Thulium vs holmium
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Holmium YAG laser Vs Thulium Fiber laser
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Thulium vs holmium
- 1. Holmium YAG laser Vs Thulium Fiber laser Thulium fiber laser : the new player for kidney stone treatment Dr Rojan Adhikari Urology Resident SDNTC
- 2. Introduction • Holmium : YAG laser has been the gold standard lithotrite for stone surgery over the past two decades; 1 • Despite many advantages, the Holmium : YAG laser technology still faces limitations with regards to size of stones amenable to ureteroscopic laser lithotripsy; 2 • Thulium fiber laser has shown early promise in being able to overcome the limitations of Holmium : YAG; 3 1. Kronenberg P, Traxer O (2015) 2. Turk et al , 2016, 2018 3. Fried et al, (2018)
- 3. Holmium : YAG laser
- 4. Compared to other lithotripsy techniques, the Holmium:YAG laser presents several important advantages: • suitability for fragmentation of all known urinary stone types into small stone particles ; • ability to operate with thin and fexible delivery fibers with limited energy losses and with core diameters as small as 200 µm • favorable safety profile with minimal tissue penetration depth and low risk of undesirable tissue damage due to the relatively high absorption coefficient of the Holmium:YAG laser wavelength in water • versatility which allows a Holmium:YAG laser system to be used for soft tissue applications additionally to stones, which partially offsets the costs of high-power systems
- 5. Limitations 1. Fragment are big and technique is time consuming 2. Inefficient design requires large cooling systems and high power requirements 3. Systems large bulky and difficult to move 4. Fragility with mirrors 5. Multimodal spatial beam profile limits ability to focus laser and limits use to fibers with >2oo micrometer core diameter 6. Pulse frequency of individual cavities limited to <30 Hz and multi- cavity lasers required to reach a maximum frequency Nazif et al (2004) , Scott et al (2009) Kronenberg P, Traxer O (2015)
- 6. Next-generation laser lithotripsy: what do we need? A New Laser with : • Small fiber • Lower pulse energy • Higher frequency
- 7. Small fiber
- 8. If we are moving from regular fiber 273 micron, lets take a example lets take a thin fiber 150 microns the diameter decreses by 1.8, if we consider the surface of the fiber there will be division by 3.3 . In terms of impact over the surface of stone, we need to multiplicate by 3.3 time.
- 9. Lower pulse energy If we consider energy we distribute in fiber, lets take example of 1 Joule in specific setting . In a regular fiber, energy density will be 17 J/mm2. Energy density means distribution of energy into the fiber. If we use same energy 1J in 150 micron fiber , the energy density will be 56 Joule /mm2. its very higher its means high energy in a spot on the surface of stone, so that bigger fragments will be produce and fiber tip may get damaged. Decrease surface by 3.3 so energy density increases by 3.3. so to decrease energy density the energy should be decreased. Concluding this slide we need a new system able to produce very low energy for small fragments and to prevent fiber tip degeneration at high pulse energy.
- 10. • How can we go Faster?? • If we are using small fiber with low energy we will be efficient. Since the fiber is smaller we need much more impacts. It should be increased with 3.3 times • If we need to compensate
- 11. Higher frequency • IF we want faster or to compensate , we need a new system which can produce high frequency . Otherwise it will take much longer time. • In this, frequency should be multipled by at least 3.3 . • So the system should produce 300 or 400 or 500 Hz. • As detailed above, any decrease in laser fiber core diameter also requires a proportionate decrease in pulse energy. To keep up with stone ablation effcacy (amount of stone ablated over time), a compensatory increase in pulse repetition rate (frequency) is necessary.
- 13. Thulium fiber laser Schematic representation of a Thulium fiber laser. Thulium fiber laser consists of a very thin and long silica fiber , 10–30 m long (red tube with green spots) and which has been chemically doped with Thulium ions of 10–20 µm core diameter is used as a gain medium for the generation of a laser beam . For laser pumping, multiple diode lasers are used to excite the Thulium ions. The emitted laser beam has a wavelength of 1940 nm and can operate either in a continuous mode or adopt a pulsed mode within a large range of various energy, frequency, and pulse shape settings . laser fibers as small as 50 µm (blue) is used.
