PDF Publication Title:
Text from PDF Page: 012
Penetration depth “is defined as the depth at which the intensity of the radiation inside the material falls to 1/e (about 37%) of its original value at (or more properly, just beneath) the surface." In other words, the penetration depth is technically defined as the depth that a light penetrates a specific type of substance where it loses 63% of its overall light intensity/irradiance. In most human tissue (and this depends on the specific type of tissue, whether fat vs. bone, for example), red/NIR light may have a technically defined “penetration depth” of 3-6mm. Then over the next 3-6mm, it may lose another 63% of that remaining light, and then over the next 3-6mm, another 63% is lost, and so on. In other words, the deeper you go, the more of the overall light doesn’t reach as it is absorbed in the tissues closer to the surface. So a light may have a technically-defined “penetration depth” of 5mm, but you can take that light and shine it through your hand that is more than an inch (25mm) thick and see light coming out the other side. How does that make sense? Well, the light that penetrates all the way through your hand is not at the same light intensity as it went into your hand. That’s because 63% of the light was absorbed in the first 5mm of tissue, then another 63% was lost in the next 5mm, and another, and so on, such that maybe only 5-15% of the light photons that are emitted actually penetrate all the way through your hand and out the other side. In fact, we even know that near-infrared light can penetrate through bone (like the human skull) into the brain. According to Hamblin et al., “One of the best studies on penetration was provided by Tedford et al. in 2015. They performed a light-penetration study on human unfixed cadaver brain tissue ... They compared 660-nm, 808-nm, and 940-nm laser penetration. 808 nm achieved the best penetration, and they concluded that 808-nmwavelength light penetrates the scalp, skull, meninges, and brain to a depth of approximately 40 mm.” 372 Penetration depth is also a confusing topic when it comes to red/NIR light because many light device manufacturers make claims about how their lights penetrate deeper than other light devices. Some also make claims about the particular pulsation of the light (“super pulses”) and claim that affects penetration. (Note: Based on the evidence, pulsation of the light does not appear to affect penetration depth.) These claims make it hard to know what’s really going on. But it is true that higher power devices will deliver more light to deeper tissue depths. To sum up all the confusing concepts around penetration depth, here’s what you really need to know: Red and near-infrared light can penetrate several centimeters (close to 2 inches) into your body, and a high-power light with the right wavelengths (especially near-infrared) can even penetrate through the thick and dense human skull to deliver light directly into the brain. Hamblin has given the general rule of red/NIR light penetration of “up to 5cm,” which is almost exactly 2 inches. So that gives you a sense of how deep this light is actually getting into your body. As you can see, “penetration depth” is not actually as simple a concept as one would think. But the general point here is that with high-power light sources, red/NIR light can deliver significant amounts of therapeutic light inches into human tissue.PDF Image | Red Light Therapy Ultimate Guide
PDF Search Title:
Red Light Therapy Ultimate GuideOriginal File Name Searched:
The-Ultimate-Guide-to-Red-Light-Therapy-Ultimate-Guide-To-Dosing.pdfDIY PDF Search: Google It | Yahoo | Bing
Cruise Ship Reviews | Luxury Resort | Jet | Yacht | and Travel Tech More Info
Cruising Review Topics and Articles More Info
Software based on Filemaker for the travel industry More Info
The Burgenstock Resort: Reviews on CruisingReview website... More Info
Resort Reviews: World Class resorts... More Info
The Riffelalp Resort: Reviews on CruisingReview website... More Info
| CONTACT TEL: 608-238-6001 Email: greg@cruisingreview.com | RSS | AMP |