Method and apparatus for evaluating the degree of quenching in scintillation spectrometry

Claim 5

A method according to claim 1, wherein said sample has a plurality of radioactive isotopes, wherein said predetermined amplitude range is so selected as to include decay events of the most energetic of said radioisotopes only.

Claim 6

A method according to claim 1, of producing quantitative indications of the degree of quenching occuring in n samples each having one at least of two radioactive isotopes having different energy spectra, comprising the steps of : separately determining the decay event rate due to each of said samples in a first predetermined amplitude range including contribution by the more energetic of the two radioisotopes only and in a second predetermined amplitude range encompassing the major portion at least of the decay events due to the less energetic of the two radioisotopes, separately accumulating the amplitudes of the decay events counted in said first and second predetermined amplitude ranges, and dividing the result of the accumulation by the count rate for that of the energy spectra which provides the more accurate determination of the amplitude corresponding to the centroid.

Claim 7

In liquid scintillation spectrometry, a method of determination of the activity of a radioisotope or radioisotopes contained in test samples, comprising the steps of : determining in the case of a number N of reference samples having known amounts of activity the counting efficiency E of said radioisotope or radioisotopes and the value of a quench correlation parameter r, determining for each test sample the value of the correlation parameter r, deducing the value of the corresponding value of the efficiency E for said radioisotope or radioisotopes contained in the test sample under analysis, and correcting the net counting rate obtained for the test radioisotope by utilizing the value of E as thus determined, wherein the improvement consists in using as correlation parameter r the amplitude which corresponds to the centroid of a predetermined part at least of the amplitude of the light pulses delivered by said radioisotope or by the higher-energy of said radioisotope in said test samples.

Claim 8

In liquid scintillation spectrometry, a method of determination of the activity of a radioisotope or radioisotopes contained in test samples, comprising the steps of : determining in the case of a number N of reference samples having known amounts of activity the counting efficiency E of said radioisotope or radioisotopes and the value of a quench correlation parameter r, determining for each test sample the value of the correlation parameter r, deducing the value of the corresponding value of the efficiency E for said radioisotope or radioisotopes contained in the test sample under analysis, and correcting the net counting rate obtained for the test radioisotope by utilizing the value of E as thus determined, wherein the improvement consists in using as correlation parameter r the amplitude which corresponds to the centroid of a predetermined part at least of the amplitude of the light pulses delivered by said radioisotope or by the higher-energy of said radioisotope in said test samples.

Claim 9

A metHod according to claim 4, wherein one operating parameter of the spectrometer at least is adjusted in response to the value of r and the same sample is counted with the adjusted parameter for the activity with a precisely known value of the counting efficiency

Claim 10

A method according to claim 4, including the preliminary step of measuring and storing the values r1, r2, . . . rN and E1, E2, . . . EN of r and E, respectively, for a set of N reference sample each having a known activity of said radioisotope, wherein the value of E for each test sample is automatically computed after the value of r for said test sample has been determined by interpolating between n sets of stored values (n being a predetermined integer higher than 1 and lower than N) corresponding to stored values of r which are some of them larger than and the other smaller than the value of r for said test sample.

Claim 11

A method according to claim 6, wherein the sets of values r and E for the reference samples are analyzed immediately before the test samples are analyzed, said reference samples are arranged in a sequence corresponding to continuous increase or decrease of the degree of quenching and the value of r for each sample is compared to the successive stored values of r for selection of said n sets of values.

Claim 12

In a liquid scintillation spectrometer wherein an external source of penetrating radiation is adapted to be positioned in operative relation with a test sample containing a beta emitting radioisotope within a liquid scintillation medium, a method of determination of the degree of quenching in said sample, comprising determining the amplitude corresponding to the centroid of that part of the curve plotting the net count rate of pulses due to Compton interactions within the sample and delivered by a transducer system delivering pulses having amplitudes in direct relation with the energies of the scintillations in the sample, vs the amplitudes of said pulses in a predetermined amplitude range, and comparing said amplitude of the centroid with a calibration curve correlating said amplitude of the centroid and the degree of quenching for said radioisotope.

Claim 13

In a liquid scintillation spectrometer wherein an external source of penetrating radiation is adapted to be positioned in operative relation with a test sample containing a beta emitting radioisotope within a liquid scintillation medium, a method of determination of the degree of quenching in said sample, comprising determining the amplitude corresponding to the centroid of that part of the curve plotting the net count rate of pulses due to Compton interactions within the sample and delivered by a transducer system delivering pulses having amplitudes in direct relation with the energies of the scintillations in the sample, vs the amplitudes of said pulses in a predetermined amplitude range, and comparing said amplitude of the centroid with a calibration curve correlating said amplitude of the centroid and the degree of quenching for said radioisotope.

