Therapeutic applications of lasers in urology: an update

Histopathological assessment of depth of coagulation necrosis with Holmium, Moses, and Thulium fiber lasers in human prostate tissue

PURPOSE

To evaluate coagulation necrosis depth (CND) of Holmium (HL), Moses (ML), and Thulium fiber laser (TFL) in ex vivo human prostate tissue at various energy settings.

METHODS

After endoscopic HL enucleation, small prostate tissue fragments were removed from the bladder with graspers and used for study. Immediately after surgery, a single incision was made on the surface of the tissue kept under normal saline at room temperature using a hand-held 550-µm laser fiber. Variable energy settings were tested for all three lasers. Two pathologists measured the CND with light microscopy using ocular micrometer. Impact of various laser settings on CND was analyzed. The differences in CND of all three lasers at similar laser power were compared.

RESULTS

Mean CND was 0.56 ± 0.53 mm for long-pulse HL, 0.54 ± 0.53 mm for ML, 0.67 ± 0.67 mm for low-pulse TFL, and 0.81 ± 0.78 mm for high-pulse TFL. There was no significant difference between mean CND of HL and ML at various laser settings ranging from 10 to 120 W and CND with long- and short-pulse settings of TFL at settings from 10 to 60 W. There was a trend of increasing CND in HL and ML with increasing laser power; however, it was not statistically significant. TFL had similar tissue effects as HL and ML.

CONCLUSION

There is no significant difference in CND of HL, ML, and TFL in ex vivo human prostate tissue. Other factors besides laser type and settings need to be studied to explain clinical differences among various lasers used for prostate enucleation.

Retrospective analysis of 1470-/980-nm dual-wavelength laser en bloc resection versus transurethral resection of bladder tumor for primary non-muscle-invasive bladder cancer

To compare the safety and efficacy of en bloc resection of non-muscle-invasive bladder cancer (NMIBC) using a 1470-/980-nm dual-wavelength laser (DwLRBT) compared to the gold standard, transurethral resection (TURBT). The study group included 251 patients with a confirmed diagnosis of NMIBC, 97 in the DwLRBT group and 154 in the TURBT group. Clinical characteristics, complications, and recurrence-free survival were compared between the two groups. There were no differences between the two groups with regard to age, sex, mean tumor size, mean tumor number, tumor location, risk, fever, and reoperation. Compared to TURBT, DwLRBT was associated with a shorter hospitalization time (mean±standard deviation: 5.81±1.48 days vs. 4.96±1.32, respectively, p=0.001), shorter catheterization time (4.98±1.47 vs. 4.20±1.48 days, respectively; p=0.035), and smaller volume of intraoperative bleeding (8.43±6.21 ml vs. 6.15±5.08, respectively; p=0.003). Recurrence-free survival (RFS) was better for DwLRBT than TURBT in the overall cohort (hazard ratio [HR], 0.4323; 95% confidence interval [CI], 0.2852-0.6554; p=0.0004) and for the following subgroups and tumor types: intermediate-risk (HR, 0.2654; 95%CI, 0.1020-0.6904; p=0.0245) and high-risk (HR, 0.4461; 95% CI, 0.2778-0.7162; p=0.0027) groups; and for pedunculate bladder tumors (HR, 0.4158; 95%CI, 0.2401-0.7202; p=0.0063), single bladder tumors (HR, 0.4136; 95%CI, 0.2376-0.7293; p=0.0072), and multiple bladder tumors (HR, 0.2727; 95%CI, 0.1408-0.5282; p=0.0014). DwLRBT is associated with better operative and postoperative outcomes, including, importantly, a longer RFS, compared to TURBT.

Randomized prospective trial of the severity of irritative symptoms after HoLEP vs ThuFLEP

PURPOSE

To compare the short-term postoperative functional outcomes and severity of irritative symptoms following holmium and thulium fiber laser enucleation (HoLEP and ThuFLEP).

