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1064 nm Nd:YAG dose for onychomycosis

Discussion in 'General Issues and Discussion Forum' started by Mart, Oct 3, 2013.

  1. Mart

    Mart Well-Known Member


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    There has been a fair bit of discussion kicking around on this forum and elsewhere regarding the merits of using 1064 nm Nd:YAG for onychomycosis

    Other than lack of good evidence of efficacy there remains an issue regarding dose.

    It is widely speculated that therapeutic mechanism may be from selective heat damage to dermatophytes compared to host .

    http://www.podiatry-arena.com/podiatry-forum/showpost.php?p=290825&postcount=438

    If this is true then it seems likely that dose is important and currently there seems little to guide this other than anecdote.

    Last year we did a pilot study here of 80 cases selected with severe involvement onychomycosis. There was lack significant clinical signs of improvement after 2 doses of Nd:YAG laser at two months interval of any of this cohort using the manufacturer's guide for dosage.

    I remain curious that our outcome seemed disparate with the claims of others.

    Our protocol was to debride nail plate to the nail bed prior to treatment, then use manufacturers recommended dose; the reasoning was not to "waste energy" on nail which could be mechanically removed. We speculated subsequently that ironically we may have removed a therapeutically valuable effect of storage of heat energy within the nail mass by the debridement and possibly lowered tolerance to a higher surface temperature by removing the thermal barrier to heat nocioceptors within the nail bed.

    Attached is typical kind of "scientific evidence" cited within "marketing.

    View attachment 5842

    I feel that in this report a clinically useful endpoint was not used and that the claim of 75% efficacy therefore moot.

    That said, I remain keen to explore this further and currently have access to a machine to pilot some ideas.

    Please could anyone with interest and experience with this technology feed this post with anecdotal accounts of their approach to dosage, how they evaluate the clinical endpoint of treatment and any other ideas which they feel are important which allows them success.

    Arbitrarily my starting point is to dose a single nail, proximal nail fold and skin margins continuously for 15 minutes such that mild discomfort is initiated then temperature measured at nail surface is maintained as close as possible slightly below pain threshold - this seems within range of 38 - 48 degrees C. If the effect of heat is the the therapeutic mechanism this seems an appropriate approach as a staring point to test this idea.

    My colleague Amar is trying a different approach. He uses the manufactures guidelines of total of 400 pulses to hallux nail and 200 to lesser toes. This is applied by applying beam to pain threshold, allowing complete cooling then repeating until total dose is delivered.

    We are both using the the parameters which are controllable set to factory default for onychomycosis and are

    Power: 14 J/cm2 - pulse width: 0.3 ms - pulse frequency 3 Hz

    Kudos to Cutera for their encouragement for us to do this.

    Cheers

    Martin

    Foot and Ankle Clinic
    1365 Grant Ave.
    Winnipeg Manitoba R3M 1Z8
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  2. Tim Foran

    Tim Foran Active Member

    Hi Martin

    [​IMG]

    [​IMG]

    This was a recent patient protocol was 500j @ 10w 10ms/on 10ms/off. Applied until 500j reached. Stopped once during treatment as toenail got too hot (was able to start straight away with finishing dosage though)
     
  3. Admin2

    Admin2 Administrator Staff Member

  4. Mart

    Mart Well-Known Member

    Thanks Tim

    Please can you add the area the beam covers and total duration of treatment. Please also confirm the units as absolute energy ie Joules or is this rate of power delivery i.e. J/second or photon density ie j/ cm2.j

    What you stated suggests that total exposure time was 100 seconds and was there a surface temperature measurement?

    cheers Martin

    Sent from my Iphone
     
  5. Tim Foran

    Tim Foran Active Member

    7mm spot size. Covered the whole nail extending approx 4mm past sulcus and eponychium. Absolute energy 500 joules. 100sec's. No surface temperature measured. I have lased myself before and can tell you it does get hot.
     
  6. Paul Bowles

    Paul Bowles Well-Known Member

    We routinely use 10.0W 5/10MS 700-1000J per hallux nail or 300-500J per lesser digit nail - no surface temp measurement (this is useless as its sub ungual measurement you are after and im not sure how you would get that.

    I'm sure over-debridement causes issues with effectiveness as well!

    Our results have been shown in the other 1064nm thread.....but mirror others on here such as Tim
     
  7. Mart

    Mart Well-Known Member

    Thanks Paul

    assuming the machine power output calibration is accurate (this may be an issue) I think that we need to be thinking in dose not only in terms of Joules but, if heat is therapeutic mechanism, then temperature and duration of elevated temperature also. The reasoning is that 1000 J will have a different heat (therapeutic) effect according to the time it is delivered over so the rate of heating is likely key for this idea.

    As you say, measuring temperature is limited to nail surface and it seems that your approach it to maintain maximal tolerated temperature elevation. I think that measuring duration of temperature elevation may have value as an index of dose. Out of curiosity I may try measuring temperature gradient through some total nail avulsion specimens and see if there might be some coefficient which is has useful CIs.

    Anyone else thinking along the same lines?

    Cheers

    Martin

    Foot and Ankle Clinic
    1365 Grant Ave.
    Winnipeg Manitoba R3M 1Z8
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  8. Mart

    Mart Well-Known Member

    Hi Paul

    I just started collecting some data to measure the cooling rate on a mycotic TNA specimen to check reliability and noise in my method. Using the Cutera surface thermometer I found little difference on deep vs superficial aspects of a nail measuring approx 2mm thick after raising temperature to 50 degree C. Your premise that surface temporary measurement is useless may be flawed.

