ND: YAG Nomogram Dosimetry Scale for the Bladder

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Abstract
Bowel perforation and damage to surrounding organs is probably the most significant risk with the use of Nd-YAG laser in the bladder. To prevent this unwanted damage, a nomogram dosimetry scale was developed by delivering different settings of laser energy via a cystoscope to 25 female pigs. One week following treatment, exploratory laparotomy and cystectomy were performed. Microscopic analysis of the depth of laser irradiation was accomplished. From this study it was learned that, although the greater the energy delivered, the deeper the tissue damage, this is not uniform. Pulsed energy produced a deeper effect than continuous energy. The use of 30 watts of either pulsed or continuous energy for no longer than 15 seconds (450 joules) or 10 watts of either form of energy for less than 30 seconds (300 joules) did not produce bowel perforation. Other different combinations of high number of watts or pulses translated into transmural necrosis of the bladder with or without perforation and with or without bowel injury. Other factors such as density, thickness, color and temperature of tissue, type and wave length of laser and optimal focusing played a significant role in the final outcome. Useful information for human clinical use may be extrapolated from this experimental model.