Abstract
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The EDGE Research Consortium conformed by recognized innovators and pioneers in endourology, in their article, defined and described in a very didactic style the characteristics of each of the two questioned primary laser lithotripsy techniques. They explained, briefly, how laser energy produces jets that are projected against stones and also the effect of laser pulse duration. The authors attempt to homologize terminology and nomenclature, describe the evolution of laser settings for lithotripsy, and expose the range of energy setting (i.e., Hertz and Joules) among the commercial laser consoles available.
Matlaga and collaborators list the most efficient and common energy settings used in a clinical scenario on the “Fragmentation with Extraction” (Low Frequency/High Energy: Frequency 6–10 Hz/Energy 1.0–1.2 J) and “Dusting” (High Frequency/Low Energy: Frequency 12–15 Hz [< 30W laser devices], >50 Hz [100/120 W laser devices]/Energy 0.2–0.4 J) techniques, focusing the reader on the goal of surgical techniques (i.e., how to approach stones and laser fiber more efficiently on each technique), mentioned potential advantages and disadvantages of each approach, and also in terms of cost and scope longevity. The EDGE group found no significant differences in stone-free rates, operative time, and complication rates among the current small published data available when comparing both laser lithotripsy techniques.
The authors also stated that discussions appear to be limited to flexible ureteroscopic stone treatment, and the role of these techniques with semirigid ureteroscopy has not yet been characterized. The authors also gave us important information in a meta-message: the EDGE members carried out a diagnosis of the status quo about the flexible laser lithotripsy as “Fragmentation with Extraction” and “Dusting” techniques in terms of very limited research, and also it is a very motivating challenge to discover how to take advantage of the wider range of laser energy settings to do lithotripsy and the other multiple variables that are involved in the process.
According to a recent worldwide survey of contemporary practice pattern of flexible ureteroscopy for treating renal stones, the “Dusting” technique (i.e., low pulse energy and high frequency; 0.2–0.5 J, ·30–50 Hz) was used by 67% of the respondents.
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The increasing popularity of this technique is an interesting phenomenon, but the limited information about randomized clinical trials gives us the big and unique opportunity to funnel all this enthusiasm and efforts to better characterize the advantages or disadvantages of each primary technique at least in the clinical field. Urologic associations might support researchers and also might become coordinators and codesigners of multicenter trials considering the most significant variables in terms of comparing the two laser “techniques.” The Clinical Research Office of the Endourological Society would be an excellent coordinator of worldwide efforts in this field (
The “Dusting” laser technique emerged due to the development of newer laser consoles that permitted to the user to explore a wider range of frequency and energy combination settings that resulted in “Dusting” urinary stones effect instead of only “Fragmentation” 3 or another phenomenon known as the “pop corn” effect. 4 That is why there is another area of potential research on the interaction of wider range of laser energy settings with urinary calculi among several variables involved, but focused on the basic science principles.
A higher desired level of research in urinary stone lithotripsy using laser energy devices would be the sharing of the discoveries obtained in the basic science arena and the findings gotten in the clinical field. In this scenario, the implementation of Translational Medicine 5 would help to match a multidisciplinary, highly collaborative, “bench-to-bedside” approach within biomedical research, with a focus on cross-functional collaborations with multidirectional feedback (e.g., academic centers, foundations, industry, researchers, and clinicians), leveraging new technology and new treatments to reach the patients in shorter time and with the best cost-efficiency. It would also minimize the “divorce” existing between these important areas of knowledge. Scientists should be more involved in clinical scenario and clinicians should be more related to the basic science field in close collaborations.
Three decades ago there was a question of which extracorporeal shockwave lithotripsy (electrohydraulic, piezoelectric, and electromagnetic) devices would be the best to treat renal stones, and also the recent debate in the past decade of which energy (pneumatic, ultrasonic, or combination of both) lithotrite devices are the most efficient for percutaneous nephrolithotomy in terms of stone-free rates. 6,7 In the case of laser energy lithotripter, no matter the brand and manufacturer, we are using the same energy device, same tool, but with a wider capacity of laser energy settings.
Different to the previous analogies, in the laser lithotripsy it might not be necessary to evaluate which device is better, but which frequency/energy ratio combinations are the best according to our purpose for treating urinary stones, considering, for example, stone burden, stone composition, 8 and stone hardness among other variables that impact laser lithotripsy effectiveness. It has also been recognized that fiber tip preparation and lithotripter settings influence tip degradation and the newly developed long-pulse laser modes. 3 Personally, I consider the Dusting and Fragmentation with Extraction techniques not as “different” laser techniques for lithotripsy, but as different potential capacities of the same newer laser devices, like an “all terrain” vehicle can be set according to the needs we have on the road.
To study and for better understanding of the interaction between urinary stones and laser energy for lithotripsy, it is recommended to go back to the basics, as reading interesting articles already published on this issue. 3,9
For example, Kronenberg and Traxer did a very detailed exploration of an in vitro fragmentation efficiency of holmium:yttrium aluminum garnet (Ho:YAG) laser lithotripsy comprehensive study considering variables such as frequencies, pulse energies, and total power levels using 200 and 550 μm core laser fibers in artificial stone models. In a very didactic article, they reported that low frequency/high power settings (5–10 Hz/1.2 J) were 4.5 (standard deviation 1.4)-fold more ablative against artificial stone models than high frequency/low power settings (25–40 Hz/0.2–0.3 J), producing statistically significant deeper and wider fissures on studied stones, in which the laser fiber diameter did not affect stone fragmentation volume except when using 550 μm at very low pulse energies (0.2 J), wherein it was less efficient (P = 0.015). 9
There is a special scenario in which physics and physician match and interact in the healing of our patients suffering from urinary calculi. The shared greco-latin etymology roots of these two words conduct us to the concepts about “mother nature, matter, energy and their interactions.” 10 A urinary stone represents a high concentration of mineral, (atoms), condensed as mass and matter and kept as one piece by some kind of energy (i.e., electrons) to attract one atom to another and to consolidate urinary calculi. Laser beam is generated as high concentrated form of energy and is emitted by light stream that is capable of destroying those forces (i.e., electrons, neutrons, etc.), mass and energy that keep the matter merged, in our case, as a form of urinary stone. Understanding this specific mass–energy interaction for improving outcomes is basic for those involved in treating patients with laser lithotripsy.
It is highly recommended to include the deep study of the Laser physics in the curriculum and hand-on laboratory sessions on this issue in urologic and endourologic academic centers. We might think and proceed not only as physicians, but also physicists when manipulating and controlling the laser energy interaction with calculi, to disintegrate urinary stone burden in order to get safe and cost-effective treatments for our patients. To treat urinary calculi with laser lithotripsy should be a very dynamic process and might be determined mainly by the nature (components) of the stone we are treating, among other variables (i.e., stone burden, stone hardness, anatomy of the urinary system, etc). Each case should be treated individually. For example, some stone layers or stone areas would need “Fragmentation with Extraction” mode of laser energy settings and other stone layers or stone areas would best be treated with “Dusting” laser energy settings. It is necessary to characterize the laser energy interaction with urinary stones including all the variables involved in the procedure in more detail to determine the ideal scenario for applying these “two techniques” or those discovered or proposed in the near future. Perhaps in the future, a helpful nomogram might be developed in this field to make better clinical decisions.
The acronym DUST has been used for another purpose (i.e., Developments in Urinary Stone Tecnologies). This time, considering that the goal for lithotripsy is to disintegrate urinary stones and follow the suggestion about thinking and proceeding not only as physicians but also as physicists when treating urinary calculi, I propose humbly for your consideration the “DUST” (Disintegration of Urinary Stone Techniques) term among other potential acronyms to include in current and future effective forms, frequency and energy combinations for lithotripsy and its understanding, but not exclusive for laser lithotripsy.
Further research is needed in order to compare these two described energy settings of Ho:YAG laser lithotripsy named “Fragmentation with Extraction” and “Dusting” techniques and to determine whether they are similarly effective in terms of stone-free rate among other variables and to define in which scenario each of them offers the best option for our patients.