Method and apparatus for determining accuracy of radiation measurements made in the presence of background radiation

Claim 3

A method as set forth in claim 1, wherein: said determining steps are performed from time to time during said second-mentioned measuring step; and said method further includes the steps of comparing the determined error value of the determined radiation of the sample with a desired error value, and terminating said second-mentioned measuring step when the determined error value reaches the desired error value.

Claim 4

A method as set forth in claim 1, and further including the step of storing the measured value of background radiation and the associated error value, for subsequent use by said steps of determining sample radiation and its associated error value.

Claim 7

A method as set forth in claim 4, wherein said step of determining the error value ±E s is performed in accordance with the expression: ±E.sub.s = ± √ (E.sub.b) .sup.2 + (E.sub.s+b) .sup.2.

Claim 8

A method as set forth in claim 4, wherein: said determining steps are performed from time to time during said step of measuring R s+b ; and said method further includes the steps of comparing the determined error value ±E s with a desired error value, and terminating said step of measuring R s+b when the magnitude of the error value ±E s reaches the desired error value.

Claim 9

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.

Claim 10

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.

Claim 11

Apparatus as set forth in claim 7, and further including display means for visually displaying values of the radiation rate attributable to the sample alone, and its associated error value determined in said error value correction circuit means.

Claim 12

Apparatus as set forth in claim 7, and further including: comparator means for comparing error values determined from time to time by said error value correction circuit means with a desired error value; and means for terminating operation of said event counting means when said comparator means detects that the determined error value has reached the desired error value.

Claim 13

Apparatus as set forth in claim 7, wherein: the error values relating to the radiation rates from the background alone and the background and sample together are ±E b and ±E s+b , respectively; and the error value determined by said error value correction circuit means is given by the expression ±E s = ± √ (E b ) 2 + (E s+b ) 2 .