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Choosing the Treatment Head in Animal Laser Therapy

How are different wavelengths used in photobiomodulation?

In animal laser therapy, the choice of treatment head affects the tissue targeted by the light and the biological dose that can practically reach the target tissue. In photobiomodulation (PBM therapy), different wavelengths are not unequivocally better or worse; rather, they behave differently in tissue.

Therefore, the selection of the treatment head is not based solely on power or the number of diodes. Practically, the choice is influenced by tissue depth, the structure to be treated, the animal's size, coat, pigment, and the extent of the treatment area. Successful laser therapy is achieved when the right type of light is delivered to the correct tissue with a biologically appropriate dose.

The treatment heads used in the theraluxVET DT device represent three practically different wavelength ranges: 660 nm, 808 nm, and 904 nm. Their differences are primarily related to tissue optics, i.e., how light is absorbed, scattered, and attenuated in tissue.

Why does wavelength matter?

Biological tissue does not transmit all light in the same way. Some light is reflected, some is absorbed by the tissue, some is scattered, and only some penetrates deeper. Wavelength affects the extent to which these phenomena occur.

In the red light region, such as 660 nm, light is more effectively absorbed by superficial structures, hemoglobin, and melanin. Therefore, a larger proportion of the energy acts closer to the tissue surface.

In the near-infrared light region, such as 808 nm and 904 nm, light generally penetrates tissue better than red light. This makes near-infrared a practical option when targeting muscle areas, joints, tendon structures, or larger animals. However, deep penetration does not mean unlimited penetration. Light intensity decreases with increasing tissue depth, and therefore, the application technique, quality of contact, treatment time, coat, and dosage also affect the outcome.

660 nm – for superficial tissues and localized targets

660 nm falls within the visible red light spectrum. It is efficiently absorbed by superficial tissues, hemoglobin, and melanin, which is why its effect is concentrated near the tissue surface.

In practice, the 660 nm treatment head is particularly suitable for skin, mucous membranes, superficial muscles, subcutaneous structures, and small, localized treatment targets. It is a precise option when the area to be treated is limited and the tissue is located close to the surface.

Typical applications include wounds, skin lesions, scar tissue, paw pads, superficial skin irritations, and small localized soft tissue areas. The treatment of trigger points, acupuncture points, and other defined superficial muscle areas can also benefit from 660 nm.

However, 660 nm is generally not the primary choice when the target is deep, the animal is large, muscle mass is thick, the coat is dense, or the treatment area is extensive. For example, deep back muscles of horses, hip areas, large muscle groups, and deep tendon structures often require a wavelength that penetrates tissue more effectively.

808 nm – for general use on muscles, joints, and medium-deep tissues

808 nm falls within the near-infrared light spectrum. It generally penetrates tissue more effectively than red light and scatters less in superficial tissues. Therefore, 808 nm is a versatile option for situations where the target is not entirely superficial but also not extremely deep.

In practice, 808 nm offers a good balance between tissue penetration, biological response, and everyday usability. The four-diode design allows for a larger treatment area and more practical energy output than single-diode localized treatment.

In animal treatment, 808 nm is particularly suitable for muscle areas, joint areas, and soft tissues. It is often used for medium-deep muscle areas, strain-related muscle problems, muscle tightness, and supporting recovery. For joint areas, it is a practical option for treating canine elbow and knee joints, as well as other medium-deep joint areas.

808 nm is often a good primary choice when a general-purpose PBM treatment head is needed for animal physiotherapy, rehabilitation support, or as an everyday tool for professionals. It is particularly well-suited for small and medium-sized animals and for situations involving muscle, joint, or soft tissue areas without requiring extremely deep tissue penetration.

904 nm – for larger animals, broader areas, and deeper tissues

904 nm also falls within the near-infrared light spectrum. It penetrates tissue better than visible red light wavelengths and is therefore particularly suitable for situations where the target is deeper or the treatment area is large.

The six-diode design enables a broader energy output, making the 904 nm treatment head a practical option for large treatment areas. This is especially relevant for treating horses, large dogs, and thick tissue areas.

For horses, 904 nm is particularly suitable for deep muscle areas, such as back muscles, the pelvic region, the area around the SI joint, and large muscle groups. It can also be used to support the treatment of deeper soft tissue, joint, and tendon structures when the treatment situation and overall context warrant it.

904 nm is especially beneficial when the animal is large, the tissue is thick, the coat is dense, or the treatment area is extensive. However, it is important to note that while 904 nm penetrates tissue better than 660 nm, light does not travel indefinitely within the tissue. Deep tissue still receives only a fraction of the energy delivered to the surface.

Therefore, for the 904 nm treatment head, the same basic principles as in all laser therapy are emphasized: contact technique, dosage, treatment time, consideration of the coat, and application technique all influence the biological dose that ultimately reaches the target tissue.

Practical summary of treatment head selection

The table below summarizes the practical differences between the treatment heads. It is not an individualized treatment guide but helps to understand which situations different wavelengths are particularly suitable for.

Treatment Head Best Application  Practical Strength
660 nm / 1 diode skin, wounds, superficial tissues precise localized use near the tissue surface
808 nm / 4 diodes general use, muscles, joints versatile general use on various animals and treatment areas
904 nm / 6 diodes deep tissues, large animals practical option for large and deeper treatment targets


In simplified terms, 660 nm is particularly suitable for superficial targets, 808 nm for versatile muscle and joint area treatment, and 904 nm for larger animals, broader areas, and supporting the treatment of deeper tissues.

Treatment head selection is not just a technical decision

In animal laser therapy, the choice of treatment head is always part of a larger whole. The same wavelength does not behave in the same way on a short-haired dog, a horse with a winter coat, or a dark-pigmented animal. The coat and pigment can significantly alter how much light reaches the tissue.

Also, the size of the animal and the thickness of the tissue affect the choice. A muscle or joint area in a small dog can be optically a completely different situation than in a large horse. Similarly, a large muscle area requires a different approach than a small localized skin target.

For this reason, when choosing a treatment head, it is not advisable to ask which wavelength is generally the best. A better question is: where is the tissue to be treated located, how deep is the target, and with which treatment head can biologically effective light most likely be delivered to the correct tissue with an appropriate dose.

Summary

Different treatment heads and wavelengths serve various application needs in animal laser therapy. 660 nm is particularly suitable for superficial tissues, skin, wounds, and localized targets. 808 nm is a versatile general-purpose option for muscles, joints, and medium-deep soft tissues. 904 nm is particularly suitable for large animals, broad areas, and supporting the treatment of deeper tissues.

What is crucial is not a single wavelength or the number of diodes, but how well the treatment head, application technique, dosage, and treatment time correspond to the animal's size, tissue, coat, pigment, and treatment situation.

The best practical outcome is achieved when the right type of light is delivered to the correct tissue with the correct biological dose.

References

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