Development of an automatic focusing system for a precise laser ablation system in neurosurgery

In treatment of diseases such as encephaloma using neurosurgery, it is very important to remove the tumor accurately at the boundary between the tumor and normal tissue. This is to prevent the recurrence of cancer. To achieve this precise removal of the tumor, we have proposed a new treatment method using 5 Aminolevulinic Acid (5-ALA) and a microlaser with a wavelength of 2.8 μm. In this method, the tumor is labeled by 5-ALA induced fluoresced and is cauterized by the microlaser. Since the ablation by microlaser depends on the displacement from the focal point, it is necessary to keep the distance between the laser probe and the target the focal length. In this research, we have developed the automatic focusing mechanism using two guide lasers and a CCD camera. We have performed focusing accuracy evaluation experiment and irradiation experiment using in porcine pig. Experimental results showed that the focusing accuracy was within 0.5 mm and possibility of clinical application was demonstrated.