The document compares Holmium YAG laser and Thulium fiber laser for kidney stone treatment. Holmium YAG laser has been the gold standard for over 20 years but has limitations treating larger stones. Thulium fiber laser shows promise in overcoming Holmium YAG limitations by allowing for smaller fiber sizes down to 50 microns, lower pulse energies as low as 0.025 Joules, and higher pulse repetition rates up to 2000 Hz. This allows for faster stone ablation rates, avoids fiber tip damage, and could enable instrument miniaturization for ureteroscopes. In conclusion, Thulium fiber laser surpasses Holmium YAG laser in many aspects important for effective lithotripsy.

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