Diode lasers proliferate at BiOS symposium
Kathy Kincade
When physicians, not just researchers, are debating the merits of 980-nm versus 810-nm diode lasers for soft-tissue applications, you know diode lasers have made their way into the medical-laser mainstream. That`s what happened during several sessions at this year`s Biomedical Optics (BiOS) symposium, held here as part of Photonics West. It seems hard to believe that only two years ago Diomed (Cambridge, England) introduced the first surgical diode-laser system at what was then OE/LASE.
Diode-laser presentations could be found in nearly every session at this year`s BiOS meeting, including urology, ophthalmology, photodynamic therapy (PDT), tissue welding, otolaryngology, diagnostics, and imaging, with wavelengths ranging from 810 to 1000 nm. In addition, several suppliers of diode lasers and diode-laser systems--including Applied Optronics (South Plainfield, NJ), Diomed, Power Technology (Mabelvale, AR), and Star Medical (Pleasanton, CA)--displayed their products during BiOS`s two-day commercial exhibit.
The urology sessions featured some of the most advanced clinical comparisons of diode-laser wavelengths, particularly for treating benign prostatic hyperplasia (BPH)--swelling of the prostate gland, which can inhibit urinary function. The issue here is what laser approach--ablation or coagulation (or a combination thereof) using a free-beam or contact fiber, or interstitial thermal coagulation--provides the patient with the best long-term alleviation of BPH.
While the urologists at BiOS acknowledged that patient outcomes following visual laser-assisted prostatectomy have been shown to be equivalent to transurethral resection of the prostate (TURP, a nonlaser procedure long considered the "gold standard" for treating BPH), they were less willing to identify which approach, laser, or wavelength is "best," indicating that technique is more important than technology. Still, these physicians are drawn to the compactness, wavelength range, and tissue effects of the diode-laser system, though one doctor did pose the question: "Will current Nd:YAG protocols be suitable for diode lasers?"
Along these lines, other presentations included a comparative study of the thermal response of prostatic tissue to Nd:YAG (1064 nm) and diode (805 and 980 nm) laser irradiation, visual laser ablation of the prostate with a cylindrically diffusing fiber and an 805-nm diode laser, a histopathological analysis of Nd:YAG and diode (805 nm) laser-induced thermal coagulation, and interstitial laser treatment of BPH using an 820-nm diode-laser system.
Clinical investigations
Other sessions featured a wide range of potential clinical applications using diode lasers. In otolaryngology, for example, researchers from New England Medical Center (Boston, MA) reported on preliminary investigations using an 810-nm diode laser in place of a CO2 laser for various applications in the larynx to reduce scarring. Further studies are under way to determine the clinical usefulness of the diode laser for these applications.
In tissue welding, a grou¥from Oregon Medical Laser Center (Portland, OR) reported on their work using a 790-810-nm diode laser and indocyanine green dye to weld artificial patches made of an elastin-based biomaterial onto large blood vessels. Here again, early study results have been promising; in particular, the researchers found that they could get high-quality welds when pressure was applied to the patch during lasing.
And in ophthalmology, researchers from the Massachusetts Institute of Technology (Cambridge, MA) and Tufts University (Boston, MA) have developed a diode-laser-based optical coherence tomography system for diagnosing and evaluating a variety of ophthalmic problems, such as macular holes, retinal detachments, diabetic macular edema, glaucoma, and AIDS-related macular degeneration. This system is now being commercialized by Humphrey Instruments (San Leandro, CA).
Diode lasers are also being used in dermatology applications such as the treatment of psoriasis; however, this year`s BiOS meeting conflicted with the annual meeting of the American Academy of Dermatology, so there were only a handful of dermatology-related presentations, mostly in the tissue-welding session. Among these was a preliminary study that showed again how a pulsed 810-nm diode laser can be used in place of other pulsed lasers to reduce scarring. In another study, a 75-W, 800-nm diode-laser system was used to weld tibial nerves in rats to reduce the operating time required in conventional microsurgical nerve repair.