Comparison of holmium:yttrium-aluminium-garnet (YAG), thulium fiber laser, and pulsed thulium:YAG lasers on soft tissue: an ex vivo study.

OBJECTIVES: To assess laser-tissue interactions through ablation, coagulation, and carbonisation characteristics in a non-perfused porcine kidney model between three pulsed lasers: holmium (Ho): yttrium-aluminium-garnet (YAG), thulium fiber laser (TFL), and pulsed thulium (p-Tm):YAG. MATERIALS AND METHODS: A 150-W Ho:YAG, a 60-W TFL, and a 100-W p-Tm:YAG lasers were compared. The laser settings that can be set identically between the three lasers and be clinically relevant for prostate laser enucleation were identified and used on fresh, unfrozen porcine kidneys. Laser incisions were performed using stripped laser fibers of 365 and 550 µm, set at distances of 0 and 1 mm from the tissue surface at a constant speed of 2 mm/s. Histological analysis evaluated shape, depth, width of the incision, axial coagulation depth, and presence of carbonisation. RESULTS: Incision depths, widths, and coagulation zones were greater with Ho:YAG and p-Tm:YAG lasers than TFL. Although no carbonisation was found with the Ho:YAG and p-Tm:YAG lasers, it was common with TFL, especially at high frequencies. The shapes of the incisions and coagulation zones were more regular and homogeneous with the p-Tm:YAG laser and TFL than with Ho:YAG laser. Regardless of the laser used, short pulse durations resulted in deeper incisions than long pulse durations. Concerning the distance, we found that to be effective, TFL had to be used in contact with the tissue. Finally, 365-µm fibers resulted in deeper incisions, while 550-µm fibers led to wider incisions and larger coagulation zones. CONCLUSION: Histological analysis revealed greater tissue penetration with the p-Tm:YAG laser compared to the TFL, while remaining less than with Ho:YAG. Its coagulation properties seem interesting insofar as it provides homogeneous coagulation without carbonisation, while incisions remained uniform without tissue laceration. Thus, the p-Tm:YAG laser appears to be an effective alternative to Ho:YAG and TFL lasers in prostate surgery.

Comparison of Thulium Fiber Laser versus Holmium laser in ureteroscopic lithotripsy: a Meta-analysis and systematic review.

OBJECTIVES: To compare the efficacy and safety of thulium fiber laser (TFL) to holmium: YAG (Ho: YAG) laser in ureteroscopic lithotripsy for urolithiasis. METHODS: PubMed, Web of Science, Embase, CENTRAL, SinoMed, CNKI database, VIP and Wanfang Database were systematically searched for all relevant clinical trials until September 2023. References were explored to identify the relevant articles. Meta-analysis was carried out for the retrieved studies using RevMan5.4.1 software, and the risk ratio, mean difference and 95% confidence interval were expressed. Statistical significance was set at p < 0.05. The main outcomes of this meta-analysis were stone-free rate (SFR), perioperative outcomes and intraoperative or postoperative complications. RESULTS: Thirteen studies, including 1394 patients, were included. According to the results of pooled analysis, TFL was associated with significantly higher stone-free rate (SFR) [0.52, 95% CI (0.32, 0.85), P = 0.009], shorter operation time [-5.47, 95% CI (-8.86, -2.08), P = 0.002], and less stone migration [0.17, 95% CI (0.06, 0.50), P = 0.001]. However, there was no significant difference in terms of the laser time, duration of hospital stay, drop of hemoglobin level, total energy, postoperative ureteral stenting, the incidence of intraoperative complications or postoperative complications between TFL and Ho: YAGs. CONCLUSION: The findings of this study demonstrated several advantages of TFL in terms of higher SFR, shorter operative time and less stone migration. TRIAL REGISTRATION: The protocol of this systematic review was listed in PROSPERO ( www.crd.york.ac.uk/PROSPERO ) (Protocol number: CRD42022362550).

Analysis of lithotripsy efficiency and stone retropulsion displacement according to pulse characteristics of Ho: YAG laser with Moses effect.

BACKGROUND AND OBJECTIVES: Compared to the conventional Ho: YAG laser, a Ho: YAG laser device has been reported that has a Moses effect to reduce stone retropulsion and increase lithotripsy efficiency. The principle of this equipment is to convert a single laser pulse into two pulses. Most studies on such lasers are limited to lithotripsy efficiency and the prevention of stone retropulsion; studies according to each pulse condition have not been performed. Therefore, the purpose of this study was to quantify the bubble shape, lithotripsy efficiency, and stone retropulsion displacement in a ureteral phantom according to the modulation of the first pulse characteristics of the Moses effect laser under conditions that maintained the total energy and repetition rate. MATERIAL AND METHODS: In this study, a Ho: YAG laser system (Holinwon Pro, Wontech Inc., Korea) with an emission wavelength of 2.10 µm and a Moses effect was used. To verify the Moses effect based on the changes in the pulse, a water tank was fabricated, and the ureteral phantom was manufactured in a structure that could be easily installed in the water tank. Additionally, a spherical artificial stone in the ureteral phantom was prepared by mixing calcined gypsum (Cacinated Gypsum) and water at a ratio of 3:1. In the ureteral phantom, a high-speed camera (FASTCAM NOVA S12, Photron Inc.) and visible light were used to record pulse-dependent image analysis of bubbles and stone retropulsion. RESULT: After mounting the artificial stone in the ureteral phantom, the pulse duration and energy of the first pulse of the Moses effect laser were varied; 30 laser shots for 3 s at a repetition rate of 10 Hz were applied to quantify the lithotripsy efficiency and stone retropulsion displacement, and the experimental values were compared. The fragmentation efficiency was confirmed by measuring the mass before and after the laser pulse application, the original position of the stone retropulsion displacement, and the distance moved. The minimum value of stone retropulsion displacement appeared when the pulse duration of the first pulse was 300 µs, the pulse energy was 100 mJ, and the value was approximately 0.28 mm. The highest fragmentation efficiency was observed under the same conditions, and the mass loss of the artificial stone at that time was approximately 3.7 mg. CONCLUSION: Quantitative indices, such as lithotripsy efficiency and stone retropulsion displacement, were confirmed using ultrahigh-speed cameras to determine the effect of the first pulse energy and duration of the Ho: YAG laser with the Moses effect on stone removal. It was confirmed that the longer the duration of the primary pulse and the lower the energy, the higher the fragmentation efficiency. In this study, the possibility of manufacturing a laser with an optimal stone-removal effect was confirmed according to the first-pulse condition of the laser with the Moses effect.

Safety of flexible ureteroscopic lithotripsy with 365 µm fibers of Ho: YAG laser: a short-term follow-up.

Our previous study first reported the efficacy of FURL using 365 µm fibers with holmium: yttrium aluminum garnet (Ho: YAG) laser lithotripsy. This study evaluates the 16-week safety of this procedure. A prospective cohort study was conducted, and the clinical characteristics of patients who underwent FURL using 365 µm fibers with Ho: YAG laser were retrospectively collected. Descriptive statistics were reported, and logistic regression analysis was conducted to identify risk factors influencing the stone-free rate (SFR). Infection-related laboratory parameters, including white blood cell count (WBC), procalcitonin (PCT), and C-reactive protein (CRP), were collected. Regression analysis was conducted to identify risk factors for the development of urosepsis post-surgery. Additionally, a 16-week follow-up was conducted in outpatient clinics, and kidney function was assessed. A total of 274 patients participated in this study. The 4-week stone-free rate (SFR) following FURL with 365 µm fibers of Ho: YAG laser was significantly associated with stone size and composition. No severe complications were observed following FURL procedures. There were no significant differences in white blood cell count (WBC), C-reactive protein (CRP), and procalcitonin (PCT) in peripheral blood before and after FURL procedures. Urosepsis was diagnosed in 1.82% of patients. Preoperative white blood cell count (WBC) in urine and preoperative urine culture results were identified as significant risk factors. Kidney function remained stable at 4 and 16 weeks following FURL. This prospective cohort study demonstrated the high safety of FURL with 365 µm fibers of Ho: YAG laser, as infection-related parameters during the perioperative period showed no significant differences, and kidney function remained stable throughout the 16-week follow-up.

Thulium fiber laser vs Ho:YAG in RIRS: a prospective randomized clinical trial assessing the efficacy of lasers and different fiber diameters (150 µm and 200 µm).

INTRODUCTION: The aims of the study: (1) to compare the Super Pulse Thulium Fiber Laser (SP TFL) and the holmium: yttrium-aluminium-garnet (Ho:YAG) lasers in retrograde intrarenal surgery (RIRS); (2) to compare the efficacy of SP TFL laser fibers of different diameters (150 µm and 200 µm). METHODS: A prospective randomized single-blinded trial was conducted. Patients with stones from 10 to 20 mm were randomly assigned RIRS in three groups: (1) SP TFL (NTO IRE-Polus, Russia) with fiber diameter of 150 µm; (2) SP TFL with 200-µm fiber; and (3) Ho:YAG (Lumenis, USA) with 200-µm fiber. RESULTS: Ninety-six patients with kidney stones were randomized to undergo RIRS with SP TFL using a 150-µm fiber (34 patients) and a 200-µm fiber (32 patients) and RIRS with Ho:YAG (30 patients). The median laser on time (LOT) in the 200-µm SP TFL group was 9.2 (6.2-14.6) min, in 150-µm SP TFL-11.4 (7.7-14.9) min (p = 0.390), in Ho:YAG-14.1 (10.8-18.1) min (p = 0.021). The total energy consumed in 200-µm SP TFL was 8.4 (5.8-15.2) kJ; 150-µm SP TFL - 10.8 (7.3-13.5) kJ (p = 0.626) and in Ho:YAG-15.2 (11.1-25.3) kJ (p = 0.005). CONCLUSIONS: Irrespective of the density, RIRS with SP TFL laser has proven to be both a safe and effective procedure. Whilst the introduction of smaller fibers may have the potential to reduce the duration of surgery, SP TFL results in a reduction in the LOT and total energy for stone ablation in RIRS compared with Ho:YAG.

Dusting efficacy between the regular setting of holmium laser (Ho:YAG) versus Vapor Tunnel pulse modality for non-complex kidney stones.

The new pulse modality Vapor-Tunnel™ (VT) consists of a very long pulse that uses the minimum peak power, causing the energy to pass through a previously created vapor channel or tunnel. The first part of the pulse creates a vapor channel, whereas the remaining energy is discharged immediately after, passing straight through the previously created tunnel. The aim of this study is to compare the dusting efficacy between Ho:YAG laser with long pulse and Ho:YAG laser with VT for non-complex kidney stones. A retrospective comparative study of 236 patients who underwent retrograde intrarenal surgery using Ho:YAG laser (long pulse vs. VT) was performed. Stone size, stone density, laser settings, laser emission time, and total operative time were recorded. We also assessed the lithotripsy efficacy (J/mm3). The stone-free rate was defined as the absence of stone fragments in a non-contrast abdominal computed tomography 4 weeks after the procedure. A total of 118 patients were included in each group. There was no significant difference in age, gender, and body mass index. Median stone volume (737 mm3 vs. 636 mm3) and stone density (788 HU vs. 656 HU) were higher in the VT group. Total energy used (14.5 J vs. 18.2 J), the laser emission time (20 min vs. 26 min), and the total operative time (79.5 min vs. 95 min) were significantly lower in the VT group. The stone-free rate was comparable between both groups (74.5% for VT and 66.1% for the long-pulse group, p = 0.15). When we evaluated the efficacy of laser lithotripsy, a significantly lower difference was obtained in the VT group (median 12.5 J/mm3 vs. median 23.1 J/mm3). The VT pulse modality was associated with decreased laser time and operative time. Additionally, it increased lithotripsy efficacy compared to Ho:YAG long pulse laser, but with a comparable free-stone rate.

