Radiation detectors, employed in X-ray medical imaging, consist of a scintillating (fluorescent) screen emitting visible light coupled to optical sensors. Screens are fabricated by specially developed scintillators (phosphors). Up to now scintillation screens were prepared by sedimentation on fused silica substrate (spectrosil B) in a form of transparent disk 30mm in diameter and 3mm in thickness. A new sedimentation method is proposed by deposition of scintillation powders on rectangular Borosilicate glass substrate 22x22 mm2 with thicknesses of 0.13-0.17 mm (Waldemar Knittel-GmbH). The optical properties of the substrate were examined in terms of light absorption and transmission in the range between 200-800nm (visible range) and found adequate for use with the common scintillation powders (transmissivity 95%). New screens of various coating thicknesses were examined under medical X-ray irradiation, placed in direct contact with a CMOS (RadEye) optical detector. X-ray images of a test object demonstrate the fine quality and spatial resolution of the above screens. Due to the rectangular shape of the substrate images taken from the prepared screens are indicative for their potential use in the X-ray digital medical systems.