NEW LASER PROTOTYPE

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Phil

 

Emil S Valchinov1 and Nicolas E Pallikarakis1 Design and testing of low

intensity laser biostimulator. Biomed Eng Online. 2005; 4: 5. Published

online 2005 January 13. doi: 10.1186/1475-925X-4-5. 2005

Valchinov and Pallikarakis; licensee BioMed Central Ltd. 1Department

of Medical Physics, University of Patras, Patras 26500, Greece

Corresponding author. Emil S Valchinov: emil;

Nicolas E Pallikarakis: nipa Received November

11, 2004; Accepted January 13, 2005. This is an Open Access article

distributed under the terms of the Creative Commons Attribution

License (http://creativecommons.org/licenses/by/2.0), which permits

unrestricted use, distribution, and reproduction in any medium, provided

the original work is properly cited.

 

Abstract Background. The non-invasive nature of laser biostimulation

has made lasers an attractive alternative in Medical Acupuncture at the

last 25 years. However, there is still an uncertainty as to whether they

work or their effect is just placebo. Although a plethora of scientific

papers published about the topic showing positive clinical results, there

is still a lack of objective scientific proofs about the biostimulation effect

of lasers in Medical Acupuncture. The objective of this work was to

design and build a low cost portable laser device for stimulation of

acupuncture points, considered here as small localized biosources

(SLB), without stimulating any sensory nerves via shock or heat and to

find out a suitable method for objectively evaluating its stimulating

effect. The design is aimed for studying SLB potentials provoked by

laser stimulus, in search for objective proofs of the biostimulation effect

of lasers used in Medical Acupuncture.

 

Methods. The proposed biostimulator features two operational modes:

program mode and stimulation mode and two output polarization

modes: linearly and circularly polarized laser emission. In program

mode, different user-defined stimulation protocols can be created and

memorized. The laser output can be either continuous or pulse

modulated. Each stimulation session consists of a pre-defined number

of successive continuous or square pulse modulated sequences of

laser emission. The variable parameters of the laser output are:

average output power, pulse width, pulse period, and continuous or

pulsed sequence duration and repetition period. In stimulation mode the

stimulus is automatically applied according to the pre-programmed

protocol. The laser source is 30 mW AlGaInP laser diode with an

emission wavelength of 685 nm, driven by a highly integrated driver.

The optical system designed for beam collimation and polarization

change uses single collimating lens with large numerical aperture, linear

polarizer and a quarter-wave retardation plate. The proposed method

for testing the device efficiency employs a biofeedback from the subject

by recording the biopotentials evoked by the laser stimulus at related

distant SLB sites. Therefore measuring of SLB biopotentials caused by

the stimulus would indicate that a biopotential has been evoked at the

irradiated site and has propagated to the measurement sites, rather

than being caused by local changes of the electrical skin conductivity.

Results. A prototype device was built according to the proposed design

using relatively inexpensive and commercially available components.

The laser output can be pulse modulated from 0.1 to 1000 Hz with a

duty factor from 10 to 90 %. The average output power density can be

adjusted in the range 24 – 480 mW/cm2, where the total irradiation is

limited to 2 Joule per stimulation session. The device is controlled by an

8-bit RISC Flash microcontroller with internal RAM and EEPROM

memory, which allows for a wide range of different stimulation protocols

to be implemented and memorized. The integrated laser diode driver

with its onboard light power control loop provides safe and consistent

laser modulation. The prototype was tested on the right Tri-Heater (TH)

acupuncture meridian according to the proposed method. Laser evoked

potentials were recorded from most of the easily accessible SLB along

the meridian under study. They appear like periodical spikes with a

repetition rate from 0.05 to 10 Hz and amplitude range 0.1 – 1 mV.

 

Conclusion. The prototype's specifications were found to be better or

comparable to those of other existing devices. It features low

component count, small size and low power consumption. Because of

the low power levels used the possibility of sensory nerve stimulation

via the phenomenon of shock or heat is excluded. Thus senseless

optical stimulation is achieved. The optical system presented offers

simple and cost effective way for beam collimation and polarization

change. The novel method proposed for testing the device efficiency

allows for objectively recording of SLB potentials evoked by laser

stimulus. Based on the biopotential records obtained with this method, a

scientifically based conclusion can be drawn about the effectiveness of

the commercially available devices for low-level laser therapy used in

Medical Acupuncture. The prototype tests showed that with the

biostimulator presented, SLB could be effectively stimulated at low

power levels. However more studies are needed to derive a general

conclusion about the SLB biostimulation mechanism of lasers and their

most effective power and optical settings.

 

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