WAVELENGHTS
What it is:
Light is an oscillating wave. The length of a single oscillation of this wave is, appropriately enough, called the wavelength. In more lay terms, wavelength is the color of light, and for visible light, this distance is so small it is measured in nanometers (nm; billionths of a meter). Light that we see as blue is that which has wavelengths around 450 nm. Green light has a wavelength of around 510nm, and red around 640 nm. But the range of light goes well beyond our visible range. X-rays are light that have wavelengths shorter than 10 nm, and Ultraviolet (UV) light is between 10 and 300nm. On the other side of the visible range, infrared light spans the 700nm to 1mm range, followed by microwaves (1mm – 1m) and radiowaves (1m-1km+).
Why it’s important:
Simply speaking, the wavelength of light determines how light will interact with whatever material it encounters. Light can either be absorbed or scattered by things in its path. At any interface, both absorption and scattering are possible, so since there are MANY pieces of light in a laser beam (there are more than ten billion billion of what we call photons in 1 Joule of light; that’s right, the word billion is supposed to be there twice), the wavelength determines what percentage of each interaction takes place. The only other factor is the type of material onto which the light is incident. Some materials absorb light more, while others scatter more, and other still have very low probabilities of each and so the material is transparent to some light.
Since in the therapeutic world our aim is to penetrate through the skin and to some depth in the tissue, then get absorbed there so that beneficial healing effects can occur, the obvious goal is to use a wavelength that is relatively weakly absorbed in the skin (the barrier to the external world) and water (the main component of our tissues). This will allow the best penetration. At the same time you would hope to use a wavelength that is relatively strongly absorbed in the parts of the body responsible for enhancing cellular metabolism and all the secondary effects that lead to quicker and more efficient healing. The top two materials that fit this description are the mitochondria of cells (the site where metabolism takes place) and hemoglobin (the part of red blood cells that can be targeted to release oxygen, which is the fuel that cells use to make energy).
How doctorVet fits in:
doctorVet was designed with all of the above in mind. We employ wavelengths of 800 and 915 nm. Within the near-infrared (NIR) spectrum of light, these two wavelengths fall into the very small window where melanin in the skin/fur and water in our tissues absorb the least.
This leads to two important advantages. First, since a smaller percentage of light is absorbed in the skin and water, the deeper the penetration of light and the higher percentage is absorbed in the beneficial stuff.
On a related note, when light is absorbed in tissue, the vast majority of the light is converted into heat. So the second advantage come from the idea that the less superficial absorption, the less localized heat. Excess heat leads to patient discomfort and an overall thermal saturation of the area. To get around this, other laser companies teach the technique of moving the handpiece faster during treatment. While fundamentally there is nothing wrong with this (the light moves faster than your hand…by a lot), it does prohibit the ability to capitalize on a second, more effective technique. And that is being able to stop at specific points within the treatment area, apply pressure, and gently massage the tissue. Penetration increases drastically when the distance to the target is decreased, and applying pressure to trigger points or between spinous processes or in gaps in the joint capsule allow for just that.
Which wavelengths have the most interactions on which materials in the body?
This is the easier way to ask the more technical question, “what is the absorption spectrum of the body”. Like we’ve covered in other articles (link), the wavelength of light determines the probability of interaction with the incident material. The body is made up of many different tissues, each with different densities and constituents. What makes this question fairly simple is that two main materials dominate the absorption of light: melanin and water. Compared to these, other materials are either far-weaker absorbers or they are far less prevalent in the body.
Melanin exists in very high concentrations in the skin and fur of our patients. It is the result of an evolutionary adaption needed to protect animals from the harmful effects of ultraviolet light. Ultraviolet light (with wavelengths from 10-300 nm) has enough energy per photon of light to break chemical bonds in materials. When this happens inside biological tissue, it can lead to broken DNA that leads to mutation which can lead to cancers or cell death, with cell death actually being the more favorable of the two (we have lots of cells, so if some die, it is not that big of a deal; but if they mutate and start to grow and spread quickly, this can be very bad).
So the body developed melanin as a shield to outside light. While it’s best absorption happens in the UV spectrum where the harmful part of the sun’s light lives, the tails of its absorption linger into the visible and infrared. So as you increase in wavelength from about 400nm t0 800nm the absorption strength of the skin and fur decreases steadily. Beyond 800nm melanin becomes virtually translucent to the light and does not act as nearly the barrier to external light source.