METHODS

This prospective randomized single-blinded study was performed in accordance with CONSORT. The inclusion criteria were IPSS > 20 or Qmax < 10 ml/s. Patients were randomized between HoLEP and ThuFLEP. Demographics, objective data (PSA, prostate volume, etc.), data on urinary and sexual function (IPSS, IIEF, QoL, QUID, Qmax, ICIQ-MLUTS) were collected. Detailed perioperative information and postoperative data on functional outcomes at 1, 2, 3, 4, 6, 8, 10, 12 weeks and 6 months were collected.

RESULTS

Data on 163 participants were included (77-HoLEP, 86-ThuFLEP). No differences were found in surgery duration; number of postoperative complications (Clavien-Dindo I-III), catheterization time and hospital stay. Functional outcomes up to 6 months didn't differ between the groups (IPPS, IIEF, QoL, QUID, ICIQ-MLUTS, Qmax, p > 0.05). Total ICIQ-MLUTS, bother and voiding scores at 1 and 3 months significantly increased compared with the baseline in both groups (p < 0.05). No difference between the groups were observed. In HoLEP the SUI series rate was 1.3% and 1.3% after 3 and 6 months following the procedure; in ThuFLEP: it was 3.5% and 2.3% respectively (p = 0.35 and p = 0.54).

CONCLUSION

The preliminary results of the study showed no apparent differences in functional outcomes (IPSS, Qmax), rate of SUI or irritative symptoms. Both ThuFLEP and HoLEP are efficient ways of treating benign prostatic obstruction. Both surgeries are comparable in terms of duration and postoperative complication rates.

Preliminary experience in endoscopic section of posterior urethral valves using the Holmium: YAG laser

INTRODUCTION

Refinements in endoscopic instrumentation, the widespread popularization of endourology and the minimal invasiveness of endoscopic approaches have led to evolving interest in expanding applications for their use and now include incision of posterior urethral valves (PUV). We aimed to report our paediatric experience of PUV incision with Holmium:YAG laser updating of the endoscopic technique, how we set parameters for the laser energy and provide some tips and tricks to increase the likelihood of completing treatment.

METHODS

A monocentric, prospective, continuous series of boys with PUV were treated endoscopically using a Holmium: YAG laser (1.2 J, 20 Hz, 800 μs). Feasibility was evaluated using operative time in minutes, spontaneous normal micturition after bladder catheter removal, and the duration of bladder catheterization in days in the absence of satisfactory micturition. Peri-operative complications were recorded. A VCUG was performed at 6 weeks postoperatively to exclude residual valves.

RESULTS

Since September 2018, 18 children with PUV were included. The median age at the time of endoscopic laser incision was 12 days (1 day-5 years). The median operative duration was 28 min (17-35). The urinary catheter was systematically removed on the first postoperative day. There were no intraoperative or anaesthesia-related complications. More specifically, no urethral injuries and no bleeding were recorded. No incomplete VUP incision was found on follow-up VCUG, and no endoscopic revision was necessary thus far, with a median follow-up of 44 months (6 months-60 months).

DISCUSSION

The use of the Holmium: YAG laser introduces new perspectives in the treatment of PUV. Its mechanism of action is considered a photothermic effect with a vapourization effect. The laser energy released by the Holmium: YAG source has a short tissue penetration distance and is strongly absorbed in an aqueous environment and therefore limits thermal tissue damage and favours early tissue re-epithelialization, reducing the risk of urethral stricture and decreasing postoperative oedema. The use of the laser in "incision" mode is the setting that most solicits the capacities of the laser (high energy, high frequency, and long pulse). The use of laser energy has the advantage of allowing tissue vapourization while ensuring maximal haemostasis and the possibility of introducing the laser fibre through the working channels of small, 6-Fr paediatric endoscopes.

CONCLUSION

In our experience, endoscopic PUV incision using the Holmium: YAG laser appears to be a safe and efficient technique.