    I collected 2 sets of data from the same nail - I'll see if it creates a reasonably predicable line/curve and feed that back to those interested

    Cheers

    Martin
     
  9. Paul Bowles

    Paul Bowles Well-Known Member

    How did you test that exactly Martin?

    The suggestion that I have put forward thus far is the "blanket theory" - that as the nail is onycolytic and there is a "cavity" between the nail and the skin, it is this air in this cavity which in fact heats faster and remains at temperature longer than lets say the air outside the nail.

    If your test doesn't replicate that "cavity" effect you may want to adjust it so it does.

    I don't know if surface nail temp measurement is useless - I would just expect it to be lower than sub surface nail temp - as above the nail heat can dissipate to atmosphere faster than below the cover of nail - i.e. the blanket theory. I am always the first to put my hand up and say though that as in any good research piece or discussion I may be wrong!

    Also has anyone given thought to the possibility that more sub ungual debris from the mycotic infection would absorb more radiation and either a) cause more/less heat or b) cause a longer heat up period or c) cause theraputic differences in detectable temperature? This could also play a role in how you are currently testing Martin.

    Thanks for putting some effort with us into this Martin - good to see some more interesting discussion.
     
  10. Mart

    Mart Well-Known Member

    Thanks Paul and we are on same page with this.

    I think first step in trying to understand the temperature issue is validating the measurement ideas; I am just starting that.

    I am trying to get the manufacturer to get involved in helping us understand their technology as a starting point.

    I agree that we need to understand how closely using an avulsed nail might model an in vivo nail - this will take some imagination and effort but I have some ideas if we can first validate some tools.

    To get a crude sense of the model and get a handle on plausibility of idea I did 2 trials simply by mounting the nail, marking a measurement location and recording cooling data by videoing the machine screen then manually inputting measurements. I have asked Cutera if it is possible to get this data out of the machine since this is horribly inefficient.

    specimen.jpg

    specimen 2.jpg

    setup.jpg

    I found that the data from this approach seemed good enough to take this idea to a more rigorous level. The noise was acceptable and the R2 much better than I expected. The regression of the cooling rate slope looked like it may be reproducible under these conditions.

    Trial 1 Graph.jpg

    Trial 2 Graph.jpg

    2 data sets are of consecutive measures as shown in photos of superficial surface.

    I am going to wait to see if it is possible to get data feed from machine before taking this idea further to speed up data collection.

    I think one way of testing the model in terms of cooling behavior is to compare slope of model superficial and deep surfaces and in vivo superficial surface and see if:

    a is data reliable?
    b is there a correlation?

    If we can create a little "podarena" research group on this it would be great to share the load and fun to collaborate. Anyone with a machine who might be up for that please post an interest.

    Cheers

    Martin


    Foot and Ankle Clinic
    1365 Grant Ave.
    Winnipeg Manitoba R3M 1Z8
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
    Last edited: Oct 3, 2013
  11. Paul Bowles

    Paul Bowles Well-Known Member

    Yes you know I am in - problem with your method above is the "blanket" concept I mention (also the nail is dark, hence darker colours absorb more radiation hence getter hotter). Also it would be better to measure it with a digital thermometer. May I suggest a different model. Secure the base of the nail in material (ZO tape maybe?) with a digital sensor connected to a digital thermometer in the space between the tape and the nail- as this would place the nail on a surface with a cavity mimicking somewhat the o/lysis effect? Crude, but easy and quick and should show some result I would think if there is a difference.

    On a cadaver study if would be easy to implant a digital thermometer in the tissue below the toenail. I can get hold of a cadaver specimen if we submit an ethics proposal through UNSW in Sydney. Maybe something to think about?

    Also has anyone thought about the analogy of the radiotherapy on tumour cells concept? Is there any comparison between 1064nm laser and this therapeutic management of cellular destruction?

    I'm past the point of determining whether laser works or not - I know it does, the question is in what cases does it work better and how exactly does it work?
     
  12. Mart

    Mart Well-Known Member

    Not sure what you mean by digital thermometer - do you mean a thermistor? The advantage of using IR as the Cutera built in does is that it is very responsive and doesn't have any effect on the tissue wheras a thermistor might be more likely to influence temperature because it has to be heated to make measurement.

    My idea is that if there is a critical temperature which needs to be reached and maintained for a critcal time then this might then correlate with improved outcomes. If the built in mearsurement system in the Cutera machine is reliable then it may be a useful tool. The idea being that if the cooling rate can be predicted then the rate of power delivered might be tuned for each individual to maintain an optimal and predictably useful temperature and duration. I think that is what I am striving to discover.

    cheers Martin

    Sent from my Iphone
     
  13. hols

    hols Welcome New Poster

    Hi

    Hi Paul

    i am curious to know how many treatments you are providing to your patients. At what point do you decide that the laser has been affective and do you monitor with follow up?

    We have been using laser in our clinic however i have been finding our clients need multiple treatments with higher amounts of J per toe than advised by the laser company. They are also educated extensively on minimising re-infection - provided with a spray for their shoes to be done daily, antifungal cream for 1 week following each treatmen t( mainly around sulic), treatment of socks and hosiery and advised not to wear nail polish.

    Are other laser uses finding the need for multiple treatments?

    cheers

    Hollie
     
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