US4497062A — Digitally controlled X-ray beam attenuation metho…

Claim 1

Independent Claim 262 words

X-ray beam compensation apparatus for forming a compensation mask to be inserted between an X-ray source and an object comprising: (a) X-ray image receptor means for receiving X-rays passed through the object and providing an output signal indicative of the X-ray intensity at positions in the field of the X-ray fluence received by the receptor means; (b) image processing means for receiving the output signal from the image receptor means and providing an output signal indicative of the X-ray intensity value from the receptor means at each pixel in a selected two dimensional array of pixels covering at least a portion of the image field of the receptor means; (c) mask generating control means for receiving the output signal from the image processing means, determining the minimum indicated intensity value from the image processing means in any pixel, determining an attenuation number for each pixel in the array related to the difference between the indicated intensity value for that pixel and the minimum indicated intensity value, and providing a control signal indicative of the attenuation number for each pixel in the array; and (d) mask forming means for receiving the control signal from the control means and forming a compensation mask by depositing on at least one substrate X-ray attenuating masses in a two dimensional array of mask pixels which corresponds to the two dimensional array of pixels in the image field of the receptor means, the thickness of the attenuating mass in each mask pixel being proportional to the attenuation number for such pixel determined by the mask generating control means.

Claim 2

Dependent Claim 262 words

X-ray beam compensation apparatus for forming a compensation mask to be inserted between an X-ray source and an object comprising: (a) X-ray image receptor means for receiving X-rays passed through the object and providing an output signal indicative of the X-ray intensity at positions in the field of the X-ray fluence received by the receptor means; (b) image processing means for receiving the output signal from the image receptor means and providing an output signal indicative of the X-ray intensity value from the receptor means at each pixel in a selected two dimensional array of pixels covering at least a portion of the image field of the receptor means; (c) mask generating control means for receiving the output signal from the image processing means, determining the minimum indicated intensity value from the image processing means in any pixel, determining an attenuation number for each pixel in the array related to the difference between the indicated intensity value for that pixel and the minimum indicated intensity value, and providing a control signal indicative of the attenuation number for each pixel in the array; and (d) mask forming means for receiving the control signal from the control means and forming a compensation mask by depositing on at least one substrate X-ray attenuating masses in a two dimensional array of mask pixels which corresponds to the two dimensional array of pixels in the image field of the receptor means, the thickness of the attenuating mass in each mask pixel being proportional to the attenuation number for such pixel determined by the mask generating control means.

Claim 3

Dependent Claim 21 words

The apparatus of claim 1 wherein the X-ray attenuating masses are formed of a carrier material having X-ray absorbing material therein.

Claim 4

Dependent Claim 23 words

The apparatus of claim 2 wherein the mask forming means includes a dot matrix printer which prints the attenuating masses onto the substrate.

Claim 5

Dependent Claim 12 words

The apparatus of claim 3 wherein the X-ray absorbing material is cerium.

Claim 6

Dependent Claim 46 words

The apparatus of claim 1 wherein the mask forming means forms the compensation mask outside of the path of the X-ray beam from the X-ray source, and including means for indexing the mask to register it in proper position in the X-ray beam from the source.

Claim 7

Dependent Claim 66 words

The apparatus of claim 5 wherein the mask is registered at a position a distance L from the focal spot of the X-ray source determined from the relation L=w m D/W where D is the distance of the image receptor means from the focal spot, W is the width of the field of the image receptor means, and w m is the width of the mask.

Claim 8

Dependent Claim 64 words

The apparatus of claim 1 wherein the image receptor means includes a video camera producing a video output signal varying in amplitude as the image field is scanned, and wherein the image processing means receives the video output signal and includes an analog-to-digital converter for converting the video signal to digital data and convolution circuit means for providing convolution of the digital video data.