Thulium fiber laser in urology: physics made simple

PURPOSE OF REVIEW

In this narrative review, we will focus on a novel thulium fiber laser's physical properties in terms of its clinical applicability.

RECENT FINDINGS

TFL has successfully moved forward from the preclinical trials into clinical practice and now is being widely used in clinics around the world. The available data suggest that the device effectively operates in soft tissues - benign prostate hyperplasia (BPH) and bladder tumors, as well as in lithotripsy. Also, the first promising results were obtained from laparoscopic surgery showing its possible applicability in the management of renal cell carcinoma. The constructional changes in fiber laser's design, lead to alteration of laser-tissue interactions, which resulted in clinical advantages of the device. Yet, the exact mechanism often is considered complex for understanding. With this work, we are aiming to build a bridge between biophysics and clinical practice and give a simple explanation of how the devices is working and why the knowledge of it is important for a clinician.

SUMMARY

The more effective wavelength (closer to the water absorption peak), favorable beam profile, different modes of action allowing to decrease carbonization on one hand and retropulsion on the other, all this makes TFL an evolution in urologic surgery. Further trials investigating on the possible pros and cons of the device are awaited.

Evaluation of Biological Activity of Different Wavelengths of Low-Level Laser Therapy on the Cancer Prostate Cell Line Compared With Cisplatin

Introduction: Cancer is one of the most important problems in the world. Low-level laser therapy (LLLT) has been emerged as a new approach, having both stimulation and inhibition effects on cellular function. The goal of this study was to analyze and compare the different concentrations of cisplatin and wavelengths of laser therapy on the LnCap cell lines. Methods: LnCap cells were cultured and treated with different concentrations of cisplatin (0.1, 0.4, 0.8, 1.2 and 2 µg/mL for 24 hours) and wavelengths of laser therapy (610, 630 and 810 nm) (0.45 J/cm²) separately. The viability of cells was examined by MTT assay and IC50 was also calculated. Furthermore, a combination of cisplatin IC50 (24 hours) and different wavelengths of the laser was examined. Results: The results of this study showed that 2 µg/mL of cisplatin has the most significant reduction effect on the cell viability of the LnCap cell line. Cisplatin decreased the viability of cells in a dose-dependent manner. Moreover, IC50 of cisplatin was 1.24 µg/mL. On the other hand, LLLT with wavelengths of 610, 630 and 810 nm did not show notable biological effects on cell viability. Conclusion: As known, cisplatin has the capability to reduce the viability of LnCap cell lines. However, LLLT cannot be a remarkable option for the treatment of prostate cancer. Therefore, although laser therapy showed praiseful therapeutic activity against some cancer cell lines, in this study the results indicated that defined laser wavelengths had no inhibitory effects against the prostate cancer cell line.

A review of thulium-fiber laser in stone lithotripsy and soft tissue surgery

PURPOSE OF REVIEW

To evaluate emerging evidence and practical applications of thulium-fiber laser (TFL) for genitourinary soft tissue disease and urinary stone disease treatment.

RECENT FINDINGS

A systematic review was developed using the PubMed, ScienceDirect, Wiley, SpringerLink and Mary Ann Liebert Scopus databases between 2012 and 2020 years, using the PRISMA statement. We analyzed recent publications including in vitro and in humans outcomes of surgery using TFL. This new laser technology can be used in soft tissue diseases and stones present in the genitourinary system. Most of the comparisons are made with the Ho:YAG laser, using completely different settings. Nevertheless, TFL is safe, feasible and effective in the management of urologic diseases, showing superiority to Ho:YAG even in some studies.

SUMMARY

The introduction of pulsed TFL technology has enabled the ablation of stones at rates comparable to or better than currently existing lasers in vitro, while also potentially reducing stone retropulsion. TFL is effective in treating genitourinary soft tissue diseases, including benign prostatic hyperplasia, and early data indicate that it may be effective in the treatment of urinary stone disease. More clinical studies are needed to better understand the indications for this novel technology and clarify its position in the urologic endoscopy armamentarium.

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.

The laser of the future: reality and expectations about the new thulium fiber laser-a systematic review

The Holmium:yttrium-aluminum-garnet (Ho:YAG) laser has been the gold-standard for laser lithotripsy over the last 20 years. However, recent reports about a new prototype thulium fiber laser (TFL) lithotripter have revealed impressive levels of performance. We therefore decided to systematically review the reality and expectations for this new TFL technology. This review was registered in the PROSPERO registry (CRD42019128695). A PubMed search was performed for papers including specific terms relevant to this systematic review published between the years 2015 and 2019, including already accepted but not yet published papers. Additionally, the medical sections of ScienceDirect, Wiley, SpringerLink, Mary Ann Liebert publishers, and Google Scholar were also searched for peer-reviewed abstract presentations. All relevant studies and data identified in the bibliographic search were selected, categorized, and summarized. The authors adhered to PRISMA guidelines for this review. The TFL emits laser radiation at a wavelength of 1,940 nm, and has an optical penetration depth in water about four-times shorter than the Ho:YAG laser. This results in four-times lower stone ablation thresholds, as well as lower tissue ablation thresholds. As the TFL uses electronically-modulated laser diodes, it offers the most comprehensive and flexible range of laser parameters among laser lithotripters, with pulse frequencies up to 2,200 Hz, very low to very high pulse energies (0.005-6 J), short to very long-pulse durations (200 µs up to 12 ms), and a total power level up to 55 W. The stone ablation efficiency is up to four-times that of the Ho:YAG laser for similar laser parameters, with associated implications for speed and operating time. When using dusting settings, the TFL outperforms the Ho:YAG laser in dust quantity and quality, producing much finer particles. Retropulsion is also significantly reduced and sometimes even absent with the TFL. The TFL can use small laser fibers (as small as 50 µm core), with resulting advantages in irrigation, scope deflection, retropulsion reduction, and (in)direct effects on accessibility, visibility, efficiency, and surgical time, as well as offering future miniaturization possibilities. Similar to the Ho:YAG laser, the TFL can also be used for soft tissue applications such as prostate enucleation (ThuFLEP). The TFL machine itself is seven times smaller and eight times lighter than a high-power Ho:YAG laser system, and consumes nine times less energy. Maintenance is expected to be very low due to the durability of its components. The safety profile is also better in many aspects, i.e., for patients, instruments, and surgeons. The advantages of the TFL over the Ho:YAG laser are simply too extensive to be ignored. The TFL appears to be a real alternative to the Ho:YAG laser and become a true game-changer in laser lithotripsy. Due to its novelty, further studies are needed to broaden our understanding of the TFL, and comprehend the full implications and benefits of this new technology, as well its limitations.

Laparoscopic nephroureterectomy with laser endoscopic transuretral disinsertion in lateral decubitus: progressive adaptation to retroperitoneocopic approach

BACKGROUND

The ureteral disinsertion with bladder cuff technique continues to evolve. We present the endoscopic laser transurethral technique combined with a transperitoneal and retroperitoneal laparoscopic approach in lateral decubitus, without patient repositioning, for treating urothelial carcinomas of the upper urinary tract.

MATERIALS AND METHODS

We present 3 laparoscopic nephroureterectomies: 1 transperitoneal and 2 retroperitoneal. Disinsertion was performed in lateral decubitus using a flexible cystoscope and a 365-μm holmium laser fiber. The endoscopic technique was progressively adapted to 3-port and single-port retroperitoneoscopic approaches. Before laparoscopic handling of the kidney, ureter was clamped below the tumour. The endoscopic technique was then started. Both approaches were simultaneously employed.

RESULTS

Nephroureterectomies were achieved performing en bloc endoscopic disinsertion of the bladder cuff and ensuring a closed system comparable to open technique. The second case required reconversion due to technical problems and extension of the surgical time. No relapses were diagnosed during follow-up.

