Yet another evaluation of the evaluators
Laser phototherapy is a complicated therapy containing many parameters to pay attention to in order to obtain a good clinical result. The availability of unbiased education in this field is scarce and practitioners are often in the hands of training by the manufacturers. Quality of this training differs considerably. Unbiased expert evaluations are therefore much needed. Unfortunately, several of these evaluations, including the Cochrane Collaboration obviously lack competence in this field. We have previously presented a critical analysis of the Blue Cross analysis group on LaserWorld. Here is another:
Effectiveness of low level laser therapy in treating various conditions. A rapid review
By WorkSafeBC Evidence-Based Practice Group , British Columbia, Canada.
http://www.worksafebc.com/health_care_providers/Assets/PDF/low_level_laser_therapy.pdf
The aim of the literature review was to check of these was any scientific documentation for chiropractic use of laser phototherapy. Literature search was done up till 2008. The outcome was very negative. Here is why:
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Of the 38 references, 15 were later than the year 2000. The majority of qualified clinical studies and reviews have been published during the passed decade.
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One literature review quoted is from 1995
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The only reference on rheumatoid arthritis is a Russian abstract using blood irradiation
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3 references are on combined LED/Laser therapy
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2 references are in vitro studies
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2 references are congress abstracts
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1 is on macular degeneration
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2 are on postmastectomy complications, not finding the relevant Carati study.
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1 is on leukemia
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1 is on the growth of bacteria
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1 is on orthodontics
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1 is a comment in a journal
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No study is from Photomedicine and Laser Surgery
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Now, the questions are:
- Are these studies relevant to chiropractic treatment?
- Is the selection of references reflecting the present availability of scientific evidence?
- Is the search for literature thorough?
- Will this review meet the aim of the work?
- Will chiropractors be better informed by reading this review
The answer to all questions is NO.
Is the Blue Cross Meta analysis reliable?
Jan Tunér
Swedish Laser Medical
Society
As often pointed out, it takes a combined knowledge of medicine, scientific methods and physics to evaluate (or to perform) a study of the therapeutic laser modality. This combination is not always seen, and it can lead to incorrect conclusions. Such incorrect analyses are sometimes the basis for governmental authorities in charge of funding clinical studies and reimbursement.
The basic problem of several negative evaluations is a lack of understanding of laser parameters. For a correct outcome of a study, the researchers must have complete control (and understanding) of the dosage windows and the different properties of the wavelengths. Positive results from laser studies are found within “therapeutic windows” of dosage. If negative and positive studies are carefully scrutinised, it is obvious that the vast majority of negative results is due to low dosage or, rarely, over dosage. This window is fairly wide but most negative reports still do not fall within its frame. It is also very important to be able to make an independent analysis of the dosage claimed. Further to that, it is not uncommon that the dosage is miscalculated.
It has previously been found [1,2,3] that the first three Cochrane evaluation of the effect of laser therapy [4,5,6] are of little value. The critical comments on [4] are available on the Cochrane home page, but obviously not observed by the several authors, since they do make a reference to the wound healing analysis, but without any of the critical comments. Re-evaluations of negative Meta analyses of laser therapy for musculoskeletal conditions have turned out positive [7] if an analysis of the dosage has been included in the study.
As and example of the situation, we have here chosen a report names Wound-Healing Technologies: Low-Level Laser and Vacuum-Assisted Closure prepared for: Agency for Healthcare Research and Quality, U.S. Department of Health and Human Services, and prepared by Blue Cross and Blue Shield Association Technology Evaluation Center Evidence-based Practice Center (EPC) Chicago, Illinois. Year of publication: 2004.
The authors have identified 11 studies said to be meeting the inclusion criteria. Reading the manuscript one can see that the authors are very qualified in the field of medicine and scientific methodology, but still lacking adequate knowledge about the field they are about to evaluate. Pressure ulcers and crural ulcers are “put in the same basket” but do not have same pathology and require different treatment parameters. The main problem with pressure ulcers is that the patient continuously is exposed to the pressure and the possibilities for healing are lower than for crural ulcers. If laser is used and the pressure is removed, healing is faster than for conventional therapy alone [8]. And further to that, all wavelengths in this analysis are put into the same basket. But each wavelength has a different therapeutic window.
