Temperature changes of renal calyx during high-power flexible ureteroscopic Moses holmium laser lithotripsy: a case analysis study

PURPOSE

The risk of thermal damage increases with the introduction of high-power lasers during holmium laser lithotripsy. This study aimed to quantitatively evaluate the temperature change of renal calyx in the human body and the 3D printed model during high-power flexible ureteroscopic holmium laser lithotripsy and map out the temperature curve.

METHODS

The temperature was continuously measured by a medical temperature sensor secured to a flexible ureteroscope. Between December 2021 and December 2022, willing patients with kidney stones undergoing flexible ureteroscopic holmium laser lithotripsy were enrolled. High frequency and high-power settings (24 W, 80 Hz/0.3 J and 32 W, 80 Hz/0.4 J) were performed for each patient with room temperature (25 °C) irrigation. In the 3D printed model, we studied more holmium laser settings (24 W, 80 Hz/0.3 J, 32 W, 80 Hz/0.4 J and 40 W, 80 Hz/0.4 J) with warmed (37 °C) and room temperature (25 °C) irrigation.

RESULTS

Twenty-two patients were enrolled in our study. With 30 ml/min or 60 ml/min irrigation, the local temperature of the renal calyx did not reach 43 °C in any patient under 25 °C irrigation after 60 s laser activation. There were similar temperature changes in the 3D printed model with the human body under the irrigation of 25 °C. Under the irrigation of 37 °C, the temperature rise slowed down, but the temperature in the renal calyces was close to or even exceeded the 43 °C at the setting of 32 W, 30 ml/min and 40 W, 30 ml/min after continuing laser activation.

CONCLUSION

In the irrigation of 60 ml/min, the temperature in the renal calyces can still be maintained within a safe range after continuous activation of a holmium laser up to 40 W. However, continuous activation of 32 W or higher power holmium laser in the renal calyces for more than 60 s in the limited irrigation of 30 ml/min can cause excessive local temperature, in such situation room temperature perfusion at 25 ℃ may be a relatively safer option.

Cut-to-the-light technique is useful for complete obstruction of a Wallace ureteroileal anastomosis

Introduction

Obstruction of a ureteroileal anastomosis after urinary diversion is an unpleasant situation for patients and clinicians alike.

Case presentation

A 48-year-old man who underwent a radical cystectomy for muscle-invasive bladder cancer and urinary diversion using the Wallace technique complained of right back pain. Computed tomography showed right hydronephrosis. Cystoscopy via the ileal conduit revealed complete obstruction of the ureteroileal anastomosis. We performed a bilateral approach (antegrade and retrograde) to use the cut-to-the-light technique. A guidewire and 7Fr single J catheter could be inserted.

Conclusion

The cut-to-the-light technique was useful for complete obstruction of the ureteroileal anastomosis, the length of which was <1 cm. Herein, we report on the cut-to-the-light technique with a literature review.

Comparison of low power and high power holmium YAG laser settings in flexible ureteroscopy

PURPOSE

To compare the efficacy of conventional low power and high power holmium: yttrium aluminum-garnet (Ho: YAG) laser lithotripsy settings during retrograde intrarenal surgery (RIRS).  METHODS: The prospective study was conducted in patients undergoing RIRS for renal stones less than 2 cm diameter. Pulsed Ho:YAG laser (Lumenis^® Pulse TM P120 H) was used for laser lithotripsy and the patients were randomized into low power (LP) and high power (HP) laser lithotripsy settings groups. The lasing duration, total laser energy used (Joules), laser energy used to ablate 1 mm³ of stone (Joules/mm³), operative duration, stone ablation speed (mm³/s) and stone free rate were compared.

RESULTS

A total of 120 underwent RIRS with 63 and 57 patients in LP and HP group, respectively. Median stone volume and stone density were comparable between the groups. The total energy used and laser energy used to ablate 1mm³ of stone (Joules/mm³) were significantly higher in the HP group than in LP group (27.9 (16.4-46.2) J/ mm³ vs 9.7 (5.3-17.7) J/ mm³) (p < 0.01). Median (IQR) ablation speed were 0.8 (0.5-1.3) mm³/s and 0.6 (0.4-1) mm³/s in the LP and HP groups, respectively. The median lasing time, operative time and stone free rate were similar in both the groups.

CONCLUSION

The total energy used and J/mm³ were lower in the LP group than in HP group with similar lasing duration, operative duration, ablation speed and stone free rate for renal stones less than 2 cm.

Use of holmium laser for umbilical cord transection in a monoamniotic pregnancy threatened by an acardiac co-twin: a case report

Background

Twin reversed arterial perfusion sequence is a rare complication of monochorionic multifetal pregnancies. In this syndrome, the acardiac twin has a nonfunctional heart, while the other twin, the pump twin, has normal development. The pump twin perfuses the acardiac twin and is therefore at risk for cardiac decompensation. In monoamniotic cases, the normal co-twin is also at risk of sudden death due to cord entanglement. Treatment consists of coagulation and transection of the acardiac’s umbilical cord. We report the first intrauterine use in pregnancy of a Ho:yttrium aluminum garnet laser to safely and successfully transect the umbilical cord after Nd:yttrium aluminum garnet coagulation.

