Camera-free NIR-II fluorescence molecular tomography via single-pixel spatial frequency domain imaging with photon...

While fluorescence molecular tomography (FMT) in the second near-infrared window (NIR-II) offers improved penetration and contrast, quantitative deep-tissue recovery remains fundamentally ill-conditioned due to photon diffusion and is constrained by the cost, noise floor, and scalability limitations of short-wave infrared (SWIR) focal-plane arrays. We report a camera-free NIR-II FMT architecture integrating NIR-I spatial-frequency-domain (SFD) structured illumination with NIR-II single-pixel photon-counting detection. Co-registered excitation-reference and fluorescence measurements are fused through a multi-frequency normalized Born formulation to reconstruct the effective fluorescence-yield distribution. Phantom experiments demonstrate millimeter-scale dual-inclusion separability and sub-millimeter axial localization at depths up to approximately 7 mm, with a near-linear fluorescence-yield response. This hardware-efficient framework provides a scalable route toward high-sensitivity NIR-II fluorescence tomography.