Claim 9

Dependent Claim 65 words

The apparatus of claim 1 wherein the image processing means provides an output signal proportional to the logarithm of the X-ray intensity value from the receptor means at each pixel, and wherein the mask forming means deposits attenuating masses in layers in the mask pixels, the number of layers of attenuating mass in each mask pixel being proportional to the attenuation number for such pixel.

Claim 10

Dependent Claim 20 words

The apparatus of claim 8 wherein the X-ray attenuating masses are formed of a carrier having X-ray absorbing material therein.

Claim 11

Dependent Claim 23 words

The apparatus of claim 9 wherein the mask forming means includes a dot matrix printer which prints the attenuating masses onto the substrate.

Claim 12

Dependent Claim 12 words

The apparatus of claim 10 wherein the X-ray absorbing material is cerium.

Claim 13

Dependent Claim 46 words

The apparatus of claim 8 wherein the mask forming means forms the compensation mask outside of the path of the X-ray beam from the X-ray source, and including means for indexing the mask to register it in proper position in the X-ray beam from the source.

Claim 14

Dependent Claim 66 words

The apparatus of claim 12 wherein the mask is registered at a position a distance L from the focal spot of the X-ray source determined from the relation L=w m D/W where D is the distance of the image receptor means from the focal spot, W is the width of the field of the image receptor means, and w m is the width of the mask.

Claim 15

Dependent Claim 78 words

The apparatus of claim 8 wherein the image receptor means includes a video camera producing a video output signal varying in amplitude as the image field is scanned, and wherein the image processing means receives the video output signal and includes an analog-to-digital converter for converting the video signal to digital data, convolution circuit means for providing convolution of the digital video data, and means for providing the logarithm of the intensity data from the convolution circuit means.

Claim 16

Dependent Claim 92 words

The apparatus of claim 8 wherein the mask generating control means determines the attenuation number n for each pixel in accordance with the expression n=(P-MIN)/A μx where A is a logarithmic transformation gain constant, μ is the linear attenuation coefficient for the attenuating mass material, x is the thickness of one layer of attenuating mass material, MIN is the minimum logarithmic intensity value, and P is the logarithmic intensity value for the pixel, the number of attenuating mass layers in each mask pixel being equal to the attenuation number for such pixel.

Claim 17

Dependent Claim 248 words

In an X-ray system having an X-ray source and an X-ray receptor receiving X-rays passed through an object and providing an output signal indicative of the X-ray intensity at positions in the field of the X-ray fluence received by the receptor, the improvement comprising: (a) image processing means for receiving the output signal from the image receptor and providing an output signal proportional to the logarithm of the X-ray intensity value received by the receptor at each pixel in a selected two dimensional array of pixels covering at least a portion of the image field of the receptor means; (b) mask generating control means for receiving the output signal from the image processing means, determining the minimum logarithmic intensity value in any pixel, determining an attenuation number for each pixel in the array proportional to the difference between the logarithmic intensity value for that pixel and the minimum logarithmic intensity value, and providing a control signal indicative of the attenuation number for each pixel in the array; and (c) mask forming means for receiving the control signal from the control means and forming a compensation mask by depositing on at least one substrate X-ray attenuating masses in layers in a two dimensional array of mask pixels which corresponds to the two dimensional array of pixels in the image field of the receptor, the number of attenuating mass layers in each mask pixel being proportional to the attenuation number for such pixel determined by the mask generating control means.

Claim 18

Dependent Claim 248 words

In an X-ray system having an X-ray source and an X-ray receptor receiving X-rays passed through an object and providing an output signal indicative of the X-ray intensity at positions in the field of the X-ray fluence received by the receptor, the improvement comprising: (a) image processing means for receiving the output signal from the image receptor and providing an output signal proportional to the logarithm of the X-ray intensity value received by the receptor at each pixel in a selected two dimensional array of pixels covering at least a portion of the image field of the receptor means; (b) mask generating control means for receiving the output signal from the image processing means, determining the minimum logarithmic intensity value in any pixel, determining an attenuation number for each pixel in the array proportional to the difference between the logarithmic intensity value for that pixel and the minimum logarithmic intensity value, and providing a control signal indicative of the attenuation number for each pixel in the array; and (c) mask forming means for receiving the control signal from the control means and forming a compensation mask by depositing on at least one substrate X-ray attenuating masses in layers in a two dimensional array of mask pixels which corresponds to the two dimensional array of pixels in the image field of the receptor, the number of attenuating mass layers in each mask pixel being proportional to the attenuation number for such pixel determined by the mask generating control means.

