Early-photon fluorescence tomography: spatial resolution improvements and noise stability considerations

Area of Science:

• Biomedical optics
• Medical imaging
• Photon transport in tissues

Background:

• Near-infrared in vivo tissue imaging, including diffuse optical tomography (DOT) and fluorescence molecular tomography (FMT), faces challenges with low spatial resolution and poor contrast due to significant photon scattering.
• Current FMT resolution is limited to 5-10% of the imaged tissue diameter, comparable to nuclear medicine performance.

Purpose of the Study:

• To introduce the mathematical formalism explaining how fast time-domain optical signal acquisition can significantly improve FMT resolution.
• To demonstrate the potential for enhanced resolution in FMT using early time-gated signals.

Main Methods:

• Mathematical formalism based on singular-value analysis of the time-gated inverse problem.
• Analysis focused on weakly diffused photons.
• Simulations relevant to mouse imaging, comparing steady-state and time-domain approaches.

Main Results:

• Early time-gated intensities (within 200-400 ps) can resolve small fluorescent targets (1.5-2.5 mm radii).
• These targets can be separated by less than 1.5 mm, a significant improvement over steady-state imaging.
• Simulations indicate a substantial resolution enhancement in FMT with time-domain signals.

Conclusions:

• Fast time-domain signal acquisition offers a pathway to significantly improve FMT resolution.
• Early time-gated analysis is key to resolving small, closely spaced fluorescent targets in vivo.
• This advancement holds promise for more precise molecular imaging in preclinical studies.