Abstract: In a method and CT device for scanning an examination subject, a radiation beam emanates from a focus of a radiation source which can be displaced around a system axis and strikes a detector system. If, during scanning, a body part of an examiner moves into an examination space covered by the radiation beam, this is automatically detected and the effective radiation is automatically reduced for a volumetric region which includes the body part of the examiner, with respect to a comparable second volumetric region, in which no body part of the examiner is located. The effect of this is to diminish the radiation dose to the examiner. Control for this purpose is performed, for example, by varying the tube current, by adjusting a beam diaphragm, or by an absorber inserted into the beam path. A parameter associated with the body part of the examiner also is detected and the size of the first volumetric region is automatically adjusted dependent on this parameter.

Abstract: In an image reconstruction method for computed tomography the reconstruction of an image from datasets is accelerated so that, with adequate image quality, dynamic studies of moving organs or monitoring of moving therapeutic instruments are possible. To this end, data segments for a sub-scan reconstruction are taken from the continuously measured and pre-processed data stream. The starting angle of the individual data segments is not restricted to a fixed grid. The grid can be arbitrarily defined according to the current computing capability of the reconstruction computer.

Abstract: A medical imaging apparatus includes a measurement unit with an x-ray source and a radiation detector rotatable around an examination subject to conduct a scan of the examination subject and thereby to obtain a data set, which is supplied to a computer. Within the computer, a shadowgraph of the examination subject is calculated in real time as the examination subject is displaced during the scan relative to the measurement unit. The data used to construct the shadowgraph are obtained at a selected projection angle, which is reached a number of times by the measurement unit during the scan. The shadowgraph is displayed in real time as well, to an extent correlated with the amount of relative displacement between the examination subject and the measurement unit. The shadowgraph can be calculated using a convolution equation, wherein the data are twice convolved, once in the longitudinal direction, i.e.