Claim 19

Dependent Claim 20 words

The system of claim 16 wherein the X-ray attenuating masses are formed of a carrier having X-ray absorbing material therein.

Claim 20

Dependent Claim 23 words

The system of claim 17 wherein the mask forming means includes a dot matrix printer which prints the attenuating masses onto the substrate.

Claim 21

Dependent Claim 12 words

The system of claim 18 wherein the X-ray absorbing material is cerium.

Claim 22

Dependent Claim 46 words

The system of claim 16 wherein the mask forming means forms the compensation mask outside of the path of the X-ray beam from the X-ray source, and including means for indexing the mask to register it in proper position in the X-ray beam from the source.

Claim 23

Dependent Claim 64 words

The system of claim 21 wherein the mask is registered at a position a distance L from the focal spot of the X-ray source determined from the relation L=w m D/W where D is the distance of the image receptor from the focal spot, W is the width of the field of the image receptor, and w m is the width of the mask.

Claim 24

Dependent Claim 77 words

The system of claim 16 wherein the image receptor includes a video camera producing a video output signal varying in amplitude as the image field is scanned, and wherein the image processing means receives the video output signal and includes an analog-to-digital converter for converting the video signal to digital data, convolution circuit means for providing convolution of the digital video data, and means for providing the logarithm of the intensity data from the convolution circuit means.

Claim 25

Dependent Claim 92 words

The system of claim 16 wherein the mask generating control means determines the attenuation number n for each pixel in accordance with the expression: n=(P-MIN)/A μx where A is a logarithmic transformation gain constant, μ is the linear attenuation coefficient for the attenuating mass material, x is the thickness of one layer of attenuating mass material, MIN is the minimum logarithmic intensity value, and P is the logarithmic intensity value for the pixel, the number of attenuating mass layers in each mask pixel being equal to the attenuation number for such pixel.

Claim 26

Independent Claim 207 words

A method of compensating the X-ray image of an object, comprising the steps of: (a) exposing an object to a first beam of X-rays; (b) determining the X-ray intensity passed through the object at each pixel in a two dimensional image array of pixels extending over an image field; (c) determining a transformed intensity value for each pixel in the image array as a function of the X-ray intensity passed through the object which compensates for non-linear transmission through the object; (d) forming a compensation mask having a two dimensional mask array of pixels having X-ray attenuation masses located in selected pixels with each pixel in the mask array corresponding to a pixel in the image array, the thickness of the masses in each pixel in the mask array being related to the difference between the transformed intensity value of the corresponding pixel in the image array and the minimum transformed intensity value found in any pixel in the image array; (e) inserting the compensation mask in registered position between the X-ray source and the object; and (f) exposing the object to a second X-ray beam passed through the compensation mask and recording the image of the X-ray beam after passing through the mask and the object.

Claim 27

Independent Claim 207 words

A method of compensating the X-ray image of an object, comprising the steps of: (a) exposing an object to a first beam of X-rays; (b) determining the X-ray intensity passed through the object at each pixel in a two dimensional image array of pixels extending over an image field; (c) determining a transformed intensity value for each pixel in the image array as a function of the X-ray intensity passed through the object which compensates for non-linear transmission through the object; (d) forming a compensation mask having a two dimensional mask array of pixels having X-ray attenuation masses located in selected pixels with each pixel in the mask array corresponding to a pixel in the image array, the thickness of the masses in each pixel in the mask array being related to the difference between the transformed intensity value of the corresponding pixel in the image array and the minimum transformed intensity value found in any pixel in the image array; (e) inserting the compensation mask in registered position between the X-ray source and the object; and (f) exposing the object to a second X-ray beam passed through the compensation mask and recording the image of the X-ray beam after passing through the mask and the object.

