Jens Cordes

Destruction of Stone Extraction Basket During an In Vitro Lithotripsy—A Comparison of Four Lithotripters

BACKGROUND Various techniques are available for intracorporeal disintegration of renal and ureteral stones, among them ballistic lithotripsy, ultrasonic lithotripsy and laser lithotripsy. The therapeutic effectiveness of these devices has been sufficiently studied and compared. This does not apply, however, to the risk of destroying the stone basket. MATERIALS AND METHODS The time until destruction of the wires of various baskets with use of four different lithotripsy devices (LithoClast, EMS; LithoRapid, Olympus; Calcuson 27610029, Storz; Vera Pulse, Coherent) was measured in a model closely aligned with the clinic. RESULTS As expected, the direct application of laser pulses (wavelength 2.1 μm) irrespective of thickness and shape led to a melting of all wires of the stone extraction basket in less than 50 seconds (pulse energy: 800 mJ, pulse repetition rate: 8 hertz; fiber diameter: 365 μm). The purely kinetic functioning lithotripters (electrokinetic-ballistic and pneumatic-ballistic) were not able to destroy any wire within the set time limit of one minute. The sonotrode of the ultrasonic device, which is considered to be very tissue-conserving, separated all wires of baskets with a diameter of 1.8F (4 wires), 75% of baskets with a diameter of 2.5F (9 of 12), but only 8.3% of baskets with a diameter of 3.5F (1 of 12). Plaited wires demonstrated a good resistance (0 of 4) in comparison with the sonotrode. CONCLUSION Our study consequently shows that in addition to the laser, the ultrasonic probe can also easily destroy nitinol (nickel titanium) baskets.

Damage of Stone Baskets by Endourologic Lithotripters:A Laboratory Study of 5 Lithotripters and 4 Basket Types

Background. In some cases, the ureteral stone is simultaneously stabilized by a stone basket when endourologic lithotripsy is performed. This stabilization can be either on purpose or by accident. By accident means that an impaction in the ureter occurs by an extraction of a stone with a basket. A stabilization on purpose means to avoid a retropulsion of the stone into the kidney during lithotripsy. At this part of the operation, stone baskets have been frequently damaged. This severing of wires can lead to ureteral trauma because of hook formation. Material and Methods. In a laboratory setting, the time and the pulse numbers were measured until breaking the wires from four different nitinol stone baskets by using five different lithotripsy devices. The endpoint was gross visibledamage to the wire and loss of electric conduction. Results. The Ho:YAG laser and the ultrasonic device were able to destroy almost all the wires. The ballistic devices and the electrohydraulic device were able to destroy thin wires. Conclusion. The operating surgeon should know the risk of damagefor every lithotripter. The Ho:YAG-laser and the ultrasonic device should be classified as dangerous for the basket wire with all adverse effects to the patient.

Stone/tissue differentiation for holmium laser lithotripsy using autofluorescence

Holmium laser lithotripsy is a safe and effective method to disintegrate urinary stones of all compositions in an endoscopic procedure. However, handling and safety could be improved by a real‐time feedback system permanently monitoring the position of the treatment fiber. The laser is fired only when the fiber is identified as being placed in front of stone. This work evaluates the potential of fluorescence detection with an excitation wavelength of 532 nm for this purpose.

Stone/tissue differentiation for Holmium laser lithotripsy using autofluorescence: Clinical proof of concept study

Holmium laser lithotripsy is the gold standard for intracorporeal fragmentation of urinary calculi. Usually, a visible beam is superimposed on the IR treatment laser as an aiming beam to guide the surgeon. In vitro tests showed that this aiming beam (532 nm, power <1 mW) excites strong fluorescence on human calculi. Tissue, in contrast, emitted much weaker fluorescence. If this is verified in vivo, the fluorescence signal induced by the aiming beam could be used to implement a feedback loop, preventing the Holmium laser being fired on tissue.

Stone/tissue differentiation during intracorporeal lithotripsy using diffuse white light reflectance spectroscopy: In vitro and clinical measurements

Holmium laser lithotripsy is the ‘gold standard’ for intracorporeal fragmentation of stones. However, there is a risk of damaging and perforating the ureter wall when the laser is accidentally fired while the fiber is in contact with tissue. The aim of this study was to evaluate if white illumination light, diffusely reflected back into the treatment fiber and spectrally analyzed, can be used for differentiating between stone and tissue.

Differentiation of tissue and kidney stones for laser lithotripsy using different spectroscopic approaches

Holmium lasers are nowadays the gold standard for endoscopic laser lithotripsy. However, there is a risk of damaging or perforating the ureter or kidney tissue when the vision is poor. An automatic tissue/stone differentiation would improve the handling and safety of the procedure. To achieve this objective, an easy and robust real-time discrimination method has to be found which can be used to realize a feedback loop to control the laser system. Two possible approaches have been evaluated: White light reflectance and fluorescence spectroscopy. In both cases, we use the treatment fiber for detection and evaluate the possibility to decide whether the fiber is placed in front of tissue or calculus by the signal that is delivered by the surface in front of it. White light reflectance spectroscopy uses the standard light source for endourologic surgeries: Radiation of a Xenon light source is coupled to the ureteroscope via a liquid light guide. The part of the white light that is reflected back into the fiber is spectroscopically analyzed. In a clinical proof of concept study reflection signals were measured in vivo in 8 patients. For differentiation of stone and tissue via autofluorescence, excitation as well as detection was done via the treatment fiber. A suitable excitation wavelength was chosen with in vitro measurements (UV / visible) on several human renal calculi and porcine tissues. For verification of the positive results with green excitation in a clinical proof of concept study, a measurement set-up was realized which allows the recording of fluorescence signals during an endourological intervention.

Could titanium oxide coating from a sol–gel process make stone baskets more resistant to laser radiation at 2.1 μm?

BackgroundStone baskets could be easily destroyed by Holmium:YAG-laser at an endourologic treatment, with respect to this, we try to improve the resistance by coating them with a titanium oxide layer. The layer was established by a sol–gel-process.Materials and methodsSix new baskets (Equadus, Opi Med, Ettlingen, Germany) were used: 1.8 Ch. with 4 wires (diameter 0.127 mm). Three baskets were coated with a layer of titanium oxide established by a sol–gel process at the BioCerEntwicklungs GmbH in Bayreuth (~100 nanometres thickness). The lithotripter was a Holmium:YAG laser (Auriga XL, Starmedtec, Starnberg, Germany). 10 uncoated and 10 coated wires were tested with 610 mJ (the minimal clinical setting) and 2 uncoated and 2 coated wires were tested with 110 mJ. The wires were locked in a special holding instrument under water and the laser incident angle was 90°. The endpoint was gross visible damage to the wire and loss of electric conduction.ResultsOnly two coated wires resisted two pulses (one in the 610 mJ and one in the 110 mJ setting). All other wires were destroyed after one pulse.ConclusionThis was the first attempt at making stone baskets more resistant to a Holmium:YAG laser beam. Titanium oxide deposited by a sol–gel-process on a titanium-nickel alloy did not result in better resistance to laser injuries