The skin and fur still do scatter the light. The good thing here is that this scatter is not the same in all directions. When light scatters off of relatively big particles (like the melanosomes in the skin) who size is on the order of the wavelength of light, the scattering is highly forward-pointing. This means that instead of half of the light reflecting (back-scatter) and half pointing into the body, the proportion is more like 80% forward-pointing (into the body) and 20% reflection. So in general, beyond about 800nm the skin is much less of a barrier to our therapy.
The second principal absorber is water. Water absorbs well on the opposite side of the spectrum: in the mid-infrared all the way to the microwave region (wavelengths from 960nm to several cm). This is why we buy microwave ovens instead NIR ovens to heat our food and why we use Er:YAG and CO2 lasers (2,940 nm and 10,600nm) to do surgery and remove moles. Again the problem is that this absorption doesn’t just drop off at any one wavelength. Instead the spectrum gradually falls off in the mid-infrared. It’s last strong absorption peak is at 980nm, albeit a relatively weak absorption compared to that for CO2’s wavelength.
But that brings up the second part of the issue. Even things with very weak absorption rates can lead to a lot of NET absorption if there is a lot of that material present. Water makes up about 80% of the volume of tissues in our body. And when the water molecules absorb light, all of the light energy gets converted into heat. To avoid excessive heat, there are two options: use much less light (which doesn’t do us much good if we are trying to deliver therapy to relevant treatment volumes in feasible treatment times) or use a wavelength that is much more weakly absorbed by water. Because of the vast presence of water in our bodies, a huge majority of the light will eventually be absorbed in water. But if wavelengths of light with weaker absorption are used, the deeper this light can penetrate and so the more other beneficial reactions can occur along its path.
doctorVet employs two wavelengths in its therapy: 800 and 915nm. Both these wavelengths are relatively weakly absorbed by melanin and so pass through the skin barrier efficiently. They also lie far enough from the peaks of water absorption so as not to accumulate as much heat superficially. Slipping past these two barriers of light, doctorVet’s wavelengths are most effective in targeting the biochemically important targets within the body, namely the mitochondria of cells and hemoglobin in blood. To learn more about what wonderful bio-chemical reactions occur when these two materials absorb light, see our article on Laser Mechanisms of Action.
WAVELENGHTS
What it is:
Light is an oscillating wave. The length of a single oscillation of this wave is, appropriately enough, called the wavelength. In more lay terms, wavelength is the color of light, and for visible light, this distance is so small it is measured in nanometers (nm; billionths of a meter). Light that we see as blue is that which has wavelengths around 450 nm. Green light has a wavelength of around 510nm, and red around 640 nm. But the range of light goes well beyond our visible range. X-rays are light that have wavelengths shorter than 10 nm, and Ultraviolet (UV) light is between 10 and 300nm. On the other side of the visible range, infrared light spans the 700nm to 1mm range, followed by microwaves (1mm – 1m) and radiowaves (1m-1km+).
Why it’s important:
Simply speaking, the wavelength of light determines how light will interact with whatever material it encounters. Light can either be absorbed or scattered by things in its path. At any interface, both absorption and scattering are possible, so since there are MANY pieces of light in a laser beam (there are more than ten billion billion of what we call photons in 1 Joule of light; that’s right, the word billion is supposed to be there twice), the wavelength determines what percentage of each interaction takes place. The only other factor is the type of material onto which the light is incident. Some materials absorb light more, while others scatter more, and other still have very low probabilities of each and so the material is transparent to some light.
Since in the therapeutic world our aim is to penetrate through the skin and to some depth in the tissue, then get absorbed there so that beneficial healing effects can occur, the obvious goal is to use a wavelength that is relatively weakly absorbed in the skin (the barrier to the external world) and water (the main component of our tissues). This will allow the best penetration. At the same time you would hope to use a wavelength that is relatively strongly absorbed in the parts of the body responsible for enhancing cellular metabolism and all the secondary effects that lead to quicker and more efficient healing. The top two materials that fit this description are the mitochondria of cells (the site where metabolism takes place) and hemoglobin (the part of red blood cells that can be targeted to release oxygen, which is the fuel that cells use to make energy).
How doctorVet fits in:
doctorVet was designed with all of the above in mind. We employ wavelengths of 800 and 915 nm. Within the near-infrared (NIR) spectrum of light, these two wavelengths fall into the very small window where melanin in the skin/fur and water in our tissues absorb the least.
