Method and apparatus for computed tomography imaging

Claim 1

Computerized tomography scanning apparatus for imaging a cross-sectional slice of a subject comprising: an array of closely spaced radiation sensing detectors; a radiation source rotatably mounted to direct radiation through siad subject to said detector array from a number of positions; means for storing indications of the radiation intensity after the radiation has been attenuated by said subject as the radiation from said moving source reaches the detector array; means for approximating intensity values for nonfunctioning detectors in said array by assigning values to said nonfunctioning detectors; and means for manipulating the intensity data from those functioning detectors and the values assigned to nonfunctioning detectors to create a reconstructed computed tomography image and for presenting said image in a form for discerning density variations in the cross-sectional slice; characterised in that, in said means for approximating intensity values for non- functioning detectors, said assigned values correspond to a preferred function of the intensity values from closely positioned functioning detectors.

Claim 3

A method in computerized tomography employing a stationary detector array for imaging the cross-section of a patient comprising the steps of: ascertaining which of the multiple detectors comprising the detector array are functioning and which are not; directing a spread beam of radiation from a moving radiation source through the cross-section to impinge upon successive portions of said stationary array; sensing radiation intensity from those detectors which are functioning; assigning computed tomography data for the non- functioning detectors; and using the data from those detectors which are functioning and the data assigned to those detectors which are not functioning to reconstruct an image of said cross-section suitable for determining density variations in said cross-section; characterised in that the step of assigning computed tomography data for the nonfunctioning detectors is performed by calculating a preferred difference in data between closely adjacent operating detectors and then calculating and assigning data to each non-functioning detector based upon the preferred difference.

Claim 4

A method in computerized tomography employing a stationary detector array for imaging the cross-section of a patient comprising the steps of: ascertaining which of the multiple detectors comprising the detector array are functioning and which are not; directing a spread beam of radiation from a moving radiation source through the cross-section to impinge upon successive portions of said stationary array; sensing radiation intensity from those detectors which are functioning; assigning computed tomography data for the non- functioning detectors; and using the data from those detectors which are functioning and the data assigned to those detectors which are not functioning to reconstruct an image of said cross-section suitable for determining density variations in said cross-section; characterised in that the step of assigning computed tomography data for the nonfunctioning detectors is performed by calculating a preferred difference in data between closely adjacent operating detectors and then calculating and assigning data to each non-functioning detector based upon the preferred difference.

Claim 7

A method for imaging a cross-sectional slice of a subject in computed tomography comprising the steps of: positioning a plurality of closely spaced radiation detectors in a circular array; positioning the subject so that said slice coincides with a center of said circular array; orbiting a source of x-radiation around said subject along a circular path having a radius less than the radius of said circular detector array; sensing radiation intensities along different x-radiation paths as the radiation is attenuated by said subject; storing the sensed intensities from those detectors in said array which are functioning; filtering the intensity data from said functioning detectors to provide filtered data; assigning filtered data values to nonfunctioning detectors; and using the data from both functioning and non- functioning detectors to backproject an image of said slice; characterised by the steps of calculating a difference in filtered data between closely spaced functioning detectors at closely spaced times and choosing a preferred difference to define a gradient; and assigning filtered data values to non-functioning detectors on said gradient by applying a function of data from functioning detectors along said gradient.

Claim 8

A method for imaging a cross-sectional slice of a subject in computed tomography comprising the steps of: positioning a plurality of closely spaced radiation detectors in a circular array; positioning the subject so that said slice coincides with a center of said circular array; orbiting a source of x-radiation around said subject along a circular path having a radius less than the radius of said circular detector array; sensing radiation intensities along different x-radiation paths as the radiation is attenuated by said subject; storing the sensed intensities from those detectors in said array which are functioning; filtering the intensity data from said functioning detectors to provide filtered data; assigning filtered data values to nonfunctioning detectors; and using the data from both functioning and non- functioning detectors to backproject an image of said slice; characterised by the steps of calculating a difference in filtered data between closely spaced functioning detectors at closely spaced times and choosing a preferred difference to define a gradient; and assigning filtered data values to non-functioning detectors on said gradient by applying a function of data from functioning detectors along said gradient.

Claim 10

A method in computerized tomography employing a stationary detector array for imaging the cross-section of a patient comprising the steps of: ascertaining which of the multiple detectors comprising the detector array are functioning and which are not; directing a spread beam of radiation from a moving radiation source through the cross-section to impinge upon successive portions of said stationary array; sensing radiation intensity from those detectors which are functioning; assigning computed tomography data for the non- functioning detectors; and using the data from those detectors which are functioning and the data assigned to those detectors which are not functioning to reconstruct an image of said cross-section suitable for determining density variations in said cross-section; characterised in that the step of assigning computed tomography data for the nonfunctioning detectors is performed by calculating a preferred correlation in data between closely adjacent operating detectors and then calculating and assigning data to each non-functioning detector based upon the preferred correlation.

Claim 11

A method in computerized tomography employing a stationary detector array for imaging the cross-section of a patient comprising the steps of: ascertaining which of the multiple detectors comprising the detector array are functioning and which are not; directing a spread beam of radiation from a moving radiation source through the cross-section to impinge upon successive portions of said stationary array; sensing radiation intensity from those detectors which are functioning; assigning computed tomography data for the non- functioning detectors; and using the data from those detectors which are functioning and the data assigned to those detectors which are not functioning to reconstruct an image of said cross-section suitable for determining density variations in said cross-section; characterised in that the step of assigning computed tomography data for the nonfunctioning detectors is performed by calculating a preferred correlation in data between closely adjacent operating detectors and then calculating and assigning data to each non-functioning detector based upon the preferred correlation.