The search for studies is not too impressing. A number of studies are listed as excluded from the study, and for very good reasons, since they are not at all related to the studied topic (tooth extraction, muscle injuries, etc). If high standard laser therapy studies in general were to be identified, the list would have looked quite different.
Papers using a proper dose analysis concept are e.g. [10, 11, 14].
Let us now look at the eleven studies:
Crural ulcers
Franek, Krol, and Kucharzewski, 2002. (810 nm), 4 J/cm2
No serious objections.
Bihari and Mester, 1989. HeNe, HeNe/830, 4 J/cm2
This early positive study does have shortcomings in design and reporting. It is interesting to note that it is the only study using HeNe, beside Santoianni, and HeNe is the best wavelength for wound healing [13] but not for pain relief.
Santoianni, Monfrecola, Martellotta, et al., 1984. HeNe
Appears to be a sound study but a confirmation on the used dosage cannot be extracted from the text.
Lundeberg and Malm, 1991. GaAs. Disqualified study
This study has previously been criticized for complete lack of dose control and other shortcomings. Lundeberg has been exposed as a scientific cheater. This study is not qualified for any evaluation.
Iusim, Kimchy, Pillar, et al., 1992: Not a laser study
The instrument used here is not a laser but an incoherent light source.
Lagan, McKenna, Witherow, et al., 2002. Not a laser study
This is a combined laser/LED study ((660-950 nm) and should therefore be excluded.
Nussbaum, Biemann, and Mustard, 1994. Not a laser study
The authors used a combination of 820 nm laser and an array of 30 LED:s of three different wavelengths. Thus, again, this is not a laser study.
Crous and Malherbe, 1988 . Unknown parameters
The scarce reporting of parameters in this paper does not offer an opportunity for evaluation.
Pressure ulcers
Malm and Lundeberg, 1991 GaAs. Disqualified study
This study has previously been criticized for complete lack of dose control and other shortcomings. Lundeberg has been exposed as a scientific cheater. This study is not qualified for any evaluation
Lucas , van Gemert, and de Haan, 2003 , 904 nm. A good study, 1 J/cm2. on stage III pressure ulcers. Possible negative feature: same irradiation over wound and skin.
Lucas, Coenen,and De Haan, 2000 (pressure)
904 nm, 1 J/cm2 stated. 12 x 8 mW, 125 s (12 J) spread over a standard area of 30 cm2 = 0.4 J/cm2. Spread over 30 cm2 irrespective of wound size. 0.4 J/cm2, 904 nm for open wound is fair, over skin too low.
As can be seen from the above:
- 6 studies should not have been included because of unavailable information or because they were not laser studies.
- 3 acceptable studies for crural ulcers. 2 different wavelengths.
- 2 acceptable studies for pressure ulcer, one wavelength.
- No dosage analysis has been performed or discussed
- No treatment technique difference has been addressed
Conclusions:
Two conclusions can be drawn from the above:
- Even with a better and more updated selection of studies and a proper evaluation of these, LPT for crural and pressure ulcers would still not lead to the conclusion that the documentation is at an acceptable level.
- The material of the study is not sufficient for a meta analysis
- From the Blue Cross study one would get the impression that the lack of effect of laser therapy for the conditions is confirmed by the chosen studies. Such a conclusion cannot be drawn. The present documentation does not confirm the effectiveness of laser therapy for these conditions, nor does it disprove it. It simply shows that there are not enough qualitative studies for the time being. Future and better designed studies are needed before any definite conclusions can be made, and it is not yet time to throw out the baby with the bathing water.
What can be done to improve future studies?
The World Association for Laser Therapy has published dosage recommendations for musculoskeletal conditions (www.walt.nu) and is working on a similar document for wound healing. The association has also published Standard for conduct of randomized controlled trials and Standard for conduct of systematic reviews and meta-analyses [12] Although these concern musculoskeletal conditions, much can be applied to other conditions. The Scientific Secretary of WALT is also available for advice.
References:
1. Tunér J. The Cochrane analyses - can they be improved? Laser Therapy. 1999; 11 (3): 138-143.
2. Tunér J, Hode L. The Cochrane analyses – can they be improved?
(http://www.laser.nu/lllt/lllt_editorial7.htm)
3. Bjordal J M. Can a Cochrane review in controversial areas be biased? A sensitivity analysis based on the protocol of a systematic Cochrane review Low Level Laser Therapy in Osteoarthritis. Photomed Laser Surg. 2005; 23 (5):453-458.
