High-flux entangled photon generation via clinical megavoltage radiotherapy beams for quantum imaging and...

To evaluate whether clinical megavoltage radiotherapy beams can function as dual-purpose sources that deliver therapeutic dose while simultaneously generating high-flux entangled 511 keV photon pairs for quantum ghost imaging and Quantum Theranostics (QTX). Approach. Geant4 Monte Carlo simulations modeled water-equivalent spherical phantoms containing gold nanoparticle (10 mg/mL)-loaded tumors irradiated with 6, 10, and 15 MV clinical beams. We quantified entangled photon-pair yields, positronium lifetime sensitivity, Doppler and Compton broadening, voxel-level signal-to-noise ratios (SNR), and entanglement retention as functions of depth and beam energy, incorporating detector performance and coincidence gating. Main results. AuNP-loaded tumors produced entangled photon-pair yields of 5.0×10⁷-1.5×10⁸ pairs Gy⁻¹ cm⁻³ (10⁷-10⁹ pairs s⁻¹ at clinical dose rates), with per-voxel SNR of 128-44,395 across 27 configurations (5-15 cm depth, 5-20 mm tumor radius). Doppler broadening (≈1-3 keV), AuNP-induced line broadening (≈0.5-1 keV), and Compton shifts (≈13-171 keV) provided spectroscopic sensitivity to tissue composition, nanoparticle uptake, and microenvironmental heterogeneity, while depth-dependent coherence analysis showed that a substantial fraction of entangled pairs survive to support ghost imaging at clinical depths.

These results indicate that clinical MV beams can act as practical high-flux entangled photon sources, enabling simultaneous therapy and quantum-enhanced imaging. By combining time-resolved positronium lifetimes with energy-resolved Doppler and Compton spectroscopy, the proposed QTX platform could deliver real-time mapping of tumor microenvironment and composition during treatment, extending quantum imaging concepts from optical to therapeutic energy scales. .