Case presentation

A 30-year-old Caucasian woman was referred to our fetal–maternal medicine unit at 9 weeks gestation with a monochorionic–monoamniotic twin pregnancy complicated by an acardiac twin. After counseling, she opted for an elective intervention to minimize the risks to the pump twin. At 16 weeks, fetoscopy was performed using a single 2-mm entry port. Through this port, a 1.0-mm fetoscope and a 0.365-mm laser fiber were introduced. Under fetoscopic sight and ultrasound (Doppler) guidance, the umbilical cord of the acardiac twin was first coagulated by laser energy using a Nd:yttrium aluminum garnet laser and then, using the same fiber, transected using a Ho:yttrium aluminum garnet laser. The patient underwent cesarean section at 38 weeks and delivered a healthy baby.

Conclusions

We present the first report on intrauterine use of an Ho:yttrium aluminum garnet laser in human pregnancy. Ho:yttrium aluminum garnet laser energy can be successfully and safely used for umbilical cord transection and carries fewer risks than other methods of transection.

[Application of laser technologies in the treatment of non-muscle-invasive bladder cancer]

This review includes the facts of bladder treatment by means of laser technologies application in historical perspective. Advantages and disadvantages of different laser technologies were considered in comparison with the traditional TUR of the bladder wall.

Laser Fiber Displacement Velocity during Tm-Fiber and Ho:YAG Laser Lithotripsy: Introducing the Concept of Optimal Displacement Velocity

BACKGROUND

Endocorporeal laser lithotripsy (EL) during flexible ureteroscopy (URS-f) often uses "dusting" settings with "painting" technique. The displacement velocity of the laser fiber (LF) at the stone surface remains unknown and could improve EL's ablation rates. This in vitro study aimed to define the optimal displacement velocity (ODV) for both holmium:yttrium-aluminium-garnet (Ho:YAG) and thulium fiber laser (Tm-Fiber).

METHODS

A 50W-TFL (IRE Polus^®, Moscow, Russia) and a 30W-MH1-Ho:YAG laser (Rocamed^®, Signes, Provence-Alpes-Côte d'Azur, France), were used with 272 µm-Core-Diameter LF (Sureflex, Boston Scientific^©, San Jose, CA, USA), comparing three TFL modes, "fine dusting" (FD: 0.05-0.15 J/100-600 Hz); "dusting" (D: 0.5 J/30-60 Hz); "fragmentation" (Fr: 1 J/15-30 Hz) and two Ho:YAG modes (D: 0.5 J/20 Hz, Fr: 1 J/15 Hz). An experimental setup consisting of immerged cubes of calcium oxalate monohydrate (COM) stone phantoms (Begostone Plus, Bego^©, Lincoln, RI, USA) was used with a 2 s' laser operation time. LF were in contact with the stones, static or with a displacement of 5, 10 or 20 mm. Experiments were repeated four times. Stones were dried and µ-scanned. Ablation volumes (mm³) were measured by 3D-segmentation.

RESULTS

ODV was higher in dusting compared to fragmentation mode during Ho:YAG lithotripsy (10 mm/s vs. 5 mm/s, respectively). With Tm-Fiber, dusting and fragmentation OVDs were similar (5 mm/s). Tm-Fiber ODV was lower than Ho:YAGs in dusting settings (5 mm/s vs. 10 mm/s, respectively). Without LF displacement, ablation volumes were at least two-fold higher with Tm-Fiber compared to Ho:YAG. Despite the LF-DV, we report a 1.5 to 5-fold higher ablation volume with Tm-Fiber compared to Ho:YAG.

CONCLUSIONS

In dusting mode, the ODV^Tm-Fiber is lower compared to ODV^Ho:YAG, translating to a potential easier Tm-Fiber utilization for "painting" dusting technique. The ODV determinants remain unknown. Dynamic ablation volumes are higher to static ones, regardless of the laser source, settings or LF displacement velocity.

Comparison of Holmium:YAG and Thulium Fiber Lasers on the Risk of Laser Fiber Fracture

Objectives: To compare the risk of laser fiber fracture between Ho:YAG laser and Thulium Fiber Laser (TFL) with different laser fiber diameters, laser settings, and fiber bending radii. METHODS: Lengths of 200, 272, and 365 μm single use fibers were used with a 30 W Ho:YAG laser and a 50 W Super Pulsed TFL. Laser fibers of 150 µm length were also tested with the TFL only. Five different increasingly smaller bend radii were tested: 1, 0.9, 0.75, 0.6, and 0.45 cm. A total of 13 different laser settings were tested for the Ho:YAG laser: six fragmentation settings with a short pulse duration, and seven dusting settings with a long pulse duration. A total of 33 different laser settings were tested for the TFL. Three laser settings were common two both lasers: 0.5 J × 12 Hz, 0.8 J × 8 Hz, 2 J × 3 Hz. The laser was activated for 5 min or until fiber fracture. Each measurement was performed ten times. Results: While fiber failures occurred with all fiber diameters with Ho:YAG laser, none were reported with TFL. Identified risk factors of fiber fracture with the Ho:YAG laser were short pulse and high energy for the 365 µm fibers (p = 0.041), but not for the 200 and 272 µm fibers (p = 1 and p = 0.43, respectively). High frequency was not a risk factor of fiber fracture. Fiber diameter also seemed to be a risk factor of fracture. The 200 µm fibers broke more frequently than the 272 and 365 µm ones (p = 0.039). There was a trend for a higher number of fractures with the 365 µm fibers compared to the 272 µm ones, these occurring at a larger bend radius, but this difference was not significant. Conclusion: TFL appears to be a safer laser regarding the risk of fiber fracture than Ho:YAG when used with fibers in a deflected position.

