Dosimetry study of Nd:YAG laser damage to canine renal cortex

A dosimetry study of factors affecting the extent of tissue damage inflicted upon the canine renal cortex by the Neodymium:Yttrium Aluminum Garnet (Nd:YAG) laser was undertaken. Laser parameters and renal tissue conditions were varied independently in duplicate in the following manner: (1) power - 5, 10, 20, 50, 75, 100 watts with a spot size of 1.2 mm; (2) exposure duration - 1, 2, and 4 seconds; (3) kidney perfusion and temperature--renal artery unclamped (perfused) without cooling; renal artery clamped (non-perfused) without cooling; and renal artery clamped with cooling. Five days following application of the laser, the animals were sacrificed and serial sections of the renal cortex were examined for maximum depth and width of tissue damage and ablation. Multiple linear regression analysis of the data indicated a direct linear relationship between the joules (watts X seconds) of energy delivered to the renal cortex and the depth and width of tissue damage and ablation (p less than 0.001 for joule regression coefficient for each variable). Seconds and/or watts alone were not major predictors of the outcome after accounting for joules. Clamping the main renal artery significantly reduced the depth and width of laser damage when compared to the perfused kidney (p less than 0.001 for each variable). The depth of damage was similar in the cooled and the non-cooled non-perfused kidney. These data suggest that increased laser energy and kidney perfusion significantly increase renal cortical laser induced damage. Adjustment of these parameters may permit controlled tumor ablation or tissue incision with minimal damage to adjacent normal tissue.