This 12-month postdoctoral position focuses on X-ray metrology and spectrometry for medical imaging. The context is the need for beam-quality traceability, since current standards (IEC 61267) do not cover the new filtration combinations (silver, gold, tin) used in spectral computed tomography (sCT), a technique involved in over 60 million CT exams annually in Europe. The position comprises two independent strands. The first (tasks 1-3) covers drafting methodological guides, qualifying LNHB's two spectrometry benches (CdTe and HPGe), establishing new reference radiation conditions, on-site clinical measurements, and participation in an inter-laboratory comparison. The second strand (tasks 4-5) concerns an instrumented dosimeter dedicated to radiological imaging, stemming from a thesis currently being finalized: pre-series fabrication, calibration, full metrological characterization, clinical validation in a hospital setting, and building a demonstrator.