LASERS : ASPECTS OF EFFECTIVENESS AND SAFETY*

The use of laser therapy by physiotherapists has shown a marked increase in popularity over recent years. Effective­ ness and safety of lasers is essential. The results of an investigation by the CSIR of some infrared lasers is reported, highlighting, e.g., that all that SAYS laser may not BE laser. New legislation that will ensure that lasers conform with the minimum requirements to be safe and effective products, is discussed. The risk of laser radiation and product/premises licenses as a means of ensuring safe use of lasers, are explained. OPSOMMING


INTRODUCTION
L a s e r t h e r a p y is fa s t b e c o m in g a p o p u l a r m o d a lity in physiotherapy.This form of phototherapy has been gaining ground in proportion to the increased marketing of various lasers in South Africa over the last couple of years.
Safety and effectiveness is of great importance in performing our professional service.When a new treatm ent modality is intro duced, ensuring effectiveness and safety may however be difficult, for two main reasons.
Firstly, control over the electronic equipm ent/products accord ing to set standards of safety and reliability initially may not exist.Such control may only be instituted after some time and could possibly take years.
Secondly, lack of relevant information, training, understanding of the uses, potential dangers, method of application, and estimating the proper dosage is a problem.Ft is not uncommon for physiother apists in private practice and hospitals to start using a new modality when the only information available is from m anufacturer's bro chures, manuals, etc.It usually takes some time for workshops to be held on the subject for qualified physiotherapist.It may also take some time for the subject to be included in the undergraduate curriculum.Scientific research may often be very sparse, even non existent.This is certainly the case for laser therapy.
This paper deals with the effectiveness and safety of laser equipm ent and their safe use.The results of an investigation of some infrared lasers as well as regulatory control of laser products and its implications for South African physiotherapists are discussed.

DEFINITION
A laser is a device which em its optical radiation (radiation in the ultraviolet, visible and infrared regions of the electromagnetic spectrum ) with unique characteristics due to the process of Light Amplification by the Stim ulated Emission of Radiation (for which LA SER is an acronym )1.Such radiation is typically monochromatic (of a single wavelength o r lying within a very narrow wavelength band), of high energy and power density, coherent (all waves bein^ in phase) and unidirectional (parallel; having minimal divergence)1' -.

MEDICAL USE OF LASERS
In medicine lasers are either used for bringing about definite .Biostimulation is achieved by laser treatm ent with a dose rate that causes no immediate detectable tem perature rise in treated tissue and no macroscopically visible change in tissue structure .This is term ed "low level laser therapy" (LLLT) by Ohshiro and Calderhead 7. O ther term s used in connection with biostimulation are cold/soft/mid laser.

LASER SOURCES: LASER WAVELENGTHS
M o st c o m m e rc ia l in stru m e n ts use a laser so u rc e w hich is wither a small helium-neon (He-Ne) (gas) laser with a continuous wave (cw) power, o r a diode laser which may be cw o r pulsed ' .
A He-Ne laser produces optical radiation at a wavelength of 632.8 nm (visible red light)5, whereas the combination of elem ents that make up a sem iconductor laser diode determ ines the wave- Wavelengths in the near infrared region, e.g.904 nm, is relatively common for physiotherapeutic use.
The ability of the laser diode (depending on their composition) to emit at different wavelengths together with their low cost (relative to the H e-He tubes of higher power ranges), small size and robust ness has made this type of laser medium very popular with the m anufacturers of biomedical laser systems.It must however be noted that not all diodes are made with the same optical properties o r the same method of manufacturing so a variation of quality of beam radiance, divergence, wavelength bandwidth) is expected .It is im portant that m anufacturers provide adequate radiation specifi cations of the laser product.

CREDIBLE LASER
To reproduce the clinical results that is reported in the lit- Reproduced by Sabinet Gateway under licence granted by the Publisher (dated 2013.) erature, it must be ensured that the characteristics of the laser radiation is identical.F or instance, a narrow bandwidth of wave lengths is supposed, together with the expected high intensity due to the process of amplification.
In the past it was assumed that potentially hazardous electronic products, e.g.lasers, would be imported almost exclusively from recognised manufacturers that maintain internationally accepted norms for safety and effectivity.M ore recently, however, more and more products of less well known and even unknown origin, includ ing locally m anufactured products, have appeared on the South African market, often not complying with the required standards8.

CSIR INVESTIGATION
Against this background, the Division of Production T echnol ogy of the CSIR was commissioned by the University of Stellenbosch during 1989 to investigate by means of radiom etric measurements th e c h ara cte ristics o f five n e a r in frared rad iatio n so u rc es (la se r diodes) used in physiotherapy (table 1.).The devices were charac terised with regard to spectral properties, radiant power and beam divergence.

