A method for fluorescent X-ray measurement, wherein the presence of fluorescent target particles is acquired in the object (1) to be examined and the existing target particles are located in the object (1), is (a) X Producing an X-ray beam (2) by a source device (10), the line beam (2) extending through the object (1) in an X-ray beam direction parallel to the first projection direction； (b) Irradiating the object (1) with the X-ray beam (2) at a number of scanning positions in the first projection plane, the scanning positions being set by the scanning device (20), and being scanned by the scanning device. The source device and the object (1) are moved relative to each other, and (c) from the object (1) at each scan position using a detector array device (30) firmly connected to the source device (10). A step of detecting emitted X-rays in a plurality of spatial directions, the detector array device (30) comprising a number of spectrally selective radiation arranged to detect the emitted X-rays in a plurality of spatial directions. The detector element (31) and the detector element (31) extending in a radial direction with respect to the X-ray beam direction and shielding the detector element (31) from the emitted X-rays scattered in the object (1), A plurality of screen lamellas (32) arranged to be able to detect emitted X-rays from all locations within the volume of the X-ray beam in the object (1), (d) Detection of detector elements for obtaining fluorescent X-rays of target particles within the detected radiation X-rays and, if fluorescent X-rays are obtained, for locating the target particles within the target (1). For each of a number of predetermined scan positions, a significant subset of detector elements (31) is determined, the detector signal of the detector elements being the remaining detector elements (31). 31) facilitates the acquisition of fluorescent X-rays of the target particle by increasing statistical significance, and the presence of the targe
