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MLS Master Class - Veterinary Imaging
Presented by CelticSMR Ltd
Celtic SMR
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General recommendations for laser therapy

Carl Gorman BVSc MRCVS

Key words : Laser, therapeutic, analgesia, inflammation, healing

 

In the previous module we explored the conditions that could benefit from laser therapy.  Just as there are a wide range of conditions to be treated, there are a variety of different settings for the delivery of laser energy to the affected area.

Energy delivery can be varied by:

  • Power
  • Frequency
  • Duration

The MLS laser has a large number of preset programs which calculate the optimum delivery mode and duration for each condition.  There is scope to alter and adjust any of the settings so as to vary the treatment for a specific case.  Be prepared to alter the standard settings if the clinical outcome is not as expected. For example, if the clinical signs remain unchanged for more than three sessions.

Before starting laser therapy, it is important to know the patient's medical history and to be reasonably certain of the clinical diagnosis.  This allows selection of the appropriate program, and targeting the affected tissue.

Laser therapy is non-invasive, non-painful and non-toxic.  When applied correctly it poses no risk of burns or discomfort.  It is important to know what medication the patient is taking to avoid or be aware of the very rare occurrence of possible photosensitivity reactions.  (Fig 1)

Laser2F1

Fig 1  An example of photosensitisation in a horse.  In this case the sensitisation was caused by eating plants, such as St John's Wort, that contain phototoxic chemicals

The following drugs might commonly be associated with photosensitisation in people:

  • Tetracyclines (e.g. doxycylcine)
  • Sulphonamides
  • Fluoroquinolones
  • Phenothiazine based drugs (e.g. chlorpromazine)
  • Voriconazole
  • Hydrochlorothiazide
  • Aciclovir

Reports of photosensitisation due to medications in companion animals are very rare, though, and unlikely to occur with POM-V medicines.  However, if reactions such as hyperaemia,  skin inflammation or pruritus are seen, the patient's medication and treatments should be reviewed.

General Recommendations Fig 2

Fig 2 Laser therapy is suitable for a range of animal species

Preparation of the patient

In normal use, the patient will not feel any direct effect the laser during therapy.  It is not recommended that the patient be sedated or anaesthetised during treatment, so that in the unlikely event of the patient becoming distressed or uncomfortable, it will be able to communicate this and allow the operator to moderate the treatment accordingly.

Hair, dirt and organic material will absorb some of the laser energy.  Ideally the area to be treated will be shaved and scrubbed with a disinfectant, removing any creams or gels as well as any pus or necrotic material.    This particularly applies to wounds.   Some breeds with thick or dense coats would benefit from shaving, but if this is not an option for whatever reason, the hair should be parted and the handpiece placed in direct contact with the skin.  Very pale or sensitive skin may develop a progressive pigmentation during therapy, which will fade once the laser sessions are complete.

Try to have a quiet room where the operator and patient, together with owner or assistant can be comfortable and undisturbed.  Ensure that all personnel in the treatment area are wearing the appropriate protective glasses.  If there is a risk to the patient, soft bandage or a mask can be used to cover its eyes.  Protective goggles for patients are now available.  A comfortable bed for the patient to lie on will improve compliance, and low seats or kneel pads will help with operator comfort if the session is likely to last more than a few minutes.  Most treatments can be delivered in a relatively short time.

Frequency of treatments

A standard treatment cycle will involve 2 to 10 sessions depending on the condition being treated and its severity.  As a rule, acute pathologies need fewer treatments, while chronic ones will require more sessions.  Skin wounds should be treated daily until they are completely healed.

Other than skin wounds, conditions can be treated every other day or every 3 days.  In the maintenance phase, it is possible to deliver treatments once or twice a month depending on the condition of the patient and its response.

Laser emission frequency

Depending on the acuteness of the pathology being treated, there are different recommendations for the frequency of the pulsed portion of the laser.

  • Hyperacute conditions (up to 48 hours after onset)
    • Use very low frequencies (1-100 Hz)
  • Acute conditions (more than 48 hours but less than 3 weeks after onset)
    • Use low frequencies (100-200 Hz)
  • Chronic conditions (more than 3 weeks after onset)
    • Use medium-high frequencies (200-2000 Hz)

Normally the preset laser program will allow for this, but some variation for each case may be needed depending on the clinical presentation.

Dosage

Dosage of laser therapy is calculated as energy delivered per cm2 of surface area (measured in Joules/cm2).  As we have seen, this can be moderated by the power of the laser, the frequency of the pulsed wave and by the time of application. (Fig 3)

General Recommendations Fig 3

Fig 3  A wide variety of menu choices are available to optimise treatment for species, condition and chronicity of the problem.

