Lasers are an important tool for treating a variety of diseases and are continually enabling new therapy options. For example, an emerging procedure known as laser interstitial thermal therapy (LITT), or laser-thermo ablation, is providing neurosurgery with a new option for minimally invasive treatment in the brain. The procedure can be used to eliminate tumor cells in areas of the brain that are hard to reach with traditional surgery. It can also be used to destroy small areas of soft tissue that cause seizures in patients with drug-resistant epilepsy. Patient recovery times are minimal because laser light is delivered to the target area using a small laser catheter. This flexible catheter with a fiber core is inserted into the brain through a tiny hole in the skull, without the need for a craniotomy.

Controlling light with precision for a homogeneous light output

LITT uses high-power laser light to heat and ablate pathologic cells in a very predictable, consistent way. To achieve the necessary level of precision, small self-cooling probes containing sub-mm fiber-based diffusers deliver laser light to targeted areas of the brain. SCHOTT’s glass-based diffusers are ideal for this application because they allow surgeons to perform interstitial irradiation or thermal therapy with greater control. The circumferential distribution of energy from these diffusers is highly reproducible by consistently emitting the laser light in a highly homogenous and efficient manner. Such characteristics ensure optimum thermal continuity in the surrounding region, thus controlling the photo thermal damage to the targeted tissue.

With the use of real-time MRI thermographic imaging, the visualization system clearly maps temperature changes and allows surgeons to perform tissue ablation with precision. Providing enough heat to kill cells requires high laser powers for necessary photonic absorption and thermal conduction. Made from glass-based fibers, SCHOTT’s diffusers are robust to high laser powers, and eliminate the risk of melting or overheating. Even though heat is key to LITT, it is precise temperature control that ensures the prevention of overheating or tissue damage near critical structures. SCHOTT’s diffusers meet this need by delivering to the target area laser power that is evenly distributed across the entire length of the diffuser. This gives surgeons precise control of the laser power, which makes it much easier to maintain a temperature range leading to more predictable results.

LITT applications often use cylindrical diffusers with a 360 degree diffusing laser tip and a coated distal end to virtually eliminate forward emission. These diffusers are typically 10 millimeters long with core fiber diameters of 400 microns. They can deliver laser light powers of 20 watt or more with efficiencies of over 80 percent for visible and near-IR laser radiation, for instance in the important 980 nanometer and 1064 nanometer wavelengths.

Custom solutions for your application

SCHOTT’s glass-based diffusers are available in a variety of geometries besides cylindrical shapes, including versions that radiate light only from the tip of the fiber as well as spherical shapes featuring a ball-shaped component. Custom biocompatible coatings and surface treatments can also be used with cylindrical designs to limit the diffuser’s emission to a specific angle (vs. 360 degrees), achieving for example a defined side diffusion in order to give the surgeon a more precise radiation profile launching into a targeted region.

SCHOTT’s experts can help with your light-delivery needs by assisting with early-stage development, device design, prototyping, application engineering and customization. Thanks to our ISO 13485 certification and long experience in the medical device industry, we can provide support in a large variety of regulatory affairs. When it comes to production, the company offers high-volume serial production that is price competitive, an ISO class 7 cleanroom, and medical production facilities registered with regulatory authorities. Our competencies and experience allow us to offer highly reproducible product quality at reliable manufacturing sites around the world.