[European Association of Urology guidelines on laser technologies]

LASER-INDUCED OCULAR LESIONS WITH THULIUM FIBER LASER IN ENDOUROLOGY : AN EX VIVO STUDY

INTRODUCTION AND OBJECTIVES

The Thulium Fiber Laser(Tm-F) is currently studied as an alternative to the Holmium:YAG laser(Ho:YAG), the gold-standard for endocorporeal laser lithotripsy. We aimed to evaluate the ex vivo effects of an accidental Tm-F laser exposure on bovine eyes and to test the protective action of different eyeglasses in preventing eye lesions in case of accident.

METHODS

A 50W-TFL-generator(IPG Photonics®, Russia) with a wavelength of 1940nm and 200µm-core-diameter-fibers(CDF) were used. The laser fiber tip was pointed perpendicularly at different distances(0, 1, 3, 5, 8, 10, respectively) to the pupil center of the bovine eye. The Tm-F laser was activated for 1 or 3 seconds at three different settings(0.5J-20Hz, 1J-10Hz, and 2J-10Hz, respectively). The experiment was repeated using laser safety glasses and eyeglasses. After lasering, eye samples were immersed in a 0,5 % fluorescein serum (Faure-Ciba-Geigy®, Switzerland), then rinsed with saline solution. White- and blue-light examinations looked for localized epithelial burns(LEB), extended epithelial burns(EEB), superficial corneal ulcerations(SCU) and deep corneal ulcerations(DCU).

RESULTS

A total of 68 bovine eyes were used. Despite the laser settings, both DCU(contact) and SCU (1cm) developed without eye protection, for 1 and 3 seconds of lasering. At 3cm fiber-eye distance, only burning lesions were observed. Over 5cm, no lesion was found. At contact or 1 cm fiber-eye distance, pulse energy did not change lesion grade, but at 3cm, high pulse energy led to higher grade corneal lesions(0,5J-10Hz:LEB; 1J-10Hz:EEB). Despite the fiber-eye distance, no corneal lesions were reported in the laser safety glasses or eyeglasses groups for 1 second laser exposure.

CONCLUSION

Our study highlights the risk of eye damage caused by Tm-F. Without proper eye protection Tm-F can cause corneal lesions up to 5cm in distance for 1 second of exposure, despite laser settings. Only dedicated protective eyeglasses are effective for long exposures.

Tissue effects of a newly developed diode pumped pulsed Thulium:YAG laser compared to continuous wave Thulium:YAG and pulsed Holmium:YAG laser

Purpose

The objective of this study is to evaluate the laser-tissue effects of laser radiation emitted by a newly developed high frequency pulsed Tm:YAG laser in comparison to the continuous wave Tm:YAG laser and the pulsed Ho:YAG laser.

Methods

Ex-vivo experiments were performed on freshly slaughtered porcine kidneys in a physiological saline solution. Experiments were performed using two different laser devices in different settings: A Tm:YAG laser was operated in a pulsed mode up to 300 Hz and in a continuous wave (CW) mode. Results were compared with a 100 W standard pulsed Ho:YAG laser system. Comparative tissue experiments were performed at 5 W, 40 W and 80 W. The incision depth and the laser damage zone were measured under a microscope using a calibrated ocular scale.

Results

Increased laser power resulted in increased incision depth and increased laser damage zone for all investigated lasers in this set-up. The Ho:YAG created the largest combined tissue effect at the 5 W power setting and seems to be the least controllable laser at low power for soft tissue incisions. The CW Tm:YAG did not incise at all at 5 W, but created the largest laser damage zone. For the new pulsed Tm:YAG laser the tissue effect grew evenly with increasing power.

Conclusion

Among the investigated laser systems in this setting the pulsed Tm:YAG laser shows the most controllable behavior, insofar as both the incision depth and the laser damage zone increase evenly with increasing laser power.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00345-021-03634-4.

Laser transurethral resection of the prostate: Safety study of a novel system of photoselective vaporization with high power diode laser in prostates larger than 80mL

OBJECTIVE

To present the feasibility of photoselective vaporization of the prostate (PVP) with of a new diode laser-resection system. Surgical treatment of benign prostatic hyperplasia (BPH) is constantly evolving. Laser techniques are increasingly used in prostates of large size.

METHODS

A prospective study was performed to evaluate operative data and patient outcomes with PVP using high-power diode laser (HPD) and a novel quartz-head fiber with shovel shape in patients with prostate>80mL. Demographic data, operative time, hemoglobin loss, operative results (IPSS, quality of life (QoL), Qmax, post void residue (PVR), IIEF-5 and micturition diary) and complications following Clavien-Dindo classification are described.