Claim 28

Dependent Claim 29 words

The method of claim 24 wherein the step of determining a transformed intensity value comprises determining the logarithm of the intensity value for each pixel in the image array.

Claim 29

Dependent Claim 26 words

The method of claim 24 in which the step of forming the mask includes the steps of forming the mask in layers on a non-attenuating substrate.

Claim 30

Dependent Claim 42 words

The method of claim 24 wherein the step of forming the mask includes the steps of printing X-ray attenuating material in layers onto a non-attenuating substrate at the proper positions to define the attenuating masses within the pixels of the mask array.

Claim 31

Dependent Claim 30 words

The method of claim 24 wherein the step of forming the compensation mask is performed outside of the path of a beam of X-rays from the source to the object.

Claim 32

Dependent Claim 78 words

The method of claim 24 wherein the step of exposing the object to a first beam of X-rays is performed at a first selected X-ray energy level, the step of exposing the object to a second beam of X-rays is performed at a second selected energy level, and wherein the thicknesses of the attenuating masses in the pixels are chosen to provide substantial cancellation of a selected material in the object at the selected second X-ray energy level.

Claim 33

Independent Claim 230 words

A method of compensating the X-ray image of an object, comprising the steps of: (a) exposing an object to a first beam of X-rays; (b) determining the X-ray intensity passed through the object at each pixel in a two dimensional image array of pixels extending over an image field; (c) determining a logarithmic intensity value for each pixel in the image array which is equal to a constant times the logarithm of the X-ray intensity for each pixel in the array; (d) determining the minimum logarithmic intensity value for any pixel in the image array; (e) determining the difference between the logarithmic intensity value at each pixel in the image array and the minimum logarithmic intensity value; (f) determining an attenuation number for each pixel equal to the difference between the pixel logarithmic intensity value and the minimum logarithmic intensity value times an adjustment coefficient; (g) depositing attenuating mass material in layers on a non-attenuating substrate to form a compensation mask having a two dimensional array of pixels corresponding to the two dimensional image array of pixels with the number of layers in each pixel in the two dimensional mask array proportional to the attenuation number for such pixel; and (h) exposing the object to a second X-ray beam passed through the compensation mask and recording the image of the X-ray beam after passing through the mask and the object.

Claim 34

Independent Claim 230 words

A method of compensating the X-ray image of an object, comprising the steps of: (a) exposing an object to a first beam of X-rays; (b) determining the X-ray intensity passed through the object at each pixel in a two dimensional image array of pixels extending over an image field; (c) determining a logarithmic intensity value for each pixel in the image array which is equal to a constant times the logarithm of the X-ray intensity for each pixel in the array; (d) determining the minimum logarithmic intensity value for any pixel in the image array; (e) determining the difference between the logarithmic intensity value at each pixel in the image array and the minimum logarithmic intensity value; (f) determining an attenuation number for each pixel equal to the difference between the pixel logarithmic intensity value and the minimum logarithmic intensity value times an adjustment coefficient; (g) depositing attenuating mass material in layers on a non-attenuating substrate to form a compensation mask having a two dimensional array of pixels corresponding to the two dimensional image array of pixels with the number of layers in each pixel in the two dimensional mask array proportional to the attenuation number for such pixel; and (h) exposing the object to a second X-ray beam passed through the compensation mask and recording the image of the X-ray beam after passing through the mask and the object.

Claim 35

Dependent Claim 43 words

The method of claim 30 wherein the step of depositing attenuating mass material includes the steps of printing X-ray attenuating material in layers onto a non-attenuating substrate at the proper positions to define the attenuating masses within the pixels of the mask array.

Claim 36

Dependent Claim 30 words

The method of claim 30 wherein the step of depositing attenuating mass material is performed outside of the path of a beam of X-rays from the source to the object.

