# Interferometric Speckle Visibility Spectroscopy for Brain Activity Associated Cerebral Blood Flow Monitoring

> **NIH NIH R21** · CALIFORNIA INSTITUTE OF TECHNOLOGY · 2021 · $287,750

## Abstract

Abstract
 Optical monitoring of brain activities is intrinsically associated with a range of operational advantages:
a. non-ionizing and safe radiation, b. simple and relatively lightweight apparatus, c. readily available
commercial optical advanced systems that can be cross adapted for our usage. While the prevalent optical
brain monitoring methods are based on measuring blood oxygenation level dependent (BOLD) signal
associated with the absorption spectral shift of blood to oxygen level changes, optical methods based on
measuring cerebral blood flow (CBF) signal associated with scattering dynamics that scale with the blood flow
in the brain may provide a promising alternative with certain advantages. Some of these advantages include:
1) Provide neurovascular information that is complementary to BOLD information – the combination of which
can reveal a more complete picture of the neurovascular interactions. For example, the combination of BOLD
and CBF measurements may be used to compute metabolic oxygen uptake rate in the brain. 2) As CBF
measurements do not depend on the absorption spectrum of hemoglobin, there is a potential that CBF
methods can penetrate deeper into the brain by using longer wavelengths. 3) Optical CBF methods are
relatively simple to implement. We envision that a high-density full brain surface coverage CBF instrument
can be implemented in a portable fashion.
 For this R21 project, we propose to develop and evaluate a novel CBF measurement method, known
as interferometric speckle visibility spectroscopy (iSVS), for the task of high sensitivity and multi-point brain
monitoring. The iSVS method is substantially different from the current optical CBF method of choice – diffuse
correlation spectroscopy (DCS). Whereas DCS requires sampling of the speckle fluctuations at a rate much
faster than the decorrelation time (typically ~ 100 microseconds), iSVS can perform measurements at a much
slower rate of ~ 100 Hz and still provide superior measurement SNR by exploiting the multiple pixels available
on commercial cameras.
 We propose to implement and test a parallel CBF monitoring prototype that can monitor 50 locations
simultaneously with an update rate of 100 Hz. We will then compare sensitivity and specificity of the developed
iSVS to relative CBF changes evoked by simple motor and visual tasks in the primary motor and visual cortex
of the human brain. If successful, the technology will fill a vital measurement gap that existing optical, MRI,
ultrasound and PET methods have not been able to address.

## Key facts

- **NIH application ID:** 10294139
- **Project number:** 1R21EY033086-01
- **Recipient organization:** CALIFORNIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** CHANGHUEI YANG
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $287,750
- **Award type:** 1
- **Project period:** 2021-09-30 → 2023-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10294139

## Citation

> US National Institutes of Health, RePORTER application 10294139, Interferometric Speckle Visibility Spectroscopy for Brain Activity Associated Cerebral Blood Flow Monitoring (1R21EY033086-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10294139. Licensed CC0.

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