrum for scintillations produced in the solution in response to the light flashes, determining a unique point on such pulse height spectrum, and relating the unique point to a corresponding pulse height value, such pulse height value providing an indication of quench associated with the solution. The wavelength of light preferably excites essentially only the solvent and the light flash intensity and duration is such that the pulse height spectrum produced in response to the light flashes does not overlap a pulse height spectrum for the sample in the solution. An attribute of the shape of the light pulse height spectrum may be examined to provide an indication of the homogeneous or non-homogeneous nature of the quench present in the solution.

Method and apparatus for indicating quench of a liquid scintillation

In a liquid scintillation counter, a standard radioactive source is supported in a bead position of a bead chain, flexible conveyor. The conveyor is guided for movement along a closed-loop conveyor path in sliding engagement within a conduit guideway for conveying the source between an operating position adjacent the counting chamber and a remote shielded position. The conveyor may support one or more sources for conveyance to one or more counting chambers along the conveyor path.

Apparatus for positioning an external radioactive standard in a liquid

A method for use with liquid scintillation flow systems including flowing a mixture comprising a sample and a liquid scintillation medium through a flow detector, the liquid scintillation medium including a radionuclide marker having an energy distribution different from the sample. A pulse height distribution spectrum is determined and a unique point on the portion of the pulse height distribution spectrum representing the energy spectrum of the medium is found, a pulse height value related to such unique point providing a value related to the degree of quench present in the mixture. By comparing such pulse height value to a pulse height value obtained in a like manner for a calibration standard, a degree of quench present in the mixture is indicated. Furthermore, the counts detected for the liquid scintillation medium during a measurement period may be related to the specific activity of the liquid scintillation medium to determine the volume of liquid scintillation medium flowing during the measurement period. The volume of sample flowing during such period may also be determined by relating the liquid scintillation medium volume to a ratio of sample to liquid scintillation medium flowing through the flow detector. Sample count rate is corrected for quench and sample specific activity is determined.

Quench, volume and activity determinations in a liquid scintillation

A method and related apparatus for the determination of a random coincidence count attributable to chance coincidences of single-photon events which are each detected in only a single detector of a scintillation counter utilizing two detectors in a coincidence counting technique. Real and apparent coincidences of pulses are accumulated in a first counting device (28), and all pulses from the detectors (12) are accumulated in a second counting device (38), without regard for coincidence in time. The two counting devices are monitored during at least one random coincidence monitoring time occurring simultaneously with part of a sample counting period. The length and frequency of occurrence of the random coincidence monitoring times can be selected for particular counting measurement applications.

Method and apparatus for determining random coincidence count rate in a

A method of quench correction in liquid scintillation counting which compensates for the effect of sample quench. A quench corrected pulse height window is established for measuring sample scintillations. A pulse height threshold is established distinguishing regions for which a measure of sample quench, derived conventionally, is either proportional to or not proportional to the actual effect of quench on the sample pulse height spectrum. The quench corrected window is compared with the pulse height threshold, and the relative position of the corrected window is adjusted if the comparison step indicates that the window lies in the region of nonproportionality.

Quench correction in liquid scintillation counting

Method for testing a liquid scintillation sample to determine whether it is separated into different phases. Scintillations emitted by the sample in response to radiation from an external radiation source are analyzed. If the distribution of the intensities of the scintillations has a characteristic indicating it is the superposition of the intensity distributions of scintillations emitted by two or more distinct phases, then the sample is adjudged to be separated into different phases.

Detecting phase separation in liquid scintillation samples

A method and related apparatus for the reliable determination of a random coincidence count attributable to chance coincidences of single-photon events which are each detected in only a single detector of a scintillation counter utilizing two detectors in a coincidence counting technique. A first delay device is employed to delay output pulses from one detector, and then the delayed signal is compared with the undelayed signal from the other detector in a coincidence circuit, to obtain an approximate random coincidence count. The output of the coincidence circuit is then applied to an anti-coincidence circuit, where it is corrected by elimination of pulses coincident with, and attributable to, conventionally detected real coincidences, and by elimination of pulses coincident with, and attributable to, real coincidences that have been delayed by a second delay device having the same time parameter as the first.

