Abstract: For automatically controlling or adjusting the X-ray dose when scanning an examination subject in a CT apparatus, a series of reference measurements are initially made by obtaining CT images of respective phantoms having different attenuation. The tube current for each phantom that produces an image of the phantom having an acceptable noise level, and thus an acceptable image quality, is stored in a table. In a subsequent CT scan of an examination subject, the tube voltage is automatically adjusted when irradiating a region of the subject having attenuation comparable to the attenuation of one of the phantoms, so as to employ the tube current when irradiating the examination subject that produced the image of acceptable quality for the comparable phantom.

Abstract: For automatically controlling or adjusting the X-ray dose when scanning an examination subject in a CT apparatus, a series of reference measurements are initially made by obtaining CT images of respective phantoms having different attenuation. The tube current for each phantom that produces an image of the phantom having an acceptable noise level, and thus an acceptable image quality, is stored in a table. In a subsequent CT scan of an examination subject, the tube voltage is automatically adjusted when irradiating a region of the subject having attenuation comparable to the attenuation of one of the phantoms, so as to employ the tube current when irradiating the examination subject that produced the image of acceptable quality for the comparable phantom.

Abstract: In a computed tomography apparatus and a method for automatic exposure control in computed tomography scanning, an exposure controller, during a first half of a revolution of an X-ray focus around a subject, calculates an actual attenuation profile of a slice of the subject from electrical signals generated by the radiation detector in the first half of the revolution, and calculates an extrapolated attenuation profile of the slice for a second half of the revolution from the actual attenuation profile, and adjusts an operating parameter of the X-ray source, such as the tube current, to modify the radiation dose emitted by the X-ray source during the second half of the revolution dependent on the extrapolated attenuation profile.

Abstract: In a computed tomography apparatus and a method for automatic exposure control in computed tomography scanning, an exposure controller, during a first half of a revolution of an X-ray focus around a subject, calculates an actual attenuation profile of a slice of the subject from electrical signals generated by the radiation detector in the first half of the revolution, and calculates an extrapolated attenuation profile of the slice for a second half of the revolution from the actual attenuation profile, and adjusts an operating parameter of the X-ray source, such as the tube current, to modify the radiation dose emitted by the X-ray source during the second half of the revolution dependent on the extrapolated attenuation profile. The extrapolated attenuation profile can be calculated to achieve a predetermined target pixel noise in the image for the slice currently being scanned.

Abstract: In a method for reducing a radiation dose in an x-ray CT (computed tomography) system, a maximum x-ray attenuation per projection is computed for every projection or for every n.sup.th projection and the measured angular attenuation profile for a last half rotation of the x-ray beam around a subject is stored, an extrapolation method is conducted for computing an extrapolated attenuation profile for a next half rotation based on the measured angular attenuation profile for the last half rotation, and a process is conducted for setting a dose level for the x-ray beam for a next projection, based on the extrapolated attenuation profile. The x-ray beam can be modulated, with characteristics of the beam modulation being set or controlled dependent on the extrapolated attenuation profile.

Abstract: The digital subtraction angiography method useful for three dimensional (3D) imaging of a selected volume of a body comprises the following steps. Acquiring first and second 3D data sets representative of an image of substantially the same selected volume in the body, the first and second data sets being acquired at different times corresponding to a pre- and a post injection of a contrast medium, respectively. Determining common reference points for spatially corresponding subvolumes in the data sets. Comparing in a 3D spatial manner data in subvolumes of the second data set with data in corresponding subvolumes in the first data set in order to determine a new reference point in each of the subvolumes of the first data set which results in a best match of the spatial similarity of the data in the corresponding subvolumes of the second data set.

Abstract: A method for automatically editing a plurality of CT image slices to provide a three dimensional view of a selected object located within a patient's body comprises providing at least one slab of CT image slices produced by CT scanning system and computing a top MIP image of the slab. An undesirable object is automatically removed from the top MIP image by first detecting all the pixels having illuminating intensity values which represent the undesirable object. Then all the pixels of the object to be removed are set to a substantially zero illuminating intensity value in order to remove the object from the top MIP image of the slab. After the undesirable object is removed from the top MIP image, the edits made thereto are applied to each CT image slice in the slab. The present invention also includes apparatus for performing a 3D reconstruction of CT angiographic images to visualize a selected object located within a patient's body.

Abstract: An apparatus for identifying nuclear magnetic spectra from spatially selectable regions of an examination subject supplies pulse signals to the examination subject in the following sequence. A first, non-selective 90.degree. RF pulse is supplied to the patient so that the magnetization of the examination subject is oriented out of the z-direction into an x-y plane perpendicular thereto. A first, selective 180.degree. RF pulse is then supplied simultaneously with a first magnetic gradient G.sub.z which effects a dephasing of the spins outside of a first, selected slice S.sub.1. A second, selective 180.degree. RF pulse is then supplied simultaneously with a second magnetic gradient G.sub.x disposed perpendicularly to the first magnetic gradient. The second magnetic gradient effects a dephasing of the spins outside of a second selected slice S.sub.2. A second, selective 90.degree. RF pulse is then supplied simultaneously with a third magnetic gradient G.sub.