Hi Jennifer, Steve and everyone,

I thought I would try and help with the line vs dot question with some of
the equations as to how this is worked out being the output power, while
important is not the only parameter we need to be aware of. Firstly however,
to simply answer your question.... If a laser manufacturer is using a 5mW
diode which is situated at the very tip of the laser probe using a lens
configuration, you will automatically lose (depending on the lens) up to 10%
of the power through the lens so you could be essentially starting with a
4.5mW output power. Secondly, over time the diode will age (most diodes
have an approximate 10,000 hour life span so depending on how much you use
your laser you will lose output power over the life of the diode. This is
one reason why it is a good idea to get your laser tested regularly.
Lastly, some manufacturers will use a limiting resistor on the diode to
reduce the output power and prolong the life of the diode (basically a
diodes output is based on the current it receives ie: max current = max
output, reduced current = reduced output) . For example, a manufacturer may
start with a 5mW diode but limit it to say 3mW with an appropriate resistor
hence running the diode at 60% of its max output and considerable
lengthening the life of the diode. However, in this example you are now
starting with a 3mW diode and allowing for up to 10% loss through the lense
you are actually receiving a 2.7mW laser at point of sale which will reduce
over time as the diode ages. Therefore, yes, you can use a higher output
power diode such as a 20mW diode, limit the output power by utilising an
aprropriate resistor to limit the current so that the diode is running at
say 6mW and allowing for approximately 10% loss through the lenses you are
starting with an output power of 5.4mW. What does change however between
output powers, lenses used, whether the laser is pulsed (pulsed will change
the mean average output ) or continuous wave and where the diode is sitting
in the probe is the power density and hence the energy density dosage given
per treatment.

The trick to all of this is what you are using the laser for in relation to
clinical applications. For example laser Acupuncture, or neurovascular or
neurolymphatic reflex points would typically only need a low output power
due to the superficial nature of the points being treated. For standard
musculo/skeletal remedial laser therapy much higher output powers are used
to gain deeper penetration into the tissue to affect a standard remedial
laser healing response. The use of laser therapy in relation to
bioenergetic treatments is different again in that based on the energetic
level of what you are treating, the nature of tensegrity structures and the
treatment philosophy used; much lower powers can be used. At the end of the
day however, it is completely up to the individual practitioner and their
own experience and also based on what manufacturers are out there and what
target market the manufacturers are aiming the design of their product too.
No manufacturer is wrong in their design, just different.. And most
manufacturers will modify specifications of a laser that is built for a
reasonable fee if the individual practitioner so desires.

The difficulty for all laser manufacturers is to come up with a laser with
an appropriate beam diameter (ie: spot... Line etc) that covers most
requirements for clinical practice when it comes to laser therapy. This
isn't an easy thing to do hence most manufacturers will have a range of
probes and at the end of the day it is purely up to the individual
application that the practitioner is using as I have said. Having said
this, there are a number of factors that are involved in the nominal output
power at the aperture of a laser probe such as:

1. Where the diode is situated in the probe: Some laser manufacturers
actually have the diode situated slightly back from the portion of the probe
that touches the skin (keeping in mind that most laser applications are best
applied with the laser in skin contact as this reduces any reflection and
loss of power from the skin etc) and some manufacturers have the diode right
at the tip of the laser probe so the diode is virtually in touch with the
skin (usually with a lense configuration of some type sitting over the face
of the diode). Depending on the lense use and where the diode is situated,
you may have vastly different power densities.

2. Obviously the output power of the diode.

3. Whether the diode is only a pulsed diode or whether the diode is a
continuous wave diode that can be pulsed. Pulsing will definitely change
the output power at the aperture based on duty cycles and pulse rate.

4. Whether the diode is naturally divergent, collimated or focused and what
typical power losses occur through the lense used as all lenses with produce
some loss of output power.

All laser diodes are naturally divergent with I think an approximately 20 to
30 degree typical divergence across one axis and approximately 12 to 15
degrees across the second axis being that most lasers utilise elliptical
beams, but this changes vastly depending on the manufacturer of the diode
and what it is manufactured for, however I think most diode source rate
their divergence in Milli Radians. Because of this reason, most laser
therapy probes will generally have a collimating lense which turns a
divergent (widening over time) beam into a parallel line (rather than the
natural inverted cone shape of a divergent beam). This makes output power
and power density calculation much easier at skin contact in that you are
starting with a definite beam size! However, different lenses can give you
whatever configuration of beam that you wish, whether it be a very small
spot (focussing lense), a very neat stable beam size (collimating lense) or
a very large beam size (divergent lense). The last thing to remember is
that most laser therapy probe beam spots and lines are elliptical beams not
circular spots or actual rectangular lines. Lines produced by a single
diode will more often than not be an elliptical beam that has had the
circular edges cut off by the type of lense that is used.

