Abstract: The present invention provides an X-ray attenuation correction method, image generating apparatus, X-ray CT apparatus, and image generating method for correcting for the attenuation of X-ray beam at the boundary where the X-ray absorption rate of a subject is changing. Boundary information comprised of the boundary position where the X-ray absorption rate is changing and the magnitude of change is extracted from the projection information of the subject, then the boundary information is used to multiply the amount of scattered X-ray by the amount corresponding to the magnitude of change at the boundary position, to correct for the attenuation of X-ray at the boundary position. The attenuation of X-ray at the boundary position may be corrected for along with the scattered X-ray correction of the projection information, allowing alleviating artifacts developed in a tomographic image.

Abstract: The present invention is intended to improve the quality of a tomographic image to be produced by an X-ray CT apparatus including an X-ray area detector represented by a multi-array X-ray detector or a flat-panel detector. A conventional (axial) or cine scan is performed on the first and second scanned positions in the direction of a z axis. Projection data items produced by scanning the first scanned position and projection data items produced by scanning the second scanned position are used to reconstruct a tomographic image.

Abstract: An imaging method for an X-ray CT apparatus having an X-ray source and an X-ray detector disposed to face the X-ray source with a subject placed therebetween, for rotating at least one of the X-ray source and X-ray detector around the subject and detecting X-rays emitted from the X-ray source toward the subject by the X-ray detector, comprises the steps of: defining a reconstruction plane for the subject in a plane non-parallel to a plane formed by rotation of at least one of the X-ray source and X-ray detector around the subject; scanning the subject by emitting cone-shaped X-rays from the X-ray source; and reconstructing a tomographic image of the subject based on the defined reconstruction plane.

Abstract: An object of the present invention is to calculate a more accurate beam-hardening correction coefficient. A phantom having an oblong section or a phantom having an annular (sector) section and a uniform thickness is positioned in an X-ray CT system, and scanned from plural directions in order to acquire a plurality of views. The results of the scan are used to calculate a correction coefficient that is used to correct projection information to be acquired from a subject.

Abstract: A method for compensating scattering includes acquiring the projective length of non-subject entities and acquiring the projective length of an object of radiography wherein the object of radiography is radiographed with a beam thickness set to the same value as a detector thickness and the object of radiography is radiographed with the beam thickness set to a value larger than the detector thickness. An amount of scattering is calculated based on the difference between the object data from the first scan and the object data from the second scan and stored in association with the sum of projective lengths. A subject is radiographed to produce data and the projective length of the subject is calculated along with the projective length of the non-subject entities having affected the data. The amount of scattering associated with the sum of the projective length and the projective length is then determined.

Abstract: An X-ray computed tomographic (CT) system includes: a beam-hardening correction block that corrects first projection information in terms of the beam-hardening effect so as to produce second projection information; a first fitting block that fits a first function to the second projection information so as to produce third projection information; a second fitting block that fits a second function to the third projection information values that are provided as functions having as independent variables the second projection information values sampled in relation to all the views and each of the channels of an X-ray detector; and a correction coefficient modification block that modifies a second correction coefficient, which is calculated using a second phantom larger in dimensions than a first phantom, using a first correction coefficient calculated using the first phantom.

Abstract: An apparatus for reducing the influence by scatter rays and improving image quality of a tomographic image. The apparatus includes an X-ray detector and a calculation/control apparatus for generating tomographic image data for a tomographic image of the subject based on the projection data. The X-ray detector includes a plurality of detector channels for detecting the radiation, extending in a two-dimensional manner in two arrangement directions, i.e., in channel and column directions, the channel direction being contained in a plane of rotation of the X-ray source, the column direction being orthogonal to the channel direction and aligned along the axis of rotation; and collimators for confining an angle at which X-rays impinge upon the detector channels, provided at borders between the detector channels adjoining in the column direction.

Abstract: The present invention provides an X-ray dose compensation method for X-ray dose compensation of the detector signals from a multiple array detector with improved SNR, used for the detector signal detected by using the multiple array detector in which a plurality of X-ray detector channels placed in one dimensional array in the channel direction is stacked in a plurality of rows in the row direction to form X-ray detector channels of two dimensional matrix. A plurality of specific X-ray detector channels in the multiple array detector or X-ray planar detector or X-ray image intensifier are used as the X-ray dose reference channels for the X-ray dose compensation by means of signal sum or mean of detector signals from those X-ray dose reference channels.

Abstract: A collimator control method for an X-ray CT apparatus includes changing an aperture of the collimator according to a position of a helical scan on the body axis of the subject in the progress of the helical scan.

Abstract: A method for decreasing the streak artifact in the reconstructed image due to the existence of foreign matter of high X-ray absorption rate such as metals. The method includes separating discrete region containing the data having abrupt change of value the projection data in the sequential order of radiographic detector elements, transforming the data to continuous data such that the value gradually smoothly changes, filtering the continuous data, composing the filtered data with the data of the discrete regions to form the projection data used for the image reconstruction.

Abstract: A cross-talk correction method for easily removing leakage of fluorescent light occurring between scintillators adjacent in a slice direction, wherein first function fitting means in a channel direction and second function fitting means in a slice direction determine an ideal projection length, from slope phantom projection information, Equation (1) is then used to determine leakage coefficients ?+ and ??, and subsequently, cross-talk removing means determines intensity information Dn from detected information Sn making up subject projection information on a subject using Equation (2) and the leakage coefficients ?+ and ??; thus, the leakage component for scintillators adjacent in the slice direction contained in the subject projection information is removed by a simple method to eliminate artifacts due to leakage in the slice direction, hence improving image quality.