Spectral properties
On the basis of the relatively broad band of wavelengths (895 q 75 nm) of one of the two proves of the Lasdac, it was concluded that it was an ordinary light emitting diode (L E D ) (or infrared emitting diode) as distinguished from a laser diode9.The advertise ment of this probe as a laser diode would be misleading.
This indicates that quite a num ber of physiotherapists wlio had bought Lasdac laser units during o r before 1989 were not/are not treating with true laser when using the 895 nm probe.Clinical effects could th e re fo re not be ascribed to laser ra d ia tio n .R e p o rts o f c o m parative results using the two different probes may be of interest.
It has also come to light that the peak wavelength of some of the products (mesolaser, Lasdac) differs from that which is stated by the m anufacturer1^'1 '(tab le 2).This may be of importance when reporting on clinical research, or when comparing the effects of radiation of different wavelengths.

Radiant power
Table 3 shows approximate average power measured for each source in comparison to the m anufacturer's specifications.
The measured average power of the M esolaser (a pulsed source) differs from that calculated by the formula Pav = f x pw x Pp, where Pav = average laser power in watts, f = pulse frequency in hertz, pw = pulse .width in seconds, Pp = peak power in w atts2, .This is apparently because the pulse width is actually less than 200 ns9,10.This would indicate that output measurements are vital when reporting research results.
A nother interesting observation is that most of the radiation sources tested, excluding the LA W O, showed a lack of power sta bility, especially just after switch-on, when drops in output power in excess o f 10% were observed.In assessing the dosage this observa tion should be noted.2 On the "30W " peak power setting, after being on for several minutes.

Source
3 The lower power reading was obtained first, and actually exceeded im W .However, when switched from the "30W " setting down again to the " 1W" setting, the value had dropped to about half, but started slowly to rise again, including thermal changes in the laser.
4 Normally just under 200ns, for both the Laserex and Mesolaser, as checked with a fast detector.-However, pulses as short as 100ns were also on occasion observed with the Mesolaser, on the low power setting.

Beam divergence
Beam divergence spread was tested and docum ented and is applicable for all probes.Divergence and distance from the skin is of much im portance with regards to determining o r calculating dosage, e.g. for treatm ents in contact versus treatm ent at 1 cm from the skin.At a distance of 1 cm, according to the inverse square law, the irradiance (power/cm2) is one tenth of the irradiance at a distance of 0,3cm.

LICENCING OF LASER PRODUCTS
Prospective buyers of laser o r any o th er electrotherapy appara tus should take note that regulatory control of these products in South Africa was instituted on 14 April 1989.U nder the Hazardous Substances Act (Act IS of 1973) , the list o f electronic products declared as G roup III hazardous substances (referred to as listed electronic products) was then added to include, apart from X-ray equipm ent, products o r equipm ent capable of emitting ionising and non-ionising radiation, o r sonic, infrasonic o r ultrasonic waves13.Lasers, ultraviolet em itting devices, diatherm y units, infrared heaters and medical ultrasound devices then became controllable under the Act, requiring users o f these products to be licenced.A second set o f regulations was also published13, enabling control o f the manufac turers and sellers of electronic products.They now also need to be licenced.
Since then the D epartm ent of National Health and Population Developm ent controls the sale of G roup III electronic products, by ensuring that each model of all m anufacturers of a specific listed product, including lasers, conform with certain minimum standards o f safety (primarily), before a licence will be issued permitting the m odel to be sold.
Such product licence will guarantee the safety and reliability of these expensive products to the end user.Any supplier of a laser product o r other listed electronic products is now expected to display a sticker of the Dept, o f National H ealth on the product, indicating that the product has been licenced for the purposes of sale.

SAFE USE OF LASERS
T he control o f lasers under the A ct10 is due to the potential health hazards, and users are required to adhere to safety precau tions.

