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Published on: December 9, 2013
Dual-ratio approach for detection of point fluorophores in biological tissue
Giles Blaney1, Fernando Ivich2, Angelo Sassaroli1
1Tufts University, Department of Biomedical Engineering, Medford, Massachusetts, United States.
Insights
Dual ratio (DR) diffuse in vivo flow cytometry (DiFC) may improve detection depth by suppressing noise and autofluorescence. This technique shows potential for enhanced in vivo cell detection if noise is below 10% and autofluorescence is surface-weighted.
Area of Science:
- Biomedical Optics
- Fluorescence Sensing
- In Vivo Imaging
Background:
- Diffuse in vivo flow cytometry (DiFC) enables non-invasive detection of circulating cells.
- Limited measurement depth of DiFC is primarily due to background tissue autofluorescence (AF) and signal-to-noise ratio (SNR) constraints.
Purpose of the Study:
- To investigate the combination of dual ratio (DR) optical measurement and near-infrared (NIR) DiFC.
- To enhance the maximum detectable depth and SNR for circulating cells in vivo.
Main Methods:
- Utilized phantom experiments to estimate parameters for a diffuse fluorescence excitation and emission model.
- Implemented Monte Carlo simulations to model DR DiFC, varying noise and AF parameters.
- Assessed advantages and limitations of the DR DiFC technique.
Main Results:
- DR DiFC requires noise cancellation fraction below 10% for acceptable SNR.
- DR DiFC offers SNR advantages when tissue AF contributors are surface-weighted.
- Simulations identified key parameters influencing DR DiFC performance.
Conclusions:
- DR DiFC shows potential advantages over traditional DiFC for in vivo cell detection.
- Successful implementation depends on managing cancelable noise and AF distribution.
- Further development is warranted based on promising simulation results.
Significance:
Diffuse in vivo flow cytometry (DiFC) is an emerging fluorescence sensing method to non-invasively detect labeled circulating cells in vivo. However, due to signal-to-noise ratio (SNR) constraints largely attributed to background tissue autofluorescence (AF), DiFC's measurement depth is limited.
Aim:
The dual ratio (DR)/dual slope is an optical measurement method that aims to suppress noise and enhance SNR to deep tissue regions. We aim to investigate the combination of DR and near-infrared (NIR) DiFC to improve circulating cells' maximum detectable depth and SNR.
Approach:
Phantom experiments were used to estimate the key parameters in a diffuse fluorescence excitation and emission model. This model and parameters were implemented in Monte Carlo to simulate DR DiFC while varying noise and AF parameters to identify the advantages and limitations of the proposed technique.
Results:
Two key factors must be true to give DR DiFC an advantage over traditional DiFC: first, the fraction of noise that DR methods cannot cancel cannot be above the order of 10% for acceptable SNR. Second, DR DiFC has an advantage, in terms of SNR, if the distribution of tissue AF contributors is surface-weighted.
Conclusions:
DR cancelable noise may be designed (e.g., through the use of source multiplexing), and indications point to the AF contributors' distribution being truly surface-weighted in vivo. Successful and worthwhile implementation of DR DiFC depends on these considerations, but results point to DR DiFC having possible advantages over traditional DiFC.
