Abstract
PURPOSE: Laser surgery can use photo-chemical, photo-thermal, photo-ablative, and photo-mechanical effects to treat various tissues in the human body, and has unique advantages of extremely high precision, non-invasive penetration, and fast operation speed. However, at present, the effective penetration depth of directly illuminating light in the body is only several millimeters. Therefore, increasing the safe operating depth for non-invasive laser surgery will have important, widespread, and irreplaceable applications in the future. METHODS: The method is based on improving a recently emerged technique. Its principle involves using a negative dispersion device to broaden the width of the short light pulse first. Then, after the pulse enters the body, as its peak intensity is reduced, the skin and healthy tissues in the laser propagation path cannot be injured. Meanwhile, since body tissues have positive dispersion, the broadened width of the laser pulse will be shortened back. When the broadened pulse is completely shortened, a thin inner light layer with high intensity will be formed in the body and used as a scalpel to treat target tissue. RESULTS: The theoretical calculation results have shown that the designed apparatus has excellent performance. Its safe non-invasive operating depth can be more than 70 millimeters with the possibility of up to 130 millimeters. Surgery precisions are around 1 micron transversely and about 1 millimeter longitudinally in theory. CONCLUSION: An improved method of non-invasive laser surgery with deep operation depth has been investigated theoretically. The calculations show that the designed apparatus has excellent performance. The proposed method depends on two well-known physical phenomena: light pulse broadening and shortening caused by optical negative and positive dispersions, and thus has solid basis. The developed method will have important, widespread and irreplaceable applications in the medical surgery field.