Multisensorial Assessment of Laser Effects on Shellac Applied on Wall Paintings

The assessment of five different laser treatments in the conservation of wall paintings was devised on the basis of the surface temperature monitoring by infrared thermography (IRT), ultraviolet-induced fluorescence-visible (UV-VIS) imaging, and optical coherence tomography (OCT). A series of yttrium-aluminum-garnet (YAG) lasers were tested for removal of shellac layers from wall painting mock-ups. The mock-ups were realized as buon fresco with different mineral based pigments (earths and iron oxide) on a lime- and sand-based mortar. After the carbonatation process, all the samples were treated with shellac (5% in ethanol). The effects of neodymium (Nd):YAG, holmium (Ho):YAG, and erbium (Er):YAG laser sources, in different operative modes, on average temperature of the surface, color, and morphology were inspected with complementary sensors. The results show the necessity to adopt a combined approach in establishing safe laser operating conditions to avoid any undesired effects induced on the artefacts by the laser treatments. We demonstrate, for the first time, the performance of the Ho:YAG laser in the removal of a conservation treatment.

Clinical Comparison of Super Pulse Thulium Fiber Laser and High-Power Holmium Laser for Ureteral Stone Management

Purpose: To evaluate the efficacy of new super pulse thulium fiber laser (SP TFL) and compare it with holmium laser for ureterolithotripsy. Patients and Methods: A total of 174 patients with solitary ureteral calculi were enrolled in 2016 to 2018. Stone sizes ranged between 0.6 and 2.4 cm. The SP TFL FiberLase U2 and 120H Ho:YAG laser with fibers diameters of 400 and 365 μm, respectively, were used. The laser settings were 1 J × 10 Hz = 10 W for both devices. All patients were randomized into two groups. The age, stone size, location, and density were comparable in both groups. The evaluated parameters were operation time, endoscopic view quality, retropulsion grade, stone-free rate, and complication rate. Results: The total operation time and lasering time were longer in the Ho:YAG group (24.7 ± 0.7 minutes vs 32.4 ± 0.7 minutes, p = 0.05), and postoperative stenting was necessary in one vs four cases, respectively. At 30 days of follow-up, no residual stones were observed in the SP TFL group (vs five cases of Ho:YAG). Conclusion: SP TFL technology was associated with excellent efficacy/safety ratio. The SP TFL may be considered as a viable alternative to Ho:YAG laser stone management.

Complete ureteral stenosis after ureteroscopic lithotripsy successfully managed using a simultaneous retrograde and antegrade flexible ureteroscopic approach

Both retrograde and antegrade approach contributed to the success of a delicate endoscopic procedure. Even when guidewire did not pass thorough to the stenosis lesion, lightning and contrast reagents contributed the way through to the stenosis lesion.

Ex vivo study of Ho:YAG and thulium fiber lasers for soft tissue surgery: which laser for which case?

The goal of this study was to assess the ablation, coagulation, and carbonization characteristics of the holmium:YAG (Ho:YAG) laser and thulium fiber lasers (TFL). The Ho:YAG laser (100 W av.power), the quasi-continuous (QCW) TFL (120 W av.power), and the SuperPulsed (SP) TFL (50 W av.power) were compared on a non-frozen porcine kidney. To control the cutting speed (2 or 5 mm/s), an XY translation stage was used. The Ho:YAG was tested using E = 1.5 J and P_av = 40 W or P_av = 70 W settings. The TFL was tested using E = 1.5 J and P_av = 30 W or P_av = 60 W settings. After ex vivo incision, histological analysis was performed in order to estimate thermal damage. At 40 W, the Ho:YAG displayed a shallower cutting at 2 and 5 mm/s (1.1 ± 0.2 mm and 0.5 ± 0.2 mm, respectively) with virtually zero coagulation. While at 70 W, the minimal coagulation depth measured 0.1 ± 0.1 mm. The incisions demonstrated zero carbonization. Both the QCW and SP TFL did show effective cutting at all speeds (2.1 ± 0.2 mm and 1.3 ± 0.2 mm, respectively, at 30 W) with prominent coagulation (0.6 ± 0.1 mm and 0.4 ± 0.1 mm, respectively, at 70 W) and carbonization. Our study introduced the TFL as a novel efficient alternative for soft tissue surgery to the Ho:YAG laser. The SP TFL offers a Ho:YAG-like incision, while QCW TFL allows for fast, deep, and precise cutting with increased carbonization.

Evaluations on laser ablation of ex vivo porcine stomach tissue for development of Ho:YAG-assisted endoscopic submucosal dissection (ESD)

Endoscopic submucosal dissection (ESD) is clinically used to remove early gastric cancer in stomach. The aim of the current study is to examine a therapeutic capacity of pulsed Ho:YAG laser for the development of laser-assisted ESD under various surgical parameters. Ex vivo porcine stomach tissue was ablated with 1-J Ho:YAG pulses at 10 Hz at different number of treatments (NT = 1, 2, and 3) and treatment speeds (TS = 0.5, 1, and 2 mm/s) without and with saline injection. Regardless of saline injection, straight tissue ablation showed that ablation depth increased with increasing NT and decreasing TS. At NT = 3 and TS = 0.5 mm/s, no saline injection yielded the maximum ablation depth (3.4 ± 0.3 mm), partially removing muscularis propria. However, saline injection confined the tissue ablation within a submucosal layer (2.1 ± 0.3 mm). Thermal injury was found to be 0.7~1.1 mm in the adjacent tissue with superficial carbonization. Circular tissue ablation (2 cm in diameter) at NT = 3 and TS = 0.5 mm/s presented that no saline injection yielded a reduction in the lesion area, whereas saline injection maintained the ablated lesion area. Histological analysis revealed that unlike no saline injection, saline injection ablated the entire mucosal layer without perforation in the muscular propria. The pulsed Ho:YAG laser can be a potential surgical tool for clinical ESD to incise a target lesion without adverse perforation. Further investigations will validate the efficacy and safety of the Ho:YAG laser-assisted ESD in in vivo porcine stomach models for clinical translation.