Mechanisms of injury, critical organs, contributing factors
T hree primary mechanisms of injury exists for exposure to laser radiation, i.e. therm al, photochemically induced and thermo-mechanical injury ' .Since laser radiation is not very penetrating (1-2 mm for wavelength 630 nm, o r twice that at 800-900 nm )6, the eye and skin a re critical o rg a n s o f injury.T h e type o f biological effect, injury thresholds and damage mechanisms on these organs vary significant ly with laser power and wavelength .Generally the effects o f laser radiation are not different from the effects of optical radiation from a conventional source with the sam e wavelength range, exposure duration and irradiance .L aser radiation however engenders con cern due to the special properties associated with is radiation : the high intensity, o r energy into one point -its concentration and directional "targeting" .T he eye is of special concern, since it is capable o f increasing the light intensity many hundreds of times due to its focusing properties.
The harmful effects o f exposure to different spectral bands of ordinary light is well known to physiotherapists.Table 4 tabulates the adverse health effects of laser radiation.
12 Risk according to class Some idea o f the risk/hazard associated with laser radiation can be derived from a laser's allocation to one o f four designated classi fications.The level o f radiation to which hum an access is^possible and its associated hazard determ ine the class o f the product .Accessible emission limits (A E L ) is determ ined fo r each class.T he A E L is the maximum accessible emission level perm itted within a particular class com putable as a function of emission duration and wavelength .
Each laser in class II-IV should have a yellow warning sign and explanatory label, including the laser class.
T he risk for each class o f laser is sum m arised in table 5.

Practical safety measures
M ost lasers used in physiotherapy are class lllb (o r lower) lasers.Even for contact o r n ear contact (rlc m ) treatm ents by means of a probe it is advisable that the' patient and o perator w ear appro priate glasses1.In the case of treatm ent near the eye o r when using a laser which radiates from a distance, protection of the eye is essential 4. Preferably no spectators should be allowed.

ELECTRONIC PRODUCT/PREMISES LICENSES
Control of the use o f laser products (applicable to class lllb and class IV lasers) is exercised according to a requirem ent of the licence for the purposes o f the sale that the user of such products must be in possession of a valid pro duct/prem ises licence before he/she uses the pro duct 3 In granting a prem ises licence the following fa cto rs a r e ta k e n in to c o n sid e ra tio n : E n g in e erin g controls -the product; controls such as d oor inter locks, filtered viewing optics, etc. Personnel protec tion -proper personal protective equipm ent, e.g.suitable eyewear, clothing and gloves.Administrative and procedural controls -7 standard operating p ro cedures, adequate education and training o f' users, posting of warning signs and labels, regular m ainten ance and servicing o f the equipm ent and designation of a laser safety officer.
Such premises/electronic license is a m eans of ensuring that the end user will comply with safety r e q u i r e m e n t s w h e n u s in g th e l a s e r o n h is /h e r premises.Provision is m ade in the Regulations for radiation control officers to inspect facilities and p ro cedures to ensure safe use o f the equipm ent .

Bladsy26
Fisioterapie, Mei 1991, deel 47 no 2 Reproduced by Sabinet Gateway under licence granted by the Publisher (dated 2013.) All p h y s io th e ra p is ts /h o s p ita ls /p ra c tic e s using la s e r sh o u ld apply to the D epartm ent of National Health for premises licenses.A premises licence is also required for lasers purchased prior to 14 April 1989.If you are in possession of a laser, please inform the D epart ment so that a register of laser users can be compiled.Such a register will aid th e d e p a rtm e n t in d is trib u tio n o f in fo rm a tio n , in sp e c tion/monitoring, as well as the facilitation of training/education.

Address for applications
Application should be made to the D irectorate of Radiation Control, D epartm ent of National Health and Population Develop ment, Private Bag X62, Bellville 7535.This D irectorate is available as a source of information and consultation.

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therm al changes and/or destruction of tissues , o r for its biostimula-345 tory effects ' ' .High power (hot) lasers are used in various medical applica tions, including surgery, ophthalm ology and dermatology.The carb on dioxide (C O 2) laser (wavelength 10,6 f m ) is used for surgical cutting and coagulation.The argon laser (wavelength 488/514 nm) is used in ophthalm ic surgery for "welding" detached retinas.The n e o d y m iu m -y ttriu m -a lu m in iu m -g a rn e t (N D -Y A G ) la se r (w a v e length 1064 nm) is used for arresting haem orrhage and destroying

2 . 5
length o f the ra d ia tio n w hich is p ro d u c e d .G allium A rsen id e (GaAs) and the gallium aluminium arsenide (GaAIAs) diodes are b o th c o m m o n ly used a n d p ro d u c e invisible in frare d ( IR ) light.

*
This article is published with permission of the CSIR (Contract report C/DPT95).** C P Malherbe, BSc in Physiotherapy, Part-time lecturer, D epartm ent of Physiotherapy, University of Stellenbosch.Bladsy24Fisioterapie, Mei 1991, deel 47 no 2

TABLE 2 : SPECTRAL PROPERTIES OF DIFFERENT SOURCES Source Class Average total power Presumed total power lllb lllb
* Pulsed lasers: Peak power is in excess o f 1000 times average power, as the pulse width is less than 200ns4 with a repetition rate of 5000/s. 1 On the " 1W" peak power setting.