Time share digital integration method and apparatus for processing X-ray images
First Claim
1. A signal processing method for processing signals output from an array of N X-ray radiation detectors arranged to receive X-ray radiation emanating from an object irradiated by a source beam of X-ray radiation from an X-ray radiation source incident upon an object, said method comprising the steps of;
- a. repetitively sampling P times a detector channel output voltage indicative of X-ray radiation incident upon each of N detectors of an array of detectors, where P is an integer,b. accumulating a value proportional to a sum of said P samples of each said output voltage in a separate one of N accumulators, where N is an integer, andc. outputting from each of said N accumulators an output signal having a value proportional to said accumulated value,d. concatenating said output signals to form a column array of said output signals each of which has a value proportional to X-ray radiation incident upon a corresponding individual detector of said array of detectors, said column array of values being indicative of an image slice of said object incident upon said detector array,e. causing relative scanning motion between said object and said X-ray radiation source, in a direction transverse to a direction which said detectors are arranged, said detector array outputting a sequence of signal values corresponding to image slices of an object formed on said detector array, said sequence of image slices corresponding to side-by-side image slices of said object, said sequence of output image slices being formed during a scan line time period approximating that of a time period equal to a width of said detectors-divided by a velocity of said scanning motion,f. sequentially arranging side-by-side a plurality of column arrays of signal values to form a two-dimensional array of signal values which is indicative of a two-dimensional view of adjacent image slices of said object, andg. wherein said step of outputting from said N accumulators an output signals having values proportional to accumulated signal values indicative of a first in a sequence of object image slices is performed at least partially simultaneously with said step of sampling detector channel output voltages corresponding to a different object image slice.
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Abstract
A method and apparatus for processing signals output from an array of X-ray radiation detectors which receive X-ray radiation emanating from an object irradiated by a source beam of X-ray radiation, to thereby produce an visual image of internal object features, utilizes repetitive sampling P times and digital accumulation of signals output from each detector to increase signal-to-noise ratio of the images by the factor 1/✓P. In a basic embodiment, each of the N detectors in a linear detector array is sampled P times. In another embodiment, artifacts resulting from decay of detector pre-amplifier output voltages on capacitors of low-pass filter circuits, referred to as pseudo-integrators, are reduced by sequentially sampling and accumulating each of N detector amplifier output voltages P times in turn, and repeating the sampling and accumulating sequence Q times, thereby reducing variations in the P×Q accumulated values between the first and last detector channels of an N detector array.
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Citations
42 Claims
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1. A signal processing method for processing signals output from an array of N X-ray radiation detectors arranged to receive X-ray radiation emanating from an object irradiated by a source beam of X-ray radiation from an X-ray radiation source incident upon an object, said method comprising the steps of;
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a. repetitively sampling P times a detector channel output voltage indicative of X-ray radiation incident upon each of N detectors of an array of detectors, where P is an integer, b. accumulating a value proportional to a sum of said P samples of each said output voltage in a separate one of N accumulators, where N is an integer, and c. outputting from each of said N accumulators an output signal having a value proportional to said accumulated value, d. concatenating said output signals to form a column array of said output signals each of which has a value proportional to X-ray radiation incident upon a corresponding individual detector of said array of detectors, said column array of values being indicative of an image slice of said object incident upon said detector array, e. causing relative scanning motion between said object and said X-ray radiation source, in a direction transverse to a direction which said detectors are arranged, said detector array outputting a sequence of signal values corresponding to image slices of an object formed on said detector array, said sequence of image slices corresponding to side-by-side image slices of said object, said sequence of output image slices being formed during a scan line time period approximating that of a time period equal to a width of said detectors-divided by a velocity of said scanning motion, f. sequentially arranging side-by-side a plurality of column arrays of signal values to form a two-dimensional array of signal values which is indicative of a two-dimensional view of adjacent image slices of said object, and g. wherein said step of outputting from said N accumulators an output signals having values proportional to accumulated signal values indicative of a first in a sequence of object image slices is performed at least partially simultaneously with said step of sampling detector channel output voltages corresponding to a different object image slice. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An apparatus for processing signals output from an array of N X-ray radiation detectors arranged to receive X-ray radiation emanating from an object irradiated by at least one source beam of X-ray radiation, said apparatus comprising;
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a. a plurality of N pre-conditioner circuits each having an input terminal connected to an output terminal of a separate one of said N X-ray radiation detectors, and each having a separate output terminal, b. at least a first analog-to-digital converter circuit module having an input terminal connectable to an output terminal of a selected one of said pre-conditioner circuits for converting an electrical signal output from a said selected one of said pre-conditioner circuits to a digital signal at an output terminal of said analog-to-digital converter indicative of intensity of X-ray radiation incident upon said X-ray radiation detector connected to said pre-conditioner circuit, c. a plurality of N digital accumulators, each of which has an input port connectable to said output terminal of said analog-to-digital converter, and d. a scan and transfer control circuitry module which performs functions of; I. connecting an output terminal of a first selected one of N detector channels comprising a particular detector and associated pre-conditioner circuit to said input terminal of said analog-to-digital convertor, ii. repetitively sampling P times a digital signal value output from said analog-to-digital converter indicative of X-ray radiation incident upon said detector of said detector channel, iii. accumulating a sum of said P digital values in a first one of said N accumulators, iv. connecting an output terminal of a next one of said N detector channels to said analog-to-digital converter and repeating step (I), (ii) and (iii) to accumulate a sum of P digital signal values in said next one of said N accumulators, v. repeating steps (I), (ii), (iii) and (iv) until P signal values of each of said N detector channels have been accumulated in said N accumulators, and vi. outputting from each of said N accumulators an output signal having a value proportional to said accumulated value. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification