Transcranial photobiomodulation (tPBM) is still a relatively young field, and with that comes a lot of unknowns, especially when it comes to accurately measuring the light output of these devices. One of the biggest challenges we’ve encountered (and we’re not alone) is the lack of clear, industry-wide guidelines or standardized testing procedures.
At Neuronic, we’re not just engineering and measuring our own tPBM devices. We're also committed to leading the way in creating more transparency and setting new standards in how the field reports and understands light measurements.
Why Measuring Light Isn’t So Straightforward
Let’s take a look at measuring irradiance, a common problem in the PBM field.
It’s surprisingly easy to end up with conflicting or confusing results, even when you’re working with the same device or same LED just because the measurement method wasn’t clearly explained or standardized in the first place.
Let’s break it down to illustrate the point:
If you measure a 100 mW LED using a 1 cm² diffuser, and all the light hits the diffuser, you’ll get an irradiance reading of 100 mW/cm².
But if you measure a 100 mW LED capturing all emitted light by using a 0.25 cm² diffuser, you’ll get a much higher irradiance measurement of 400 mW/cm².
It’s the same device, same LED, but very different results.
That’s why we at Neuronic believe it’s so important to consider both irradiance and total power when measuring PBM devices. Looking at just one metric doesn’t paint the full picture.
The following picture shows how drastically irradiance values and total power outputs can vary:
What We Measured and Why It Matters
To explore this critical issue in measuring and reporting, we conducted an internal study focused on quantifying total power, irradiance, and peak wavelength of two of our devices:
We used multiple spectrometers and power meters, tested different measurement setups (including various diffusers and filters), and recorded over 2,000 individual measurements.
Here’s what we found:
