研究目的
The objective of this in vitro study was to map parameter safety boundaries and create guidelines for selection of safe laser and irrigation settings.
研究成果
This study describes methodology to determine parameter safety boundaries that can be used to guide proper selection of thermally safe laser settings and irrigation rates during ureteroscopy with laser lithotripsy. Using established thresholds for thermal tissue injury, laser lithotripsy settings and irrigation rates ranging from 2.5-50 W and 0-30 ml/min, respectively were tested in vitro and used to define a parameter safety boundary for renal calyx, renal pelvis, and ureteral scenarios. These parameter plots can be used to formulate guidance to select laser lithotripsy and irrigation settings that are thermally safe. Alternatively, these plots allow determination of the irrigation rate needed to safely control the thermal dose from specific laser settings. This methodology will also provide a framework to assess the effectiveness of various strategies to control and mitigate thermal dose.
研究不足
Data collected in this study is based on in vitro measurement and may not completely account for all factors in vivo. Another limitation of this study is that data is derived from 60 seconds of continuous laser activation. Typically, during clinical ureteroscopy cases, the laser is activated intermittently for shorter bursts of energy delivery. An additional limitation of this study is that the laser was activated without targeting on a stone.
1：Experimental Design and Method Selection:
The experimental system consisted of in vitro models simulating ureter, renal calyx, and renal pelvis placed in a water bath maintained at 37°C. Temperature was recorded during ureteroscopy with laser activation for 60 seconds. Trials were conducted at strategically selected power levels and irrigation rates. Thermal dose for each trial was calculated based on Dewey and Sapareto t43 methodology with thermal dose > 120 equivalent minutes considered to result in thermal tissue injury. A parameter safety boundary was established by plotting the maximal safe power level for each irrigation rate.
2：Sample Selection and Data Sources:
Glass cylindrical tubes terminating in a spherical bulb of 11 or 19 mm inner diameter were used to simulate renal calyx and pelvis, respectively. A ureteroscope was inserted through the model and placed at the middle of the spherical bulbs.
3：List of Experimental Equipment and Materials:
A 242 μm core laser fiber was introduced through the ureteroscope with the laser fiber tip advanced 5 mm beyond the end of the ureteroscope. Each model was placed in a water bath maintained at 37°C using an immersion heater with 10 mm extending above the water surface. A wire thermocouple was positioned with the measuring portion adjacent to the end of the ureteroscope.
4：Experimental Procedures and Operational Workflow:
Irrigation with room temperature (23°C) deionized water was provided through the working channel of the ureteroscope. The height of the irrigation bag was adjusted to provide irrigation rates of 0, 5, 10, 15, 20, 25, and 30 ml/min, respectively. Laser energy (range
5：5 - 50W) was delivered from a 120-watt holmium laser at different laser settings. During each experiment, temperature was recorded for 120 seconds:
starting with 20 seconds of baseline temperature, 20 seconds of irrigation only, 60 seconds of continuous laser activation with irrigation, and lastly 20 seconds of irrigation only.
6：Data Analysis Methods:
Thermal dose (t43) for each trial was calculated using the Dewey and Sapareto formula.
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