Before I use an example, the last thing I need to revise is the power
calculations (the real meat of the standard laser therapy story). These
are: Joules, Power Density (sometimes known as Power Intensity) and Energy
Density (sometimes known as Energy Intensity) . These three terms regularly
get mixed up and I must admit for the first few years of my "laser therapy"
life I struggled with them enormously!! The key to these is the power
density and as long as you definitely know the output power

Joules is obviously an expression of laser energy. The calculation for
Joules is : Energy (Joules) = Mean Output Power (Watts) multiplied by
Treatment Time (secs)

Power Density is a calculation to determine power of the laser for the
nominal beam size and is measured in Watts/cm. Sq: PD = Mean Output Power
(Watts) divided by Irradiated Area in sq. cm

Energy Density is another Energy Calculation which is basically the Power
Density multiplied by Treatment time: Energy Density (Joules/cm sq) = Mean
Output Power (Watts) multiplied by Irradiation Time (secs) divided by
Irradiated area in sq cm.

This may seem a little confusing at first but once you start going through
the calculations it does come easily enough.

For an example, I will use a 5mW Laser probe with a beam diameter
(elliptical beam) of 1mm x 2mm (let's call this the "laser spot" from
Steve's question) with the diode situated at the very tip of the probe (so
that skin contact will receive the energy that we calculate specifically)
with a treatment time of 10 seconds. If we go through our calculations we
find that:

Power Density (Watts/cm2) = Mean Output Power (W) / Irradiated area in
cm2 (beam diameter)

= 0.005 Watts (5mW) / 0.1cm x 0.2cm x 0.784
(this is the calculation fro area of an ellipse)

= 0.005 / 0.01568

= 0.32 Therefore this 5mW laser has a Power
Density of 320mW/cm2

Energy Density (Joules/cm2) = Mean Output Power (W) X Irradiation Time
(Secs) / Irradiated Area (cm2)

= 0.005 (5mW) X 10 seconds / 0.01568 (from
above calculation)

= 3.2 Therefore this 5mW laser has an
Energy Density of 3.2 Joules/cm2

Joules = Mean Output Power (W) X Treatment Time
(secs)

= 0.005 X 10

= 0.05 Therefore this 5mW laser applied for
10 Seconds will deliver a 0.05 Joules dosage

For the second example, I will use a 20mW Laser probe with a beam diameter
(elliptical beam) of 1mm x 2mm (let's call this the "laser spot" from
Steve's question) with the diode situated at the very tip of the probe (so
that skin contact will receive the energy that we calculate specifically)
with a treatment time of 10 seconds. If we go through our calculations we
find that:

Power Density (Watts/cm2) = Mean Output Power (W) / Irradiated area in
cm2 (beam diameter)

= 0.02 Watts (20mW) / 0.1cm x 0.2cm x 0.784
(this is the calculation fro area of an ellipse)

= 0.02 / 0.01568

= 1.28 Therefore this 20mW laser has a
Power Density of 1.28W/cm2

Energy Density (Joules/cm2) = Mean Output Power (W) X Irradiation Time
(Secs) / Irradiated Area (cm2)

= 0.02 (20mW) X 10 seconds / 0.01568 (from
above calculation)

= 12.8 Therefore this 20mW laser has an
Energy Density of 12.8 Joules/cm2

Joules = Mean Output Power (W) X Treatment Time
(secs)

= 0.02 X 10

= 0.2 Therefore this 20mW laser applied for
10 Seconds will deliver a 0.2 Joules dosage

As you can see from the above examples, if a limiting resistor is not used
to bring the 20mW laser back down as Steve has suggested, the treatment
parameters will be quite different.

For the third example, I will use a 5mW Laser probe with a beam diameter
(elliptical beam) of 1mm x 5mm (let's call this the "laser line" from
Steve's question) with the diode situated at the very tip of the probe (so
that skin contact will receive the energy that we calculate specifically)
with a treatment time of 10 seconds. If we go through our calculations we
find that:

Power Density (Watts/cm2) = Mean Output Power (W) / Irradiated area in
cm2 (beam diameter)

= 0.005 Watts (5mW) / 0.1cm x 0.5cm x 0.784
(this is the calculation fro area of an ellipse)

= 0.005 / 0.0392

= 0.13 Therefore this 5mW laser has a Power
Density of 130mW/cm2 (nearly a 40% reduction from the spot size
calculations)

Energy Density (Joules/cm2) = Mean Output Power (W) X Irradiation Time
(Secs) / Irradiated Area (cm2)

= 0.005 (5mW) X 10 seconds / 0.0392 (from
above calculation)

