Method and apparatus for improved radiation detection in radiation scanning systems
First Claim
1. An X-ray scanning system comprising:
- a. an X-ray source for producing a beam of X-rays;
b. beam receiving means disposed for receiving the X-ray beam and producing a train of pulses whose instantaneous repetition rate is indicative of the instantaneous intensity of the beams as it emerges from the object and inpinges upon an receiving means;
c. means supporting at least one of said X-ray source and beam receiving means for motion along a predetermined path relative to the object with said beam being scanned through said object during said motion;
d. timer means for generating a time signal having a value representative of the time elapsing between selected pulses of said pulse train which occur during a predetermined interval of said scanning motion;
e. a counter for counting pulses of the pulse train occurring within said time interval and producing a count signal; and
,f. means for comparing the count signal with the time signal for generating an average intensity signal indicative of the average intensity of said X-ray beam impinging on said beam receiving means in said interval.
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Abstract
An improved radiation measuring and processing unit for a radiation scanning system precisely determines the average intensity of a beam of radiation as it impinges upon a radiation detector during a primary time period of predetermined duration. The unit computes the average intensity by detecting the average rate of a train of intensity representing pulses occurring during a secondary time period whose duration is determined according to the occurrences of the pulses within the primary time period. The system is preferably a transverse section, X-ray scanning system, and the radiation detector generates a data signal having a level indicative of the intensity of the beam of X-radiation after it passes through a subject. The measuring and processing unit includes a pulse generator, preferably in the form of a charge pump integrator, for converting the data signals into the train of data pulses having a repetition rate which varies according to the level of the data signal. The unit also includes a data counter and a time counter which are operative throughout a series of the primary time periods. The time counter counts a series of clock pulses indicative of the lapse of time between the first and last data pulses occurring during the primary time period, thereby establishing the secondary time period. The data counter counts all pulses occurring during the secondary time period, i.e., the second and subsequent data pulses occurring during the primary time period. Comparison of the contents of the data and time counters at the end of the primary time period provides an accurate indication of the average intensity of the X-ray beam as it impinges upon the detector.
180 Citations
18 Claims
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1. An X-ray scanning system comprising:
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a. an X-ray source for producing a beam of X-rays; b. beam receiving means disposed for receiving the X-ray beam and producing a train of pulses whose instantaneous repetition rate is indicative of the instantaneous intensity of the beams as it emerges from the object and inpinges upon an receiving means; c. means supporting at least one of said X-ray source and beam receiving means for motion along a predetermined path relative to the object with said beam being scanned through said object during said motion; d. timer means for generating a time signal having a value representative of the time elapsing between selected pulses of said pulse train which occur during a predetermined interval of said scanning motion; e. a counter for counting pulses of the pulse train occurring within said time interval and producing a count signal; and
,f. means for comparing the count signal with the time signal for generating an average intensity signal indicative of the average intensity of said X-ray beam impinging on said beam receiving means in said interval. - View Dependent Claims (2, 3, 4, 5)
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6. A tomographic scanning system comprising:
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a. a source of penetrative radiation for producing a beam of radiation; b. source supporting means for moving said source along a predetermined path relative to a subject being scanned; c. beam receiving means comprising a detector disposed for receiving the beam of radiation emerging from the subject during said scanning motion, said beam receiving means producing a train of data pulses whose instantaneous frequency is indicative of the intensity of the radiation impinging on said detector; d. period defining means for establishing a primary time period during which a predetermined amount of scanning motion occurs; e. timing means for producing a time signal representing a time interval between selected pulses occurring within said primary time period, said time interval having a duration less than said primary time period; f. count signal producing means for producing a count signal related to the number of pulses occurring during said primary time period; and
,g. comparator means for comparing said count signal and said time signal and producing an output signal indicative of the average radiation intensity detected during the primary time period. - View Dependent Claims (7, 8, 9, 18)
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10. A method of determining the intensity of radiation detected during a tomographic examination comprising:
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a. producing a beam of penetrative radiation from a radiation source and directing the beam through a subject for examination; b. detecting radiation emerging from the subject; c. scanning the beam through the subject via a predetermined scan path by effecting relative motion between the subject and the radiation beam; d. producing a train of signal pulses having an instantaneous frequency corresponding to the instantaneous intensity of the radiation emerging from the subject; e. detecting individual pulses occurring during a predetermined segment of the scan path and producing a count signal having a value related to the number of pulses detected; f. timing the interval between pulses occurring during the scan segment and producing a corresponding time signal; g. comparing the count and time signals; and h. producing an average intensity signal having a value representing the average intensity of radiation emerging from the subject during the scan segment. - View Dependent Claims (11, 12)
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13. A tomographic scanning system for producing an image of a cross section of a subject in response to radiation emerging from the subject comprising:
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a. radiation detector means including at least a detector supported for movement along a path for receiving radiation emerging from the subject, said detector means producing a train of output pulses having an instantaneous frequency corresponding to the instantaneous intensity of the radiation as it impinges upon the detector; b. position indicating means for generating index signals indicative of the traversal by said detector through each of a series of segments constituting said path, and c. a signal processing unit responsive to said pulse train and to said index signals for generating an average intensity signal over a primary time period corresponding to the traversal of said radiation detector through one of the segments, the processing unit including; i. pulse responsive means for producing an output signal having a value depending upon the number of pulses occurring during each path segment; ii. timer means for producing an output signal having a value determined by the time elapsing between the occurrences of pulses produced during each path segment; and
,iii. comparator means for comparing the output signals produced during respective scan segments and producing an average intensity signal representing the average intensity of radiation impinging on said detector during said respective scan segments. - View Dependent Claims (14, 15, 16, 17)
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Specification