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

Lange, Birgit; Jocham, Dieter; Brinkmann, Ralf; Cordes, Jens

doi:10.1002/lsm.22611

Cited by 13 publications

(16 citation statements)

References 14 publications

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“…Besides fragmentation and movement of calculi, the fluorescence of human kidney stones was investigated in this study. Interesting approaches in this area were recently introduced that involved fluorescence excitation on kidney stones with the aiming beam of a laser system [24,25]. This enables one to develop a feedback system for the laser device to differentiate hard and soft tissue in front of the fiber tip and finally to avoid accidental laser pulse application to surrounding soft tissue [33].…”

Section: Propulsiomentioning

confidence: 99%

“…Small fragments may remain untreated clinically because of insufficient visibility and/or low contrast with the surrounding tissue under white light illumination. Suitable recognition techniques have been proposed and are still under development [23][24][25]. In view of these three clinical challenges, the following investigations on fragmentation and propulsion of artificial stones as well as fluorescence response of human calculi were performed to identify optimisation potential in the procedure of laser lithotripsy.…”

Section: Introductionmentioning

confidence: 99%

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Holmium:yttrium-aluminum-garnet laser induced lithotripsy: in-vitro investigations on fragmentation, dusting, propulsion and fluorescence

Eisel

Ströbl

Pongratz

et al. 2018

Biomed. Opt. Express

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The fragmentation efficiency on Bego artificial stones during lithotripsy and the propulsive effect (via video tracking) was investigated for a variety of laser settings. A variation of the laser settings (pulse energy, pulse duration, repetition rate) altered the total application time required for stone fragmentation, the stone break up time, and the propulsion. The obtained results can be used to develop lithotripsy devices providing an optimal combination of low stone propulsion and high fragmentation efficacy, which can then be evaluated in a clinical setting. Additionally, the fluorescence of human kidney stones was inspected endoscopically in vivo. Fluorescence light can be used to detect stone-free areas or to clearly distinguish calculi from surrounding tissue or operation tools.

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Section: Propulsiomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Holmium:yttrium-aluminum-garnet laser induced lithotripsy: in-vitro investigations on fragmentation, dusting, propulsion and fluorescence

Eisel

Ströbl

Pongratz

et al. 2018

Biomed. Opt. Express

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“…The measurement system was an improved and extended version of the one described in Lange et al : Aiming laser and reflection and fluorescence beam path were combined with that of the Ho:YAG laser within an external fiber‐fiber‐coupling beam path (see Fig. ).…”

Section: Methodsmentioning

confidence: 99%

“…All measurements were performed before the lithotripsy treatment took place. In most instances (94%), calculi gave a signal, which was at least twice that of ureteral tissue . However, with two patients, the tissue signal was strongly fluctuating probably due to bad phase matching of the lock‐in measurement: It turned out that the phase shift to optimize the correct overlapping of input and reference signal of the lock‐in amplifier had to be adjusted during the course of the study.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, both stone detection (via autofluorescence measurement) as well as fiber damage detection (via reflection measurement) were addressed: The set‐up described in Lange et al was improved by replacing the lock‐in amplifier for a model with a dual‐phase measurement. This way, one gets insensitive to changes in the relative phase of reference and signal.…”

Section: Introductionmentioning

confidence: 99%

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Exploiting the aiming beam to increase the safety of laser lithotripsy: Experimental evaluation of light reflection and fluorescence

2019

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Background and Objectives In Holmium laser lithotripsy, usually, the surgeon is guided by a visible beam superimposing the infrared (IR) treatment radiation. It has been shown that a green aiming beam excites stone autofluorescence. This fluorescence signal can be used for calculi detection to check the correct fiber position before triggering the IR laser, thus preventing damage to soft tissue and application devices. However, also the directly reflected green light from the fiber tip gives valuable information on fiber position and its surface condition. Materials and Methods An external fiber‐fiber‐coupling‐box (fiber core diameter 365 µm) for pulsed holmium laser radiation (2.1 µm) was set up containing a green diode laser module (520 nm, average power on the sample <0.5 mW) and optics and detectors for measuring the reflected light of this aiming beam as well as the fluorescence excited with it. Measurements were done via a lock‐in technique with more than 20 human calculi samples and porcine calix in vitro. After the implementation of automatic data storage signals during ongoing in vitro lithotripsy procedures were recorded with the fiber positioned on tissue, stone, or in/on medical equipment (working channel of an endoscope, stone retrieval basket). Results Stone fluorescence signals measured were a factor of 7 to >100 higher than those of tissue. Stone fluorescence was detectable in “non‐contact mode” with a linear signal decrease over a distance up to ~1 mm in front of the fiber tip (core diameter 365 µm) and with severely damaged fibers (max. decrease: 75% with pinched off fiber). Reflection signals of the fiber tip surface in air and water surrounding decreased significantly when the fiber was damaged; measured ratios of intact to damaged fiber found in the air were (5–17):1 and in water (1.6–3.7):1. Surfaces in front of the fiber aggravated the evaluation of fiber condition due to reflections but enabled to detect, for example, the working channel of a flexible endoscope in combination with the (missing) fluorescence signal. Conclusions Autofluorescence induced by a green aiming beam can be exploited for stone detection in laser lithotripsy. A reflection measurement can give further information on fiber condition and position. Implementing this kind of safety features for an automatic block of IR laser emission in case of weak or missing fluorescence and un‐normal reflections can assist the surgeon by avoiding tissue perforation, and damage to medical devices such as endoscopes. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

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Fluorescence‐guided laser lithotripsy: Estimation of the potential effectiveness and safety increase based on first clinical data

Lange

Ozimek

Wießmeyer

et al. 2023

Journal of Biophotonics

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In clinically approved laser lithotripsy systems, there is no automatic monitoring of fiber position to date. We investigated whether detecting stone autofluorescence, excited by a green aiming beam, is possible via the fiber during fragmentation by continuously recording the fluorescence signal in 12 ureterosopic lithotripsy procedures. We estimated which threshold the fluorescence signal's amplitude exceeds before laser pulses with visible stone removal by retrospective inspection of the endoscope's video data. For all procedures, blocking the laser when the fluorescence amplitude is below a threshold corresponding to the signal's baseline plus its range (maximum-minimum value) would have been appropriate to suppress ineffective pulses-the energy input could have been reduced by a mean of 14% (1%-29%) without changing the operation time. Ablation of the PTFE coating of the guidewire could have been prevented three times and cutting of a wire of the retrieval basket two times.

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

Cited by 13 publications

References 14 publications

Holmium:yttrium-aluminum-garnet laser induced lithotripsy: in-vitro investigations on fragmentation, dusting, propulsion and fluorescence

Holmium:yttrium-aluminum-garnet laser induced lithotripsy: in-vitro investigations on fragmentation, dusting, propulsion and fluorescence

Exploiting the aiming beam to increase the safety of laser lithotripsy: Experimental evaluation of light reflection and fluorescence

Fluorescence‐guided laser lithotripsy: Estimation of the potential effectiveness and safety increase based on first clinical data

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