Back to results
US 4,729,100 AGranted
CT System which convolutes projection data with a frequency varying filter function
AssigneeKabushiki Kaisha Toshiba
InventorOsamu Tsujii
Life of this patent
Estimating the term…
Abstract
X-rays are projected from different directions onto a specific slice of an object to be examined, and corresponding projection data is acquired. The projection data is divided into regions in accordance with the data characteristics. The regions are convoluted by corresponding filter functions having different frequency characteristics and are combined to obtain back-projection data, thereby reconstructing an image for the slice.
Claims14
A computerized tomographic apparatus for reconstructing a slice of an object, comprising:
- means for projecting radiation on a slice of an object to be examined along each projection direction;
- means for detecting the radiation projected by said projecting means with a spatial resolution and generating radiation projection data along each projection direction;
- and
- means for reconstructing an image by using projection data generated from said projection data generating means and producing a reconstructed image corresponding to a radiation absorption coefficient at each position of said slice,
- said reconstructed image producing means comprising:
- means for dividing the projection data by at least one threshold value in accordance with an amplitude of said projection data;
- filter function means for storing and/or calculating different types of filter functions having frequency characteristics in accordance with the data characteristics;
- and
- means for convoluting the divided projection data in accordance with the filter functions corresponding to the data characteristics and back-projecting convoluted projection data,
- whereby the convoluted data having good high-frequency responses are obtained for the projection data having a higher degree of reliability, and are back-projected to obtain the reconstructed image.
7 more elements
A computerized tomographic apparatus for reconstructing a slice of an object comprising:
- means for projecting radiation on a slice of an object to be examined along each projection direction;
- means for detecting the radiation projected by said projecting means with a spatial resolution and generating radiation projection data along each projection direction;
- and
- means for reconstructing an image by using the projection data generated from said projection data generating means and producing a reconstructed image corresponding to a radiation absorption coefficient at each position of said slice,
- said reconstructed image producing means comprising:
- means for dividing the projection data by threshold values in accordance with the data characteristics:
- filter function means for storing and/or calculating different types of filter functions having frequency characteristics in accordance with the data characteristics;
- and
- means for convoluting the divided projection data in accordance with the filter functions corresponding to the data characteristics and back-projecting convoluted projection data,
- whereby the convoluted data having good high-frequency responses are obtained for the projection data having a higher degree of reliability, and are back-projected to obtain the reconstructed image;
- wherein said reconstructed image producing means divides the projection data in accordance with additional division.
8 more elements
A computerized tomographic apparatus for reconstructing a slice of an object comprising:
- means for projecting radiation on a slice of an object to be examined along each projection direction;
- means for detecting the radiation projected by said projecting means with a spatial resolution and generating radiation projection data along each projection direction;
- and
- means for reconstructing an image by using the projection data generated from said projection data generating means and producing a reconstructed image corresponding to a radiation absorption coefficient at each position of said slice,
- said reconstructed image producing means comprising:
- means for dividing the projection data by threshold values in accordance with the data characteristics:
- filter function means for storing and/or calculating different types of filter functions having frequency characteristics in accordance with the data characteristics;
- and
- means for convoluting the divided projection data in accordance with the filter functions corresponding to the data characteristics and back-projecting convoluted projection data,
- whereby the convoluted data having good high-frequency responses are obtained for the projection data having a higher degree of reliability, and are back-projected to obtain the reconstructed image;
- wherein said reconstructed image producing means divides the projection data in accordance with proportional additional division.
8 more elements
A computerized tomographic apparatus for reconstructing a slice of an object comprising:
- means for projecting radiation on a slice of an object to be examined along each projection direction;
- means for detecting the radiation projected by said projecting means with a spatial resolution and generating radiation projection data along each projection direction;
- and
- means for reconstructing an image by using the projection data generated from said projection data generating means and producing a reconstructed image corresponding to a radiation absorption coefficient at each position of said slice,
- said reconstructed image producing means comprising:
- means for dividing the projection data by threshold values in accordance with the data characteristics;
- filter function means for storing and/or calculating different types of filter functions having frequency characteristics in accordance with the data characteristics;
- and
- means for convoluting the divided projection data in accordance with the filter functions corresponding to the data characteristics and back-projecting convoluted projection data,
- whereby the convoluted data having good high-frequency responses are obtained for the projection data having a higher degree of reliability, and are back-projected to obtain the reconstructed image;
- wherein said reconstructed image producing means comprises:
- means for calculating threshold values for dividing projection data into a predetermined number of regions;
- means for calculating filter functions having frequency characteristics corresponding to said regions divided by the threshold values;
- and
- means for convoluting the projection data of each projection direction by the filter function corresponding to each region and for obtaining data for back projection,
- whereby the convoluted data having good high-frequency characteristics are obtained for the projection data having a higher degree of reliability, and are back-projected to obtain the reconstructed image.
13 more elements
A computerized tomographic apparatus for reconstructing a slice of an object comprising:
- means for projecting radiation on a slice of an object to be examined along each projection direction;
- means for detecting the radiation projected by said projecting means with a spatial resolution and generating radiation projection data along each projection direction;
- and
- means for reconstructing an image by using the projection data generated by said projection data generating means and producing a reconstructed image corresponding to a radiation absorption coefficient at each position of said slice,
- said reconstructed image producing means comprising:
- means for dividing the projection data in accordance with degree of steepness of a change in the projection data;
- and
- means for selecting a filter function corresponding to each divided projection data,
- whereby the projection data is convoluted by using the corresponding filter functions, and convoluted projection data is back-projected to reconstruct an image for said slice.
6 more elements
Dependencies are inferred from the claim text.