CONCLUSION

Results are comparable to open surgery, technique ensured compliance to oncology principles, enabled disinsertion in lateral decubitus and avoid patient repositioning saving surgical time. The results reflect the benefits of minimally invasive surgery in all cases.

Two-micron (Thulium) Laser Prostatectomy: An Effective Method for BPH Treatment

The two-micron (thulium) laser is the newest laser technique for treatment of bladder outlet obstruction resulting from benign prostatic hyperplasia (BPH). It takes less operative time than standard techniques, provides clear vision and lower blood loss as well as shorter catheterization times and hospitalization times. It has been identified to be a safe and efficient method for BPH treatment regardless of the prostate size.

A randomized trial comparing thulium laser resection to standard transurethral resection of the prostate for symptomatic benign prostatic hyperplasia: four-year follow-up results

OBJECTIVE

To report the results of a randomized prospective trial with a 4-year follow-up, comparing the thulium laser resection of the prostate-tangerine technique (TmLRP-TT) with transurethral resection of prostate (TURP) for treatment of symptomatic benign prostatic hyperplasia (BPH).

METHODS

BPH patients (96) were randomized for surgical treatment with TmLRP-TT (47) or TURP (49). All patients were assessed pre-operatively and followed at 12, 24, 36, and 48 months post-operatively. Several parameters related to BPH were collected at each follow-up, including International Prostate Symptom Score (IPSS), quality of life (QoL), maximum urinary flow rates (Qmax), and post-void residual volume (PVR). All late complications were also recorded.

RESULTS

Dramatic improvement in micturition parameters was observed after TmLRP-TT compared with pre-operative values. Median IPSS decreased 75.6 % in the subsequent 12 months and 61.2 % in 48 months, while median QoL decreased by 80.4 and 59.1 %, respectively. Compared with baseline, numerical values of Qmax increased 1.07-fold and those of PVR decreased 73.1 % in the fourth year. Moreover, all micturition parameters in the TmLRP-TT group were similar to those of TURP patients at every annual assessment. Some late complications after the operations were also observed: one patient suffered from urethral strictures and one from bladder-neck contractures after TmLRP-TT. Re-operation rates were equal in the two groups.

CONCLUSIONS

Micturition remained stable after TmLRP-TT during the 4-year follow-up. Outcomes compared favourably with TURP, with lower peri-operative morbidity and equally low occurrence of late adverse effects. Thus, TmLRP-TT can be an available option for BPH patients, especially older, high-risk patients.

[Treating cervico-urethral obstructions with laser diode: initial clinical experience]

BACKGROUND

The first laser employment for the treatment of the cervico-urethral obstructions (CUO) dates back to the early '90s. This study begins with the analysis of laser basics in Medicine and has the purpose to weigh pros and cons (and limits as well) of laser use in CUO due to Benign Prostatic Hyperplasia (BPH). That is an ageing man's typical disease and there is a huge need of minimally invasive treatments, because people affected by this kind of illness suffer very often from comorbidities, and that could make traditional surgery quite risky.

AIM OF THE STUDY

The target of this study is the in vivo experimentation of a brand new laser diode, crated to be specifically used in BPH, and to verify its efficacy and safety.

MATERIALS AND METHODS

The subject of the study is the whole laser diode supply, with its double-band laser source (980 nm + 1470 nm), which gains a 140 W-power and is equipped with Water-Free optical fibers of different kinds of tip. We have tested a conical tip fiber on a standard 24-26 F-resectoscope instead of a standard diathermic loop. The conic fiber optimizes the energy on the treated tissue. We recruited 14 patients with CUO caused by BPH, 56 to 70 years old, with a prostatic volume between 33 and 53 cc, and we treated them with laser surgery using the power of 100-110 W. We considered the operative time, the intra-surgery complications and the specific side effects such as hematuria, pain, catheter removal time and the presence or not of acute urinary retention, in order to evaluate the efficacy and safety of this new technique.

RESULTS

The possibility of using the same resectoscope as the one used in transurethral resection of prostate (TURP) made everything more comfortable and easy because of the immediate feeling with the new instrument and the actual time of Light Vaporization between 30 and 40 minutes, which is more or less the same time of a standard TURP procedure.

CONCLUSIONS

The idea of a double-band-emitting laser used with conical tip fibers appears to be a great solution in the BPH treatment: it uses the principle of low power density plasma in order to treat bigger prostatic tissue areas but never going in depth. In our clinical results, the efficacy of the double-band-emitting laser source (1470 nm + 980 nm) appears to be similar, but even potentially greater, to the actual surgical laser options (such as HoLEP with Ho:YAG laser and PVP with KTP laser), and it is also similar to traditional TURP.

Intravesical tension-free vaginal tape removal: is there a single solution?

Stress urinary incontinence (SUI) affects 10–20% of women in the general population. Surgery for stress incontinence has been performed on women for over a century, but with the advent of new urogynaecological sling procedures for its management, urological surgeons are having to deal with an increasing number of patients presenting with associated complications. With no clarity on the full range of possible complications or certain consensus on their optimal management, the ideal treatment remains a decision for the individual surgeon. In view of this, we felt it of common interest to review the literature for the history of sling procedures, present commonly arising complications, and seek to answer the question in the title.

Laser lipolysis used to treat localized adiposis: a preliminary report on experience with Asian patients

BACKGROUND

Localized deposits of fat (adiposis) located in the face, chin, neck, and arms usually are more compact and difficult to treat using conventional liposuction. It is necessary to find an effective approach for this type of localized adiposis. This study aimed to investigate the clinical application of laser lipolysis for the treatment of localized adiposis in Asian patients.

METHODS

In this study, 35 patients with localized adiposis were treated by laser lipolysis. Neodymium:yttrium-aluminum-garnet (Nd:YAG) laser energy was transferred through an optic fiber into the adipose tissue. The optimal energy and frequency of the laser were controlled precisely to melt and destroy the adipose tissue without damage to the skin and deeper tissues. The histologic study of treated adiposis tissues, the postoperation reaction, and the clinical results were observed and studied.

RESULTS

After laser lipolysis, the localized adipose tissues were liquefied effectively, and the compact fibrous tissues were broken down into a looser structure. Bleeding was noted to be less than with conventional liposuction due to the coagulation of capillary vessels and the thermal effect of the laser. Laser lipolysis caused less edema, petechiae, and other postoperative complications, producing rapid recovery and satisfactory results.

CONCLUSION

The Nd:YAG laser has a definite lipolysis effect on compact adipose tissue and is a more effective approach for the treatment of localized adiposis than conventional liposuction.

Safety and efficacy of holmium laser resection for primary nonmuscle-invasive bladder cancer versus transurethral electroresection: single-center experience

OBJECTIVES

To assess the safety and efficacy of holmium laser resection for primary, clinically nonmuscle-invasive, bladder cancer (HoLRBT) compared with standard transurethral resection of bladder tumor (TURBT).

METHODS

The data from a total of 212 consecutive patients with primary nonmuscle-invasive bladder cancer were collected in this study. These patients were treated by holmium laser resection (HoLRBT group) or transurethral electroresection (TURBT group) and were divided into 2 groups. The patients in each group were stratified into 3 risk subgroups (low, intermediate, and high risk) according to the prognostic factors for recurrence using the European Association of Urology guidelines. The intraoperative complications and postoperative characteristics of the HoLRBT and TURBT groups were compared. Efficacy, indicated by the recurrence-free survival in the overall group and stratified subgroups, was analyzed and compared using the Kaplan-Meier technique and the log-rank test.

RESULTS

The patient demographics and tumor characteristics in the 2 groups were comparable. HoLRBT was superior to TURBT in terms of intraoperative complications and postoperative catheterization time (P < .001). Recurrence-free survival after HoLRBT was similar to that after TURBT (P = .283).