Claim 14

In a scintillation spectrometer, a device for determination of the degree of quenching comprising, in combination : detection means for producing output electrical pulses having heights in relation to the energies of the scintillations in a test sample, pulse height analyzing means receiving said pulses and transmitting those of said pulses which are in a predetermined energy channel, counting means for providing a count of said last-named pulses, means for summing the amplitudes of said last-named pulses, means for subtracting background contribution from the count and sum, and means for determining the ratio of the net sum to the net count, said ratio being indicative of the degree of quenching.

Claim 15

In a scintillation spectrometer, a device for determination of the degree of quenching comprising, in combination : detection means for producing output electrical pulses having heights in relation to the energies of the scintillations in a test sample, pulse height analyzing means receiving said pulses and transmitting those of said pulses which are in a predetermined energy channel, counting means for providing a count of said last-named pulses, means for summing the amplitudes of said last-named pulses, means for subtracting background contribution from the count and sum, and means for determining the ratio of the net sum to the net count, said ratio being indicative of the degree of quenching.

Claim 16

A scintillation spectrometer for analyzing test samples each having a transparent vial containing at least one beta emitting isotope in operative relation with a scintillator in a liquid medium, comprising means for bringing successively a plurality of samples to a counting station and a transducer assembly providing electric pulses whose height is in direct relation with the intensity of scintillations in the test sample which is placed at said station, wherein said device comprises means for determining the pulse height which corresponds to the centroid of the amplitude spectrum of the pulses within a predetermined pulse height window and due to one radioisotope in the liquid sample.

Claim 17

A scintillation spectrometer for analyzing test samples each having a transparent vial containing at least one beta emitting isotope in operative relation with a scintillator in a liquid medium, comprising means for bringing successively a plurality of samples to a counting station and a transducer assembly providing electric pulses whose height is in direct relation with the intensity of scintillations in the test sample which is placed at said station, wherein said device comprises means for determining the pulse height which corresponds to the centroid of the amplitude spectrum of the pulses within a predetermined pulse height window and due to one radioisotope in the liquid sample.

Claim 18

A spectrometer according to claim 10 for counting double-labelled test samples, wherein said device determines the centroid of that portion of the spectrum of the higher energy isotope which is located within an amplitude window in which the lower energy isotope provides no contribution to the counting.

Claim 19

A spectrOmeter according to claim 11, wherein said portion of the spectrum is the portion located within the window in which normal counting of the higher energy isotope is performed.

Claim 20

A spectrometer according to claim 10 for analyzing mixed samples some of which are labelled with two radioisotopes and others of which with only one of said two radioisotopes, wherein said means for determination of the amplitude of the centroid comprise two assemblies which take separate measurements of the data required for determination of the amplitude correspond to the centroids in two separate energy windows each corresponding to one of said two radioisotopes.

Claim 21

A spectrometer according to claim 13, wherein said device comprises means for automatic selection of the one of the two windows which affords the highest degree of accuracy for determination of the height of the centroid of the corresponding radioisotope.

Claim 22

A spectrometer according to claim 9, comprising means for modifying automatically at least one of the operating parameters thereof in order to bring back the counting efficiency of each of the test samples to a predetermined value.

Claim 23

A spectrometer according to claim 9, wherein the transducer assembly comprises logarithmic amplification means.

Claim 24

A spectrometer according to claim 9, wherein the means for determination of the height corresponding to the centroid comprise a pulse height analyzer for passing pulses whose height is in said portion of the spectrum both to a counting channel having a counter for recording pulses and to another channel provided with an analog-to-digital converter and a counter and means for dividing the result supplied from the second channel by the result supplied from the first channel.

Claim 25

A spectrometer according to claim 9, wherein said device comprises correction means for correcting background noise, having an element for displaying the background contribution to the count rate and an element for displaying the mean background level, said division means being intended first to correct the contents of the counters as a function of the displayed data and then to perform the division.

Claim 26

A spectrometer according to claim 10, wherein the means for determination of the pulse height corresponding to the centroid comprise : a pulse height analyzer which delimits said portion of the spectrum and passes pulses to a first channel which has a counter for recording pulses transmitted during a predetermined time interval and to a second channel which has a shaping circuit for giving a constant duration to all pulses, a capacitor for storing the charges carried by the shaped pulses, an analog-to-digital converter and means for triggering the D-A converter at the end of said predetermined time interval; and means for dividing the output of said D-A converter by the count registered by the counter.