Back in 2010 we ran a simultaneous fMRI-NIRS experiment (see publication here). At that time we borrowed a 10m long optical fibers from Hitachi (Thank them!). The participants had to wear a NIRS cap (with probes) while lying in a fMRI scanner.
![NIRS-fMRI NIRS-fMRI](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3021967/bin/nihms256402f1.jpg)
And this is one of the Hitachi ETG 4000 probes.
![Hitachi ETG 4000 probe Hitachi ETG 4000 probe](https://www.alivelearn.net/wp-content/uploads/2016/01/nirs_probe.png)
As an experimenter, I needed to try and test the experiment myself. The lying position can sometimes make the probe push too hard to my head. As a result, after ~30 minutes of the experiment, the probes left a dent on my head (only temporarily). It was pretty painful.
![NIRS probe leaves a dent on head NIRS probe leaves a dent on head](https://www.alivelearn.net/wp-content/uploads/2016/01/nirs-probe-on-head.png)
How to make the NIRS experiment more comfortable to our participants is a regular topic in our NIRS meeting. Even today, we do not have a satisfying solution.
Also to the best of my knowledge there are no good solutions for pressureless optodes.
@Alex
Thanks for sharing. Too bad there is no such a solution.