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: With the objective of evaluating whether a dose is excessive for a subject, such a dose that image noise reaches less than or equal to a predetermined value is estimated upon an axial scan on the basis of projection data acquired by a scout scan. The dose is set as a maximum dose. An area other than air, of an image obtained by the axial scan is partitioned into a plurality of small areas i. Image noises N(i) at the respective small areas i are calculated. A warning image G1 in which all of pixel values of pixels in small areas in which the image noises N(i) are less than or equal to a predetermined value, are substituted with pixel values expressed in black level, is created and displayed.

Abstract: With the object of enhancing operability and executing imaging efficiently, a moving speed adjustment unit adjusts a speed at which a table section is moved within an imaging space of a scanning gantry, on the basis of a command from an operator when the scanning gantry scans a subject.

Abstract: An imaging condition determining method for an x-ray CT apparatus for performing imaging by a helical scan. The method includes making a table of various imaging conditions in advance, extracting at least one imaging condition from the table in accordance with age, imaging region, imaging length of the patient as well as the highest-priority objective specified by a user, and displaying the exposure dose of the patient under the at least one imaging condition, enabling the user to adjust the exposure dose, and determining the imaging condition adjusted in response to the adjustment of the exposure dose to the at least one imaging condition.

Abstract: A CT image reconstruction method includes substituting other projection data, which has a predetermined positional relationship to projection data that is found defective during scanning, for the defective data, and interpolating back projection data using a value and information on a scanned position that are contained in the substitute data.

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: 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 of measuring a modulation transfer function (MTF) includes detecting the center of a line spread function (LSF) image in order to calculate an MTF. For this purpose, an enlarged image of a portion of an image containing the LSF image is created, and binary-coded based on a threshold. A morphological operation is performed on the binary-coded image. Coordinates representing points that define the contour of the resultant image are sampled, and used to work out coordinates representing the center of a circle through Hough transform. The coordinates representing the center are transformed into coordinates representing a point in an original image.

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: An apparatus for improving the tomographic image quality by preventing the tomographic image contrast from degrading and preventing artifact from occurring even if many scattered radiations occur. An X-ray detection array obtains first detection data using the X-ray detection elements corresponding to an area not shielded by a collimator. Further, the X-ray detection array obtains second detection data using the X-ray detection elements corresponding to an area shielded by the collimator. A central processing unit corrects the first detection data based on the detection data including the first and second detection data. Finally, the central processing unit generates a tomographic image for an imaging area of the imaging object.

Abstract: An X-ray CT apparatus capable of imaging a subject based on X-rays of multiple energy levels while using an ordinary X-ray detector includes an X-ray tube which generates X-rays from multiple focal points of different 3-dimensional positions sequentially on a time-division basis, a plurality of filters which implement the filtering individually for the X-rays generated individually from the focal points, a collimator which equalizes the irradiation range of the X-rays generated individually from the focal points, collection means which collects projection data of multiple views of a subject of imaging for the X-rays generated individually from the focal points, and reconstruction means which reconstructs an image based on the projection data. The anode of the X-ray tube has multiple impingement portions where electrons released by the cathode impinge at multiple positions on the trajectory of electrons sequentially on a time-division basis.

Abstract: An imaging condition determining method for an x-ray CT apparatus for performing imaging by a helical scan. The method includes making a table of various imaging conditions in advance, extracting at least one imaging condition from the table in accordance with age, imaging region, imaging length of the patient as well as the highest-priority objective specified by a user, and displaying the exposure dose of the patient under the at least one imaging condition, enabling the user to adjust the exposure dose, and determining the imaging condition adjusted in response to the adjustment of the exposure dose to the at least one imaging condition.

Abstract: In order to control a collimator so that an X-ray impingement position on an X-ray detector is kept constant, an error of the impingement position of a fan-shaped beam (400) in the direction of side-by-side arrangement of a plurality of detector element rows in a detector element array (24) is detected (101), and the collimator is controlled (103) based on the detected error so that the impingement position of the fan-shaped beam is kept at a constant position.