Temperature profiles of calyceal irrigation fluids during flexible ureteroscopic Ho:YAG laser lithotripsy

PURPOSE

To evaluate calyceal irrigation fluid temperature changes during flexible ureteroscopic Ho:YAG laser lithotripsy.

METHODS

Between May 2019 and January 2020, patients with kidney stones undergoing flexible ureteroscopic Ho:YAG laser lithotripsy were enrolled. A K-type thermocouple was applied for intraoperative temperature measurement. Laser was activated at different power (1 J/20 Hz and 0.5 J/20 Hz) and irrigation (0 ml/min, 15 ml/min and 30 ml/min) settings, temperature-time curve was drawn and time needed to reach 43 °C without irrigation was documented.

RESULTS

Thirty-two patients were enrolled in our study. The temperature-time curve revealed a quick temperature increase followed by a plateau. With 15 ml/min or 30 ml/min irrigation, 43 °C was not reached after 60 s laser activation at both 1 J/20 Hz and 0.5 J/20 Hz. At the power setting of 1 J/20 Hz and irrigation flow rate of 15 ml/min, the temperature rise was significantly higher than other groups. Without irrigation, the time needed to reach 43 °C at 1 J/20 Hz was significantly shorter than that at 0.5 J/20 Hz (8.84 ± 1.41 s vs. 13.71 ± 1.53 s).

CONCLUSION

Ho:YAG laser lithotripsy can induce significant temperature rise in calyceal fluid. With sufficient irrigation, temperatures can be limited so that a toxic thermal dose is not reached, when irrigation is closed, the temperature increased sharply and reached 43 °C in a few seconds.

Pediatric bilateral ureteral stone successfully removed using single-use flexible ureteroscopy with a holmium: YAG laser

A 12-year-old boy received steroid for his minimal change nephrotic syndrome for 10 years, and bilateral renal and ureteral stones and hydronephrosis were observed. Single-use flexible ureteroscopy is usable for pediatric lithotripsy with Ho: YAG laser.

Temperature changes during laser lithotripsy with Ho:YAG laser and novel Tm-fiber laser: a comparative in-vitro study

AIM

The aim of this study was to compare the thermal effects of Ho:YAG and Tm-fiber lasers during lithotripsy in an in-vitro model via real-time temperature measurement.

METHODS

We compared a Ho:YAG laser (p_av up to 100 W, Lumenis, Yokneam, Israel) and a superpulse Tm-fiber laser (SP TFL, p_av up to 40 W, NTO IRE-Polus, Fryazino, Russia), both equipped with 200 µm bare-ended fibers. The following settings were used: 0.2 J, 40 Hz (nominal p_av 8 W). Power meter FieldMaxII-TO (Coherent, Santa Clara, CA, USA) was used to verify output laser power (p_av). Each laser was fired for 60 s in two setups: (1) thermos-insulated (quasi-adiabatic) cuvette; (2) actively irrigated setup with precise flow control (irrigation rates 0, 10, 35 mL/min).

RESULTS

Power measurements performed before the test revealed a 10% power drop in Ho:YAG (up to 7.2 ± 0.1 W) and 6.25% power drop in SP TFL (up to 7.5 ± 0.1). At the second step of our experiment, irrigation reduced the respective temperatures in the same manner for both lasers (e.g., at 35 mL/s SP TFL - 1.9 °C; for Ho:YAG laser - 2.8 °C at 60 s).

CONCLUSION

SP TFL and Ho:YAG lasers are not different in terms of volume-averaged temperature increase when the same settings are used in both lasers. Local temperature rises may fluctuate to some degree and differ for the two lasers due to varying jet streaming caused by non-uniform heating of the aqueous medium by laser light.

A Novel Combination Technique: Three Points of Epiduroscopic Laser Neural Decompression and Percutaneous Laser Disc Decompression With the Ho:YAG Laser in an MSU Classification 3AB Herniated Disc

AIM

The aim of this study was to examine the effects of simultaneous epiduroscopic laser neural disc decompression (ELND) and percutaneous laser disc decompression (PLDD) applications using a holmium:yttrium-aluminum-garnet (Ho:YAG) laser in Michigan State University (MSU) classification 3AB herniated discs on VAS and Oswestry Disability Index (ODI) scores.

METHODS

In this prospective observational study, ELND and PLDD procedures performed between January 2016 and December 2017 were examined. Preoperative, postoperative week 2, postoperative month 2, and postoperative month 6 ODI and VAS scores were obtained from patient files, and postoperative month 12 ODI and VAS scores were obtained from face-to-face interviews with patients and recorded.

RESULTS

The data of 41 patients treated with simultaneous ELND and PLDD using a Ho:YAG laser were included in this study. Postoperative VAS scores of the patients were compared with preoperative values, and it was found that postoperative week 2, postoperative month 2, postoperative month 6, and postoperative month 12 VAS and ODI scores were significantly different compared to preoperative scores (P = 0.001; P < 0.01). 17.1% (n = 7) of the patients had a history of postoperative open surgery. Although dural puncture occurred in 7 patients (17%), only 1 patient had headache.

