A Brief History of Cold Laser Thearapy

The use of Low Level Laser Therapy (LLLT) or sometimes called Low Energy Laser Therapy (LELT), in medicine goes back to the late 1960s, only 8 years after the first laser was developed by Theodore Maiman, Maiman's system was built around a ruby crystal and produced an intense millisecond beam of pure, visible red light which was capable in that ultra-short time of drilling a neat hole through a stack of razor blades. First ophthalmologists and then dermatologists saw the possibilities of using this intense light energy beam in their respective fields, and other applications were quickly found. These applications increased in direct proportion to the development of other wavelengths, with their own particular absorption characteristics, and by 1964, the mainstay lasers still used today in laser surgery had made their appearance. 1961 saw the development of the helium neon (HeNe) and neodymium-yttrium aluminum garnet (Nd:YAG) lasers. In 1962, the argon laser appeared, followed in 1964 by the carbon dioxide (CO2) laser. In late 1964, semiconductor laser sources were being developed, including the first gallium arsenide laser chip.

The ruby laser, with a visible red beam, still has applications in dermatology. The HeNe, with a visible orange/red beam, is used as an aiming beam for the invisible light lasers, the Nd:YAG and the CO2. However, the HeNe has also gained fame as one of the most used systems in LLLT. The argon laser is used principally in ophthalmology and dermatology, because of its visible blue/green beam's biological pigment specificity. The Nd:YAG is used for deep vaporization of tissue mass, and with contact sapphire tips, as an incisive tool. The YAG also is used in LLLT, as its wavelength characteristics give it deep penetration. The CO2 remains one of the most versatile of the surgical medical lasers. It can produce very high power densities, capable of clean, precise linear and bulk vaporization and can also coagulate. Recent experimental data point to the possible application of CO2 lasers in low reactive-level laser therapy (LLLT).

Birth of LLLT

Incision, vaporization and coagulation seemed to be the way to use this new light source in medicine, However, the late Professor Endre' Mester, the grandfather of "'what he termed 'laser biostimulation', felt that the lower-powered beams could produce non-thermal effects in irradiated tissue, and starting in 1968 he used ruby, argon and HeNe lasers at low output powers in in-vitro experimentation on cellular behavior following low-powered irradiation, This was followed with animal in-vivo work in 1969, and in late 1969 he first published his, by now, well known work on the use of low-reactive level laser therapy, or LLLT, to induce healing in torpid non-healing or slow-to-heal ulcers, which had remained resistant to conventional therapeutic methodologies.

His work was followed by others, noticeably Freidrich Plog in Canada, who used HeNe in both acupoint and trigger point irradiation for pain attenuation: and I.B. Kovacs, another Hungarian, who also presented data on the effectiveness of HeNe on in-vivo wound healing acceleration, By the mid-70s, the base of data was increasing, but still was not readily accepted by the majority of Western medical practitioners

In 1979, a French scientist and engineer, Joseph Skovajsa, developed and patented a diode laser system for medical applications, and it is on his work that many of the present-day diode systems are based. There was a subsequent surge of interest in low level laser therapy and the emergence of 'laser acupuncture' dates from that time. In 1981, the 4th Congress of the International Society for Lasers in Surgery and Medicine, held in Tokyo, had for the first time a section dedicated to 'Laser Acupuncture'. The effectiveness of laser acupuncture was high. In addition, some papers appeared on non-acupuncture applications, including papers by Mester and Kovacs. The diode laser made its literature debut at that Congress, in a comparative study with the Nd:YAG laser for pain attenuation authored by Calderhead and Chadwick Smith.

Development of the Diode Laser System

Diode lasers were at first restricted to gallium arsenide (GaAs) systems, which usually produced a 904 nm beam, although the Japan Medical Laser Laboratory was working on an 830 nm GaAs system. GaAs systems were typically difficult to run for long periods in continuous wave because of the propensity of the chip to overheat. From late 1979, experiments were being carried out using a new diode, the gallium aluminum arsenide (GaAlAs) chip, which could produce a variety of wavelengths from 720 to 904 nm and could moreover run in continuous wave without overheating, From available data, a tissue penetration window could be observed at 820-840 nm due to the low water absorption at that waveband. The Japan Medical Laser Laboratory (JMLL) worked on developing a GaAIAs system for medical applications producing an 830 nm beam. Together with Matsushita Electrical Company (better known as National Electronics), a battery-powered, hand-held 15 mW 830 nm continuous wave system made its debut also at 'Laser Tokyo '81'. In fact, Professor Leon Goldman often referred to as the 'Godfather' of the surgical laser, was one of the first to try out and enjoy the therapeutic properties of this new totally self-contained handheld system at that 1981 Congress.

In early experimental work, including in-vivo animal experiments, this 15 mW system proved more effective than the previous GaAs system, and better than the 1064 nm Nd:YAG system, even for more deeply located tissue targets, but without the heat-related side effects noticed with the YAG system used in LLLT. Particularly, the influence of its beam on vascular proliferation was noted. Spurred on by this success, the JMLL experimented with a number of output powers from 15-100 mW and wavelengths from 790-904 nm with pulsed, frequency-modulated, and continuous wave beam types, As for output powers, for anything below 60 mW a distinct falling off in immediate and delayed effective pain removal and decreased microvascular reaction was observed, At 100 mW, effects of a quasi-photothermal nature were noted, such as exacerbation of the pain involuntary muscular spasms and nerve syncope, The ideal output power was finally set at 60 m. From 60 mW up to the side-effect-producing 100 mW range there was no noticeable improvement. The wavelength experiments showed a peak penetration effect at 820-840 nm, with a corresponding increase in the effectiveness of laser beams within that waveband. Finally, JMLL produced, once again in cooperation with Matsushita, the first of the second-generation GaAlAs diode laser systems, the Panalas 4000. This was followed up with the independent JMLL design and construction of an updated third-generation microprocessor-controlled GaAlAs system, the OhLase-3DI, commercially available through Proli Japan, Ltd. The diode laser has shown itself to be superior in penetration to others, and it is based on the GaAlAs diode laser that the practical applications of LLLT have been demonstrated.