Tomography signal processing system
First Claim
1. In a tomography system for exposing a body to radiation to provide image data representative of the density of the body in a cross-sectional plane, of the type having:
- source means for providing radiation passing through the body;
detector means for receiving the radiation passing through the body along a plurality of paths and for providing output signals representative of radiation intensity received; and
scanning means for providing for rotation of the source and detector means with respect to said body and for periodically causing emission of radiation from the source means during said rotation to provide a scan having a plurality of projections at a corresponding plurality of projection angles;
the tomography processor comprising;
corrector means for correcting the output signals from the detector means to provide corrected data points, each representative of a line integral of the density of the body along the path traversed by the radiation producing the corresponding detector means output signal;
first memory means for storing the corrected data points from a projection and for retrieving the stored, corrected data points from a projection at a later time;
convolver means for convolving with a deblurring function the corrected data points from a projection, retrieved by the first memory means, to produce a plurality of convolved data points from a projection;
second memory means, coupled to the convolver means, for storing the convolved data points from a projection and for retrieving the stored, convolved data points from a projection at a later time;
image memory means for storing data representative of the density of the body in said cross-sectional plane and having a plurality of memory locations each for storing a value representative of the density of a corresponding area of the body in said cross-sectional plane;
reconstructor means, coupled to said second memory means, and operative in response to data retrieved by said second memory means, for back-projecting the convolved data points from a projection by determining the corresponding convolved data point for each location in image memory and adding data derived from the corresponding convolved data point to the value stored in that location in image memory.
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Abstract
A tomography processor system for processing data from a plurality of projections in essentially real time to produce a reconstructed image immediately following completion of a scan. The system includes specialized high-speed processing stages for performing required calculations and operating in concert with a low-cost computer providing overall system control. These processing stages form a multi-stage pipeline processor capable of performing the correction, convolution, interpolation, and back projection functions required to reconstruct the desired final image. The invention makes use of a reconstruction algorithm particularly adapted to implementation in the manner disclosed and claimed.
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Citations
68 Claims
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1. In a tomography system for exposing a body to radiation to provide image data representative of the density of the body in a cross-sectional plane, of the type having:
- source means for providing radiation passing through the body;
detector means for receiving the radiation passing through the body along a plurality of paths and for providing output signals representative of radiation intensity received; and
scanning means for providing for rotation of the source and detector means with respect to said body and for periodically causing emission of radiation from the source means during said rotation to provide a scan having a plurality of projections at a corresponding plurality of projection angles;the tomography processor comprising; corrector means for correcting the output signals from the detector means to provide corrected data points, each representative of a line integral of the density of the body along the path traversed by the radiation producing the corresponding detector means output signal; first memory means for storing the corrected data points from a projection and for retrieving the stored, corrected data points from a projection at a later time; convolver means for convolving with a deblurring function the corrected data points from a projection, retrieved by the first memory means, to produce a plurality of convolved data points from a projection; second memory means, coupled to the convolver means, for storing the convolved data points from a projection and for retrieving the stored, convolved data points from a projection at a later time; image memory means for storing data representative of the density of the body in said cross-sectional plane and having a plurality of memory locations each for storing a value representative of the density of a corresponding area of the body in said cross-sectional plane; reconstructor means, coupled to said second memory means, and operative in response to data retrieved by said second memory means, for back-projecting the convolved data points from a projection by determining the corresponding convolved data point for each location in image memory and adding data derived from the corresponding convolved data point to the value stored in that location in image memory. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
- source means for providing radiation passing through the body;
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15. A fan-beam tomography system for providing data representative of the density of a body in a cross-sectional plane, comprising:
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source means for emitting a fan-beam of radiation passing through the body; detector means for receiving radiation passing through the body along a plurality of paths and for providing corresponding output signals representative of radiation intensity received along each of said paths; scanning means for providing for relative rotation about an axis of the source and detector means with respect to the body and for causing the source means to emit radiation during said rotation to provide a scan made up of a plurality of projections at a corresponding plurality of projection angles; the detector means including a plurality of detectors, each for detecting radiation intensity and for producing an output signal representative thereof, located along a semi-circle having a center located at the source, each of the detectors being located at a respective detector angle with respect to a line passing through the source means and the axis of rotation; corrector means for receiving each of the output signals from the detector means and for providing in response thereto, a corresponding corrected data point representative of a line integral of the density of the body along the corresponding path of the radiation received by the detector means, including; means for performing calculations to compensate for previously measured errors between the output signals produced by the detector means and the actual intensity of radiation received thereby and to compensate for beam-hardening of the radiation passing through the body; and means for multiplying the output signal from each of the detectors by the cosine of the respective detector angle to provide the corrected data points; first memory means for storing the corrected data points from a projection and for