Towards pH-sensitive imaging of small animals with photon-counting difference diffuse fluorescence tomography.

Area of Science:

• Biomedical Optics
• Medical Imaging
• Fluorescence Spectroscopy

Background:

• Cellular pH is crucial for cell activity, disease pathology, and drug metabolism.
• In vivo pH monitoring and imaging offer vital physiological and pathological insights, particularly for cancer research.
• Near-infrared diffuse fluorescence tomography (DFT) is a key technique for pH-sensitive fluorescence imaging in tissues.

Purpose of the Study:

• To investigate the feasibility of quantifying pH-induced fluorescence changes in turbid media using a continuous-wave difference-DFT technique.
• To develop and validate a novel computed tomography-analogous photon counting system and image reconstruction scheme for pH imaging.

Main Methods:

• Employed a continuous-wave difference-DFT technique for quantitative pH imaging.
• Utilized a specifically designed computed tomography-analogous photon counting system.
• Applied a Born normalized difference image reconstruction scheme for data analysis.
• Validated the methodology using a small-animal-sized phantom with pH-varying inclusions.

Main Results:

• The proposed approach accurately localized targets with pH-sensitive fluorescence variations.
• Quantitative resolution of pH-sensitive fluorescence yield changes was achieved.
• Demonstrated the feasibility of in vivo pH monitoring in turbid media.

Conclusions:

• The developed continuous-wave difference-DFT technique provides accurate and quantitative pH imaging in turbid media.
• This method offers a promising alternative for pH-sensitive fluorescence imaging, complementing existing techniques like fluorescence-lifetime imaging.
• The approach holds potential for advancing diagnostics, therapeutics, and understanding of diseases like cancer.