Trace-level radionuclides in vivo counting experiment (TRACE): 210Pb measurement in the skull

This is the authors' abstract. We don't add key points for this paper.

Accurate assessment of health risks from chronic low-dose ionizing radiation is limited by large uncertainties, largely due to the absence of reliable individual exposure data, particularly for long-term internal exposure. In vivo counting provides a direct and non-invasive approach for quantifying trace-level radionuclides retained in the human body and supporting retrospective exposure assessment. The Trace-level RAdionuclides in vivo Counting Experiment (TRACE) is a prospective study aimed at developing experimental methodologies relevant to low-dose radiation exposure. The current focus is on cumulative radon ( 222 Rn) exposure through in vivo measurement of 210 Pb activity in the skull. With a half-life of 22.3 years and bone-seeking behavior, 210 Pb accumulates in skeletal tissue over decades and can serve as an indicator of long-term radon intake. Practical implementation is challenged by extremely low signal levels, subject-dependent efficiency calibration, and uncertainties in internal dose modeling. To address these issues, TRACE has made progress in three aspects. A small-scale shielding prototype has been constructed to validate background suppression strategies, demonstrating a background reduction of approximately two orders of magnitude. In parallel, a source-free efficiency calibration method using CT-derived computational skull phantoms shows agreement with experimental measurements within ∼4%. In addition, a respiratory deposition model incorporating anatomical and physiological parameters representative of the Chinese population has been established to improve internal dose assessment. By improving the reliability of retrospective exposure assessment at the individual level, TRACE aims to support health-oriented risk evaluation and efforts to promote health and well-being.