Abstract: For the purpose of reconstructing a plurality of X-ray tomographic images having a plurality of practical slice thicknesses while reducing the number of X-ray detector arrays and simplifying configuration, X-rays generated by an X-ray tube 4 are emitted via a slit 15 of a collimator 6 toward a detector 8 disposed opposite to the X-ray tube 4; the length (width) of the collimator 6's slit 15 in the D1 direction and the position of the collimator 6 in the D1 direction are adjustable; the detector 8 is comprised of four X-ray detector arrays; and the widths of the two outer X-ray detector arrays in the D1 direction are larger than the widths of the two center X-ray detector arrays.

Abstract: In order to control a collimator so that an X-ray impingement position on an X-ray detector is kept constant, an error of the impingement position of a fan-shaped beam (400) in the direction of side-by-side arrangement of a plurality of detector element rows in a detector element array (24) is detected (101), and the collimator is controlled (103) based on the detected error so that the impingement position of the fan-shaped beam is kept at a constant position.

Abstract: For the purpose of determining a radiation dose without excess or insufficiency with respect to an allowed value of image noise in performing a helical scan by a CT apparatus comprising a multi-detector, a method comprises the steps of: selecting an image thickness of an X-ray tomographic image to be produced by a helical scan by an X-ray CT apparatus comprising a multi-detector (Step ST1); provisionally determining an X-ray dose in obtaining the X-ray tomographic image having the image thickness by single-slice CT using a single-slice CT radiation dose determining algorithm (Step ST2); selecting a scan protocol (Step ST3); reading a dose correction factor from a dose correction factor table that matches the selected image thickness (Step ST4); correcting the X-ray dose by the dose correction factor (Step ST5); determining tomographic imaging scan conditions by specifying at least one of the tube current and the emission time (Step ST6); and performing the helical scan and displaying an X-ray tomographic imag

Abstract: For the purpose of reconstructing a plurality of X-ray tomographic images having a plurality of practical slice thicknesses while reducing the number of X-ray detector arrays and simplifying configuration, X-rays generated by an X-ray tube 4 are emitted via a slit 15 of a collimator 6 toward a detector 8 disposed opposite to the X-ray tube 4; the length (width) of the collimator 6's slit 15 in the D1 direction and the position of the collimator 6 in the D1 direction are adjustable; the detector 8 is comprised of four X-ray detector arrays; and the widths of the two outer X-ray detector arrays in the D1 direction are larger than the widths of the two center X-ray detector arrays.

Abstract: A method of generating an image representing fat distributions, comprising the steps of scanning two different levels of tube voltage using a phantom containing a sample rod of a fat standard material and a plurality of sample rods with different densities of a bone mineral equivalent material, to generate two cross sectional image data; detecting the CT number of each pixel in an entire region or an objective region of the cross sectional image data as the CT number of a tissue including fat (.alpha.wf); detecting the CT number of the bone mineral equivalent material to calculate a linear regression between the CT number and the density of the bone mineral equivalent material and to define the CT number of a tissue excluding fat (.alpha.nf); detecting the CT number of the fat standard material (.alpha.ff), while detecting the CT number of a soft tissue standard material (.alpha.st), wherein individual CT numbers are applied to the equation.alpha.wf=.alpha.nf+.beta..multidot.(.alpha.ff-.alpha.st)with .beta.

Abstract: A method for quantitatively determining bone mineral mass by a CT system, comprising scanning an objective region together with a plurality of samples produced by mixing a water equivalent material with various ratios of a standard material equivalent to bone mineral mass and determining the bone mineral density of the objective region with reference to the CT numbers of the samples, wherein a plurality of samples are scanned together with the objective region at one or multiple levels of tube voltage and a corrected CT number of each sample is calculated by substituting the CT number of each of the samples with the CT number of blood or a standard material equivalent to blood. By scanning at a single level of tube voltage, bone mineral density is determined, on the basis of the CT number of the objective region and with reference to the corrected CT numbers.