CONCLUSION

We believe that the new combined technique of ELND and PLDD using a Ho:YAG laser is a reliable method in patients with MSU classification 3AB herniated discs, with an acceptable success rate and a low complication rate within 12 months after treatment. We think that randomized controlled studies are required for this method to be included in treatment algorithms.

How Lasers Ablate Stones: In Vitro Study of Laser Lithotripsy (Ho:YAG and Tm-Fiber Lasers) in Different Environments

Introduction: There are two main mechanisms of stone ablation with long-pulsed infrared lasers: photothermal and photomechanical. Which of them is primary in stone destruction is still a matter of discussion. Water holds importance in both mechanisms but plays a major role in the latter. We sought to identify the prevailing mechanism of stone ablation by evaluating the stone mass loss after lithotripsy in different media. Materials and Methods: We tested a holmium:yttrium-aluminum-garnet (Ho:YAG) laser (100 W; Lumenis), a thulium-fiber laser U1 (TFL U1) (120 W; NTO IRE-Polus, Russia), and a SuperPulse thulium-fiber laser U2 (TFL U2) (500 W; NTO IRE-Polus). A single set of laser parameters (15 W = 0.5 J × 30 Hz) was used. Contact lithotripsy was performed in phantoms (BegoStones) in different settings: (a) hydrated phantoms in water, (b) hydrated phantoms in air, (c) dehydrated phantoms in water, and (d) dehydrated phantoms in air. Laser ablation was performed with total energy of 0.3 kJ. Phantom mass loss was defined as the difference between the initial phantom mass and the final phantom mass of the ablated phantoms. Results: All lasers demonstrated effective ablation in hydrated phantoms ablated in water; no visual differences between the lasers were detected. The ablation of dehydrated phantoms in air was also effective with visible vapor during ablation and condensation on the cuvette wall. Dehydrated phantoms in water and in air show minimal to no ablation accompanied with formation of white crust on phantom surface. Among laser types, TFL U2 had the highest phantom mass loss in all groups except for dehydrated phantoms ablated in air. Conclusions: Our results suggest that both photothermal and thermomechanical ablation mechanisms (explosive vaporization) occur in parallel during laser lithotripsy. In Ho:YAG and TFL U2 stone ablation explosive vaporization prevails, whereas in TFL U1 ablation photothermal mechanism appears to predominate.

Effects of Ho:YAG Laser Ablation on Postoperative Low Back Pain and Functional Status After Transforaminal Endoscopic Lumbar Discectomy: Minimum of 2-Year Follow-Up

OBJECTIVE

To evaluate effects of holmium:yttrium-aluminum-garnet (Ho:YAG) laser ablation on postoperative low back pain and improving functional status in patients with lumbar disc herniation undergoing transforaminal endoscopic lumbar discectomy (TELD).

METHODS

The study enrolled 220 patients with lumbar disc herniation who underwent TELD or TELD with Ho:YAG laser from August 2015 to September 2016. Parameters including operative time, hospitalization, complications, and recurrence were recorded. Clinical outcomes were assessed according to visual analog scale for back pain and leg pain, Oswestry Disability Index for functional status, and modified MacNab criteria for patient satisfaction.

RESULTS

Minimal 2-year follow-up was completed by 186 patients: 76 patients who underwent TELD and 110 patients who underwent TELD with Ho:YAG laser. In the group undergoing TELD, clinical outcomes of back pain and functional status exhibited a V-shaped upward trend after surgery; there were no statistically significant differences in visual analog scale for back pain and Oswestry Disability Index scores at final follow-up compared with preoperatively (P > 0.05). In the group undergoing TELD with Ho:YAG laser, postoperative visual analog scale for back pain and Oswestry Disability Index scores significantly improved compared with preoperatively (P < 0.05) exhibiting relatively consistent improvement after surgery. The only laser-related complication was a burning sensation in the ipsilateral lower limb during the thermal procedure in 2 cases.

CONCLUSIONS

Performing Ho:YAG laser ablation with TELD prolonged low back pain relief and improved functional outcome during 2-year follow-up compared with TELD alone in patients with symptomatic lumbar disc herniation.

In vitro bactericidal effect of Ho:YAG laser and pneumatic lithotripsy on ureteral stones colonized with Escherichia coli and Enterococcus faecalis

The endoscopic treatment of urolithiasis has a high success rate and the complications decreased after the development of lithotripsy techniques. The aim of this study is to investigate the in vitro bactericidal effect of laser and pneumatic lithotripsy on urinary stones colonized with Escherichia coli and Enterococcus faecalis. A total of 40 natural calcium oxalate stones, which were obtained from the patients' urinary systems with rigid ureteroscopy were used in the study. Surfaces of the stones were colonized with E. coli and E. faecalis strains. The fragmentation of the stones was performed using holmium:yttrium-aluminum-garnet laser (Ho:YAG laser) and pneumatic lithotripters in vitro in Eppendorf tubes filled with liquid. After fragmentation, samples taken from Eppendorf tubes were inoculated on blood and EMB agar. The number of colonies was evaluated after 18-24-hour incubation period. The laser lithotripsy technique reduced the number of colonies by 100% and had bactericidal effect on E. coli and E. faecalis. Pneumatic lithotripsy technique had no bactericidal effect on these strains (0%). In the fifth minute of laser irradiation, the average temperature in the Eppendorf tube was 51-55 °C, and the average temperature in the tenth minute was 54-60 °C. The temperatures did not change in the fifth and tenth minutes with the pneumatic lithotripsy procedure. The present study revealed the bactericidal effect of Ho:YAG laser on E. coli and E. faecalis in vitro. Increased ambient temperature during Ho:YAG laser lithotripsy is thought to play a role in the bactericidal effect. But the question of whether an ideal lithotripter efficiently inactivates or destroys bacteria has still not been answered in urology practice. This preliminary study showed the bactericidal effect of Ho:YAG laser lithotripsy, but further studies are needed to investigate the bactericidal effect of Ho:YAG laser in vivo.