CONCLUSIONS

Our results have indicated that HoLRBT is a feasible, safe, and effective alternative for the management of primary, clinically nonmuscle-invasive, bladder cancer compared with TURBT, with similar recurrence-free survival and fewer perioperative complications. It also can provide sufficient material for the pathologic evaluation.

Laser-induced (endo)vascular photothermal effects studied by combined brightfield and fluorescence microscopy in hamster dorsal skin fold venules

The putative features of the (endo)vascular photothermal response, characterized by laser-induced thermal denaturation of blood and vessel wall constituents, have been elucidated individually, but not simultaneously in dynamic, isolated in vivo systems. A hamster dorsal skin fold model in combination with brightfield/fluorescence intravital microscopy was used to examine the effect of laser pulse duration and blood flow velocity on the size of the thermal coagulum, its attachment behavior, and laser-mediated vasomotion. The size of the coagulum and the extent of vasoconstriction and latent vasodilation were proportional to the laser pulse duration, but pulse duration had no effect on coagulum attachment/dislodgement. Blood flow velocity exhibited no significant effect on the studied parameters. The (endo)vascular photothermal response is governed predominantly by laser energy deposition and to a marginal extent by blood flow velocity.

The future of lasers in urology

The use of laser applications in urology has undergone significant advances over the past 20 years. Laser technology is now used in a wide variety of procedures, and has become the primary treatment modality or standard of care for many urologic conditions. Despite these advances, a number of challenges still face laser utilization in urologic practice. Recent work has illuminated the potential improvement and further optimization of this field. Improvements in types of lasers, the wavelength of energy used, optical fiber delivery systems, precision of laser application and cost reduction have served to further improve laser technology and extend the potential applications.

An Er:YAG laser endoscopic fiber delivery system for lithotripsy of salivary stones

BACKGROUND AND OBJECTIVES

Endoscopic applications of Erbium:YAG lasers are still very limited due to lack of appropriate fiber delivery capabilities. Recent reports on potential advantages of this laser for lithotripsy of ureteral stones prompted us to develop an Er:YAG fiber delivery system for endoscopic lithotripsy of salivary stones. We report on the development of this system and its clinical use on 17 patients.

STUDY DESIGN/MATERIALS AND METHODS

Ho:YAG and Er:YAG laser fragmentation performances were initially compared. Optimal laser parameters for lithotripsy of salivary stones were then established ex vivo using a commercial dental Er:YAG laser (Lumenis Opusdent 20). Metal hollow waveguides optimized for Er:YAG laser transmission were end sealed with a polished sapphire rod of 0.63 mm diameter and designed to adapt to the Opusdent laser and to a Storz sialoendoscope. The system was tested ex vivo for durability and clinical compatibility at input energies up to 700 mJ, 10-20 Hz. Following Helsinki approval the system was clinically tested on 17 patients with sialolithiasis.

RESULTS

Lithotripsy threshold was around 80 mJ/pulse (26 J/cm2) while efficient fragmentation, with microscopic fragments, was observed at an output energy range of 150-300 mJ/pulse. At 10 Hz, fragmentation rates of about 1.8 mm3/second were achieved enabling lithotripsy of a 6 mm stone in about 2 minutes. Front surface damage to the sapphire rod occurred but did not contribute to significant loss in fragmentation efficiency. Of the 21 stones treated clinically, 5 were fully fragmented, 7 were prepared for extraction by mini forceps, and 9 were released from surrounding soft tissues for subsequent removal. Fifteen of the 18 treated glands returned to normal function without any symptoms.

CONCLUSIONS

The Er:YAG endoscopic delivery system described is a clinically viable and cost-effective device for a range of hard and soft tissue wet field applications accessible through rigid or semi-rigid endoscopes. Further improvements in the waveguide may allow access also through fully flexible endoscopes.