RESULTS

Thirty-one patients were included in the study. Sixteen (51.6%) were on active antiplatelet treatment and 12 (38.7%) had received anticoagulants before surgery. All cases were followed at least 6mo. No intraoperative or postoperative major complications occurred. Three patients (9.7%) had minor complications according to Clavien-Dindo classification. Twenty-seven (87.1%) were discharged on postoperative day one without catheter. There were significant improvements in IPSS, QoL, Qmax and PVR, both at 3 and 6mo (P<.0001), but sexual function according to IIEF-5 showed no differences. Urgency (any grade) increased at 3mo (48.4%; P=.002) and considerably decreased at 6mo (9.7%; P<.0001).

CONCLUSION

This pilot experience with shovel shape fiber and HPD is encouraging. It shows that laser-resection is a safe procedure, achieving excellent results in terms of IPSS, QoL and Qmax in large prostates even in high-risk patients. Longer follow-up, comparative and randomized controlled studies are needed to widespread these results.

The role of lasers in modern urology

INTRODUCTION

The functioning of modern urological departments and the high level of service they provide is possible through, among other things, the use of modern laser techniques.

MATERIAL AND METHODS

Open operations have been replaced by minimally invasive procedures, and classical surgical tools by advanced lasers. The search for new applications with lasers began as technology developed. Among many devices available, holmium, diode and thulium lasers are currently the most popular.

RESULTS

Depending on the wavelength, the absorption by water and hemoglobin and the depth of penetration, lasers can be used for coagulation, vaporization and enucleation. In many centres, after all the possibilities of pharmacological treatment have been exhausted, lasers are used as the primary treatment for patients with benign prostatic hyperplasia, with therapeutic results that are better than those obtained through open or endoscopic operations. The use of lasers in the treatment of urolithiasis, urinary strictures and bladder tumours has made treatment of older patients with multiple comorbidities safe, without further necessity to modify the anticoagulant drug treatment. Laser procedures are additionally less invasive, reduce hospitalization time and enable a shorter bladder catheterization time, sometimes even eliminating the need for bladder catherterization completely. Such procedures are also characterized by more stable outcomes and a lower number of reoperations.

CONCLUSIONS

There are also indications that with the increased competition among laser manufacturers, decreased purchase and maintenance costs, and increased operational safety, laser equipment will become mandatory and indispensable asset in all urology wards.

Virtual reality simulator for training on photoselective vaporization of the prostate with 980 nm diode laser and learning curve of the technique

OBJECTIVE

The utility of a virtual reality simulator for training of the photoselective vaporization of the prostate with diode laser was studied.

MATERIAL AND METHOD

Two experiments were performed with a simulator (VirtaMed AG, Zürich, Switzerland) with software for specific training in prostate vaporization in contact mode with Twister fiber (Biolitec AG, Jena, German). Eighteen surgeons performed ablation of the prostate (55 cc) twice and compared the score obtained (190 points efficacy and 80 safety) in the second one of them by experience groups (medical students, residents, specialists). They also performed a spatial orientation test with scores of 0 to 6. After, six of these surgeons repeated 15 ablations of the prostate (55 and 70 ml). Improvement of the parameters obtained was evaluated to define the learning curve and how experience, spatial orientation skills and type of sequences performed affects them.

RESULTS

Global efficacy and safety score was different according to the grade of experience (P=.005). When compared by pairs, specialist-student differences were detected (p=0.004), but not specialist-resident (P=.12) or resident-student (P=.2). Regarding efficacy of the procedure, specialist-student (p=0.0026) and resident-student (P=.08) differences were detected. The different partial indicators in terms of efficacy were rate of ablation (P=.01), procedure time (P=.03) and amount of unexposed capsule (p=0.03). Differences were not observed between groups in safety (P=.5). Regarding the learning curve, percentage median on the total score exceeded 90% after performing 4 procedures for prostates of 55 ml and 10 procedures for prostate glands of 70 ml. This course was not modified by previous experience (resident-specialist; P=.6). However, it was modified according to the repetition sequence (progressive-random; P=.007). Surgeons whose spatial orientation was less than the median of the group (value 2.5) did not surpass 90% of the score in spite of repetition of the procedure.

CONCLUSION

Simulation for ablation of the prostate with contact diode laser is a good learning model with discriminative validity, as it correlates the metric results with levels of experience and sills. The sequential repetition of the procedure on growing levels of difficulty favors learning.