Ablation of subsurface tumors using an ultra-short pulse laser

• Published in: Optics and lasers in engineering 2011-03, Vol.49 (3), p.451-456
• Main Authors: Yousef Sajjadi, Amir, Mitra, Kunal, Grace, Michael
• Format: Article
• Language: English
• Subjects: Ablation; Ablation depth; Damage; Effectiveness; Focused laser beam; Focusing; Irradiation; Lasers; Mice; Mouse with mammary tumor; Position (location); Subsurface tumor ablation; Tumors; Ultra-short pulse laser
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/j.optlaseng.2010.11.020

This paper demonstrates the novel technique of ablating subsurface tumors with minimal thermal damage to surrounding healthy tissue using a focused laser beam from an ultra-short pulse diode laser source. Experiments were performed on anesthetized healthy mice as well as mice with mammary tumors in order to demonstrate the fundamental advantages of using a focused-beam, ultra-short pulse laser to ablate subcutaneous tissues. The technique was demonstrated through histological analysis of tissue samples after irradiation of anesthetized mice with or without mammary tumors. To demonstrate the efficacy of subsurface focusing, temperature was monitored at the subsurface tumor location and at the surface in an untranslated sample while irradiating with a focused ultra-short pulsed 1552 nm laser. Results show that temperature rise was dramatically greater at the focal depth than at the surface. Irradiation at the subsurface tumor location while translated over time across the tumor location resulted in precise ablation of the tumor. This work shows that a focused-beam ultra-short pulse 1552 nm laser results in precise ablation at the desired location with high efficacy and a minimal zone of collateral thermal and/or mechanical damage. ►In this work, a minimally invasive technique for ablating subsurface tumors was developed through the use of a converging beam from an ultra-short pulsed laser focused at the tumor location. ►Ablation characteristics in anesthetized mice with subsurface mammary tumors demonstrate that focusing the beam from an ultra-short pulse laser directly at the tumor site results in precise, clean ablation without significantly affecting the surrounding epidermal and dermal layers. ►When the beam intensity is less than the optical breakdown threshold but higher than thermal damage threshold, significant thermal damage is possible due to thermal accumulation caused by longer exposure time. ►Thus, the optimal scanning beam velocity should be selected to control the size of ablation volume and eliminate possible thermal damage in surrounding tissue. ►It can be inferred that with careful focusing techniques, control of laser parameters, and appropriate selection of scanning velocity, precise tissue ablation is possible with minimal thermal damage to tissue surrounding the laser irradiation site.