[Laser in laparoscopic urology]

Nowadays, various laparoscopic instruments for tissue dissection and vessel coagulation are available. However, there are ongoing studies dedicated to "ideal" type of energy suitable for this aim. Laser radiation has been used for many years in medical practice and it is established as reliable and effective method in surgical armamentarium. The ability to provide highly precision and well-controlled action on the tissues, improved hemostasis, easy adaptability to fiber-optic and minimally invasive delivery systems, as well as the possibility of facilitating complex dissection made lasers an important tool for surgeons. The mechanism and methods of laser energy using in urology have been studied since 1980s, but there is still no consensus on the optimal type of laser and its settings during urological surgeries, which determines the importance of further researches dedicated to this promising form of energy.

How to perform the dusting technique for calcium oxalate stone phantoms during Ho:YAG laser lithotripsy

BACKGROUND

To determine the most efficacious setting of Holmium:yttrium-aluminum-garnet (Ho:YAG) laser with a maximum power output of 120 W with in vitro phantom-stone dusting technique.

METHODS

A laser was used to treat two 4 × 3 × 3 mm³ sized phantom stones in 5 mL syringes with 1 mm-sized holes at the bottom. According to the pulse width (short 500, middle 750, long pulse 1000 μsec), maximal pulse repetition rates from 50 to 80 Hz were tested with pulse energy of 0.2, 0.4, 0.5, and 0.8 J. Six times of the mean dusting times were measured at each setting. Dusting was performed at continuous firing of the laser until the stones become dusts < 1 mm.

RESULTS

The mean Hounsfield unit of phantom stones was 1309.0 ± 60.8. The laser with long pulse generally showed shorter dusting times than short or middle pulse width. With increasing the pulse energy to 0.5 J, the dusting time decreased. However, the pulse energy of 0.8 J showed longer dusting times than those of 0.5 J. On the post-hoc analysis, the pulse energy of 0.5 J, long pulse width, and the repetition rates of 70 Hz demonstrated significantly shorter dusting times than other settings.

CONCLUSIONS

The results suggest that long pulse width with 0.5 J and 70 Hz would be the most efficacious setting for dusting techniques of plaster stone phantoms simulating calcium oxalate stones using the 120 W Ho:YAG laser.

The application of a single-use fiberoptic flexible ureteroscope for the management of upper urinary calculi

OBJECTIVE

To evaluate the clinical outcomes with a Chinese single-use fiberoptic flexible ureteroscope (YouCare Tech) from a prospective database.

MATERIALS AND METHODS

A prospective study was conducted in a single center in China between January 2016 and October 2017. All consecutive patients who underwent flexible ureteroscopy performed by YouCare flexible ureteroscope were analyzed. Patients' demographics, clinical characteristics, intraoperative parameters, postoperative complications, and stone-free rate were evaluated and recorded. Stone-free status was defined as no visible stones or clinically insignificant residual stones < 2 mm on a postoperative image study.

RESULTS

A total of 684 procedures were performed for 653 patients (31 patients had bilateral stones). A double J stent had been previously placed in 431 patients. The location of the calculi was upper calyx, middle calyx, lower calyx, and renal pelvis and proximal ureter in 74, 101, 211, 115, and 183 patients, respectively. The median operative time was 52 min. The postoperative stone-free rate for the first 2 weeks after surgery was 78.5%, which increased to 91.1% at the first month. The overall stone-free rate was 95.2%. The complication rate was minor and short-term, such as gross hematuria or flank pain.

CONCLUSION

YouCare flexible ureteroscope can be considered effective and safe in the treatment of both upper ureteral and renal stones in selected patients. Further evaluation of comparison with other FURS's surgical outcomes and cost-effectiveness analysis will help to present the best utility of this single-use FURS in clinical practice.

Evaluation of 200 Mm, 365 Mm and 500 Mm Fibers of Ho:YAG Laser in Transurethral Lithotripsy of Ureteral: A Randomize Control Trial

Introduction: Presently, different holmium: yttrium aluminum garnet (Ho:YAG) laser calibers are used for endoscopic stone treatment, which include 200, 365, 500 and 1000 Mm fibers. Currently, there are not enough studies to compare the performance of these fibers. In this retrospective investigation, we compared the outcome of 200, 365 and 500 Mm fibers of Ho:YAG laser in transurethral lithotripsy of ureteral stone. Methods: From January 2016 to June 2017, 74 subjects with mean age of 35.3 ± 5.6 were randomly allocated to 3 groups according to the caliber of laser, 200, 365 and 500 Mm for transurethral lithotripsy. The main purpose of this investigation was to evaluate mean operation time (MOT), stone free rate (SFR) and complications. Results: MOT and SFR were significantly different in 500 Mm laser caliber (P=0.046, P=0.029, respectively). There was no remarkable difference between the 3 groups in this regard. Conclusion: Based upon our data, the clinical potency of the Ho: YAG laser was great in all 3 fiber calibers. The most important results of this comparison were the significantly higher SFR with increased laser caliber.