The appropriate laser dose can be worked out according to the chronicity of the condition, or alternatively by the depth of the lesion being treated.  Both factors should be taken into consideration.

Dose by chronicity:

                Acute conditions:                          0.5-2 J/cm2

                Sub-acute conditions                     2-4 J/cm2

                Chronic conditions:                        4-10 J/cm2

Start treatments using the lowest suggested dosage then gradually increase dosage while checking the response of the condition to treatment.

Dose by location of lesion:

Superficial wounds:                                                                                     1-4 J/cm2

Tendons, ligament and conditions not more than 1-2 cm deep                   4-6 J/cm2

Deeper musculoskeletal conditions:                                                             6-10 J/cm2

                                       

Overdosing an acute condition may actually worsen the clinical signs because of excess energy delivery ('rebound effect').  If the patient appears worse and this may be the cause, the interval between treatments could be increased and/or the energy delivered in the treatment can be reduced.

A lack of a positive result after treatment may be because of excess energy delivery, use of the wrong frequency for that tissue or too long or short an interval between treatments.

Application of treatment

General principles:

  • Hold the handpiece at 90 degress to the skin surface
  • For intact skin the handpiece should be in contact with the skin
  • For open wounds the handpiece should be held as close as possible to the skin but without touching the surface (0.5-1 cm)
  • If metal implants (plates, screws, pins, cerclage wires or ESF pins) are present, avoid direct laser emission to those items; direct the treatment at the adjacent tissues

Techniques

The laser can be used in either point or scanning mode.  The control panel will allow selection of either method together with the surface area to be treated.  A menu of preselected programs for different species and pathologies is provided.  The preselected settings can be altered as the operator becomes more familiar with the requirements for each animal and disease.  In the first instance, the area setting is the most likely to be altered.  When treatment area is altered, the device will automatically recalculate the energy delivery to ensure that the correct dosage per cm2 is delivered.

With either mode, the handpiece button only needs to be pressed to initiate each segment of treatment (each point, or whole scanning treatment).  The unit will automatically stop after treatment.  (Fig 4)

General Recommendations Fig 4

Fig 4  Using an ultra head to apply laser energy in point mode  

                Point mode

                The handpiece is held in one specific spot, or moved very slightly in concentric circles so that the energy dose is delivered in measured fractions.  The vet handpiece emission covers 3.14 cm2, and generally a 50 cm2 treatment area will be covered by 6 points.  Press the handpiece button to initiate treatment and the unit will automatically stop after the correct dose has been delivered, allowing the operator to move to the next point and press the button again. (Fig 5)

General Recommendations Fig 5

Fig 5  Point mode of laser delivery

                Point mode is most useful for small areas with an irregular surface (e.g. joints) or when a high degree of accuracy is required (e.g. for trigger points).

                Scanning  mode

                The handpiece is moved in a slow and regular motion over the area to be treated. (Fig 6)

General Recommendations Fig 6

Fig 6  Scanning mode of laser delivery

 

Scanning mode is most useful for large smooth areas, muscle bellies or over large open wounds.

Practical overview

  • Turn on the MLS device
  • Ensure the operator and assistant(s) are wearing protective eyewear
  • Choose the animal species on the home screen
  • Select the desired treatment from the list on the screen
  • Select treatment mode (point or scanning)
  • Select the patient hair colour (W for light, B for dark)
  • Select the size of the area to be treated (S - 50 cm2, M - 100 cm2, L - 150 cm2 or select manually)
  • Modify the treatment parameters (frequency, time, intensity) if necessary
  • Place the handpiece in contact with the skin or, if treating wounds, at a distance of 0.5 - 1 cm, perpendicular to the treatment area
  • Click the green 'Start' button to commence treatment
  • Wait until the end of the acoustic signal and the flashing of the warning light until the device has performed an automatic safety test and is ready to start the session
  • Press the handpiece button once
  • Treatment can be temporarily interrupted by pressing the handpiece button
  • While in Point mode (P), the laser emission is automatically stopped when the energy dose pet set point is reached, and the device stands by until the handpiece button is pressed again, allowing the operator to move to the next point.  At the end of the session the device stops the laser and the button on the handpiece will cease to function
  • In Scan mode (S) the laser emission is stopped automatically when the treatment time finishes with an 'S' size; when half the treatment time is reached if the size is 'M'; when 1/3 and 2/3 or the total time has elapsed if the size selected is 'L'.  The device remains in standby until the button is pressed again
  • At the end of the treatment switch the unit off with the main On/Off button