# ICTER hybrid iNIRS resolves blood flow by photon time of flight in two healthy volunteers

- Published: 2026-11-06 05:59 UTC
- Section: Science › Instruments & experiments
- Tags: hybrid iNIRS, time-of-flight blood flow, multi-speckle heterodyne detection, CW-πNIRS, diffuse optical monitoring, swept-source sweep rate, cuff occlusion, forehead blood flow, ICTER
- URL: https://realtech.media/news/rt-d2ce65bab80d3809dc9f45bd_icter_hybrid_inirs/

**Polish researchers combined swept-source interferometric NIRS with camera-based multi-speckle detection, a prototype tested on the forearm and forehead of two healthy volunteers.**

![ICTER hybrid iNIRS resolves blood flow by photon time of flight in two healthy volunteers](https://sgzwpqqelzmajkcubgkl.supabase.co/storage/v1/object/public/rt-media/2026/11/f39453f177b750a5.jpg)
*nature.com*

Researchers associated with the International Centre for Translational Eye Research (ICTER) at the Institute of Physical Chemistry of the Polish Academy of Sciences built a hybrid swept-source interferometric near-infrared spectroscopy (hybrid iNIRS) system. According to an open-access paper on nature.com, published in Scientific Reports, they tested it on the forearm and forehead of two healthy volunteers [1]. The authors, Marcin Marzejon and Dawid Borycki, combined time-of-flight (TOF) encoding with multi-speckle heterodyne detection on a camera [1]. The laser wavelength was approximately 780 nm [1].

## Why two approaches were combined

Conventional iNIRS sorts signals by the time light takes to cross tissue. However, single-mode collection limits photon throughput, and a single-channel implementation demands high analogue bandwidth and digitization rates [1]. Continuous-wave parallel interferometric NIRS (CW-πNIRS) collects more photons by spatial multiplexing on camera sensors. It loses TOF information and is limited by camera readout [1]. The hybrid platform is meant to keep TOF contrast while raising photon detection [1].

The task matters because optical blood-flow measurement at the forehead returns mixed information. Part of the signal comes from scalp circulation and part from deeper tissues, which makes it hard to interpret what a change says about the brain's blood supply [1].

## Sweep rate and in vivo results

Liquid-phantom experiments mapped the trade-off between sweep speed and speckle decorrelation. Under controlled conditions, sweep rates of 10 kHz and above were sufficient to outpace decorrelation while preserving TOF contrast [1]. In vivo measurements needed higher sweep rates, typically 50–100 kHz, to follow faster physiological dynamics [1].

Forearm and forehead measurements showed depth-resolved blood flow during cuff occlusion [1]. On the forehead, a headband was used to restrict scalp circulation. Late-arriving light showed a weaker response during tightening, which suggests a greater contribution from deeper tissues [1]. The authors also report that an appropriately analyzed camera signal can reproduce the blood-flow response seen with iNIRS for late-arriving photons [1].

The work is a demonstration with two healthy volunteers. The authors state that the approach overcomes both the photon-starvation and electronic-bandwidth limits and provides a scalable hardware foundation for haemodynamic sensing in vivo [1].

## Sources

1. [nature.com](https://www.nature.com/articles/s41598-026-62288-7)
2. [EurekAlert](https://www.eurekalert.org/news-releases/1150540)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-d2ce65bab80d3809dc9f45bd_icter_hybrid_inirs/