" Why do I keep blowing blast shields? "


There are a few reasons that a blast shield is damaged.  The most common is, without a doubt, contamination on the proximal (connector) end of the fiber.  If there is enough debris on the face of the fiber when the laser is fired, the debris will absorb the energy and flash or burn.  The subsequent plume of smoke and particles will contaminate the blast shield and etch the surface or “blow” the blast shield.

The second most common reason for ‘blowing’ blast shields is mis-aligned lasers.  If the laser beam is focused so that some of the energy is outside of the fiber core, then any combustible material in the field will be vaporized and contaminate the blast shield. 

Mis-alignment can be the result of the laser not being properly focused or it can result from thermal lensing within the laser.  Thermal lensing occurs because of the heating of the laser source material.  When the outside of a laser rod becomes hotter than the center, the spot size gets larger.  In an older laser or one without sufficient cooling capacity, the spot size can be larger than the core of the fiber.  We have even seen evidence of laser beams hitting the metal of the connector and thereby blowing metal particles back onto the blast shield and destroying it.

We have heard of sales people telling customers that blast shields are blown as a result of “flash back” from a stone as it is being treated during Lithotripsy.  This is not true.  There is no known physical mechanism whereby a flash from a stone at the tip of the fiber can contaminate or “blow” a blast shield in the laser.  If the tip of the fiber comes in contact with a stone or other tissue, a flash of light can occur but there is no way that such a flash can damage a blast shield in the laser.  It will, however, cause erosion of the fiber tip.


" What can I do to prevent blown blast shields? "


First, inspect the face of each fiber before it is mounted onto the laser and if needed clean the fiber of any debris.  Second, use a fiber with a built in blast shield, such as Optical Integrity, Inc.’s ScopeSafe™ fibers.  The built in blast shield protects against errant energy from mis-alignment or thermal lensing and cleaning the surface of the fiber at the connector will prevent flash back when the laser is fired.


" Why are my flexible scope repair bills so high? "


Flexible endoscopes carry notoriously high repair costs at almost every health care institution in the United States.  Analysis of repair data indicates four main causes:  Laser fibers breaking in the scope at the point of maximum bend; laser fibers being pulled back into the scope while firing; laser fibers being advanced forward through the bent scope puncturing or scratching the inside of the scope; and scopes aging and losing their ability to bend into a small enough diameter to be useful. 

Some research studies have indicated that fibers breaking in the working channel may be the most common of the reasons that flexible scopes are damaged.  Optical Integrity, Inc. has found that errant energy launched into the cladding of the fiber because of laser alignment and thermal lensing is a major contributor to fibers breaking at the point of maximum deflection.  In fact, Optical Integrity, Inc. invented and developed the ScopeSafe™ technology specifically to deal with this failure mode.

One Optical Integrity, Inc. customer reported to us that his scope repair bills decrease by more than $40,000 per year when he switched to ScopeSafe Fibers!!


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