Abstract: The scanner includes a patient table having a table support and a moveable table top for receiving a patient. The scanner further includes a computer tomography (CT) imaging device for obtaining an image of a patient placed on the table top. The CT imaging device has an X-ray source and an X-ray detector mounted for rotation about an axis substantially parallel to the longitudinal direction of the table top, the table top being movable along this axis. Also included are a second conventional radiographic imaging device having a cassette for receiving a sheet of an x-ray sensitive material. The table top has a chamber for receiving the cassette of a length that is substantially equal to the length of the table top. Preferably, this chamber contains a trolley for carrying the cassette and a driving device for moving the trolley in the longitudinal direction of the table top over substantially the full length of the chamber.

Abstract: In a computer tomography apparatus in accordance with the invention the advantages of the convolution calculation are combined with the advantages of recursive filtering. The processing unit for the measurement data includes a convolution filter which has only 64 convolution factors and which performs the central part of a convolution calculation (the number of measurement data amounts to, for example 512 or 1024) and a parallel-operating recursive filter which approximates the rests of the convolution calculation situated outside the central part by recursive filtering of the measurement data. Using five different multiplication factors and a corresonding number of attenuation factors, ample accuracy is achieved. By variable of only the 64 convolution factors, a large number of different filters can be realized, without it being necessary to change the factors for recursive filtering.

Abstract: A computer tomography device, in which the row of detectors has been rotated through the quarter of a detector angle (.DELTA..psi./4) with respect to the X-ray source. The invention filters selected parallel measurement values which were measured in a single direction instead of doing so with all the selected measurement values measured in parallel and antiparallel directions. The calculating time required for filtering is reduced by a factor of 2 and the values can be pipeline processed.

Abstract: A method and device for computer tomography in which the same filtering operation can be performed for the image reconstruction, regardless of the method used to measure the measured data. Before and after the filtering the data there is performed a multiplication by a pre-conditioning factor and a post-conditioning factor, respectively. The pre-conditioning and post-conditioning factors are dependent on the type of reconstruction and on the position of a data in the group of measured data. The fact that the same filter can be used is important notably for computer tomography apparatus in which a convolution filter is embodied in circuit hardware. The back-projection device is suitable for the back-projection of measured data along diverging measuring paths as well as measured data along parallel measuring paths with only modification of some constants.

Abstract: The invention relates to a method of and a device for determining a radiation absorption distribution in a part of a body. Per measuring value a contribution of the absorption value in each element of a matrix imagined in the part is calculated. It is demonstrated that this contribution equals the value of the measuring value multiplied by a weighting factor. The weighting factor is a function of the distance between the element and the measuring path along which the measuring value is determined. A calculation method of this kind enables fast on-line calculation of an absorption distribution and the complete reconstruction of the absorption distribution is laid down in a hardware circuit. Complex operations such as F.F.T., convolution and interpolation are not required.

Abstract: A computer tomography device in which the detectors are asymmetrically arranged with respect to the connecting line between the X-ray source, the center of rotation of the source, and the detectors, produce. The detector device produces an incomplete profile of measuring values which are supplemented with "zeros" during processing in order to form a number of measuring values of a complete profile. In order to avoid artefacts which are produced by the acute transients between measuring values and "zeros", a number of measuring values adjoining the acute transients are projected around the center of rotation and multipled by a factor so that from the zeros a smoothly increasing series of adapted measuring values is obtained.