retrieving the stored, corrected data points from a projection at a later time; convolver means for convolving with a deblurring function the corrected data points from a projection, retrieved by the first memory means, to produce a plurality of convolved data points from a projection; second memory means, coupled to the convolver means, for storing the convolved data points from a projection and for retrieving the stored, convolved data points from a projection at a later time; an image memory having a plurality of memory locations each for storing a value representative of the density of a corresponding area of the body in the cross-sectional plane; and reconstructor means, coupled to said second memory means, and operative in response to data retrieved by said second memory means, for back-projecting the convolved data points from a projection, including; address means for sequentially providing address data for accessing each of the locations in image memory during each projection; locator means, responsive to data derived from said address data, for determining which of the convolved data points from a projection corresponds with the presently accessed image memory location; means for multiplying the corresponding data point determined by said locator means by a weighting factor to produce a weighted data point; and means for adding the weighted data point to the value, resulting from prior projections, stored in the presently accessed image memory location and for storing the sum thereof in the presently accessed memory location to replace the value resulting from prior projections. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. A fan-beam tomography system for providing data representative of the density of a body in a cross-sectional plane, comprising:
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source means for emitting a fan-beam of radiation passing through the body; detector means for receiving radiation passing through the body along a plurality of paths and for providing corresponding output signals representative of radiation intensity received along each of said paths; scanning means for providing for relative rotation about an axis of the source and detector means with respect to the body and for causing the source means to emit pulses of radiation during said rotation to provide a scan made up of a plurality of projections at a corresponding plurality of projection angles; the detector means including; a plurality of detectors each for detecting radiation intensity and for producing an output signal representative thereof; a plurality of integrators, each associated with a respective one of said detectors, for integrating the output signal of the associated detector during each projection to produce an integrated detector output signal representative of the integral of the output signal during each projection from the associated detector; and conversion means, responsive to each of the integrated detector output signals for providing detector means output signals representative of the inverse of the logarithm of each of the integrated detector output signals; corrector means for receiving each of the output signals from the detector means and for providing in response thereto, a corresponding corrected data point representative of a line integral of the density of the body along the corresponding path of the radiation received by the detector means, including; means for performing calculations to compensate for previously measured errors between the output signals produced by the detector means and the actual intensity of radiation received thereby; first memory means for storing the corrected data points from a projection and for retrieving the stored, corrected data points from a projection at a later time; convolver means for convolving with a deblurring function the corrected data points from a projection, retrieved by the first memory means, to produce a plurality of convolved data points from a projection; second memory means, coupled to the convolver means, for storing the convolved data points from a projection and for retrieving the stored, convolved data points from a projection at a later time; an image memory having a plurality of memory locations each for storing a value representative of the denstiy of a corresponding area of the body in the cross-sectional plane; and reconstructor means, coupled to said second memory means and operative in response to data retrieved by the second memory means, for back-projecting the convolved data points from a projection, including; address means for sequentially providing address data accessing each of the locations in image memory during each projection; locator means, responsive to data derived from said address data, for determining which of the convolved data points from a projection corresponds with the presently accessed image memory location; means for multiplying the corresponding data point determined by said locator means by a weighting factor to produce a weighted data point; and means for adding the weighted data point to the value, resulting from prior projections, stored in the presently accessed image memory location and for storing the sum thereof in the presently accessed image memory location to replace the value resulting from prior projections. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A fan-beam tomography system for providing data representative of the density of a body in a cross-sectional plane, comprising:
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source means for emitting a fan-beam of radiation passing through the body; detector means for receiving radiation passing through the body along a plurality of paths and for providing corresponding output signals representative of radiation intensity received along each of said paths; scanning means for providing for relative rotation about an axis of the source and detector means with respect to the body and for causing the source means to emit radiation during said rotation to provide a scan made up of a plurality of projections at a corresponding plurality of projection angles; corrector means for receiving each of the output signals from the detector means and for providing in response thereto, a corresponding corrected data point representative of a line integral of the density of the body along the corresponding path of the radiation received by the detector means, including; means for performing calculations to compensate for previously measured errors between the output signals produced by the detector means and the actual intensity of radiation received thereby; first memory means for storing the corrected data points from a projection and for retrieving the stored, corrected data points from a projection at a later time; convolver means for convolving with a deblurring function the corrected data points from a projection, retrieved by the first memory means, to produce a plurality of convolved data points from a projection; second memory means, coupled to the convolver means, for storing the convolved data points from a projection and for retrieving the stored, convolved data points from a projection at a later time; an image memory having a plurality of memory locations, each for storing a value representative of the density of an associated area of the body in the cross-sectional plane, each of the plurality of image memory locations being associated with an area of the body, the address of each location also being representative of coordinates of the associated body area in an