= 1.28 Therefore this 5mW laser has an
Energy Density of 1.28 Joules/cm2 (again approximately a 40% reduction from
the spot size calculations)

Joules = Mean Output Power (W) X Treatment Time
(secs)

= 0.005 X 10

= 0.005 Therefore this 5mW laser applied for
10 Seconds will deliver a 0.05 Joules dosage (notice the Joules parameter
doesn't change)


For the fourth example, I will use a 20mW Laser probe with a beam diameter
(elliptical beam) of 1mm x 2mm (let's call this the "laser line" from
Steve's question) with the diode situated at the very tip of the probe (so
that skin contact will receive the energy that we calculate specifically)
with a treatment time of 10 seconds. If we go through our calculations we
find that:

Power Density (Watts/cm2) = Mean Output Power (W) / Irradiated area in
cm2 (beam diameter)

= 0.02 Watts (20mW) / 0.1cm x 0.5cm x 0.784
(this is the calculation fro area of an ellipse)

= 0.02 / 0.0392

= 0.51 Therefore this 5mW laser has a Power
Density of 510mW/cm2 (right on the border between class3b and class 4
lasers)

Energy Density (Joules/cm2) = Mean Output Power (W) X Irradiation Time
(Secs) / Irradiated Area (cm2)

= 0.02 (20mW) X 10 seconds / 0.0392 (from
above calculation)

= 5.1 Therefore this 20mW laser has an
Energy Density of 5.1 Joules/cm2 (an obvious reduction in energy from the
spot size)

Joules = Mean Output Power (W) X Treatment Time
(secs)

= 0.02 X 10

= 0.2 Therefore this 5mW laser applied for
10 Seconds will deliver a 0.2 Joules dosage (again this parameter does not
change)

As we can see from the above examples, power densities and energy densities
will change with different output powers and will vastly affect the energy
delivery you are trying to achieve (Hence... Yes Steve, you will lose
significant amounts of power depending on the beam size of your laser). I
apologise for th elong winded nature of this response but I feel it's
important for everyone to know that the output powers are not the only
relative parameter to be aware of in that power density and energy density
calculations prove the difference of power gains or losses depending on how
your laser is set up). Again all of these factors are determined by the
variations mentioned above and need to be taken into consideration when both
choosing a laser to buy and what you want you laser to do and also so that
you know how to modify your treatment regimes based on knowing these
parameters of the laser that you are using! All of the required
specifications will be found in your laser operation manuals from your
manufacturer so that you can make these calculations.

Another important point to remember is that while I am saying that output
power is only one aspect of the parameters you need to know, there are two
camps within the standard laser therapy world, one using Joules dosage and
one using Energy Density to calculate treatment delivery. As you can see
from the above examples, these differ when you do the calculations so it's
another thing to keep in mind. As stated above, this does not necessarily
relate to the more energetic uses of laser therapy directly but still have
some validity for reproducible results in some areas.

I again apologise for the long winded response but hope that this has been
helpful in some way.

Warm Regards

Sean






-----Original Message-----
From: Therapeutic-Laser_Therapy@yahoogroups.com
[mailto:Therapeutic-Laser_Therapy@yahoogroups.com] On Behalf Of Jennifer
Ruby
Sent: Wednesday, March 15, 2006 1:34 AM
To: Therapeutic-Laser_Therapy@yahoogroups.com
Subject: Re: [Therapeutic-Laser_Therapy] Line vs Dot and power output
question..

Hi Steve!

I don't know the answer to this question.... Hoping someone with laser
manufacturing wisdom will give some insight to this question.

Health, Hope, Joy & Healing :
May you Prosper, even as your Soul Prospers 3John 2

Jennifer Ruby

Email advice is not a substitute for medical treatment.

http://www.rubysemporium.com
http://groups.yahoo.com/group/SymphonicHealth
http://groups.yahoo.com/group/Therapeutic-Laser_Therapy
http://www.lazrpulsr.com
______________________________________________
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----- Original Message -----
From: "esl5552001" <SCL555@...>
To: <Therapeutic-Laser_Therapy@yahoogroups.com>
Sent: Monday, March 13, 2006 1:56 PM
Subject: [Therapeutic-Laser_Therapy] Line vs Dot and power output question..


| I have noticed that some lasers on the market (635nm healing lasers)
| use a dot and some lasers use a line. I have heard it said that if you
| are using a 5mw line then you are losing a significant amount of power.
| For instance the Erchonia is said to only produce .6mw output of power
| at the aperture. Wouldn't it make sense to just use 15-20mw diode (or
| whatever it takes) until you arrive at the desired 5mw output at the
| aperture for a line generated laser? Then you could cover more area in
| less time with greater effect using a true 5mw. Just trying to arrive
| at the bottom line of all this laser tech(pun intended).
|




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