Abstract: A beam hardening post-processing method that can improve the accuracy of channel-by-channel correction on a BH effect easily and yet taking a non-linear effect into account, phantoms of different diameters are disposed at a position offset from an imaging center to acquire projection information having a transmission length of an X-ray beam varying from view to view, hence, acquire projection information having a projection information value varying from view to view, for each channel, correction factors are determined, and a corrective function containing even a non-linear effect is determined by higher-order function fitting from the correction factors; and therefore, correction with high accuracy can be achieved in the channel-by-channel correction on the projection information values conducted after BH correction, and moreover, correction with high accuracy can be achieved using a smaller amount of phantom projection information, thus reducing the time for calibration work.

Abstract: An imaging method for an X-ray CT apparatus having an X-ray source and an X-ray detector disposed to face the X-ray source with a subject placed therebetween, for rotating at least one of the X-ray source and X-ray detector around the subject and detecting X-rays emitted from the X-ray source toward the subject by the X-ray detector, comprises the steps of: defining a reconstruction plane for the subject in a plane non-parallel to a plane formed by rotation of at least one of the X-ray source and X-ray detector around the subject; scanning the subject by emitting cone-shaped X-rays from the X-ray source; and reconstructing a tomographic image of the subject based on the defined reconstruction plane.

Abstract: A method for correcting scatter in multi-slice imaging wherein, a projection p and a scatter correction factor R(d, do) are stored in association with each other, a projection p is determined from data D0 collected by imaging a subject with an X-ray beam with a beam thickness d using a detector with a detector thickness do, the scatter correction factor R(d, do) associated with the projection p is determined, and the data D0 is multiplied by the scatter correction factor R(d, do) to obtain scatter-corrected data D1.

Abstract: An apparatus for reducing the influence by scatter rays and improving image quality of a tomographic image. The apparatus includes an X-ray detector and a calculation/control apparatus for generating tomographic image data for a tomographic image of the subject based on the projection data. The X-ray detector includes a plurality of detector channels eh for detecting the radiation, extending in a two-dimensional manner in two arrangement directions, i.e., in channel and column directions, the channel direction being contained in a plane of rotation of the X-ray source, the column direction being orthogonal to the channel direction and aligned along the axis of rotation; and collimators for confining an angle at which X-rays impinge upon the detector channels, provided at borders between the detector channels adjoining in the column direction.

Abstract: A radiation computed tomography apparatus that includes a radiation detector having a plurality of radiation detector elements arranged in a two-dimensional manner for detecting radiation passing through a subject, and a reconstructing device for arithmetically reconstructing tomographic image data for a tomographic image of the subject based on projection data for the subject from each of the plurality of radiation detector elements, the projection data obtained from values detected by the plurality of radiation detector elements, wherein the reconstructing device corrects the projection data for each of the radiation detector elements using a corrective value that is correlated with a path length of the radiation through the subject calculated from the projection data, and generates the tomographic image data based on the corrected projection data.

Abstract: A method and apparatus for reducing the contrast of a tomographic image due to crosstalk and the occurrence of artifacts and improve the quality of the tomographic image. Detection data are subjected to fitting processing in such a manner that, of the data generated by an X-ray detected by X-ray detection elements disposed in array form in a plurality of X-ray detection modules disposed adjacent to one another, first detection data generated by the X-ray detected by X-ray detection elements adjacent to a boundary between the plurality of X-ray detection modules are adapted to waveform data based on second detection data generated by the X-ray detected by X-ray detection elements lying around the adjacent X-ray detection elements.

Abstract: For the purpose of determining an offset of the position of an X-ray tube from a prespecified position, and correcting axially projected data D1 and pixel projection data D2 based on the determined offset, proper axially projected data D1 can be obtained by an X-ray focal spot 2102 and a detector 2103 by determining axially projected data D1 at a point 2104 using projection data D0 obtained by a channel that detects an X-ray emitted from the X-ray focal spot 2102 and passing through the point 2104, and shifting the determined axially projected data D1 by a distance DIS1 in the (+)-direction of the x-axis.

Abstract: A method for decreasing the streak artifact in the reconstructed image due to the existence of foreign matter of high X-ray absorption rate such as metals. The method includes separating discrete region containing the data having abrupt change of value the projection data in the sequential order of radiographic detector elements, transforming the data to continuous data such that the value gradually smoothly changes, filtering the continuous data, composing the filtered data with the data of the discrete regions to form the projection data used for the image reconstruction.

Abstract: An X-ray computed tomographic (CT) system includes: a beam-hardening correction block that corrects first projection information in terms of the beam-hardening effect so as to produce second projection information; a first fitting block that fits a first function to the second projection information so as to produce third projection information; a second fitting block that fits a second function to the third projection information values that are provided as functions having as independent variables the second projection information values sampled in relation to all the views and each of the channels of an X-ray detector; and a correction coefficient modification block that modifies a second correction coefficient, which is calculated using a second phantom larger in dimensions than a first phantom, using a first correction coefficient calculated using the first phantom.