A laser-induced liquid jet (LILJ) was developed as a therapeutic device to achieve a balance between crushing pituitary tumors and preserving fine blood vessels and nerves. The LILJ was previously designed to exscind pituitary tumors on cranial nerves during surgery. Here, we improved the LILJ for another surgical application while maintaining its key advantage of tissue selectivity. We modified the LILJ by incorporating the bubble-jet phenomenon to improve the crushing power of the tool. To allow air into the jet, three types of applicators were manufactured by creating a small hole 0.3mm in diameter in the thin metal tube of the LILJ applicator at a position of 3, 6, or 12mm away from the tip. We also investigated the effects of replacing the thin metal tube with a glass tube having the same small hole. Injecting the liquid jet confirmed the occurrence of the bubble-jet phenomenon. Next, the bubble jet was injected into gelatin, which simulated living tissue, and the crushing effect and depth were measured using a high-speed camera. The results showed that the penetration depth exceeded that of existing instruments when the small hole was 3mm from the tip. Moreover, the crushing power was improved as the small hole was closer from the tip. To further test the applicator with improved crushing power, the jet was injected into an excised pig brain. The bubble jet did not damage the brain parenchyma, and the blood vessels and pia matter on the surface of the brain tissue were preserved. These findings indicate that the tissue-crushing capability is enhanced and the ability to preserve the micro-vessels is retained in the proposed bubble-jet-type LILJ.
