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17 February 2011 Interaction between high power 532nm laser and prostatic tissue: in vitro evaluation for laser prostatectomy
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Photoselective vaporization of the prostate (PVP) has been developed for effective treatment of obstructive benign prostatic hyperplasia. To maximize tissue ablation for large prostate gland, identifying the optimal power level for PVP is still necessary. We investigated the effect of various power levels on in vitro bovine prostate ablation with a 532-nm laser system. A custom-made 532-nm laser was employed to provide various power levels, delivered through a newly designed 750-μm side-firing fiber. Tissue ablation efficiency was evaluated in terms of power (P; 120~200W), treatment speed of fiber (TS; 2~8 mm/s), and working distance between fiber and tissue surface (WD; 1~5 mm). Coagulation depth was also estimated macroscopically and histologically (H&E) at various Ps. Both 180 and 200W yielded comparable ablated volume (104.3±24.7 vs. 104.1±23.9 mm3 at TS=4 mm/s and WD=2 mm; p=0.99); thus, 180W was identified as the optimal power to maximize tissue ablation, by removing tissue up to 80% faster than 120W (41.7±9.9 vs. 23.2±3.4 mm3/s at TS=4 mm/s and WD=2 mm; p<0.005). Tissue ablation was maximized at TS=4 mm/s and ablated equally efficiently at up to 3 mm WD (104.5±16.7 mm3 for WD=1 mm vs. 93.4±7.4 mm3 for WD=3 mm at 180W; p=0.33). The mean thickness of coagulation zone for 180W was 20% thicker than that for 120W (1.31±0.17 vs. 1.09±0.16 mm; p<0.005). The current in vitro study demonstrated that 180W was the optimal power to maximize tissue ablation efficiency with enhanced coagulation characteristics.
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Hyun Wook Kang, Yihlih Steven Peng, and Douglas Stinson "Interaction between high power 532nm laser and prostatic tissue: in vitro evaluation for laser prostatectomy", Proc. SPIE 7883, Photonic Therapeutics and Diagnostics VII, 78831E (17 February 2011);

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