A holmium:YAG (Ho:YAG) laser system transmits laser energy to the surgical site through a flexible fibreoptic delivery system called a laser fibre (or just fibre). While fibres may vary somewhat in the features they offer, the science behind the delivery of the laser energy is similar from one fibre to the next.
Fibre hub
The proximal end—or hub—of the laser fibre has a threaded coupler to establish a secure connection. A stainless-steel ferrule aligns the fibreoptic with the optical output on the laser system. Different laser systems accept different shapes of ferrules, and this is one of the factors that determines fibre compatibility. The SMA-905 connector is commonly used across the industry and can provide cross-compatibility for laser systems and fibres.
Some fibres, like Cook Medical’s Holmium Laser Fibres, have the added benefit of an integrated protective material (quartz insert) in the hub of the fibre to absorb errant laser blasts and protect the optical deck on the laser system from damage. This protective material makes the laser system’s blast shield a redundant measure.*
Another engineering design often used at the hub to protect a fibre from damage is an air well termination, also known as a well connector. Cook’s fibres feature an air well termination.
Transmitting the energy
Pulsed laser energy from the optical deck on the laser system is focused into the fibre core, which is made from transparent glass (silica). A thin cladding of a secondary reflective silica with a slightly lower index of refraction surrounds the core. The laser energy travels the length of the fibre using the principle of total internal reflection—meaning all the laser energy is confined within the more optically dense medium (core) and reflects off the less optically dense medium (cladding) while travelling along the length of fibre.
In some fibres, like Cook Medical’s Holmium Laser Fibres, a thin polymer coating surrounds the cladding to help protect the glass core and cladding from damage as the fibre bends. An ETFE jacket adds an outer layer of durability to each fibre and protects the inner lumen of the endoscope from friction. The jacket ends a few millimeters before the working end (distal tip), but the coated cladding extends the length of the fibre to ensure the laser energy is directed to the area of treatment.
Sizes
Fibres come in multiple colours and sizes, depending on their manufacturer. The diameter of the fibre’s core is a major factor that determines how much energy can be transmitted through the fibre. The smaller the fibre, the more flexible it is, but also the less power it can transmit. Many manufacturers choose to list the size of their fibres according to the outer diameter of the fibre core. See the spec table for Cook’s fibres below as an example.
| Fibre size |
Connector colour | Fibre core OD (+/- 2%) |
Overall fibre OD (+/- 5%) |
|||
| μm | Single-use | Multi-use | μm | Fr | μm | Fr |
| 150 | Red | — | 140 | .44 | 270 | .81 |
| 200 | Red | — | 200 | .6 | 375 | 1.13 |
| 273 | Red | Green | 272 | .82 | 420 | 1.26 |
| 365 | Red | Blue | 365 | 1.1 | 550 | 1.65 |
| 550 | Red | Violet | 550 | 1.65 | 750 | 2.25 |
| 940 | Red | Orange | 940 | 2.82 | 1400 | 4.2 |
Number of uses
The majority of laser fibres are intended for one-time use. However, there are also multi-use options. The number of uses depends on how carefully the fibre is handled and reprocessed. Specific step-by-step instructions must be followed to properly reprocess a fibre for reuse. The cutting, stripping, cleaving, and sterilisation necessary to return a fibre to satisfactory working condition requires exacting precision.
Lase smarter
Cook’s Holmium Laser Fibres with SmartSync® Technology provide an advanced level of functionality when used with the Rhapsody H-30® Holmium Laser System. The SmartSync microchip within the fibre communicates with the Rhapsody H-30 laser to identify the size of the attached fibre, limit the laser energy to the fibre’s maximum allowable power output, and record laser information to facilitate troubleshooting (confidential patient data are not collected).
*Only available on fibres with diameters smaller than 550 µm.