In vitro investigations of propulsion during laser lithotripsy using video tracking

OBJECTIVES

Ureteroscopic laser lithotripsy is an important and widely used method for destroying ureter stones. It represents an alternative to ultrasonic and pneumatic lithotripsy techniques. Although these techniques have been thoroughly investigated, the influence of some physical parameters that may be relevant to further improve the treatment results is not fully understood. One crucial topic is the propulsive stone movement induced by the applied laser pulses. To simplify and speed up the optimization of laser parameters in this regard, a video tracking method was developed in connection with a vertical column setup that allows recording and subsequently analyzing the propulsive stone movement in dependence of different laser parameters in a particularly convenient and fast manner.

MATERIALS AND METHODS

Pulsed laser light was applied from below to a cubic BegoStone phantom loosely guided within a vertical column setup. The video tracking method uses an algorithm to determine the vertical stone position in each frame of the recorded scene. The time-dependence of the vertical stone position is characterized by an irregular series of peaks. By analyzing the slopes of the peaks in this signal it was possible to determine the mean upward stone velocity for a whole pulse train and to compare it for different laser settings. For a proof of principle of the video tracking method, a specific pulse energy setting (1 J/pulse) was used in combination with three different pulse durations: short pulse (0.3 ms), medium pulse (0.6 ms), and long pulse (1.0 ms). The three pulse durations were compared in terms of their influence on the propulsive stone movement in terms of upward velocity. Furthermore, the propulsions induced by two different pulse energy settings (0.8 J/pulse and 1.2 J/pulse) for a fixed pulse duration (0.3 ms) were compared. A pulse repetition rate of 10 Hz was chosen for all experiments, and for each laser setting, the experiment was repeated on 15 different freshly prepared stones. The latter set of experiments was compared with the results of previous propulsion measurements performed with a pendulum setup.

RESULTS

For a fixed pulse energy (1 J/pulse), the mean upward propulsion velocity increased (from 120.0 to 154.9 mm · s^-1 ) with decreasing pulse duration. For fixed pulse duration (0.3 ms), the mean upward propulsion velocity increased (from 91.9 to 123.3 mm · s^-1 ) with increasing pulse energy (0.8 J/pulse and 1.2 J/pulse). The latter result corresponds roughly to the one obtained with the pendulum setup (increase from 61 to 105 mm · s^-1 ). While the mean propulsion velocities for the two different pulse energies were found to differ significantly (P < 0.001) for the two experimental and analysis methods, the standard deviations of the measured mean propulsion velocities were considerably smaller in case of the vertical column method with video tracking (12% and 15% for n = 15 freshly prepared stones) than in case of the pendulum method (26% and 41% for n = 50 freshly prepared stones), in spite of the considerably smaller number of experiment repetitions ("sample size") in the first case.

CONCLUSION

The proposed vertical column method with video tracking appears advantageous compared to the pendulum method in terms of the statistical significance of the obtained results. This may partly be understood by the fact that the entire motion of the stones contributes to the data analysis, rather than just their maximum distance from the initial position. The key difference is, however, that the pendulum method involves only one single laser pulse in each experiment run, which renders this method rather tedious to perform. Furthermore, the video tracking method appears much better suited to model a clinical lithotripsy intervention that utilizes longer series of laser pulses at higher repetition rates. The proposed video tracking method can conveniently and quickly deliver results for a large number of laser pulses that can easily be averaged. An optimization of laser settings to achieve minimal propulsive stone movement should thus be more easily feasible with the video tracking method in connection with the vertical column setup. Lasers Surg. Med. 50:333-339, 2018. © 2017 Wiley Periodicals, Inc.

A review study to evaluate holmium:YAG laser lithotripsy with flexible ureteroscopy in patients on ongoing oral anticoagulant therapy

The objective of this study was to evaluate the safety and efficacy of flexible ureteroscopy (FURS) and holmium:YAG laser lithotripsy for the treatment of upper urinary tract stones in patients on active oral anticoagulants. The records of 1081 patients who underwent flexible ureteroscopic holmium:YAG (Ho:YAG) laser lithotripsy for upper ureteral and renal calculi from 1999 to 2015 were retrospectively reviewed. A total of 84 patients on continuous oral anticoagulation or antiplatelet therapy (warfarin, aspirin, or clopidogrel) were identified. Of these patients, 40 were on warfarin, 25 on aspirin, 11 on clopidogrel, and 8 on both aspirin and clopidogrel. The drugs were not discontinued. The baseline characteristics, indications for anticoagulation therapy, perioperative data, stone-free rate, and complications were documented. Evaluation of outcomes was assessed at 1-, 3-, and 6-month follow-up postoperatively. Mean stone size was 19.7 ± 9.4 (range 8 to 31 mm). Twenty patients had upper ureteral and 64 patients had intrarenal calculi. Two patients had bilateral renal calculi. Mean operation time was 78.2 ± 23.8 min (range 17 to 144 min). Two procedures (2.3%) in warfarin group were terminated due to persistent bleeding causing visual impairment. No transfusions were required. The mean serum hemoglobin levels did not change significantly (12.9 ± 3.7 to 12.2 ± 3.3 g/dL). No thromboembolic or cardiac adverse events were observed perioperatively. The double-j (DJ) ureteral catheterization time was 29.6 ± 9.3 days (range 14 to 68 days) and the hospital stay was 1.6 ± 0.6 days (range 1 to 4). The stone-free rate was 95.2% (80 patients) at 6 months. Flexible ureteroscopic Ho:YAG laser lithotripsy in patients requiring long-term anticoagulation therapy seems to be a safe and effective procedure and should be considered as a first-line treatment option in such patients for the surgical management of upper urinary tract stones.

