US 5,848,114 AGranted

Computerized tomography system

AssigneeHitachi Medical Corporation

InventorsHiroyuki Kawai, Kensuke Sekihara, Nagaaki Ohyama, Masahiro Yamaguchi, Takashi Obi

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Abstract

A computerized tomography system including an X-ray source for emitting X-rays in a cone-beam shape, a two-dimensional X-ray image acquirer which is arranged so as to face the X-ray source and acquires an image of an object by using the X-rays; and rotator for rotating the X-ray source and the two-dimensional x-ray image acquirer around the object, wherein a three-dimensional reconstructed image is formed from the projection images acquired by the two-dimensional X-ray image acquirer while rotating the rotator. An iterative reconstruction calculator for forming the three-dimensional reconstructed image from the projection images is provided. The three-dimensional reconstructed image without artifacts can be acquired from a small amount of projection data.

Claims7

Dependent claims

A computerized tomography system comprising:

an X-ray source for emitting X-rays in a cone beam shape;
two-dimensional X-ray image acquiring means which is arranged so as to face the X-ray source and acquires an image of an object by using the X-rays;
rotating means for rotating the X-ray source and the two-dimensional X-ray image acquiring means around the object;
and
iterative reconstruction means for forming a three-dimensional reconstructed image from projection images acquired by the two-dimensional X-ray image acquiring means while rotating the rotating means,
wherein the iterative reconstruction means includes:
reconstruction means for acquiring the three-dimensional reconstructed image from the projection images;
estimated image calculation means for acquiring an estimated image from the three-dimensional reconstructed image;
reprojection calculation means for acquiring a projection image from the three-dimensional reconstructed image;
and
iterative means for repeatingly executing the calculations by the reconstruction means, the estimated image calculation means, and reprojection calculation means, and
the estimated image calculation means includes:
maximum value detecting means for obtaining the maximum value of the three-dimensional reconstructed image;
threshold calculation means for calculating a threshold according to the maximum value;
extracted image calculation means for extracting a region in which the value is equal to or larger than threshold or the value is equal to or less than the threshold from the estimated image, thereby acquiring an extracted image;
and
image adding means for adding the three-dimensional reconstructed image and the extracted image acquired by the previous iterative reconstruction calculation, thereby acquiring an estimated image.

14 more elements

A computerized tomography system comprising:

an X-ray source for emitting X-rays in a cone beam shape;
two-dimensional X-ray image acquiring means which is arranged so as to face the X-ray source and acquires an image of an object by using the X-rays;
rotating means for rotating the X-ray source and the two-dimensional X-ray image acquiring means around the object;
and
iterative reconstruction means for forming a three-dimensional reconstructed image from projection images acquired by the two-dimensional X-ray image acquiring means while rotating the rotating means,
wherein the iterative reconstruction means includes:
reconstruction means for acquiring the three-dimensional reconstructed image from the projection images;
estimated image calculation means for acquiring an estimated image from the three-dimensional reconstructed image;
reprojection calculation means for acquiring a projection image from the three-dimensional reconstructed image;
and
iterating means for repeatingly executing the calculations by the reconstruction means, the estimated image calculation means, and the reprojection calculation means, and
the reprojection calculation means includes:
image processing means for performing a threshold process to the three-dimensional reconstructed image on the basis of the threshold and adding the threshold processed image to the extracted image acquired by the previous iterating operation, thereby acquiring an extracted image;
reprojection calculation means for acquiring a projection image by reprojecting the extracted image acquired by the image processing means;
and
difference calculation means for calculating the difference between the projection image acquired by the reprojection calculation means and the projection image acquired by the two-dimensional X-ray image acquiring means, thereby acquiring a differential projection image.

13 more elements

A computerized tomography system comprising:

an X-ray source for emitting X-rays in a cone beam shape;
two-dimensional X-ray image acquiring means which is arranged so as to face the X-ray source and acquires an image of an object by using the X-rays;
rotating means for rotating the X-ray source and the two-dimensional X-ray image acquiring means around the object;
and
iterative reconstruction means for forming a three-dimensional reconstructed image from projection images acquired by the two-dimensional X-ray image acquiring means while rotating the rotating means,
wherein the iterative reconstruction means includes:
reconstruction means for acquiring the three-dimensional reconstructed image from the projection images;
estimated image calculation means for acquiring an estimated image from the three-dimensional reconstructed image;
reprojection calculation means for acquiring a projection image from the three-dimensional reconstructed image;
and
iterating means for repeatingly executing the calculations by the reconstruction means, the estimated image calculation means, and the reprojection calculation means, and
the estimated image calculation means includes:
maximum value detecting means for obtaining the maximum value of the three-dimensional reconstructed image;
threshold calculation means for calculating a threshold according to the maximum value;
extracted image calculation means for extracting a part in which the value is equal to or larger than the threshold or the value is equal to or less than the threshold from the estimated image, thereby acquiring an extracted image;
and
image adding means for adding the three-dimensional reconstructed image and an extracted image acquired by the previous iterative reconstruction calculation, thereby acquiring an estimated image, and
the reprojection calculation means includes:
image processing means for performing a threshold process to the three-dimensional reconstructed image on the basis of the threshold and adding the threshold processed image to the extracted image acquired by the previous iterating operation, thereby acquiring an extracted image;
reprojection calculation means for acquiring a projection image by reprojecting the extracted image acquired by the image processing means;
and
difference calculation means for calculating the difference between the projection image acquired by the reprojection calculation means and the projection image acquired by the two-dimensional X-ray image acquiring means, thereby acquiring a differential projection image.

19 more elements

A computerized tomography system comprising:

an X-ray source for emitting X-rays in a cone beam shape;
two-dimensional X-ray image acquiring means which is arranged so as to face the X-ray source and acquires an image of an object by using the X-rays;
rotating means for rotating the X-ray source and the two-dimensional X-ray image acquiring means around the object;
and
iterative reconstruction means for forming a three-dimensional reconstructed image from projection images acquired by the two-dimensional X-ray image acquiring means while rotating the rotating means,
wherein the repetitive reconstruction means includes:
reconstruction means for acquiring the three-dimensional reconstructed image from the projection images;
estimated image calculation means for acquiring an estimated image from the three-dimensional reconstructed image;
reprojection calculation means for acquiring a projection image from the three-dimensional reconstructed image;
and
iterating means for repeatingly executing the calculations by the reconstruction means, the estimated image calculation means, and the reprojection calculation means and for finishing the iteration of the calculations according to the threshold, and
the estimated image calculation means includes:
maximum value detecting means for obtaining the maximum value of the three-dimensional reconstructed image;
threshold calculation means for calculating a threshold according to the maximum value;
extracted image calculating means for extracting a region in which the value is equal to or larger than the threshold or the value is equal to or less than the threshold from the estimated image, thereby acquiring an extracted image;
and
image adding means for adding the three-dimensional reconstructed image and an extracted image acquired by the previous iterative reconstruction calculation, thereby acquiring an estimated image, and
the reprojection calculation means includes:
image processing means for performing a threshold process to the three-dimensional reconstructed image on the basis of the threshold and adding the threshold processed image to the extracted image acquired by the previous iterating operation, thereby acquiring an extracted image;
reprojection calculation means for acquiring a projection image by reprojecting the extracted image acquired by the image processing means;
and
difference calculation means for calculating the difference between the projection image acquired by the reprojection calculation means and a projection image acquired by the two-dimensional X-ray image acquiring means, thereby acquiring a differential projection image.

19 more elements

Dependencies are inferred from the claim text.