Abstract
Significance: Diffuse correlation spectroscopy (DCS) is an established optical modality that enables noninvasive measurements of blood flow in deep tissue by quantifying the temporal light intensity fluctuations generated by dynamic scattering of moving red blood cells. Compared with near-infrared spectroscopy, DCS is hampered by a limited signal-to-noise ratio (SNR) due to the need to use small detection apertures to preserve speckle contrast. However, DCS is a dynamic light scattering technique and does not rely on hemoglobin contrast; thus, there are significant SNR advantages to using longer wavelengths (>1000 nm) for the DCS measurement due to a variety of biophysical and regulatory factors. Aim: We offer a quantitative assessment of the benefits and challenges of operating DCS at 1064 nm versus the typical 765 to 850 nm wavelength through simulations and experimental demonstrations. Approach: We evaluate the photon budget, depth sensitivity, and SNR for detecting blood flow changes using numerical simulations. We discuss continuous wave (CW) and time-domain (TD) DCS hardware considerations for 1064 nm operation. We report proof-of-concept measurements in tissue-like phantoms and healthy adult volunteers. Results: DCS at 1064 nm offers higher intrinsic sensitivity to deep tissue compared with DCS measurements at the typically used wavelength range (765 to 850 nm) due to increased photon counts and a slower autocorrelation decay. These advantages are explored using simulations and are demonstrated using phantom and in vivo measurements. We show the first high-speed (cardiac pulsation-resolved), high-SNR measurements at large source-detector separation (3 cm) for CW-DCS and late temporal gates (1 ns) for TD-DCS. Conclusions: DCS at 1064 nm offers a leap forward in the ability to monitor deep tissue blood flow and could be especially useful in increasing the reliability of cerebral blood flow monitoring in adults.
| Original language | English |
|---|---|
| Article number | 097003 |
| Journal | Journal of Biomedical Optics |
| Volume | 25 |
| Issue number | 9 |
| DOIs | |
| State | Published - 1 Sep 2020 |
| Externally published | Yes |
Bibliographical note
Publisher Copyright:© The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
Funding
This work was supported by the National Institutes of Health (NIH) (Nos. R01EB025145, U01EB028660, R01HD091067, and R01NS100750). We thank Vikas Anant and Photon Spot as well as Quantum Opus for their generous offer to test SNSPD detector technology, as well as Bruce Rosen, Felipe Orihuela-Espina, and Adriano Peruch for stimulating discussions and Zachary Starkweather for fabricating the fiber-optic probes utilized in the measurements. MIT Lincoln Lab Distribution Statement: approved for public release. Distribution is unlimited. This material is based upon work supported by the Under Secretary of Defense for Research and Engineering under Air Force Contract No. FA8702-15-D-0001. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Under Secretary of Defense for Research and Engineering.
| Funders | Funder number |
|---|---|
| National Institutes of Health | R01NS100750, R01EB025145, R01HD091067 |
| National Institute of Biomedical Imaging and Bioengineering | U01EB028660 |
| Air Force Institute of Technology | FA8702-15-D-0001 |
| Office of the Under Secretary of Defense |
Keywords
- Monte Carlo simulations
- blood flow
- diffuse correlation spectroscopy
- near-infrared
- short-wave infrared