PRESS RELEASE
January 30, 2026
Researchers optimize the interferometric diffusing wave spectroscopy technique to boost the weak optical field returning from the brain
Cerebral blood flow is essential for normal brain function and often perturbed in neurological disease. If one shines a source of coherent light on perfused tissue, the detected speckles of light fluctuate at a rate proportional to blood flow in the volume sampled by the light. This concept is harnessed to measure the cerebral blood flow index (CBFi) in diffuse correlation spectroscopy (DCS). However, conventional DCS has limited brain sensitivity.
In a study published in IEEE Journal of Selected Topics in Quantum Electronics, Dr. Mingjun Zhao from New York University Langone Health, United States, and her team, has optimized a novel approach called interferometric diffusing wave spectroscopy (iDWS).
“Our novel iDWS approach involves boosting of the weak optical field returning from the brain by coherent amplification with a stronger reference field. In this way, interferometry enables a non-scientific complementary-metal-oxide-semiconductor sensor to parallelize measurements of weak coherent light fluctuations,” explains Dr. Zhao.
In this work, the researchers further optimized iDWS at 852 nm, achieving an over 20x overall improvement in signal to noise ratio. In addition, they demonstrated pulsatile CBFi monitoring at 4–4.5 cm source-collector separation in adults with moderate pigmentation. More recently, they optimized a 1,064 nm iDWS system using the concepts presented in this work and achieved pulsatile CBFi measurement at over 5 cm source-collector separation.
Compared to DCS with a 512×512 single-photon avalanche diode array, the proposed complementary-metal-oxide-semiconductor sensor is currently approximately two orders of magnitude less expensive. In addition, iDWS achieves higher brain sensitivity compared to speckle contrast optical spectroscopy, due to the short exposures that capture the rapid speckle fluctuations originating from the high brain CBFi.
“In this work, we have successfully built the system on a cart and have defined conditions for stable operation. The engineering of a demonstrably stable cart-based iDWS system represents a milestone in clinical translation of interferometric diffuse optical methods,” remarks Dr. Zhao.
With the mobile iDWS system, the team also reports preliminary clinical measurements of CBFi in a patient in the Neuro Intensive Care Unit in this work. These results push the boundaries of iDWS CBFi monitoring performance beyond previous reports.
| Reference Title of original paper Journal | Comprehensive Optimization of Interferometric Diffusing Wave Spectroscopy (iDWS) IEEE Journal of Selected Topics in Quantum Electronics |
| DOI | 10.1109/JSTQE.2025.3537642 |
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Image Caption: A human brain interferometer coherently amplifies light signals to measure cerebral blood flow with enhanced brain sensitivity.
Press Release Source: IEEE Photonics Society
Media Contact First Name: Laura A.
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