4. Flemming K, Cullum N. Laser therapy for venous leg ulcers. Cochrane Database Syst Rev 2000; (2):CD001182.
5. Brosseau L, Welch V, Wells G et al. Low level laser therapy (classes I, II and III) for treating rheumatoid arthritis. In: The Cochrane Library. Issue 4, 2000. Oxford: Update Software.
6. Brosseau L, Welch V, Wells G et al. Low level laser therapy (classes I, II and III) for treating oesteoarthritis. In: The Cochrane Library. Issue 4, 2000. Oxford: Update Software
7. Bjordal J M, Greve G. What may alter the conclusions of reviews? Physical Therapy Reviews. 1998; 3: 121-132.
8. Lanzafame R J, Stadler I, Coleman J, Haerum B, Oskoui P, Whittaker M, Zhang R Y. Temperature-controlled 830-nm low-level laser therapy of experimental pressure ulcers. Photomed Laser Surg. 2004; 22 (6): 483-488.
9. Hode L, Tunér J. Wrong parameters can give just any result. Laser Surg Med. 2006; 38: 343 (Letter to the editor).
10. Bjordal J M, Couppe C, Ljunggren A. Low level laser therapy for tendinopathies. Evidence of a dose-response pattern. Physical Therapy Reviews. 2001; 6 (2): 91-100.
11. Bjordal J M, Couppè C, Chow R T, Tunér J, Ljunggren A E. A systematic review of low level laser therapy with location-specific doses for pain from chronic joint disorders. Australian J Physiotherapy. 2003; 49: 107-116.
12. Photomed Laser Sur. 2006. 24 (6): 759762.
13. al-Watban F, Zhang X Y. Comparison of the effects of laser therapy on wound healing using different laser wavelengths. Laser Therapy. 1996; 8 (2): 127-136.
14. Bjordal J M, Johnson M I, Iversen V, Aimbire F, Lopes-Martins R A. Photoradiation in acute pain: a systematic review of possible mechanisms of action and clinical effects in randomized placebo-controlled trials. Photomed Laser Surg. 2006; 24 (2): 158-168.
Super-Luminous/Superluminescent Diode (SLD) and Light Emitting Diode – same or different?
There is a bit of confusion regarding the terminology in non-coherent light therapy. We therefore asked Peter Jenkins of Spectra-Medics to shed light on the subject.
Super-luminous - or superluminescent - light emitting diodes are an optical source whose properties are intermediate between LEDs/IREDs and Laser Diodes. In the field of laser physics, the terms super-luminous and superluminescent mean 'amplified spontaneous emission': the emission of flourescence which experiences significant optical gain within the emitting device.
SLDs are similar to laser diodes, in that they contain an electrically-driven p-n junction and an optical waveleguide, but lack optical feedback so no laser action can occur. Optical feedback in such devices is suppressed by tilting the output facet of the p-n junction relative to the waveguide, and by using anti-reflection coatings. SLDs use a double heterostructure to confine the active region under conditions of high current density, creating a population inversion and enabling amplification of light. However, as SLDs do not have positive optical feedback, only spontaneous emission of radiation is achieved.
The optical output of an SLD is more powerful and more sharply confined than a standard LED, but not as monochromatic, directional or coherent as a laser diode. Most superluminescent diodes emit radiation in the wavelength regions around 800 nm, 1300 nm, and 1550 nm, however, other wavelengths are available. The optical bandwidth is usually some tens of nanometers, sometimes even above 100 nm. The coherence lengths are often a few tens of microns, sometimes even only a few microns. The typical output power range for SLDs is a few microwatts to a few tens of milliwatts, similar to that of a single-mode laser diode.
SLDs are supplied in device packages similar to those used for laser diodes, such as butterfly mounts (Figure 1) and metal cans (Figure 2). The most common packages for laser diodes used in light therapy devices are 5.6mm and 9mm metal cans (Figure 2). Conversely, LEDs and IREDs are almost always mounted in molded plastic packages (Figure 3) which are not capable of the higher heat loads generaterd by SLDs and laser diodes.