This leads to two important advantages. First, since a smaller percentage of light is absorbed in the skin and water, the deeper the penetration of light and the higher percentage is absorbed in the beneficial stuff.
On a related note, when light is absorbed in tissue, the vast majority of the light is converted into heat. So the second advantage come from the idea that the less superficial absorption, the less localized heat. Excess heat leads to patient discomfort and an overall thermal saturation of the area. To get around this, other laser companies teach the technique of moving the handpiece faster during treatment. While fundamentally there is nothing wrong with this (the light moves faster than your hand…by a lot), it does prohibit the ability to capitalize on a second, more effective technique. And that is being able to stop at specific points within the treatment area, apply pressure, and gently massage the tissue. Penetration increases drastically when the distance to the target is decreased, and applying pressure to trigger points or between spinous processes or in gaps in the joint capsule allow for just that.
Which wavelengths have the most interactions on which materials in the body?
This is the easier way to ask the more technical question, “what is the absorption spectrum of the body”. Like we’ve covered in other articles (link), the wavelength of light determines the probability of interaction with the incident material. The body is made up of many different tissues, each with different densities and constituents. What makes this question fairly simple is that two main materials dominate the absorption of light: melanin and water. Compared to these, other materials are either far-weaker absorbers or they are far less prevalent in the body.
Melanin exists in very high concentrations in the skin and fur of our patients. It is the result of an evolutionary adaption needed to protect animals from the harmful effects of ultraviolet light. Ultraviolet light (with wavelengths from 10-300 nm) has enough energy per photon of light to break chemical bonds in materials. When this happens inside biological tissue, it can lead to broken DNA that leads to mutation which can lead to cancers or cell death, with cell death actually being the more favorable of the two (we have lots of cells, so if some die, it is not that big of a deal; but if they mutate and start to grow and spread quickly, this can be very bad).
So the body developed melanin as a shield to outside light. While it’s best absorption happens in the UV spectrum where the harmful part of the sun’s light lives, the tails of its absorption linger into the visible and infrared. So as you increase in wavelength from about 400nm t0 800nm the absorption strength of the skin and fur decreases steadily. Beyond 800nm melanin becomes virtually translucent to the light and does not act as nearly the barrier to external light source.
The skin and fur still do scatter the light. The good thing here is that this scatter is not the same in all directions. When light scatters off of relatively big particles (like the melanosomes in the skin) who size is on the order of the wavelength of light, the scattering is highly forward-pointing. This means that instead of half of the light reflecting (back-scatter) and half pointing into the body, the proportion is more like 80% forward-pointing (into the body) and 20% reflection. So in general, beyond about 800nm the skin is much less of a barrier to our therapy.
The second principal absorber is water. Water absorbs well on the opposite side of the spectrum: in the mid-infrared all the way to the microwave region (wavelengths from 960nm to several cm). This is why we buy microwave ovens instead NIR ovens to heat our food and why we use Er:YAG and CO2 lasers (2,940 nm and 10,600nm) to do surgery and remove moles. Again the problem is that this absorption doesn’t just drop off at any one wavelength. Instead the spectrum gradually falls off in the mid-infrared. It’s last strong absorption peak is at 980nm, albeit a relatively weak absorption compared to that for CO2’s wavelength.
But that brings up the second part of the issue. Even things with very weak absorption rates can lead to a lot of NET absorption if there is a lot of that material present. Water makes up about 80% of the volume of tissues in our body. And when the water molecules absorb light, all of the light energy gets converted into heat. To avoid excessive heat, there are two options: use much less light (which doesn’t do us much good if we are trying to deliver therapy to relevant treatment volumes in feasible treatment times) or use a wavelength that is much more weakly absorbed by water. Because of the vast presence of water in our bodies, a huge majority of the light will eventually be absorbed in water. But if wavelengths of light with weaker absorption are used, the deeper this light can penetrate and so the more other beneficial reactions can occur along its path.
doctorVet employs two wavelengths in its therapy: 800 and 915nm. Both these wavelengths are relatively weakly absorbed by melanin and so pass through the skin barrier efficiently. They also lie far enough from the peaks of water absorption so as not to accumulate as much heat superficially. Slipping past these two barriers of light, doctorVet’s wavelengths are most effective in targeting the biochemically important targets within the body, namely the mitochondria of cells and hemoglobin in blood. To learn more about what wonderful bio-chemical reactions occur when these two materials absorb light, see our article on Laser Mechanisms of Action.