Method and apparatus for determining accuracy of radiation measurements made in the presence of background radiation
AssigneeBeckman Instruments, Inc.
InventorDonald L. Horrocks
Life of this patent
Estimating the term…
Abstract
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.
Claims10
A method of determining the accuracy of a measurement of radioactivity of a sample alone when taken in the presence of background radiation, said method comprising the steps of:
- measuring the background radiation alone;
- measuring radiation from the sample in the presence of said background radiation;
- determining error values respectively related to said measuring steps;
- determining the radiation attributable to the sample alone, by subtracting the result of said first-mentioned measuring step from the result of said second-mentioned measuring step;
- and
- determining the accuracy of the result of said last-mentioned step by combining the error values related to said measuring steps.
A method of determining an error value .+-.E.sub.s relating to a particular probability of accuracy of a measurement of radioactivity of a sample taken in the presence of background radiation, said method comprising the steps of:
- measuring the background radiation R.sub.b alone;
- measuring radiation R.sub.s+b from the sample in the presence of the background radiation;
- determining error values .+-.E.sub.b and .+-.E.sub.s+b relating to the respective results of said measuring steps, there being a particular probability that the true values of radiation measured in said measuring steps fall within the ranges R.sub.b .+-. E.sub.b and R.sub.s+b .+-. E.sub.s+b, respectively;
- determining the radiation R.sub.s attributable to the sample alone by substracting R.sub.b from R.sub.s+b ;
- and
- determining the error value .+-.E.sub.s relating to the value of R.sub.s by combining the values of .+-.E.sub.b and +E.sub.s.+-.b.
Apparatus for determining the accuracy of a measurement of radioactivity of a sample taken in the presence of background radiation, said apparatus comprising:
- radioactivity event counting means for accumulating counts of radioactive events detected as being attributable to background radiation alone and for accumulating counts attributable to the sample taken together with the background radiation;
- dividing circuit means for providing a signal indicative of the time rate of accumulation of counts by said event counting means;
- error value calculation circuit means for determining an error value relating to a particular probability of accuracy of the values of rate of accumulation of counts;
- subtraction circuit means for subtracting a signal indicative of a radiation rate from the background from signal indicative of a radiation rate from the sample and background together, to obtain a radiation rate attributable to the sample alone;
- and
- error value correction circuit means, for combining error values relating to the rates of radiation from the background alone and from the background and sample together, and for thereby generating an error value relating to the radiation rate of the sample alone.
Dependencies are inferred from the claim text.