Siemens Aktiengesellschaft

Guenter Schwierz

Erich Hell

Peter Schardt

Karl Wiesent

Joachim Kestler

Walter Greschat

In an x-ray computed tomography apparatus the source of X-rays and the detector are able to scan a volume of the examination subject in a short time. The X-ray source contains an anode that is elongated in the z-direction, on which the focus travels by a controlled deflection of an electron beam. A primary beam diaphragm is displaced synchronously with the focus movement along the anode. The diaphragm forms a pyramid-shaped X-ray beam which always fully strikes the detector but does not overshot the detector. The detector is formed by a matrix of detector elements.

X-ray computed tomography apparatus

In an x-ray computed tomography apparatus with low radiation exposure to the patient, marks are additionally imaged during scanning of the patient, by which the geometry of the image can be determined. The marks are arranged above and/or below a region of interest in the measurement field on rings and are imaged by the x-ray beam.

X-ray computed tomography apparatus having marks for geometrical image

A computer tomography apparatus has an x-ray source which emits a fan-shaped x-ray beam which irradiates a slice of an examination subject. The x-ray source is rotatable around the examination subject to irradiate the slice from different angular directions in the plane of the slice. A row of detector elements is disposed to receive radiation attenuated by the examination subject as the x-ray source rotates around the patient. The radiation detector is disposed on a ring which is rotatable around the examination subject separately from the x-ray source. This permits to meet the conditions of the sampling theorem, applied to the projections with the focus as projection center, without increasing the number of defectors.

Computer tomography apparatus with detector which is rotatable

A computer tomography apparatus has a circular anode and a circular radiation detector in which a patient to be examined is disposed. An electron beam from an electron gun is deflected by a beam deflection system, fed by a line voltage, so that the focus of the electron beam on the anode orbits the patient, thereby irradiating the patient from different angular positions. The radiation attenuated by the patient is recorded by the radiation detector, and corresponding electrical signals are read-out from the radiation detector by a data acquisition system, from which an image of the patient is constructed. To avoid image artifacts due to fluctuations such as ripples in the line voltage which supplies the tomography apparatus, the beam deflection system and the data acquisition system are synchronized so that, at each of n revolutions of the focus, the focus movement and the read-out of the measured values ensue slightly phase-shifted compared to the preceding revolution relative to the ripple period of the line voltage.

Computer tomography apparatus which avoids image artifacts caused by

In the illustrated embodiments, detectors for receiving a fan-shaped beam are arranged in one row with dimensions to resolve a layer of maximum extent, while further detectors of the same dimensions are arranged in one or more adjacent rows and staggered relative to the first row so that the several rows provide comparable resolution for a layer of minimum extent. Thus in generating a computer tomograph of a layer of small extent (as in the neck region), the successive rows of detectors are rendered sequentially responsive to the fan shaped beam. If a physically continuously rotating detector assembly is used with mechanical lateral shifting of the x-ray detector rows into the beam path interpolation can correct for any change in the angles of the ray paths for the respective rows. By converting the x-ray beam into corresponding electronic radiation, electronic switching to successive electron detector rows may be used, thereby maintaining essentially the same focus location for each row, even with continuous rotation.

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Neunkirchen, Germany

Guenter Schwierz