Laser beam shaping for surgery and microbiopsy

Lasers are increasingly being used in surgery in a wide range of medical specialties due to their advantages over alternative surgical tools including precise material removal, limited bleeding due to coagulation around the incision site, and delivery through optical fibers enabling use in body cavities and for minimally invasive surgeries. Advancements in laser technology including new laser wavelengths and higher power continue to improve the performance and implementation of surgical lasers. Temporal beam shaping, or pulse modulation, has been implemented into clinical laser systems to increase efficiency of urological surgeries, leading to faster, safer procedures. However, the precise mechanisms of temporally shaped laser pulses on ablation are not fully understood. The effects of spatial beam shaping on laser tissue ablation have not previously been explored. Understanding the impact of temporal and spatial laser beam on laser ablation will improve the performance and increase the applications of laser surgery. In this dissertation a Ho:YAG laser was temporally and spatially altered and the effects on tissue ablation were explored. The first portion of this dissertation focuses implications of beam shaping on laser ablation efficiency. First, mechanisms of laser ablation with temporal pulse modulation are explored. We explore the mechanisms of pulse modulated ablation including experiments on phantoms and native kidney stones. We discovered that increased ablation efficiency by pulse modulation is composition dependent. Next, increased ablation efficiency by altering laser spatial shape is explored. We discovered that shaping the laser beam into an annular shape led to an increase ablation efficiency is both hard and soft tissues. The second portion of this dissertation focuses on application of spatially shaped laser ablation for laser microbiopsy. A novel method for harvesting sub-microliter (