**3. The importance of wavelength in the therapeutic application**

The response to the treatment with LED Therapy depends on several factors, but the most important is the wavelength and light penetration into the tissue beyond the physical, organic and genetic characteristics of the patients, which may provide a more efficient biological response one to another.

Some studies indicate that the wavelengths in the range of 620, 680, 760 and 820nm may be most suitable for health treatments [6]. Commercially available LEDs emit light at certain specific wavelengths, for example, 630, 660, 850 and 880nm. These values may not be accurate, it is possible to have a small variation during the operation in real time where this change can be due to temperature, input or output, electrical current and power dissipation. Currently the electronic converters and the quality of manufacture of high brightness LEDs can considerably reduce this variation. The wavelength of 630nm generated by certain LEDs can affect peak 620nm and 660nm wavelength generated by the LEDs is approaching the peak of 680nm, for example [6]. When operating the LEDs with currents in milliampere range, you can improve the input waveform of [20], this fact is important to have control of the desired wavelength.

To perform the therapy a medical evaluation is required to get the correct diagnosis and indicate the most appropriate treatment and which wavelength should be applied.

#### **3.1. Relationship between the penetration depth and the wavelength in human tissues by applying light emitted by the high brightness LEDs**

The light penetration into human tissue is directly connected to the wavelength, that is, the larger the wavelength the longer is their penetration in the human tissue, as these wavelengths are specific and are within the visible light spectrum [6, 22]. Therefore, the application of a given wavelength is directly related to the color. Each color has a certain wavelength respecting the chromaticity diagram. The color used depends on the type of treatment to be applied. The electronic converters can control the wavelength through duty cycle, which facilitates the relationship between the depth of penetration with the desired wavelength.

### **3.2. Cell photobiostimulation**

There are areas of medicine and veterinary where the LED Therapy has an important role to play, as shown in Figure 6. These are: (i) wound healing, tissue repair, prevention of tissue death; (ii) the relief of inflammation, chronic diseases and injuries, with their pain and edema associated; (iii) relieving the pain and neurogenic some neurological disorders [7].

One of the photobiology principles is that visible light can have an effect in a living biological system. Photons must be absorbed by electronic absorption bands belonging to some molec‐ ular chromophore or photoreceptor. Figure 6 depicts the biological response as a function of wavelength, frequency, or energy of the photons and should resemble the absorption spectrum of the photoreceptor molecule [24].

The fact that a structured action spectrum can be built on the hypothesis of cell photoreceptors and absorption pathways stimulated by light.

High Brightness LEDs Supplied by Electronics Converters Used in Tissue Healing and Cell Rejuvenation http://dx.doi.org/10.5772/59817 237

**Figure 5.** Action of color and depth of penetration in human tissue. Optical penetration depth.

**3. The importance of wavelength in the therapeutic application**

response one to another.

236 Advances in Bioengineering

The response to the treatment with LED Therapy depends on several factors, but the most important is the wavelength and light penetration into the tissue beyond the physical, organic and genetic characteristics of the patients, which may provide a more efficient biological

Some studies indicate that the wavelengths in the range of 620, 680, 760 and 820nm may be most suitable for health treatments [6]. Commercially available LEDs emit light at certain specific wavelengths, for example, 630, 660, 850 and 880nm. These values may not be accurate, it is possible to have a small variation during the operation in real time where this change can be due to temperature, input or output, electrical current and power dissipation. Currently the electronic converters and the quality of manufacture of high brightness LEDs can considerably reduce this variation. The wavelength of 630nm generated by certain LEDs can affect peak 620nm and 660nm wavelength generated by the LEDs is approaching the peak of 680nm, for example [6]. When operating the LEDs with currents in milliampere range, you can improve the input waveform of [20], this fact is important to have control of the desired wavelength. To perform the therapy a medical evaluation is required to get the correct diagnosis and

indicate the most appropriate treatment and which wavelength should be applied.

relationship between the depth of penetration with the desired wavelength.

**applying light emitted by the high brightness LEDs**

**3.2. Cell photobiostimulation**

of the photoreceptor molecule [24].

and absorption pathways stimulated by light.

**3.1. Relationship between the penetration depth and the wavelength in human tissues by**

The light penetration into human tissue is directly connected to the wavelength, that is, the larger the wavelength the longer is their penetration in the human tissue, as these wavelengths are specific and are within the visible light spectrum [6, 22]. Therefore, the application of a given wavelength is directly related to the color. Each color has a certain wavelength respecting the chromaticity diagram. The color used depends on the type of treatment to be applied. The electronic converters can control the wavelength through duty cycle, which facilitates the

There are areas of medicine and veterinary where the LED Therapy has an important role to play, as shown in Figure 6. These are: (i) wound healing, tissue repair, prevention of tissue death; (ii) the relief of inflammation, chronic diseases and injuries, with their pain and edema

One of the photobiology principles is that visible light can have an effect in a living biological system. Photons must be absorbed by electronic absorption bands belonging to some molec‐ ular chromophore or photoreceptor. Figure 6 depicts the biological response as a function of wavelength, frequency, or energy of the photons and should resemble the absorption spectrum

The fact that a structured action spectrum can be built on the hypothesis of cell photoreceptors

associated; (iii) relieving the pain and neurogenic some neurological disorders [7].

**Figure 6.** Schematic representation of the main areas of application of LED Therapy.

One should take into consideration some optical properties of tissues. Both the absorption and scattering of light in tissue are wavelength dependent (both much higher in the blue region of the spectrum than the red), chromophores (hemoglobin) has bands of high absorption and the wavelength less than 600nm [7]. For these reasons they are called "optical window".

The water begins to absorb wavelengths longer than 1150nm and acts tissue at wavelengths in the range of red and NIR, wherein the tissue penetration becomes maximized (Figure 7). Furthermore, blue, green and yellow light may have significant effects on the cells because its therapeutic interaction is proven every day.

**Figure 7.** Optical window in tissue due to reduced absorption of red and NIR wavelengths (600-1200 nm) by tissue chromophores.
