Frequently Asked Questions

1. What is the penetration limit for fNIRS in tissue? / How deep can one probe with NIRS?

Light intensity is heavily attenuated in tissue and falls off exponentially from the illumination point. The maximum achievable probing depth of NIRS is limited by the illumination strength - determined by the thermal damaging threshold - and the detection sensitivity. Imaging depth strongly depends on the tissue type and the application. Typical achievable transmission limits of NIRS are about 12 cm for breast tissue, and 6 cm on the arm or leg. For brain imaging, the probing depth of NIRS is about 3 cm.


2. What is the achievable spatial resolution of NIRS?

Diffuse optical tomography is a low-resolution technique owing to the physics of light propagation in scattering media. Depending on the composition and size of the target tissue, the resolution is on the order of 5-10 mm.


3. What is the temporal resolution of NIRS?

NIRx NIRS systems employ a sampling rate of 62.5Hz. The actual imaging frame rate depends on the number of steps used in the particular application; for example, a brain scan with 16 steps results in 62.5Hz/16 = 3.91Hz sampling rate. Therefore, for a particular application scan speed can be traded off against the desired coverage area (field-of-view) or source density (image resolution). Typical imaging repetition rates are on the order of a 2-15 Hz for most applications


4. Can you provide user references for your NIRS systems and software?

User references are available upon request.  Please email us at:


5. What types of scientific investigative studies is your NIRS technology currently used in?

-Language, Cognition

-Learning, Memory

-Sensory, Motor, Visual

-Brain-Computer Interface (BCI) - Neurofeedback

-Acute Care, Ischemia


-Animal Imaging: Rats

-Animal Imaging: Monkeys

-Child studies

-Traumatic Brain Injury (TBI) Studies 

-Multi-modal studies - NIRS used simultaneously with EEG, TMS, eye-tracking, tDCS, and other modalities.  

-Behavioral studies

-Motor-control & movement-related studies

-Sports performance studies


6. Are NIRx Instruments and software approved by the FDA for clinical diagnostic or treatment planning?

No, NIRx instrument systems and software are not FDA approved and not intended to support clinical diagnostic-treatment decisions.  Instead, our products are designed to support scientific investigative studies that have been IRB approved.