US4752879A — Method and apparatus for medical imaging

Claim 1

Independent Claim 188 words

A computed tomography scanner for imaging a subject, said scanner comprising: (a) means for obtaining real attenuation readings for radiation passing through a predetermined plane extending into the subject from a finite number of different angularly spaced orientations; (b) means for filtering said real attenuation readings and back projecting said filtered attenuation readings across a two dimensional array of image pixels to obtain an image corresponding to regions in said plane, and (c) post-processing means for reducing artifacts caused by there being only said finite number of angularly spaced orientations at which real readings are obtained, said post processing means including means for storing two dimensional weighing coefficients which vary as a function of image pixel location, said post processing means modifying, as a function of pixel location within said image, the represented image of at least some of said array regions by combining information by way of interpolation from said at least some regions with information scaled by said weighing coefficients corresponding to at least one nearby region in said image to approximate an image obtained by filtering and back projecting both real and interpolated attenuation readings.

Claim 2

Dependent Claim 188 words

A computed tomography scanner for imaging a subject, said scanner comprising: (a) means for obtaining real attenuation readings for radiation passing through a predetermined plane extending into the subject from a finite number of different angularly spaced orientations; (b) means for filtering said real attenuation readings and back projecting said filtered attenuation readings across a two dimensional array of image pixels to obtain an image corresponding to regions in said plane, and (c) post-processing means for reducing artifacts caused by there being only said finite number of angularly spaced orientations at which real readings are obtained, said post processing means including means for storing two dimensional weighing coefficients which vary as a function of image pixel location, said post processing means modifying, as a function of pixel location within said image, the represented image of at least some of said array regions by combining information by way of interpolation from said at least some regions with information scaled by said weighing coefficients corresponding to at least one nearby region in said image to approximate an image obtained by filtering and back projecting both real and interpolated attenuation readings.

Claim 3

Dependent Claim 69 words

The system of claim 1, wherein: said post processing means comprises means for approximating a modified image comprising the summation of the original image data, weighted by one half, plus the original image data weighted by one-fourth and rotated clockwise through an angle equal to one-half said angular spacing between the obtaining of successive readings, plus the original image weighted by one-fourth and rotated counterclockwise through the same angle.

Claim 4

Dependent Claim 164 words

In a computed tomography scanner, a method for enhancing images comprising the steps of: (a) obtaining real attenuation readings corresponding to radiation passing through a plane extending through a portion of a subject, said readings being obtained from radiation passing through said plane from each of a finite plurality of different orientations separated by angular scanning increments; (b) filtering said attenuation readings across a two dimensional array of pixels to obtain an image of regions in said plane, and (c) modifying said image subsequent to said filtering and back projecting step, and as a function of image location, for reducing artifacts caused by the spacing between orientations at which reading are obtained, said modifying step comprising producing two dimensional weighing coefficients as a function of image pixel location and combining information from a portion of said image with information scaled by said weighing coefficients from a nearby region to approximate an image obtained by filtering and back projecting both real and interpolated attenuation readings.

Claim 5

Dependent Claim 164 words

In a computed tomography scanner, a method for enhancing images comprising the steps of: (a) obtaining real attenuation readings corresponding to radiation passing through a plane extending through a portion of a subject, said readings being obtained from radiation passing through said plane from each of a finite plurality of different orientations separated by angular scanning increments; (b) filtering said attenuation readings across a two dimensional array of pixels to obtain an image of regions in said plane, and (c) modifying said image subsequent to said filtering and back projecting step, and as a function of image location, for reducing artifacts caused by the spacing between orientations at which reading are obtained, said modifying step comprising producing two dimensional weighing coefficients as a function of image pixel location and combining information from a portion of said image with information scaled by said weighing coefficients from a nearby region to approximate an image obtained by filtering and back projecting both real and interpolated attenuation readings.

Claim 6

Dependent Claim 81 words

The method of claim 3, wherein said modifying step comprises: approximating a modified image which comprises the summation of the original real image, weighted by one-half, plus the real image weighted by one-fourth and rotated clockwise through an angle equal to one-half the angular increment between successive readings, plus data corresponding to the real image weighted by one-fourth and rotated counterclockwise through an angle equal to one-half the angular increment of spacing between successive orientations at which real readings are obtained.

Claim 7

Dependent Claim 97 words

The system of claim 1, wherein: said post processing means comprises means for approximating a modified image comprising the summation of the original image date, weighted by a factor of 1/n+1, where n equals the number of synthesized views between real views, plus the summation of the real image data, rotated clockwise, by factors of k/n+1, and weighted by factors of 1/(n+1) 2 , plus the summation of the real image data, rotated counterclockwise by factors of k/n+1, and weighted by factors of n+1-k/(n+1) 2 , where k is the set of integers from 1 to n.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-06-21	1991-12-21	1992-06-21	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-06-21	1995-12-21	1996-06-21	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-06-21	1999-12-21	2000-06-21	$7700.00	Window Closed / Lapsed

Method and apparatus for medical imaging

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