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| Why laser therapy fails - and succeeds
Jan Tunér DDS
Lars Hode DrSci
Swedish Laser Medical
Society
In the editorial of Journal of Clinical Laser Medicine & Surgery
2003, 21 (6) the editor-in-chief Raymond J. Lanzafame puts the laconic
question "Why doesn't everyone use it?" We ask ourselves the
same question all too often- why doesn't everyone use it? Laser therapy
has no serious side effects; it is easy to use, quite safe and works
so well even in situations when traditional therapies have little or
no effect. So why are only you and we using it and not our colleagues?
We have spoken to dentists and doctors about e.g. mucositis. They all
admit that mucositis is a big problem and that they have very little
to offer the patient. So we show them a stage III double blind study
- should be rather convincing. But then we hear nothing. So let us consider
some possible reasons and then discuss what we could do about it!
When Mester (1) published his first article in an English speaking
journal in 1971 he was advocating 1-1.5 J/cm2 for wound healing, using
red lasers in the range 5-25 mW. In spite of these recommendations HeNe
lasers of less than 1 mW were being marketed in the early 80s. Some
positive studies were published, indeed using these very low-powered
lasers, and with doses way below those recommended by Mester. So when
researchers performed control studies, the very low doses in the latter
studies were used again - and the outcome was generally negative. Further,
most researchers in those days may have been qualified in their fields
but not in laser therapy. So a lot of mistakes were made (2, 3). In
a manner of speaking, researchers in those days were looking in the
wrong direction. And the general public continued to look in the same
direction, now "knowing" that laser therapy did not work.
Catch 22!
Then followed the publication of a number of so-called Meta Analyses
(4-8), i.e. studies based on literature search and collection and subsequent
analysis of the contents. Most of these were performed by persons well
qualified in medicine and scientific methodology, but, not in laser
physics. The most striking feature was the lack of analysis of the key
point of the therapy: the dose. Apples and oranges were mixed and conclusions
corrupted.
Now, after more than 30 years of laser therapy a lot of additional
research has been carried out and the overall quality has improved immensely.
So have the ability to analyse the literature (9-11). And so have the
laser machines. We now regularly have lasers in the 100+ mW range, providing
adequate dosage possibilities even in deeper tissues. So the question
is:" is laser therapy now well documented from a strict scientific
point of view?" My answer is, regrettably, NOT QUITE! On the other
hand, that is not unique for laser therapy. Ultrasound in physiotherapy
is less documented and even one of the most used interventions in health
medicine - NSAIDs for knee arthrosis - appears to be poorly documented.
There are more than 100 positive, double blind clinical studies (12),
hundreds of positive in vitro studies, lots of animal studies, all pointing
into one direction - it works. But this is not enough. The present "weakness"
of laser therapy lies, ironically, in its strength. Since laser therapy
works at a cellular level by improving the activity of cells in a reduced
condition, almost any pathological situation will improve through laser
therapy. But according to the way we are used to look at medical therapies,
there is no such thing as "takes it all". Being sceptical
is a good scientific quality and accepting a shift of paradigm takes
a lot of documentation! There are more than 50 different medical indications
described in the literature, 18 in the list of double blind studies.
It would have been more convincing if only four indications had been
blessed with 25 positive double blind studies each!
In our own experience the majority of laser users have some sort of
personal experience, either by being treated or by knowing somebody
who has been treated and reacted well to laser therapy. Such an experience
is more convincing than a good positive double blind study. Science
is not only pure brain power; it is also a lot of psychology and coincidence.
What else? Well, the diversity of wavelengths, powers, dosages, treatment
techniques, pulsing etc makes it rather confusing. There are not two
studies using exactly the same parameters. We know that there is a rather
wide "therapeutic window", so even with rather diverse approaches
there will be a reasonably positive effect. And the practically oriented
persons take advantage and become convinced. But the average doctor
needs more, and certainly health authorities. They will not be satisfied
with a "therapeutic window" to be applied in a rather random
fashion. They want the same kind of facts to which they are used to
from pharmacology - "1 pill of 2 mg twice daily for two weeks".
And a fine scientific documentation for it. The pharmaceutical industries
have the financial muscles to offer all this and to present it through
their sales representatives, through advertisements, seminars, free
trips to congresses, funding of new research etc. The poor laser industry
has not. And can certainly not expect any support from the pharmaceutical
industry, rather on the contrary.
So what can be done? In many respects a lot has already been done.
