Can 225Ac be imaged on a long axial field-of-view PET/CT with standard clinical settings?
Abstract
Purpose: The 225Ac decay chain includes 209Tl, whose prominent 1567 keV gamma line can create electron-positron pairs. We investigated whether a long axial field-of-view (LAFOV) PET/CT can image 225Ac using standard clinical acquisition and reconstruction methods. Methods: A syringe placed next to a vial (5.89 and 10.29 MBq of 225Ac activity) and a NEMA IEC body phantom (sphere activity concentration 4.56 kBq mL−1) were scanned for 45 and 60 min, respectively, on a Biograph Vision Quadra (Siemens Healthineers). To support our findings, FLUKA simulations scored the annihilation locations around a 225Ac point source. Results: The contours of the syringe and vial were visible despite high noise, but the NEMA spheres could not be distinguished from the background. As illustrated by the FLUKA simulations, the number of annihilation events decreases exponentially according to the mean free path of the 1567 keV photon in the surrounding medium. Conclusion: A LAFOV PET/CT can detect positrons created by pair production of the main 209Tl gamma line. However, these positrons are created where the photons interact with the surrounding medium rather than at the location of the 209Tl decays, which rules out standard PET imaging of 225Ac.
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BibTeX
@misc{mercolli2026225ac,
title = {{Can $^225$Ac be imaged on a long axial field-of-view PET/CT with standard clinical settings?}},
author = {Lorenzo Mercolli},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.19107},
eprint = {2610.19107},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.19107},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Can ^225Ac be imaged on a long axial field-of-view PET/CT with standard clinical settings?
AU - Lorenzo Mercolli
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.19107
UR - https://arxiv.org/abs/2610.19107
AB - Purpose: The ^225Ac decay chain includes ^209Tl, whose prominent 1567 keV gamma line can create electron-positron pairs. We investigated whether a long axial field-of-view (LAFOV) PET/CT can image ^225Ac using standard clinical acquisition and reconstruction methods. Methods: A syringe placed next to a vial (5.89 and 10.29 MBq of ^225Ac activity) and a NEMA IEC body phantom (sphere activity concentration 4.56 kBq mL^−1) were scanned for 45 and 60 min, respectively, on a Biograph Vision Quadra (Siemens Healthineers). To support our findings, FLUKA simulations scored the annihilation locations around a ^225Ac point source. Results: The contours of the syringe and vial were visible despite high noise, but the NEMA spheres could not be distinguished from the background. As illustrated by the FLUKA simulations, the number of annihilation events decreases exponentially according to the mean free path of the 1567 keV photon in the surrounding medium. Conclusion: A LAFOV PET/CT can detect positrons created by pair production of the main ^209Tl gamma line. However, these positrons are created where the photons interact with the surrounding medium rather than at the location of the ^209Tl decays, which rules out standard PET imaging of ^225Ac.
ER -