- 14. Thulium fiber laser >> Holmium : YAG laser • Thulium fiber laser requires less heat dissipation and can potentially operate at high-power ranges (>50 W) and high-frequency ranges (up to 2000 Hz) with forced air, compared to water-cooled Holmium : YAG lasers; 1 , 2 • Architecture of fiber lasers is insensitive to shock-related damages, unlike Holmium : YAG generators, because no mirror is involved in the fiber laser design 2 • The more uniform spatial beam profile of thulium enables simpler focusing of the beam down to a very small spot for efficient coupling and transmission of high power through ultra-small fibers (e.g.50–100 µm); 3 1. Jackson et al (2002) 2. Wilson et al (2016) 3. Blackmon et al (2014)
- 15. Thulium fiber laser >> Holmium : YAG laser • 1.5–4 times faster stone ablation rate in favor of the Thulium fiber laser 1, 2 • Damages to the proximal fiber end was not found with Thulium fiber laser, while all proximal fiber ends were damaged with Holmium: YAG lithotripsy 3 • Prevention of stone retropulsion during Thulium fiber laser delivery is done by distal fiber tip design (muzzle tip) 1, 2, 4 • Advantage in favor of smaller fibers would be the possibility to reduce the working channel diameter of ureteroscopes, thus allowing for a major overall instrument miniaturization. 5 1. Blackmon et al, (2011) 2. Hardy et al (2014) 3. Wilson et al (2016) 4. Hutchens et al (2013) 5. Wilson et al (2018)
- 17. This is the comparison of holmium vs thulium , 2 different technology two different effect Holmium --- the bubble to expand and collapse regularly Thallium fibers --- they are also producing bubbles which increase and collapse but much more then the holmium YAG
- 18. Characteristics of two generators: Holmium : YAG laser and Thulium fiber laser
- 19. Conclusion The Thulium fiber laser overcomes the main limitations reported with the Holmium : YAG laser and is more effective relating to lithotripsy .
- 20. TAKE HOME Thulium fiber laser surpasses Holmium : YAG laser in many aspects: (1) integration of smaller fibers with a core diameter as small as 50 µm; 1, 2 (2) pulse energy as low as 0.025 J; 3 (3) super-high pulse repetition rate range up to 2000 Hz; 3 1. Scott et al (2009) 2. Blackmon RL (2014) 3. Hardy et al (2017)
- 21. Thank you
Editor's Notes
- “light amplification by stimulated emission of radiation (LASER)”.
- Compared to other lithotripsy techniques, the Holmium:YAG laser presents several important advantages: suitability for fragmentation of all known urinary stone types into small stone particles ; ability to operate with thin and fexible delivery fibers with limited energy losses and with core diameters as small as 200 µm favorable safety profile with minimal tissue penetration depth and low risk of undesirable tissue damage due to the relatively high absorption coefficient of the Holmium:YAG laser wavelength in water ; versatility which allows a Holmium:YAG laser system to be used for soft tissue applications additionally to stones, which partially offsets the costs of high-power systems Limitations Fragment are big and technique is time consuming Ineffectint design requires large cooling systems and high power requirements -- 30 and 50 amp service for high watt systems -- Systems large bulky and difficult to move -- fragility with mirrors 3. Multimodal spatial beam profile limits ability to focus laser and limits use to fibers with >2oo micrometer core diameter 4. Pulse frequency of individual cavities limited to <30 Hz and multi-cavity lasers required to reach a maximum of 80 Hz
- Schematic representation of the operating mode of a Holmium : YAG laser cavity. a Broad-spectrum white light is emitted from a flashlamp (typically Xenon or Krypton). b The white light interacts with the Holmium ions that are chemically bound to the YAG crystal and excites Holmium-electrons into higher-energy quantum states. b This interaction results in the emission of new photons with a characteristic wavelength of 2120 nm. Additional white light emitted from the flashlamp adds to Holmium ions excitation, a process referred to as “laser pumping”. c The radiation is reflected between the mirrors of the laser cavity. d : Because prior laser pumping excited numerous Holmium ions to higher-energy states, the reflected radiation will interact with the excited Holmium ions and stimulate emission of multiple additional photons at 2120 nm. This phenomenon is referred to as “light amplification by stimulated emission of radiation (LASER)”. E. A transient opening of the cavity releases the radiation in the form of a pulsed laser beam
- Small fiber – 150 microns Lower pulse energy – 50 to 100 mJ Higher frequency – 300 - 500 Hz
- To produce thin particles , we need to consider size of the fiber. studies have shown multiple advantages in favor of smaller laser fbers: better irrigation flow, better instrument defection, and less stone retropulsion [46–49]. Another major potential advantage in favor of smaller fbers would be the possibility to reduce the working channel diameter of ureteroscopes, thus allowing for a major overall instrument miniaturization [50]. This would increase the space available between the ureteroscope and the ureter or access sheath, thus increasing irrigation outfow. The net result would be an overall increase of irrigation flow, higher irrigation turnover within renal cavities and most importantly better visibility
- If we are moving from regular fiber 273 micron, lets take a example lets take a thin fiber 150 microns the diameter decreses by 1.8, if we consider the surface of the fiber there will be division by 3.3 . In terms of impact over the surface of stone, we need to multiplicate by 3.3 time.