The predictive factors that total laser energy consumed during retrograde intrarenal surgery (RIRS): stone area and density.

Holmium: YAG (Ho: YAG) laser lithotripsy with flexible ureterorenoscopy can be used with high stone-free and low complication rates for renal stones. This study aimed to determine the factors affecting the total laser energy in cases with provided stone-free status after a single session of retrograde intrarenal surgery (RIRS). Data of 222 patients who underwent RIRS between October 2017 and March 2020 were evaluated retrospectively. After exclusion criteria, the study was carried out with 184 stone-free cases. All cases were performed without using a ureteral access sheath (UAS), and dusting was preferred as the lithotripsy method. The effects of age, gender, body mass index (BMI), previous RIRS history, previous shock wave lithotripsy (SWL) history, stone localization, number of stones, stone surface area, and stone density on total laser energy were analyzed. There was no significant correlation between total laser energy with gender, BMI, previous RIRS history, previous SWL history, stone localization, and the number of stones (p:0.347, p:0.482, p:0.119, p:0.167, p:0.907, p:0.933 respectively). There was a significant correlation between age and total laser energy (p = 0.032), but it was not observed when the effect of the stone surface area was removed (p = 0.354). There were significant correlations between total laser energy and stone surface area, stone density, and total laser time (p<0.001, p<0.001, and p <0.001, respectively). Stone area and stone density affect the total energy consumed during laser lithotripsy. Urologists should consider the stone area, stone density, and the power of the laser device to determine which surgical technic to prefer.

Comparison of three techniques in bladder stone surgery: Which technique is more effective and safe?

Background: In our study, we aimed to compare the success and complication rates of percutaneous cystolithotripsy (PCCL), transurethral cystolithotripsy (TUCL), and Ho: YAG laser lithotripsy in the surgery of bladder stones that occurred due to various reasons. Patients and Methods: Patients diagnosed with single or multiple bladder stones with long axis larger than 2 cm, resulting for various reasons, were included in ou study. Sizes of the stones, cystolithotripsy and discharge times, catheter removal times, complications observed, and the visual pain scale (VPS) were retrospectively evaluated separately from the surgical techniques implemented for accompanying patients and their data. Results: TUCL (group 1) was implemented in 40, PCCL (group 2) was implemented in 44, and transurethral Ho: YAG laser lithotripsy (group 3) was implemented in 30 of the 121 patients included in the study. The bladder stone long axe group 1 average was 3,7 cm (2,2-5,3), group 2 average was 3,74 cm (2,1-5,1), and group 3 average was 3,7 cm (2,3-4,7). Urethral stricture evolved in two patients who underwent TUCL. A statistically significant difference was observed on behalf of PCCL in terms of operation time. There was significance in the Ho: YAG laser cystolithotripsy group in comparison with VPS scores. No significant differences were found in terms of age, stone size, urethral catheter removal times, and discharge times. The average follow-up time was 6 months. Conclusion: Although all three methods were quite successful in bladder stone surgery, average cystolithotripsy times were significantly low in the PCCL technique. Thinking that the most common cause of bladder stone is BPH, it is stated that the suprapubic inserted tube ease the bladder drainage during transurethral resection of the prostate (TUR-P). In this way, the duration of the most common accompanying surgeries is shortened and performed more safely.

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.

The use of ureteral access sheath during mini-percutaneous nephrolithotomy with high-power holmium YAG laser.

