[en] The X-ray photographic unit comprises (a) means for fixing the place for investigation on the patient (b) a source of penetrating radiation (for eXample, X-rays); adopted for the delivery of radiation beams to a body portion of the patient; (c) a number of detectors for the pick-up of the resulting secondary beams radiating around and at a distance from the body portion of the patient, the radiation thereby forming a signal and forming an indication of the quantity of the radiation thereby produced; (d) a pick-up mechanism, consisting of I. the radiation during a first sequence of time intervals and different angular positions which are adopted, during which the source of the radiating beam during each of the first time periods remains constant; II. the radiated beam at an angular position near the application which may be adjusted during a second sequence of time periods, which fall between the first time period sequences, so that the radiation through a cross-sectional region of the patient may be picked-up, such cross-sections lying across the rotational axis of the irradiating beam, and III. the detection with respect to the radiation beam of the adjustment during this first sequence of time periods so that further detection is made of the radiation received following each of the radiated beams, and IV. means for producing a reproduction of the characteristics. (G.C.)