- If we consider energy we distribute in fiber, lets take example of 1 Joule in specific setting . In a regular fiber, energy density will be 17 J/mm2. Energy density means distribution of energy into the fiber. If we use same energy 1J in 150 micron fiber , the energy density will be 56 Joule /mm2. its very higher its means high energy in a spot on the surface of stone, so that bigger fragmnets will be produce and fiber tip may get damaged. Decrease surface by 3.3 so energy density increases by 3.3. so to decrease energy density the energy should be decreased. Concluding this slide we need a new system able to produce very low energy for small fragments and to prevent fiber tip degeneration at high pulse energy. In that respect, the Thulium fber laser offers several potential advantages over Holmium:YAG laser. Notably, it can provide energy per pulse as low as 0.025 J, is capable of long-pulse duration (up to 12 ms) and emits a more uniformly shaped temporal beam profle (e.g., top-hat or fattop) such that energy is more uniformly distributed across the duration of the pulse than the Holmium:YAG laser
- How can we go Faster?? If we are using small fiber with low energy we will be efficient. Since the fiber is smaller we need much more impacts. It should be increased with 3.3 times If we need to compensate
- IF we want faster or to compensate , we need a new system which can produce high frequency . Otherwise it will take much longer time. In this, frequency should be multipled by at least 3.3 . So the system should produce 300 or 400 or 500 Hz. As detailed above, any decrease in laser fiber core diameter also requires a proportionate decrease in pulse energy. To keep up with stone ablation effcacy (amount of stone ablated over time), a compensatory increase in pulse repetition rate (frequency) is necessary. Frequency: Frequency is the number of occurrences of a repeating event per unit of time (one cycle per second)
- Schematic representation of a Thulium fiber laser. Thulium fiber laser consists of a very thin and long silica fiber , 10–30 m long (red tube with green spots) and which has been chemically doped with Thulium ions of 10–20 µm core diameter is used as a gain medium for the generation of a laser beam . For laser pumping, multiple diode lasers are used to excite the Thulium ions. The emitted laser beam has a wavelength of 1940 nm and can operate either in a continuous mode or adopt a pulsed mode within a large range of various energy, frequency, and pulse shape settings . laser fibers as small as 50 µm (blue) is used.
- Efficiency of the fiber laser design is significantly higher than that of the flashlamp-pumped solid state Holmium: YAG laser, because the emission spectrum of the diode laser used for laser pumping precisely matches Thulium ions’ absorption line. Hence, the Thulium fber laser requires less heat dissipation and can potentially operate at high-power ranges (>50 W) and high-frequency ranges (up to 2000 Hz) with forced air (e.g., simple fan ventilation) inside the generator, compared to water-cooled Holmium:YAG lasers
- The limitation of Holmium:YAG lasers; is fibers with a core diameter≥200 µm. This is explained by the poorly focused multimode laser beam profle at the coupling interface between the laser generator and the proximal end of the delivery fber, which increases the probability of generator and fber damage by heat generation Comparatively, the Thulium fber laser generates a much more uniform and focused laser beam, which can be transmitted to laser fbers with smaller core diameters (50–150) µm [40, 42]. Consequently, the Thulium fber laser ofers the potential for miniaturized next-generation ureteroscopy that may integrate remarkably thin fbers [51].
- The Holmium:YAG laser operates at 2120 nm and is highly absorbed in liquid water, leading to a rapid formation of a vapor bubble after emission in pulsed mode [25]. This interaction with water also adds to the safety profile of Holmium : YAG lasers, as the optical penetration depth is limited to 400 µm and coagulation of tissue beyond this distance only occurs in the high pulse energy range For laser lithotripsy, the Thulium fber laser has been optimized to emit at a wavelength of 1940 nm. Because the absorption coefficient of the Thulium fber laser (approximately 14 mm−1) is more than four-fold higher than Holmium:YAG laser (approximately 3 mm−1), a lower threshold and higher ablation efficiency can be expected in favor of the Thulium fber laser at equivalent pulse energies. A lower tissue and water penetration depth may potentially also add to the safety profile of the Thulium fiber laser.
- This is the comparison of holmium vs thulium , 2 different technology two different effect Holmium --- the bubble to expand and collapse regularly Thallium fibers --- they are also producing bubbles which increase and collapse but much more then the holmium YAG This phenomenon is Moses effect, which has been first described in 1988 as a vapor channel resulting from water irradiation by laser and which leaves an open path with low absorption coefficient between the fiber tip and the stone surface [69]. Notably, a stone-suctioning effect of Thulium fiber laser has been demonstrated to be achievable under certain circumstances