High dynamic range shortwave infrared imaging of mice with an InGaAs camera

Area of Science:

• Biomedical Imaging
• Optical Engineering
• Preclinical Research

Background:

• Shortwave infrared (SWIR) imaging offers deep tissue penetration and low autofluorescence for preclinical studies.
• InGaAs cameras used in SWIR imaging have limited dynamic range (DR), restricting the analysis of fluorescence intensity.
• This limitation forces researchers to choose between imaging bright or dim features, hindering comprehensive quantitative analysis.

Purpose of the Study:

• To develop a high dynamic range (HDR) imaging method tailored for InGaAs detectors in SWIR applications.
• To enable quantitative fluorescence imaging across a broad spectrum of intensity levels.
• To overcome the dynamic range limitations of current SWIR cameras for enhanced preclinical imaging.

Main Methods:

• Adapted classical HDR algorithms for InGaAs detectors, incorporating exposure-time-dependent dark current subtraction.
• Implemented preprocessing steps to remove saturated and noisy pixels before camera response function recovery.
• Utilized dynamic weighting range adjustment to manage intensity variations across different exposure times.
• Validated the method using indocyanine green and SWIR-emitting quantum dots in mouse models.

Main Results:

• Achieved a 22-dB improvement in dynamic range compared to single exposures.
• Enabled simultaneous quantification of fluorophore concentrations spanning over three orders of magnitude.
• Demonstrated enhanced contrast-to-noise ratios across all anatomical features in vivo.
• Showcased improved vascular contrast while maintaining quantitative accuracy in preclinical studies.

Conclusions:

• The developed software-based HDR SWIR imaging method significantly enhances preclinical imaging workflows.
• It eliminates the need for exposure parameter optimization, allowing rapid processing of data.
• Enables comprehensive biodistribution analysis from a single acquisition sequence with preserved quantitative accuracy.