The Bottom Line – lazy or ignorant professors?

Irradiation parameters and dose are critical aspects of LLLT and if you are a doctor or therapist you probably trust the research you read. Prepare to be disappointed.

Many LLLT research authors, supervisors, professors & reviewers know what they are doing and they will sympathise with what I am about to say, the others should be ashamed. I could show you a hundred examples of papers that get published but incorrectly report irradiation parameters and dose, but I will constrain myself to just two that crossed my screen this week:

1) In the OA knee study in the literature watch (Alghadir et al), the abstract reports 850 nm, 50 mW, 1 mm diameter beam, 8 points treated, 6 J/point for 60 s, with a total “dosage” of 48 J/cm2 per session, twice a week for 4 weeks. MATH: 50mW for 60s is 3 joules not 6 joules as reported, but when I checked the materials and methods in the full paper, the power is reported as 100mW. This would explain the reported 6 joules. Could the supervisor or reviewers not have spotted that error? Also the 0.008 cm2 beam, from a 100mW laser = 12.7W/cm2 when applied for 60 seconds = 762J/cm2 per point not the 48J/cm2 reported. I think they meant 8 points x 6 joules = 48 joules not 48J/cm2.

2) In the trial on wound healing post tooth extraction on HIV+ patients (Halon et al), the abstract reports 820nm, 200mW, 6J, 38mm2, CW x 5 consecutive days, but where is the irradiation time and where is the irradiance? Yes, I can reverse engineer the parameters so I can work out that the time is equal to 6 joules / 200mW = 30 seconds and the irradiance is 200mW / 38mm2 = 0.526W/cm2; but in the materials and methods they also say “a dose of 6 J/cm2/day and 200 mW/day” ! Really, what does that mean? Also 0.526W/cm2 x 30 seconds = 15.8J/cm2 not 6J/cm2. Surely the authors, supervisors, professors and reviewers know the difference between Joules and J/cm2 ?

Supervisors, professors and paper reviewers should catch these errors and stop them going to press but they don’t. It may well be worse than that, with statistical errors and inaccurate conclusions being drawn as well.

The short answer is: you should be suspicious of every LLLT reported parameter you read and (ideally) check the math to see if it makes sense. If you are conducting research, please get a statistician and LLLT parameter expert in when you design your trial and get someone to check your math, and if you are the supervisor / professor please read the work you put your name to rather than leaving it up to us reviewers, and reviewers, its hard, we don’t get any reward but we have to do better than this.

About James Carroll

Founder and CEO at THOR Photomedicine Ltd. About THOR
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6 Responses to The Bottom Line – lazy or ignorant professors?

  1. Richard Godine, DVM says:

    I concur with this well stated and restrained plea for accuracy in reporting parameters. It is very frustrating when one reads a LLLT published article and have the nagging feeling one must double check the math because something isn’t adding up.

  2. sherry watson says:


    Is there any training scheduled for ALberta Canada as I missed the last one. Or any scheduled for Minnesota?


  3. Farouk Alwatban says:

    Hi James ,
    I agree with you completely, the dosimetry, not look at it most of the time, that is way mostly the results could never repeat…
    also I add the confusions of using the terminology irradiance and the irradiation time, which is merely a radiological units>>> easily confused with ionized radiations..I suggest: using the biological terminology for laser units, which is the dose and dose rate with laser treatment time…
    Thank you..
    Farouk Alwatban

    • Hi Farouk
      That is an interesting comment you make about about radiological units
      There are many terms which mean the same thing and various groups have tried to persuade me to use their nomenclature. I will investigate further and maybe write a paper about it. Thanks.

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