An improved method of evaluating laser research has been introduced
and is slowly gaining acceptance (9). So the statistical power of the
existing literature can be re-evaluated. But even so, the overall power
of the literature must be improved. Even today, the reporting of laser
parameters in laser studies is less than satisfactory, although certainly
much better than 10 years ago. This problem lies not only with the authors
but also with journal peer reviewers. There still seems to be too few
persons with a combined knowledge about scientific methods, a specialised
field of medicine and laser physics.
An obvious weakness of laser therapy is the lack of education at an
academic level. Such education is offered at some universities but the
vast majority of laser users must rely on seminars or textbooks from
manufacturers. The good exception is Russia where laser therapy is widely
taught at an academic level. But apart from that, here is yet another
Catch 22: more academic educational activities must come out of better
research papers.
An important step with regards to future scientific work is being taken
by the World Association for Laser Therapy. The Scientific secretary
and his committee members have prepared a proposal for a laser research
consensus document. This document is published on the WALT
website www.walt.nu, inviting a discussion before the congress implementation,
which will take part at WALT2006 on Cyprus in October. This document
will then serve as a guide for future researchers. The committee will
even be willing to look at the set-up of a laser therapy research project
before it is initiated, all in order to improve the reporting of parameters
and the risk of the invention of the wheel all over again.
In addition to this document, below are the suggestions presented in
the book "The Laser Therapy
Handbook" (Prima Books, 2004).
Parameters
The parameters can be separated into three categories: Technical parameters
that are related to the equipment used, treatment parameters that are
related to the treatment situation, and medical parameters that are
independent of the instrument used.
Technical parameters
Name of instrument (producer), production year.
Laser type and wavelength (e.g. 632.8 nm, HeNe laser)
Laser beam characteristics (polarised, divergent, collimated)
Number of laser sources (source distribution spatially)
Beam delivery system (fibre optics, hand held probe, scanner)
Pulsed or continuous emission (frequency, type of pulsing and duty cycle)
Output power (peak power / average power / energy per pulse)
Power density (mW/cm²) at probe aperture (aperture size)
Calibration of the instrument (external, internal, meter type)
Treatment parameters
Treatment area (size and number of sites and/or number of treated points)
Dose: Energy density (described in detail) in J/cm² and/or J/point.
Total dose per treatment session and total dose for the entire course
of treatment.
Intensity: Power density (at the treated surface) in mW/cm²
Rationale for chosen dosage
Treatment method (contact, pressure, distance illumination)
Treatment distance (spot size), type of movement, scanning
Sites of treatment (leg, knee, internal via fibre etc.)
Intended tissue target (synovia, cartilage, ganglion etc) and its approximate
distance from the skin surface.
Number of treatment sessions (is it the same for all patients?)
Frequency of treatment sessions (e.g. 2 per week for 3 weeks, then 1
per week)
Medical parameters
Description of the problem to be treated (history of disease)
Patients (number, age, sex)
Exclusion criteria (pregnancy, high blood pressure, epilepsy etc)
Inclusion criteria (how is the diagnosis defined?)
Condition of patients (acute, chronic, diabetics, other diseases)
Pre- parallel- or post-medication
Treated with other methods before (acupuncture, ultrasound, pharmaceuticals)
Dropout rate
Follow up (short- and long term)
Closer description of the technical parameters
Many of these parameters have been described previously and are well
known to workers in the field. Some are less well described, however,
and it is essential to understand them in order to know how a laser
is best used in a particular trial.
1) Name of instrument (producer)
In many studies, where many parameters are lacking, it can be helpful
to know the name (and producer) of the laser instrument. This makes
it at least possible to get some information afterwards. It may also
be useful to know the year of manufacture.
2) Laser type and wavelength
Traditionally a certain wavelength has been typical of a certain laser
type, but with the development of semiconductor laser, groups of possible
wavelengths for a certain laser type have appeared. The GaAlAs laser
can be mentioned as an example; it can have more or less any wavelength
in the region 730 to 890 nm. Tuneable lasers are also becoming more
frequent. Even a HeNe laser does not necessarily have a wavelength of
632.8 nm (possible wavelengths for the HeNe laser are 543, 594 and 612
nm, although the 632.8 nm wavelength can give the highest output power).
Furthermore, two laser types can have the same wavelength but still
give different biological results due to different coherence lengths.
