{'fraction_non_alphanumeric': 0.035622317596566526, 'fraction_numerical': 0.026609442060085836, 'mean_word_length': 4.76980198019802, 'pattern_counts': {'":': 0, '<': 3, '<?xml version=': 0, '>': 5, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
PD30-05 STRIKE RATE

INTRODUCTION AND OBJECTIVE: Different modes of laser lithotripsy (fragmentation, dusting, and popcorning) are commonly employed during ureteroscopy. While the efficiency of a single laser pulse is dependent on minimizing laser fiber-stone distance, it has been previously demonstrated that only w18% of laser pulses strike the stone during popcorn lithotripsy. In this study, we sought to measure laser fiber to stone distance for each mode of laser lithotripsy using light reflectance. METHODS: Continuous light (<1 mW) from a 660 nm (red) LED was coupled into a 200 μm fiber (Thorlabs, NJ) using a fiber X-coupler. The LED fiber was positioned immediately next to a 242 μm holmium fiber (Boston Scientific, MA) and both were passed through the working channel of a ureteroscope. One fiber was used to deliver laser energy to the stone and the other fiber was used to measure distance based on light reflected back into the fiber. For fragmentation (0.8J x 10Hz) and dusting (0.3J x 50Hz) experiments, a 5 mm BegoStone (15:5) was placed into a 20 mm 3D printed calyceal model. For popcorn experiments, 10 BegoStones (3x3x1.5 mm) were placed in an 11 mm glass calyceal model, the laser fiber was positioned 2 mm away from the stone surface. All experiments were performed by faculty endourologists for a total of 50 seconds. Data was analyzed using a Matlab software (MathWorks, MA) to report distance between the stone and laser fiber during each laser pulse. RESULTS: The percentage of laser pulses where the fiber to stone distance was <0.5 mm, 0.5-1.0 mm, and >1 mm is displayed in Figure 1 for each mode of lithotripsy. With fragmentation, >50% of laser pulses were delivered when the fiber was within 0.5 mm of the stone, compared to <10% for popcorning. Approximately 1/3 of pulses were considered less effective (delivered when fiber to stone distance was > 1mm) for fragmentation and dusting. For popcorning, >80% of laser pulses were >1 mm distance. CONCLUSIONS: Current methods of laser lithotripsy that rely on fixed firing rates are inefficient, especially for the popcorn technique. These data highlight areas for improvement by developing laser systems capable of sensing laser fiber to stone distance and appropriately gating pulse delivery to maximize lithotripsy effect for each pulse fired.