Abstract Background 225 Ac is one of the most promising short-lived radionuclides for application in targeted alpha therapy (TαT). However, quantitative detection of 225 Ac and its daughter radionuclides by γ-spectroscopy has so far been unattainable. Achieving this would enable precise organ dosimetry and better targeting of the therapeutic potential of the 225 Ac decay series. Methods In this study, an X-ray and γ-spectrum of an 225 Ac sample (89 kBq) was recorded with a Metallic Magnetic Calorimeter (MMC) detector over a wide energy range of 5 to 125 keV. Results Here, we show the feasibility of detecting γ-lines of 225 Ac, 221 Fr, 213 Bi, and 209 Tl with ultra-high-resolution spectroscopy (FWHM of 23 eV @ 5.9 keV). By analyzing characteristic X-ray fluorescence lines, it is also possible to distinguish 221 Fr, 217 At, 213 Bi, 213 Po, and 209 Pb in this sample. Additionally, particle induced X-ray emission from 225 Ac is found. Conclusions To the best of our knowledge, this first MMC based X-ray and γ-spectrum of 225 Ac demonstrates the detector’s potential, as it enables the separate detection of most nuclides in the 225 Ac decay chain (all except 221 Ra and 217 Rn) with high sensitivity, excellent energy resolution, and precise energy calibration, paving the way for key technological advancements in research and clinical applications in nuclear medicine.
Maurer et al. (Fri,) studied this question.
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