Comparative Evaluation of Effects of Laser Modalities on Shear Bond Strengths of Veneering Porcelains to Laser Sintered Substructures: An In Vitro Study

OBJECTIVE

Laser modalities and direct metal laser sintering (DMLS) have a potential to enhance micromechanical bonding between dental super- and infrastructures. However, the effect of different manufacturing methods on the metal-ceramic bond strength needs further evaluation. We investigated the effect of surface treatment with Er:YAG, Nd:YAG, and Ho:YAG lasers on the shear bond strength (SBS) of high-fusion dental porcelains (Vita and G-Ceram) to infrastructures prepared with DMLS in vitro settings.

MATERIALS AND METHODS

Study specimens (n = 128) were randomly divided into study subsets (n = 8), considering treatment types applied on the surface of infrastructures, including sandblasting and selected laser modalities; infrastructure types as direct laser sintered (DLS) and Ni-Cr based; and superstructure porcelains as Vita and G-Ceram. The SBS test was performed to assess the effectiveness of surface modifications that were also examined with a stereo microscope.

RESULTS

Considering laser procedure types, the highest SBS values were obtained by Er:YAG laser, followed by, with a decreasing efficiency, Ho:YAG laser and sandblasting procedures, and Nd:YAG laser procedure (p < 0.05). Nd:YAG laser decreases the bonding of Vita and G-Ceram in all the infrastructures compared with sandblasting. Considering porcelains, the highest SBS values were obtained by Vita (p < 0.05). Considering infrastructures, the highest SBS values were obtained by DMLS procedure (p < 0.05). The laser procedures caused surface irregularities as revealed by the stereo microscopic examination.

CONCLUSIONS

In current experimental settings, Er:YAG laser applied to DLS infrastructure veneered with Vita porcelain increases bonding strength more distinctly, and Nd:YAG laser applied to Ni-Cr-based infrastructure veneered with G-Ceram porcelain alters bonding strength unfavorably.

Fluoroscopy free flexible ureteroscopy with holmium: Yttrium-aluminium-garnet laser lithotripsy for removal of renal calculi

Objective

To evaluate the feasibility of access sheath insertion and ureteric stent placement without image guidance in flexible ureteroscopic lithotripsy with holmium:yttrium-aluminium-garnet laser for renal stones.

Patients and methods

Between March 2014 and October 2015, 80 patients with renal stones treated with flexible ureteroscopic laser lithotripsy were evaluated. Indications for surgery were renal obstruction, failed shockwave lithotripsy (SWL), stones in polycystic kidneys, and mal-rotated kidneys. A 6.5-F Cobra flexible ureteroscope was used in all cases with an access sheath of 12 F, 35/45 cm in length. Fluoroscopy was not intended for use in all cases and postoperative JJ stenting was optional. The perioperative complications were listed and the collected data were analysed.

Results

The study included 80 patients (66 male, 14 female), with a mean (SD; range) age of 48.2 (8; 28–54) years and a stone burden of 13 (3.5; range 6–23) mm. In all, 26 patients had a stone burden of >15 mm and 48 patients had lower calyceal stones. The mean (SD; range) operative time was 71.5 (20; 25–130) min. Overall, 76 (95%) access sheath insertions were performed successfully without the use of fluoroscopy. JJ stenting was used in 22 patients (27.5%). The mean (SD; range) hospital stay was 10 (8.5; 10–36) h. After one session, a stone-free rate (SFR) of 87.5% was achieved (93.3% for stones of <15 mm). A single session was successful in 87.9% of cases with lower calyceal stones, with a SFR of 91.7% for post-SWL failure cases. The perioperative complication rate was 15%.

Conclusion

Access sheath insertion without fluoroscopic guidance is feasible. This technique reduces radiation exposure in patients requiring flexible ureteroscopy.

Systematic evaluation of a holmium:yttrium-aluminum-garnet laser lithotripsy device with variable pulse peak power and pulse duration

OBJECTIVE

The Holmium:yttrium-aluminum-garnet (Ho:YAG) laser is the standard lithotrite for ureteroscopy. This paper is to evaluate a Ho:YAG laser with a novel effect function in vitro, which allows a real-time variation of pulse duration and pulse peak power.

METHODS

Two types of phantom calculi with four degrees of hardness were made for fragmentation and retropulsion experiments. Fragmentation was analysed at 5 (0.5 J/10 Hz), 10 (1 J/10 Hz), and 20 (2 J/10 Hz) W in non-floating phantom calculi, retropulsion in an ureteral model at 10 (1 J/10 Hz) and 20 (2 J/10 Hz) W using floating phantom calculi. The effect function was set to 25%, 50%, 75%, and 100% of the maximum possible effect function at each power setting. Primary outcomes: fragmentation (mm3), the distance of retropulsion (cm); ≥5 measurements for each trial.

RESULTS

An increase of the effect feature (25% vs. 100%), i.e., an increase of pulse peak power and decrease of pulse duration, improved Ho:YAG laser fragmentation. This effect was remarkable in soft stone composition, while there was a trend for improved fragmentation with an increase of the effect feature in hard stone composition. Retropulsion increased with increasing effect function, independently of stone composition. The major limitations of the study are the use of artificial stones and the in vitro setup.

CONCLUSION

Changes in pulse duration and pulse peak power may lead to improved stone fragmentation, most prominently in soft stones, but also lead to increased retropulsion. This new effect function may enhance Ho:YAG laser fragmentation when maximum power output is limited or retropulsion is excluded.