An InGaAlP-laser, for instance, can have the same wavelength as a HeNe-laser
(632.8 nm). But a HeNe laser has a higher degree of coherence and a
narrower bandwidth. (See chapter 1.5.1 "The Helium-Neon laser (HeNe)"
on page 40 and chapter 11.1.2 "Comparisons between coherent and
non-coherent light" on page 335.
The wavelength of the laser is an essential parameter. A certain wavelength
may hence be more appropriate for a certain condition than other wavelengths.
The wavelength should be given in nanometres or in micrometers. It is
not sufficient just to describe the laser as "visible" or
"infrared", though this can be added.
3) Laser beam characteristics
A laser beam is not just a laser beam. Typical characteristics are polarised
or non-polarised light, divergent light, collimated or even focused
light. Furthermore, the distribution of intensity within a beam of light
can be very different from one laser to another. A semiconductor laser
often has a fan-shaped beam.
4) Number of sources
It is not uncommon to have more than one laser source in a single instrument.
A multi-probe has more than one light source. In this case, it is important
to describe the situation carefully - how many sources, their spatial
distribution and orientation and sometimes also different wavelengths.
Always describe the outline of the diodes of a multi-probe by means
of a photo or a drawing of the end of the laser probe - a picture says
more than a thousand words!
N.B! Sometimes light emitting diodes (LEDs) are used as the active source/sources
together with laser diodes. It is of importance to describe this and
to specify the wavelength, bandwidth, power and power density of each
source. If LEDs are used as light indicators only, this should be specified.
5) Beam delivery system
Laser systems can look very different and, depending on the beam delivery
system, the distribution of the light on the surface of the tissue and
inside the tissue can vary considerably. The light can be transported
by fibre optics (which usually eliminates polarisation), or it may come
from a hand-held probe. It may be defocused to cover a larger area,
or a focused beam may be moved across a determined surface using a scanner.
6) Pulsed or continuous emission
It is important to specify whether a laser is pulsed or not, as well
as the method of pulsing. One reason is that it has been shown that
different pulse frequencies give different biological responses, even
when all other parameters are kept constant. Furthermore, there is a
connection between penetration depth, power density and output power
(peak and average output power).
However, there are many ways to pulse light (often the term "modulate"
is used). This is described in: chapter 1.2.10 "Continuous and
pulsed lasers" on page 16, chapter 1.2.12 "Average power output"
on page 17 and Figure 1.7 "Different types of pulsing" on
page 18. It is, of course, important to specify not only whether the
light is pulsed or not, but also the duty cycle.
The most important parameter for a pulsed laser is the pulse frequency.
This means the number of laser pulses per second and is measured in
Hz. In some instruments, programmes control the pulse frequency so that
at first one pulse frequency is used, and after some seconds the frequency
is changed. There are even examples of devices where the frequency is
gradually changed from low to high and back again. In the case of pulsing
with pulse trains, it is necessary to specify exactly how the pulsing
is done. In the literature there are many examples showing that different
pulse frequencies give different biological effects - (See chapter 3.3.1.13
"Pulse frequency" on page 78.) However, although research
clearly shows that pulsing is of importance, there is very little knowledge
about the clinical implication of a specific pulse frequency. And chopping
of a continuous laser and true pulsing of a GaAs laser is probably not
the same, even if the frequency happens to be the same. The author should
explain the reason for the choice of the pulsing mode.
7) Output power
The output power of a laser should be stated in watts or milliwatts
per source. If the laser is pulsed, the situation becomes a bit more
complicated. Then the following parameters must be clearly described:
Pulse frequency. One or several frequencies used?
Type of pulsing (chopping/switching, super-pulsing, modulation, e.g.
pulse trains)
Duty cycle
Peak power
Pulse shape, pulse energy.
Average output power
There is also the following relation between average power and energy
per pulse: average power = energy per pulse multiplied by the pulse
frequency.
8) Power density at probe aperture
Power density at the probe aperture is not always important, because
it is the power density in the actual problem volume that is the essential
parameter. However, this is usually not known in detail and normally
we chose a surface dose that is sufficiently high to obtain at least
a reasonable dose at the depth of the problem to be treated. However,
in order to make it possible to repeat a study, power density at the
probe aperture is essential to know. Also, when some parameters are
missing in a published study, this can be helpful to know. Power density
is stated in mW/cm². It is also important to specify the area and
shape of the aperture.
