Efficiency of disc ablation with lasers of various wavelengths

Laser application in neurosurgery

BACKGROUND

Technological innovations based on light amplification created by stimulated emission of radiation (LASER) have been used extensively in the field of neurosurgery.

METHODS

We reviewed the medical literature to identify current laser-based technological applications for surgical, diagnostic, and therapeutic uses in neurosurgery.

RESULTS

Surgical applications of laser technology reported in the literature include percutaneous laser ablation of brain tissue, the use of surgical lasers in open and endoscopic cranial surgeries, laser-assisted microanastomosis, and photodynamic therapy for brain tumors. Laser systems are also used for intervertebral disk degeneration treatment, therapeutic applications of laser energy for transcranial laser therapy and nerve regeneration, and novel diagnostic laser-based technologies (e.g., laser scanning endomicroscopy and Raman spectroscopy) that are used for interrogation of pathological tissue.

CONCLUSION

Despite controversy over the use of lasers for treatment, the surgical application of lasers for minimally invasive procedures shows promising results and merits further investigation. Laser-based microscopy imaging devices have been developed and miniaturized to be used intraoperatively for rapid pathological diagnosis. The multitude of ways that lasers are used in neurosurgery and in related neuroclinical situations is a testament to the technological advancements and practicality of laser science.

Evaluation of different laser wavelengths on ablation lesion and residual thermal injury in intervertebral discs of the lumbar spine

Laser discectomy or nucleotomy is an increasingly important method for less invasive procedures of column, but the ideal kind of laser is still not established. As the wavelength is an important parameter for water absorption, this study was performed to investigate the action of the laser emission in the near infrared (808 to 1908 nm) region in the context of surgical procedures for percutaneous intervertebral disc decompression (nucleotomy). Forty intervertebral discs from pigs lumbar spines were irradiated with laser (λ = 808, 980, 1470 and 1908 nm), 1-s on/off time cycles, for 120 cycles and 10 W of power (808, 980, and 1470 nm) or 240 cycles and 5 W of power (1908 nm), with total power of 1200 J, and subjected to microscopic evaluation through hematoxylin-eosin (HE) staining in order to measure the ablation lesions and the residual thermal injury. Ten other discs were not irradiated and worked as controls. The ablation lesions were measured (in mm) at 1.08 ± 1.25, 1.70 ± 0.63, 2.23 ± 1.02, 1.37 ± 0.39, and 0.94 ± 0.41 (median ± SD) for the control, 808, 980, 1470, and 1908 nm groups, respectively. The difference between 1908 nm and all the other groups was statistically significant (p < 0.05). The residual thermal injury was less evident in 1908 nm laser and sharper in 980 nm laser wavelengths. The laser at a wavelength of 1908 nm was considered the most efficient for the vaporization of the nucleus pulposus, followed by the laser wavelengths of 1470, 808, and 980 nm, and proved to be useful for laser nucleotomy procedure.

Preliminary assessment of the tissue effects of a 1.44-micron laser via direct fiber contact on soft tissue

BACKGROUND/OBJECTIVE

A new pulsed near-infrared laser was developed for incision of soft tissues. This article presents a preliminary investigation of the 1.44-micron laser.

METHODS

A prototype laser was used with a cleaved 600-micron quartz fiber (1.44 microns, 5-30 Hz, 30 W max.). Standardized 5-cm incisions were made on skin, striated muscle, and liver in anesthetized New Zealand White rabbits. The animals were euthanized and the tissues were immediately harvested, and histologic examination completed after hematoxylin and eosin (HE) staining. The acute zone of coagulation was measured. A wound healing study was conducted on anesthetized NZW rabbits. The hind leg muscle was exposed and four, 5-cm incisions were made using the laser (0.5 J, 25 Hz) and four incisions were made with an electrosurgical unit on coagulating current (25 W). The incisions were marked and the overlying skin reapproximated. One rabbit was euthanized on day 11 and one on day 21. The wounds were exposed and excised for histology.

RESULTS

The acute zone of injury was 1160 +/- 120 microns to 1250 +/- 110 microns for skin; 70 +/- 20 microns to 400 +/- 280 microns for muscle, and 660 +/- 120 microns to 1930 +/- 300 microns for liver. The chronic study demonstrated less inflammation in the laser wounds on day 11 and a chronic inflammatory response on day 21. No gross differences in healing were noted.

DISCUSSION/CONCLUSION

The 1.44 microns laser wavelength interacts with tissues in a manner that is substantially equivalent to the holmium laser (2.1 microns). Further studies of the 1.44 microns laser and delivery system development are warranted.