image memory coordinate system fixed with respect to the body; reconstructor means, coupled to said second memory means, and operative in response to data retrieved by said second memory means, for back-projecting the convolved data points from a projection, including; address means for sequentially providing address data for accessing each of the locations in image memory during each projection; transformation means, operative in response to address data from the address means, for performing a two-dimensional coordinate transformation to provide data representative of projection system coordinates in a coordinate system fixed with respect to the radiation source and detector means, of the body area associated with the presently accessed image memory location; locator means, responsive to projection system coordinate data from said transformation means, for determining which of the convolved data points from a projection corresponds with the presently accessed image memory location; means for multiplying the corresponding data point determined by said locator means by a weighting factor to produce a weighted data point; and means for adding the weighted data point to the value, resulting from prior projections, stored in the presently accessed image memory location and for storing the sum thereof in the presently accessed memory location to replace the value resulting from prior projections. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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51. For use in a fan-beam tomography system having a source of radiation and means for detecting radiation for providing data representative of the density of a body in a cross-sectional plane, of the type having a corrector, a convolver, and an image reconstructor respectively interconnected by two intermediate, two-bank memories and operative as a multistage pipeline processor to provide a plurality of convolved data points from each of a plurality of tomographic projections in response to data from said detecting means, an image reconstructor for performing back projection of the plurality of convolved data points taken during each of the plurality of projections, comprising:
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an image memory having a plurality of memory locations each associated with an area of the body in the cross-sectional plane, for storing data representative of the density of the associated body area, each location having an address, the address of each location also being representative of coordinates of the associated body area in an image memory coordinate system fixed with respect to the body; address means for providing address data to the image memory for accessing each of the memory locations during each projection; transformation means, operative in response to address data from the address means, for providing data representative of projection system coordinates, in a coordinate system fixed with respect to the radiation source and detecting means, of the body area associated with the presently accessed image memory location; locator means, operative in response to the projection system coordinate data from the transformation means, for selecting from among the convolved data points, the convolved data point having data representative of the density of the body area associated with the image memory location presently accessed by the address means; and means for adding the value stored in the presently accessed image memory location to data derived from the convolved data point selected by the locator means, and for storing the sum thereof in the presently accessed image memory location to replace the previously stored value. - View Dependent Claims (52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64)
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65. In a fan-beam tomography system for exposing a body to radiation to provide data representative of the density of the body in a cross-sectional plane, of the type having:
- source means for providing radiation for passage through the body;
detector means for receiving the radiation passing through the body along a plurality of paths and for providing output signals representative of radiation intensity received, and scanning means for providing rotation of the source and detector means with respect to said body and for causing emission of radiation from the source means during said rotation to provide a scan having a plurality of projections at a corresponding plurality of projection angles;the method of processing the detector means output signals, comprising the steps of; correcting the output signals from the detector means to provide corrected data points, each representative of a line integral of the density of the body along the path traversed by the radiation producing the corresponding detector means output signal; storing in a first memory the corrected data points from a projection; retrieving from the first memory the stored, corrected data points from a projection after all the corrected data points from that projection have been stored; convolving with a deblurring function the corrected data points from a projection, retrieved from the first memory, to produce a plurality of convolved data points from a projection; storing the convolved data points from a projection in a second memory; retrieving from the second memory the stored, convolved data points from a projection after all the convolved data points from the projection have been stored; providing an image memory having a plurality of memory locations corresponding with a similar plurality of areas of the body in said plane, for storing data representative of the density of the corresponding area of the body; and back-projecting the convolved data points from a projection retrieved by said second memory by; sequentially accessing each location in the image memory; determining the corresponding convolved data point for the presently accessed location in image memory; multiplying the previously-determined corresponding convolved data point by a weighting factor to provide a weighted data point; adding the weighted data point to the value stored in the presently accessed location in the image memory; and storing the results of the adding step in the presently accessed location in the image memory to replace the value previously stored therein; repeating the preceeding steps to correct, convolve, and back-project the data from each projection in a scan to produce data in each location in the image memory representative of the density of the corresponding area of the body; wherein each of the first and second memories includes a two-bank memory, having a first memory bank and a second memory bank; wherein the steps of storing and retrieving in said first and second memories include the steps of storing data in a first one of said first and second memory banks in the respective memories and concurrently retrieving data from the second one of said first and second memory banks in the respective memories in response to a selection signal designating in which bank data is to be stored and from which bank data is to be retrieved; and wherein the step of repeating includes the step of providing selection signals for the first memory so that corrected data points from a projection may be stored in one bank thereof while corrected points from a prior projection may be retrieved from the other bank thereof. - View Dependent Claims (66, 67, 68)
- source means for providing radiation for passage through the body;
Specification