The Power of Collimation IV: Going the Extra Mile November 08 2016
I’ve been asked several times if Pulsar™ HPC’s protective features adversely affect the measured efficiency of the ProFlex™ LLF fibers as compared to other, unprotected fibers. The short answer is “No”. The “why not” is below.
When we introduced ProFlex LLF to the marketplace late last year, we stressed the protective features of the Pulsar™ HPC because that’s what we thought was the most important feature. We had designed for efficiency back in 2002, with SureFlex™ and AccuFlex™ (trademarks of AMS and Boston Scientific, respectively, or collectively) and thought of ourselves as having grown beyond that superficial metric of performance. Saving scopes from damage -- from fiber hang-up, breaks and firing in the working channel – was the impetus for developing our new fiber, ProFlex LLF. It turns out that efficiency and safety are complementary goals.
The collimating feature of the Pulsar HPC was intended to forestall burn through failures by reducing the highest angles of energy propagation within the fiber to well below the numerical aperture limit. As I’ve explained before, an angular mode filled fiber is like a coiled snake ready to strike. All you have to do to set it off is bend the fiber a bit too much and POW! For fully loaded fibers it can happen when a loaded fiber is pinned to a drape or an instrument is laid atop the fiber. It can happen at the connector if the laser is facing at an acute angle to the surgical table. It can even happen within your fingers as you grip the fiber to manipulate it. That’s why we singled out burn through as a principle target of the new design.
Figure 1: Is Your Fiber Loaded?
The collimation function of the Pulsar™ HPC lens literally unloads the fiber. The Smooth Passage™ Tip eliminates fiber hang-up and prevents physical damage to the scope working channel liner, the most common cause of scope repair. Collimated energy is carried more efficiently by the fiber so more energy gets to the working tip and less energy is lost to heat in the fiber, and heat predisposes the fiber to burn through failure as well. And collimated energy exits the fiber with far less divergence so more energy gets to the stone instead of boiling water. But you knew all that.
Figure 2: Fates of Energy in Exaggerated (2X) Beam Bloom Event
What about that ‘damaging energy’ in laser foci that we talked about so much last year? Doesn’t stripping it off with the Pulsar’s annular lens reduce the amount of energy that gets to the stone?
It does not, for two principal reasons: the energy is potentially damaging because it is high angle and, as such, it wouldn’t get to the stone anyway (it’d just make a larger Moses bubble even if the fiber did survive) and such high angle energy is not present in significant amounts within laser foci unless the laser is misaligned, the lens or blast shield is damaged or the laser is tasked to produce energy for protracted periods. In other words, the annular lens basically strips nothing off unless something is wrong. It’s a failsafe, nothing more.
The red energy in Figure 2 is the potentially damaging energy, from a greatly exaggerated beam blooming event where the beam grows two-fold. This is not real even though the rays are generated by computer ray trace modeling. A beam can be, however, as far off the focus as the outer rays are in the illustration, but in one direction. The image serves to illustrate the function of critical elements within the Pulsar HPC, only: the collimating lens, centered on the fiber core, the annular lens surrounding the collimating lens to turn energy outward if it wanders too far afield, and the spiral groove that redirects the rejected energy into the sides of the connector rather than across the fiber as in some competitive fiber designs (where it could couple with the core in some circumstances, defeating the protective function).
Just how much laser ‘tasking’ is too much?
That depends upon the laser model with Trimedyne OmniPulse™ (trademark of Trimedyne) being regarded by many to be the least susceptible to overheating. Although some crystals are more susceptible to thermal lensing than others, I’ll refrain from naming a worst laser because there really isn’t a single most susceptible laser. Suffice it to say that any laser that is run at maximum output at more than 50% duty cycle for more than a few minutes will likely have some beam bloom and drift issues.
Your holmium laser may be well maintained. It may never get moved around (movement jars optics out of alignment, especially over thresholds, elevators and cable ramps). You may never have a recalcitrant stone that you have to blaze away at. But if you do, rest assured that InnovaQuartz has gone the extra mile to insure that our ProFlex™ product line is ready for just about everything. If you are an interventional urologist and you use holmium lasers for URS, PCNL or any other surgical technique and you are still on the fence about ProFlex, contact me for a sample of any size fiber(s) that you want to try out for yourself, at no charge. Standard tip fibers are ProFlex™ LLF (featuring the Smooth Passage™ working tip), orb/ball tips are ProTrac™, and extra-long fibers with orb tips are ProFlex™ SPY. Please indicate your laser model when ordering so that we can provide a fiber with the most appropriate Pulsar™ HPC. Thanks for reading.
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Smooth Passage™, Pulsar™ HPC, ProFlex™, ProFlex™ LLF, ProTrac™ and ProFlex™ SPY are trademarks of InnovaQuartz LLC. ProFlex products are protected by two US Patents. © 2016 InnovaQuartz