
Lumenis® PulseTM 60H Laser System Theory of Operation – Moses Mode
UM-20057180EN, Rev. A Page 16
Holmium laser systems can deliver the same average power at different
settings to achieve different laser tissue effect. Changing the energy of
each pulse can be described as the “bite size” of the laser effect, whereas
the frequency as the “bite rate”. For example, setting the system at 50W
can be performed using the following sets of parameters: 2.5J at 20Hz or
2.0J at 25Hz.
When working with calculi, for example, these different settings may
affect the stone by breaking it into particles versus disintegrating it into
fine dust. The selection of the appropriate energy and frequency settings is
dependent on the procedure and specific target tissue.
Each pulse is delivered at a specific time frame, leading to fast heating
rise in temperature of the target tissue. By increasing the pulse duration,
the time frame of energy delivery to the tissue changes and thereby
changing the temperature profile of the tissue. A different temperature
profile may lead to a heating rather than a vaporizing effect and is useful
for example when blood vessel coagulation is desired.
The selection of appropriate power parameters and optical fiber is
dependent on the procedure and the specific patient condition. It is
recommended that you become familiar with laser characteristics and
techniques by attending courses and consulting with colleagues in order to
utilize the lasers capabilities in a safe manner.
Theory of Operation – Moses Mode
The Lumenis Pulse 60H holmium laser emits a laser beam at a
wavelength of 2100nm. This wavelength is strongly absorbed by water.
Since soft tissue is comprised primarily of water, holmium laser energy
can be used effectively for excision, incision, ablation, and vaporization
when in direct contact with soft tissue and for coagulation when in near
contact with soft tissue. Holmium laser energy is also very effective in
lithotripsy of calculi.
In a liquid environment when laser is emitted from the holmium fiber tip,
the water surrounding the tip heats to above the boiling temperature and a
vapor bubble is created. The vapor bubble expands from the fiber tip
towards the target tissue or stone. As only a portion of the pulse is
sufficient to create the vapor bubble, the remaining pulse energy travels
through the void contained in the bubble, and is less attenuated compared
to travel through liquid water.