Claim 37

Dependent Claim 80 words

The method of claim 30 wherein the step of exposing the object to a first beam of X-rays is performed at a first selected X-ray energy level, the step of exposing the object to a second beam of X-rays is performed at a second selected energy level, and wherein the thickness of the layers in the attenuating masses in the pixels are chosen to provide substantial cancellation of a selected material in the object at the selected second energy level.

Claim 38

Dependent Claim 90 words

The method of claim 30 wherein the step of determining an attenuation number determines the number n in accordance with the expression: n=(P-MIN)/A μx where A is a logarithmic transformation gain constant, μ is the linear attenuation coefficient for the attenuating mass material, x is the thickness of one layer of attenuating mass material, MIN is the minimum logarithmic intensity value, and P is the logarithmic intensity value for the pixel, the number of attenuating mass layers in each mass pixel being equal to the attenuation number for such pixel.

Claim 39

Independent Claim 85 words

A method of compensating the X-ray image of an object, comprising the steps of: (a) printing X-ray attenuating material from a ribbon having X-ray attenuating material thereon onto a substrate in layers forming an image to provide a compensation mask; (b) inserting the compensation mask in registered position between an X-ray source and an object; and (c) exposing the object to an X-ray beam passed through the compensation mask and recording the image of the X-ray beam after passing through the mask and the object.

Claim 40

Independent Claim 85 words

A method of compensating the X-ray image of an object, comprising the steps of: (a) printing X-ray attenuating material from a ribbon having X-ray attenuating material thereon onto a substrate in layers forming an image to provide a compensation mask; (b) inserting the compensation mask in registered position between an X-ray source and an object; and (c) exposing the object to an X-ray beam passed through the compensation mask and recording the image of the X-ray beam after passing through the mask and the object.

Claim 41

Dependent Claim 24 words

The method of claim 35 wherein the attenuating material is selected from the group consisting of cerium, lead, barium, cesium, cadmium, and compounds thereof.

Claim 42

Independent Claim 131 words

A method of compensating the X-ray image of an object, comprising the steps of: (a) exposing an object to a beam of X-rays; (b) determining the X-ray intensity passed through the object at each pixel in a two-dimensional image array of pixels extending over an image field; (c) depositing attenuating material in layers to form an image on a substrate in pixels in a two dimensional array of pixels on the substrate which corresponds to the two-dimensional image array of pixels to form a compensation mask; (d) inserting the compensation mask in registered position between the X-ray source and the object; and (e) exposing the object to an X-ray beam passed through the compensation mask and recording the image of the X-ray beam after passing through the mask and the object.

Claim 43

Independent Claim 131 words

A method of compensating the X-ray image of an object, comprising the steps of: (a) exposing an object to a beam of X-rays; (b) determining the X-ray intensity passed through the object at each pixel in a two-dimensional image array of pixels extending over an image field; (c) depositing attenuating material in layers to form an image on a substrate in pixels in a two dimensional array of pixels on the substrate which corresponds to the two-dimensional image array of pixels to form a compensation mask; (d) inserting the compensation mask in registered position between the X-ray source and the object; and (e) exposing the object to an X-ray beam passed through the compensation mask and recording the image of the X-ray beam after passing through the mask and the object.

Claim 44

Dependent Claim 31 words

The method of claim 37 wherein the step of depositing attenuating material on the substrate comprises printing X-ray attenuating material from a ribbon having X-ray attenuating material thereon onto the substrate.

Claim 45

Dependent Claim 24 words

The method of claim 38 wherein the attenuating material is selected from the group consisting of cerium, lead, barium, cesium, cadmium, and compounds thereof.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1988-01-29	1988-07-30	1989-01-29	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1992-01-29	1992-07-30	1993-01-29	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1996-01-29	1996-07-30	1997-01-29	$7700.00	Window Closed / Lapsed

Digitally controlled X-ray beam attenuation method and apparatus

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