The most common treatment technique is to put a hand-held laser probe
in contact with the skin or mucosa under which there is a problem to
treat. In this case, the treated area is equal to the aperture size.
If the aperture is small (5 mm diameter or less) the treated area can
be regarded as a point and we can regard the power distribution across
the treated area as a constant (in reality it is practically never constant,
but with small treated areas it will not make any difference in the
three-dimensional power distribution deep in tissue if the power density
across the aperture is constant or not).
9) Calibration of the instrument
The output power of an instrument is often not the same as stated in
the brochure. It is recognised that, as a laser diode heats up during
use, its power tends to fall off unless the machine has an appropriate
cooling device. The power of the laser should be measured, preferably
by an independent source, before the beginning of the trial as well
as at appropriate intervals within the trial and on completion of the
trial, in order to determine that the laser power has remained constant
throughout. It also happens that a laser diode or some electronic part
breaks, leading to loss of most or all of the energy - in the worst
case, maybe the whole trial is thus invalidated.
The power meter (or equivalent) should be specified (type of detector,
wavelength sensitivity, make and producer). Some instruments have a
built-in power meter, which may often be inaccurate. The user of an
instrument needs to know if the laser source loses power over time and
correct measurements are essential in scientific work.
Closer description of the treatment parameters
Among these parameters we find the two most essential ones: the energy
density (dose) and the power density (intensity). These parameters are
more closely described in chapter 1.2.13 "Power density" on
page 17, chapter 3.3.1.4 "Power density" on page 69, chapter
3.3.1.5 "Energy density" on page 70 and chapter 10 - "The
difficult dose and intensity" on page 311.
The combination and permutation of laser therapy variables for the treatment
of different conditions is practically infinite and it can be very difficult
to make decisions about what is an optimal dose for a particular pathology
when the primary evidence is equivocal.
1) Treatment area
It is of course important to clearly specify the treatment area - if
it is one area or several, if it includes areas over deep or shallow
problems, as well as acupuncture and trigger points.
2) Dose: Energy density
In the absence of clearly defined protocols in the current literature,
decisions about dosage need to come from clinical experience, case series
and reports as well as from secondary sources of information such as
books and manufacturers' manuals. Energy density of penetrating radiation
falls off exponentially in the tissues - much higher doses at skin surface
are needed to achieve the desired dose at deeper sites. Too low doses
are certainly one of the reasons why many studies are reported as having
negative outcomes. However, when treating over a vein or artery with
low or no probe pressure, a marked fraction of the light affects the
blood cells. This is of importance for systemic effects and general
effects on the immune defence.
3) Dose per treatment and total dose
There are many methods of treatment and the description of treatments
is essential. The description should include dose per treatment session,
whether different doses are given to different areas, such as open wound
area and wound edges (acupuncture or trigger points included) as well
as the total dose for the whole series of treatment for each patient.
4) Intensity: Power density
The power density of the machine is a function of the power of the laser
and the spot size of the area being treated. When in contact with the
skin, the spot size will be the area under the probe tip. It is a measure
of the potential thermal effects of the laser beam. Very often the power
density at skin surface is determined by the aperture of the laser probe
(the aperture is the area of the beam as it leaves the probe. When treating
in contact, it is also the area of light penetration into the skin/tissue).
For small apertures it is suggested that the power density be given
in watts or milliwatts/point and for larger areas (<0.5 cm²)
in watts or milliwatts/cm².
5) Treatment method
A description of whether the laser is to be used in a scanning mode
or in contact with the surface of the skin must be given. Also, it should
be specified whether pressure is applied and if the probe area is flat
or if the aperture(s) protrude(s), (which will give a higher local pressure,
resulting in a larger blood-free volume under the contact area). Doses
will vary according to which technique is used. In some cases, manufacturers
might be able to indicate the appropriate distance from the skin surface
used to achieve a particular dosage, as calculation of the dose is dependent
on the particular characteristics of the machine. Some machines will
calculate doses and energy densities depending on the technique used.
6) Treatment distance (spot size), type of movement, scanning
In some studies, the light from a laser aperture is spread out to cover
the whole area to be treated (e.g. a leg ulcer). This results in a low
power density. An alternative is to use a narrow beam and scan it over
the surface - by hand or mechanically. This will give a higher power
density and a better result. Whatever the method, it should be described
in detail.
7) Sites of treatment
The anatomical entity that is treated should be explicitly described.