PURPOSE: To present our preliminary results and describe a technical modification of mini-PCNL (12Fr) with the insertion of a ureteral access sheath (UAS) to facilitate the procedure. METHODS: A prospective study for the time period of January 2020 to January 2021 was conducted including patients with renal stones sized ≤ 25 mm in whom prone mini-PCNL (tract size 12Fr) together with the retrograde insertion of UAS was performed. All patients had been prestented at least 1 week prior to the planned surgery. A single-step tract dilation to 12Fr diameter was performed through a nonpapillary medial puncture. The lithotripsy was achieved using high-power holmium yttrium aluminum garnet laser (Ho:YAG) with the 60 W power setting (40 Hz and 1.5 J). The follow-up investigations were planned at 1-month after the surgery. RESULTS: In total, 32 patients with the median age and stone size of 56.5 (IQR = 53-62) years and 20.8 (IQR = 19.3-22.7) mm were included. The median operative and cumulative fluoroscopy time were 34.0 (IQR = 29.9-37.5) and 1.9 (1.8-2.1) min, respectively. The stone-free rate (SFR) at 1-month follow-up was 93.8% (30/32). Only one patient developed a fever and required prolonged antibiotic administration. None of the patients experienced clinically significant bleeding. CONCLUSION: Our preliminary results showed that the use of UASs during mini-PCNL procedures is feasible and provides directed evacuation of the stone fragments reaching 93.8% SFR at a 1-month follow-up. Future well-designed studies are necessary to prove our findings.

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 Pav = 40 W or Pav = 70 W settings. The TFL was tested using E = 1.5 J and Pav = 30 W or Pav = 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.

[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.

How do we assess the efficacy of Ho:YAG low-power laser lithotripsy for the treatment of upper tract urinary stones? Introducing the Joules/mm3 and laser activity concepts.

OBJECTIVES: To estimate the total energy needed to ablate 1mm3 of stone volume (Joules/mm3) during flexible ureteroscopic lithotripsy using a low-power Ho:YAG laser device, as a proxy of lithotripsy efficacy. PATIENTS AND METHODS: We selected 30 patients submitted to flexible ureteroscopy for renal stones whose volume was bigger than 500 mm3. A 35 W Ho:YAG laser (Dornier Medilas H Solvo 35, Germany) was used for every procedure with a 272 µm laser fiber. We recorded laser parameters, the total energy delivered by the laser fiber, the time from the first laser pulse until the last one (lithotripsy time), and the active laser time as provided by the machine. We then estimated J/mm3 values and determinants, along with ablation speed (mm3/s), and laser activity (ratio between laser active time and lithotripsy time). RESULTS: Median (IQR) stone volume and stone density were respectively 1599 (630-3502) mm3 and 1040 (753-1275) Hounsfield units (HU). In terms of laser parameters, median (IQR) energy and frequency were 0.6 (0.4-0.8) J and 15 (15-18) Hz. Median (IQR) total delivered energy and lithotripsy time were 37,050 (13,375-57,680) J and 68 (36-88) min, respectively. Median (IQR) J/mm3 and ablation speed were, respectively, 19 (14-24) J/mm3 and 0.7 (0.4-0.9) mm3/s. The laser was active during 84% (70-95%) of the total lithotripsy time. HU density > 1000 was associated with reduced efficacy. CONCLUSIONS: It is possible to perform laser lithotripsy using a low-power laser device with a virtually continuous laser activity. The estimation of the pre-operative parameters as well as the J/mm3 values are fundamental for a proper pre-operatory planning.

Retropulsion force in laser lithotripsy-an in vitro study comparing a Holmium device to a novel pulsed solid-state Thulium laser.

PURPOSE: To investigate retropulsion forces generated by two laser lithotripsy devices, a standard Ho:YAG and a new pulsed solid-state Thulium laser device. MATERIALS AND METHODS: Two different Dornier laser devices were assessed: a Medilas H Solvo 35 and a pulsed solid-state Thulium laser evaluation model (Dornier MedTech Laser GmbH, Wessling, Germany). We used a 37 °C water bath; temperature was monitored with a thermocouple/data-logger. Representative sets of settings were examined for both devices, including short and long pulse lengths where applicable. For each setting, ten force values were recorded by a low-force precision piezo sensor whereby the laser fibre was either brought into contact with the sensor or placed at a 3 mm distance. RESULTS: The mean retropulsion forces resulting from the new Tm:YAG device were significantly lower than those of the Ho:YAG device under all pulse energy and frequency settings, ranging between 0.92 and 19.60 N for Thulium and 8.09-39.67 N for Holmium. The contact setups yielded lower forces than the distance setups. The forces increased with increasing pulse energy settings while shorter pulse lengths led to 12-44% higher retropulsive force in the 2.0 J/5 Hz comparisons. CONCLUSION: The Tm:YAG device not only significantly generated lower retropulsion forces in all comparisons to Holmium at corresponding settings but also offers adjustment options to achieve lower energy pulses and longer pulse durations to produce even lower retropulsion. These advantages are a promising add-on to laser lithotripsy procedures and may be highly relevant for improving laser lithotripsy performance.

