Method and circuit for correcting count rate losses of radiation events

Claim 3

A method according to claim 1, further comprising the steps of (a) generating a sequence of clock pulses; and (b) measuring the number of clock pulses generated during deadtimes occurring in each evaluation time interval; wherein said measured number of clock pulses is a measure for the fractional amount of deadtime.

Claim 4

A method according to claim 2, further comprising the steps of: (a) counting the clock pulses during deadtimes by means of a counter having a certain count capacity; and (b) generating a sequence of clock pulses, the maximum number of those clock pulses that can occur during an evaluation time interval, corresponds to the count capacity of the counter.

Claim 5

A method according to claim 1, further comprising the steps of (a) comparing the replication probability with a random number; (b) generating a signal, when the replication probability is less than the random number; and (c) generating said sequence of a number of pulses for randomly selected events dependent on said signal.

Claim 6

A method according to claim 4, further comprising the steps of (a) generating a signal for the replication number; and (b) generating said sequence of a number of pulses for randomly selected events dependent on the signal for the replication number and the signal generated when the replication probability is less than the random number.

Claim 7

A method according to claim 1, wherein the deadtime signal is provided by producing a pulse every time and as long as a detected radiation event exceeds a detection threshold.

Claim 8

A circuit for correcting count rate losses of radiation events measured by a radiation detector due to detector deadtimes during an acquisition time, comprising: (a) means for detecting radiation events which are subject to deadtime losses during the acquisition time to obtain a succession of radiation detector event triggers; (b) means for providing for each detected radiation event a deadtime signal which corresponds to the deadtime generated by the detected radiation event; (c) means for subdividing the acquisition time into a succession of evaluation time intervals; (d) means for measuring the fractional amount of deadtime within each evaluation time interval to obtain a measure for count rate losses; (e) means for evaluating from the fractional amount of deadtime a replication probability r according to the equation r=DT'/(1-DT') (m-1), wherein DT' is the fractional amount of deadtime and m is a replication number only so large as to make the replication probability be less than one for any particular fractional amount of deadtime; and (f) means for evaluating all radiation events detected between the ene of one evaluation time and the end of a following one to generate (f1) one pulse for each detected radiation event between the ends of the succeeding evaluation times; and (f2) a sequence of a number of pulses for randomly selected events which selection corresponds to the replication probability and which pulse number corresponds to the replication number.

Claim 9

A circuit for correcting count rate losses of radiation events measured by a radiation detector due to detector deadtimes during an acquisition time, comprising: (a) means for detecting radiation events which are subject to deadtime losses during the acquisition time to obtain a succession of radiation detector event triggers; (b) means for providing for each detected radiation event a deadtime signal which corresponds to the deadtime generated by the detected radiation event; (c) means for subdividing the acquisition time into a succession of evaluation time intervals; (d) means for measuring the fractional amount of deadtime within each evaluation time interval to obtain a measure for count rate losses; (e) means for evaluating from the fractional amount of deadtime a replication probability r according to the equation r=DT'/(1-DT') (m-1), wherein DT' is the fractional amount of deadtime and m is a replication number only so large as to make the replication probability be less than one for any particular fractional amount of deadtime; and (f) means for evaluating all radiation events detected between the ene of one evaluation time and the end of a following one to generate (f1) one pulse for each detected radiation event between the ends of the succeeding evaluation times; and (f2) a sequence of a number of pulses for randomly selected events which selection corresponds to the replication probability and which pulse number corresponds to the replication number.

Claim 10

A circuit according to claim 7, wherein said means for providing for each detected radiation event a deadtime signal comprises a threshold detector having a detection threshold for producing a pulse every time and as long as a detected radiation event exceeds the detection threshold.

Claim 11

A circuit according to claim 7, wherein said means for subdividing the acquisition time into a succession of evaluation time intervals comprises a pulse generator which periodically generates pulses having a duration corresponding to the evaluation time interval.

Claim 12

A circuit according to claim 7, wherein said means for measuring the fractional amount of deadtime comprises: (a) a clock for generating a sequence of clock pulses; and (b) a counter for measuring the number of clock pulses generated during deadtimes occurring in each evaluation time interval.

Claim 13

A circuit according to claim 10, wherein said counter having a certain count capacity and said clock generates a sequence of clock pulses, the maximum number of those clock pulses that can occur during an evaluation time interval, corresponds to the count capacity of the counter.

Claim 14

A circuit according to claim 10, further comprising: (a) a pulse generator which periodically generates pulses having a duration corresponding to the evaluation time interval; and (b) a gate; wherein said pulses of said pulse generator, said clock pulses of said clock and the deadtime signals are supplied to said counter via said gate.

Claim 15

A circuit according to claim 7, wherein said means for evaluating the replication probability comprises a correction table.

Claim 16

A circuit according to claim 7, further comprising: (a) a comparator; and (b) a random generator for a random number; wherein said comparator is provided for comparing said replication probability with said random number and for generating a signal, when the replication probability is less than the random number.

Claim 17

A circuit according to claim 14, wherein said means for generating said sequence of a number of pulses comprises at least one trigger monostable multivibrator for generating one pulse in addition to a detected radiation event in response to said signal of said comparator.

Claim 18

A circuit according to claim 15, wherein said trigger monostable multivibrator comprises a delay means for the delayed generating of its additional pulse.

Claim 19

A circuit according to claim 7, further comprising: (a) means for generating a signal for the replication number; and (b) means for generating said sequence of a number of pulses for randomly selected events dependent on the signal for the replication number and the signal generated when the replication probability is less than the random number.

Claim 20

A circuit according to claim 17, wherein said means for generating said sequence of a number of pulses comprises a number m-1 of trigger monostable multivibrators, wherein m is the replication number, said trigger monostable multivibrators in dependance on said signal for the replication number delivers m-1 pulses in addition to a detected radiation event in response to said signal of said comparator.

Claim 21

A circuit according to claim 18, wherein each of said trigger monostable multivibrators comprises a delay means for the delayed generating of the additional pulses.

Claim 22

A circuit according to claim 7, wherein said means for detecting radiation events comprises a trigger monostable multivibrator which upon each event trigger generates a pulse.