An automatic spectrum scanning technique for use in a proportional counting instrument, such as a gamma counter or liquid scintillation counter, by means of which a pulse-height or energy spectrum of a sample can be obtained automatically and without multichannel instrumentation. A pulse-height analyzer in the counting instrument has its upper and lower discriminator limits set to define a relatively narrow counting window, and the limits are successively changed to scan the window across the energy spectrum and thereby obtain an accurate measurement thereof. Counting at each increment of the scan is continued for a preselected maximum time interval, but is quickly terminated if the count rate falls below a preselected low threshold value, and is terminated early if the count rate is relatively high, i.e., if the statistical error value associated with the count is relatively low. A technique is also disclosed for correcting the counting statistics when the sample being analyzed has a relatively short half-life and the radioactivity of the sample falls off at a relatively rapid rate.

Method and apparatus for automatic spectrum scanning in a proportional

Method and apparatus for measuring the degree of quench in a liquid scintillation sample by irradiating the sample with a standard source, such as a cesium-137 gamma source, to produce a Compton scattered electron distribution exhibiting a Compton edge configuration as the leading edge thereof. For increasing the quench levels in the sample, the Compton edge shifts to lower pulse height values and the extent of this shift is indicative of the degree of quench. To measure the degree of quench, a unique point on the Compton edge, namely the point at which the second derivative of the edge is zero (i.e. the inflection point), is measured for the quenched sample and the pulse height value corresponding to the inflection point is determined. The pulse height value is compared with the pulse height value determined for a calibration standard in a similar manner, the difference in pulse height values indicating the degree of quench.

Quench determination in liquid scintillation counting systems

A method for the reliable determination of a random coincidence count attributable to chance coincidences of single-photon events which are each detected in only a single detector of a scintillation counter utilizing two detectors in a coincidence counting technique. The method includes the steps of measuring a coincidence count rate as indicated by essentially coincident output pulses from the detectors, measuring a single photon count rate as indicated by output pulses from both of the detectors, whether coincident or not, and determining a random coincidence count rate from the difference between the single photon count rate and the measured coincidence count rate. From the random coincidence count rate thus determined, a percentage error value can be determined, for application, if desired, to subsequently or concurrently measured sample radiation counts.

Method for determining random coincidence count rate in a scintillation

A method and apparatus for the calibration of a gamma radiation measurement instrument to be used over any of a number of different absolute energy ranges. The method includes the steps of adjusting the overall signal gain associated with pulses which are derived from detected gamma rays, until the instrument is calibrated for a particular absolute energy range; then storing parameter settings corresponding to the adjusted overall signal gain, and repeating the process for other desired absolute energy ranges. The stored settings can be subsequently retrieved and reapplied so that test measurements can be made using a selected one of the absolute energy ranges. Means are provided for adjusting the overall signal gain by varying the voltage supplied to a multiplier phototube included in the instrument, or by varying the gain of attenuators coupled to the output of the phototube. A specific technique is disclosed for making coarse, then fine adjustments to the signal gain, for rapid convergence on the required calibration settings.

Gamma counter calibration system

A method of measuring the disintegration rate of a beta-emitting radionuclide in a liquid sample by counting at least two differently quenched versions of the sample. In each counting operation the sample is counted in the presence of and in the absence of a standard radioactive source. A pulse height (PH) corresponding to a unique point on the pulse height spectrum generated in the presence of the standard is determined. A zero threshold sample count rate (CPM) is derived by counting the sample once in a counting window having a zero threshold lower limit. Normalized values of the measured pulse heights (PH) are developed and correlated with the corresponding pulse counts (CPM) to determine the pulse count for a normalized pulse height value of zero and hence the sample disintegration rate.

Method of measuring the disintegration rate of beta-emitting

A radioactivity measuring instrument, and a method related to its use, for determining the radioactivity of a sample measured in the presence of significant background radiation, and for determining an error value relating to a specific probability of accuracy of the result. Error values relating to the measurement of background radiation alone, and to the measurement of sample radiation and background radiation together, are combined to produce a true error value relating to the sample radiation alone.

Method and apparatus for determining accuracy of radiation measurements

A method for determining the source strength of a radioactive sample such as iodine-125 or cobalt-60, which emit pairs of quanta of radiation in coincidence, or near coincidence, and for determining the counting efficiency of a detection instrument analyzing such samples. A first counting channel is used to count events attributable to single quanta, a second counting channel is used to count events attributable to coincident pairs of quanta, and the sample source strength is computed from the results of measurement in these two counting channels. Then, the counting efficiency in a third channel designed for subsequent use in analyzing test samples may be determined from the counting of events in the third channel.

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Placentia, CA, United States of America

Donald L Horrocks