Feasibility and long-term safety of Ho:YAG laser lithotripsy in broncholithiasis patients.

BACKGROUND: Treatment of broncholithiasis is complex, especially in the case of a large or transbronchial broncholith. Holmium-yttrium aluminum garnet (Ho:YAG) laser lithotripsy may be a useful treatment in broncholithiasis; however, as it is not yet common practice, the optimal parameters are unknown. METHODS: We performed a single-center retrospective analysis of the clinical data of 13 broncholithiasis patients who underwent Ho:YAG laser lithotripsy from May 2012 to October 2018. RESULTS: For the 13 patients (2 males and 11 females), Ho:YAG laser lithotripsy was performed 17 times, in total. All procedures were performed under general anesthesia with rigid bronchoscopy. We initially set the Ho:YAG laser to a pulse frequency of 5 Hz and a pulse energy of 0.8 J, gradually increasing these as required. The pulse frequency range we employed was 5-15 Hz, and the pulse energy range was 0.8-1.6 J. All broncholiths were successfully extracted after lithotripsy, and all symptoms improved. Hemoptysis, bronchial esophageal fistula, and pneumonia were the most common complications; however, there were no long-term complications. CONCLUSIONS: Ho:YAG laser lithotripsy is an effective and safe treatment for broncholithiasis, over a long-term follow up.

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.

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.

Thermal effects of Ho:YAG laser lithotripsy during retrograde intrarenal surgery and percutaneous nephrolithotomy in an ex vivo porcine kidney model.

PURPOSE: To evaluate the thermal effect of high-power holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripsy in flexible/semirigid ureteroscopy (fURS/sURS) and percutaneous nephrolithotomy (PNL) in a standardized ex vivo porcine kidney model with real-time temperature assessment. METHODS: The experimental setup consisted of three models designed to evaluate the thermal effects of Ho:YAG laser lithotripsy in fURS, sURS and PNL, respectively. In all setups, a postmortem porcine kidney was placed in a 37 °C water bath. Three thermocouples were inserted into the renal parenchyma while a flexible thermocouple was placed 3-4 mm proximal to the laser fiber to measure temperature variations in the collecting system. The thermal impact was evaluated in relation to laser power between 5 and 100 W and various irrigation rates (37 °C, 0-100 ml/min). RESULTS: In all three experimental setups, sufficient irrigation was required to prevent potentially damaging temperatures into the renal pelvis and parenchyma. Even 5 W in fURS can lead to a potentially harming temperature rise if insufficient irrigation is applied. Particularly, high-power settings ≥ 30 W carry an elevated risk for critical temperature rises. The results allow the definition of a specific irrigation threshold for any power setting to prevent critical temperatures in the present study design. CONCLUSIONS: Ho:YAG laser lithotripsy bears the risk of thermal damages to the urinary tract even at low-power settings if inadequate irrigation is applied. Sufficient irrigation is mandatory to perform safe Ho:YAG laser lithotripsy. Based on the results, we developed a formula calculating the approximate ΔT for irrigation rates ≥ 30 ml/min: ΔT = 15 K × (power [W]/irrigation [ml/min]).

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 (pav up to 100 W, Lumenis, Yokneam, Israel) and a superpulse Tm-fiber laser (SP TFL, pav 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 pav 8 W). Power meter FieldMaxII-TO (Coherent, Santa Clara, CA, USA) was used to verify output laser power (pav). 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.