Laser Ablation Efficiency, Laser Ablation Speed, and Laser Energy Consumption During Lithotripsy: What Are They and How Are They Defined? A Systematic Review and Proposal for a Standardized Terminology.

Context: Laser performance for lithotripsy is currently reported using units of measurement such as J/mm, mm/J, mm/s, s/mm, and mm/min. However, there are no current standardized definitions or terminology for these metrics. This may lead to confusion when assessing and comparing different laser systems.

Objective: The primary objective was to summarize outcome values and corresponding terminology from studies on laser lithotripsy performance using stone volume in relation to time or energy. The secondary objective was to propose a standardized terminology for reporting laser performance metrics.

Evidence Acquisition: A systematic review of the literature was conducted using the search string ("j*/mm3" OR "mm3/j*" OR "mm3/s*" OR "s*/mm3" OR "mm3/min*" OR "min*/mm3" AND "lithotripsy") on Scopus, Web of Science, Embase, and PubMed databases. Study selection, data extraction, and quality assessment were performed independently by two authors.

Evidence Synthesis: A total of 28 studies were included, covering holmium:yttrium-aluminum-garnet (Ho:YAG), MOSES, and thulium fiber laser (TFL) technologies. Laser energy consumption values reported for the studies ranged from 2.0 - 43.5 J/mmin vitro and from 2.7 - 47.8 J/mmin vivo, translating to laser ablation efficiency of 0.023 - 0.500 mm/J and 0.021 - 0.370 mm/J, respectively. Laser ablation speeds ranged from 0.3 - 8.5 mm/s in vivo, translating to lasing time consumption of 0.12 - 3.33 s/mm. Laser efficacy ranged from 4.35 - 51.7 mm/min in vivo. There was high heterogeneity for the terminology used to describe laser performance for the same metrics.

Conclusions: The range of laser performance metric values relating stone volume to energy or time is wide, with corresponding differing terminology. We propose a standardized terminology for future studies on laser lithotripsy, including laser ablation efficiency (mm/J), laser ablation speed (mm/s), and laser energy consumption (J/mm). Laser efficacy (mm/min) is proposed as a broader term that is based on the total operative time, encompassing the whole technique using the laser.

Patient Summary: We reviewed studies to identify the units and terms used for laser performance when treating urinary stones. The review revealed a wide range of differing units, outcomes, and terms. Therefore, we propose a standardized terminology for future studies on laser stone treatment.