This will differ depending on the condition or site being treated as
well as the site of the pathology. A schematic picture would be desirable.
Anatomical sites should be described as well as sites of muscle insertions
or ligaments. For example, in the treatment of lateral epicondylitis,
the lateral epicondyle itself would be treated. But tender/trigger points
in the extensor muscles of the forearm and their insertions may also
be treated, as well as tender points in the neck relating to the myotome
of the affected muscles. The position of the arm/leg will affect the
distance to the patholgy in several conditions.
Where possible, a quantitative estimate of the depth of a site being
treated should be performed, by ultrasound, CT scan or MRI, to help
assess whether or not an appropriate dose has been applied to that area.
Acupuncture points should be described, using the WHO nomenclature for
acupuncture points. It is also appropriate to describe the rationale
for the point selection. Trigger points should be described according
to the muscle in which they are located, a diagram being used where
possible, and the rationale for their selection should be explained.
If the light is brought in by means of fibre optics or endoscopes, this
should be described in detail. Output power should be measured at the
aperture of the transfer system.
It is only when an explicit description of the treated sites is given
that the study will be reproducible. It will then be possible to gauge
whether or not the laser light has been able to reach the target tissue
and an appropriate dose applied.
8) Number of treatment sessions
The total number of treatment sessions given in the course of treatment
needs to be stated. Three or four sessions for laser acupuncture may
be totally inadequate when a course of ten is regarded as usual.
It is also of interest to state if all patients receive treatment on
the same number of occasions and whether all sessions are equal. Maybe
a smaller dose is given per session as the surface of an ulcer decreases.
The total number of joules per treatment session should also be stated.
If 10 contact points are treated at a rate of 1 joule/point, the total
dose will be 10 joules per session. This may have relevance in terms
of the condition treated as well as potential side effects. This may
not need to be explicitly stated if it can be calculated from the number
of points treated and the number of joules/point.
9) Frequency of treatment sessions
The intervals between sessions should be stated. Treatment once a week
may be inappropriate for an acute condition but may be appropriate for
a chronic condition. The pathology will determine the frequency of treatment.
It is rather common to start a treatment series with two or three sessions
per week and after some time go down to one treatment per week - this
should be described. In the clinical situation, the intervals can be
related to the patient's response, but in a scientific set-up the schedule
must be rigid.
References:
1) Mester E et al. Effect of laser-rays on wound healing.
Am J Surg. 1971; 122 (4): 532-535.
2) Tunér J, Hode L. It's all in the parameters: a critical analysis
of some well-known negative studies on low-level laser therapy. J Clin
Laser Med Surg. 1998; 16 (5): 245-248.
3) Tunér J. The Cochrane analyses - can they be improved? Laser
Therapy. 1999; 11 (3): 138-143.
4) Beckerman H et al: The efficacy of laser therapy for mucoskeletal
and skin disorders: a criteria-based meta-analysis of randomized clinical
trials. Physical Therapy. 1992; 7 (72):
5) Gam A N et al: The effect of low-level laser therapy on musculo-skeletal
pain: a meta-analysis. Pain. 1993; 52: 63-66.
6) Flemming K, Cullum N: Laser Therapy for venous leg ulcers (Cochrane
review). In: The Cochrane Library, 4, 2000.
7) Brosseau L, Welch V, Wells G et al: Low level laser therapy (Classes
I, II and III) for treating Osteoarthritis. The Cochrane Library. Issue
4, 2000.
8) Brosseau L, Welch V, Wells G et al: Low level laser therapy (Classes
I, II and III) for treating rheumatoid arthritis. The Cochrane Library.
Issue 4, 2000.
9) Bjordal J M, Greve G. What may alter the conclusions of reviews?
Physical Therapy Reviews. 1998; 3: 121-132.
10) Bjordal J M, Couppe C, Ljunggren A. Low level laser therapy for
tendinopathies. Evidence of a dose-response pattern. Physical Therapy
Reviews. 2001; 6 (2): 91-100.
11) Bjordal J M, Couppè C, Chow R T, Tunér J, Ljunggren
A E. A systematic review of low level laser therapy with location-specific
doses for pain from chronic joint disorders. Australian J Physiotherapy.
2003; 49: 107-116.
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little? Proc. SPIE. 1999; Vol. 4166: 226-232.
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