Journal Article

DKFZ-2026-00715

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Advancing towards cancer theragnostic by probing the 225Ac decay chain with ultra-high-resolution metallic magnetic calorimeter based detectors.

Maurer, K. ; Unger, D. ; Behe, M. ; Knecht, A. ; von Schoeler, K. ; Hengstler, D. ; Vitova, T. ; Benesova-Schäfer, M.DKFZ* ; Fleischmann, A. ; Gastaldo, L. ; Wängler, C. ; Enss, C. ; Schacherl, B.

2026
Springer Nature [London]

Abstract: 225Ac is one of the most promising short-lived radionuclides for application in targeted alpha therapy (TαT). However, quantitative detection of 225Ac 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 225Ac decay series.In this study, an X-ray and γ-spectrum of an 225Ac sample (89 kBq) was recorded with a Metallic Magnetic Calorimeter (MMC) detector over a wide energy range of 5 to 125 keV.Here, we show the feasibility of detecting γ-lines of 225Ac, 221Fr, 213Bi, and 209Tl 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 221Fr, 217At, 213Bi, 213Po, and 209Pb in this sample. Additionally, particle induced X-ray emission from 225Ac is found.To the best of our knowledge, this first MMC based X-ray and γ-spectrum of 225Ac demonstrates the detector's potential, as it enables the separate detection of most nuclides in the 225Ac decay chain (all except 221Ra and 217Rn) 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.

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Contributing Institute(s):

1. Translationale Radiotheranostik (E270)

Research Program(s):

1. 315 - Bildgebung und Radioonkologie (POF4-315) (POF4-315)

Appears in the scientific report 2026

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