Laser vaporization of the prostate in vivo: Experience with the 150-W 980-nm diode laser in living canines

In Vivo Investigation of Noncontact Rapid Photothermal Hemostasis on Venous and Arterial Bleeding

OBJECTIVE

Endoscopic surgical procedures rigorously underscore the significance of rapid hemostasis for unavoidable intraoperative bleeding, requiring advancement of the immediate hemostatic interventions for favorable clinical outcomes. Here, we report the efficacy of a new optical treatment with dual-wavelengths to develop an endoscopic hemostasis method.

METHODS

we combine visible (20-W 532 nm at 1.1 kW/cm²) and near-infrared (40-W 980 nm at 2.2 kW/cm²) wavelengths for facilitating noncontact thermal hemostasis on venous and arterial bleeders in in vivo leporine models.

RESULTS

Simultaneous irradiation of 60-W dual-wavelengths allows for an increased irradiance of 3.3 kW/cm², involving both rapid light absorption by hemoglobin and deep thermal penetration. The collective thermal effects from the combined wavelengths contribute to a significant reduction in coagulation time and a high success rate of complete hemostasis for both venous and arterial bleeders. The enhanced hemostatic potential of the dual-wavelengths treatment accompanies minimal hemorrhage, reduces inflammatory responses, and facilitates re-epithelialization.

CONCLUSION

The proposed dual-wavelengths method can achieve rapid and complete hemostasis for endoscopic procedures.

SIGNIFICANCE

We present the high-irradiance photothermal treatment using the dual-wavelengths as a novel method to regulate venous and arterial bleeding and potentially as a rapid noncontact hemostasis option to mitigate the risk associated with significant blood loss.

Comparison of Multipulse Laser Vaporesection versus Plasmakinetic Resection for Treatment of Benign Prostate Obstruction

We aimed to compare the efficacy and safety of Multipulse laser vaporesection of the prostate (MPVP) versus plasmakinetic resection of the prostate (PKRP) for treatment of patients with benign prostate obstruction (BPO) in a prospective trial. From January 2016 to April 2017, a total of 144 patients were included in the cohort study, of whom 73 patients underwent MPVP and 71 underwent PKRP. All patients received pre-operative evaluation and followed up at 1, 3, 6 and 12 months postoperatively. Baseline characteristics, perioperative data and postoperative outcomes were compared. Early (within 30 days postoperatively) and late complications were also recorded. Preoperative data, including age, prostate volume, international prostate symptom score (IPSS), International Index of Erectile Function Questionnaires (IIEF-5), the rate of anticoagulants use, Charlson comorbidity index were similar in two groups. Peri-operative parameters, including the rate of transfusion, and decrease in hemoglobin level were comparable. The operative time, the duration of catheterization and length of hospital stay were significantly shorter in the MPVP group. The voiding parameters and the quality-of-life scores (QoL) improved significantly in both groups postoperatively. There was a significantly difference in QoL at 1-year in the MPVP group (p < 0.001), under mixed model analysis with random effect and Bonferroni correction. There were no significant differences in improvement of IPSS, Qmax, IIEF-5, residual prostate volume ratio and PSA level reduction at the 1-year follow-up. MPVP was significantly superior to PKRP in terms of a reduction in overall complication rate (21.9% vs 45.0%, p = 0.004). Both treatments led to comparable symptomatic improvements. MPVP demonstrates satisfactory efficiency, shorter catheterization time and shorter hospital stay. Our data revealed that MPVP may be a promising technique which is safe and favorable alternative for patients with BPO.

Dual-wavelength-assisted thermal hemostasis for treatment of benign prostate hyperplasia

Laser treatment on a large size of prostate gland often encounters significant bleeding that can prolong the entire procedure and cause urinary complications. The current study investigates the feasibility of dual-wavelength (532 and 980 nm) application to achieve rapid hemostasis for 532-nm laser prostatectomy. Porcine kidney and bleeding phantom models were tested to quantify the degree of the irreversible tissue coagulation and to estimate the time for the complete hemostasis, respectively. The ex vivo kidney testing verifies that the dual-wavelength created up to 40% deeper and 25% wider coagulation regions than a single wavelength does. The bleeding phantom testing demonstrates that due to the enhanced thermal effects, the simultaneous irradiation yields the complete photocoagulation (~11 seconds) whereas 532 or 980 nm hardly stops bleeders. Numerical simulations validate that the combined optical-thermal characteristics of both the wavelengths account for the augmented thermal coagulation. The dual-wavelength-assisted coagulation can be a feasible treatment to entail the rapid hemostasis and to facilitate the laser prostatectomy in an effective manner.

Temperature feedback-controlled photothermal treatment with diffusing applicator: theoretical and experimental evaluations

To minimize thermal injury, the current study evaluated the real-time temperature monitoring with a proportional-integrative-derivative (PID) controller during 980-nm photothermal treatment with a radially-diffusing applicator. Both simulations and experiments demonstrated comparable thermal behaviors in temperature distribution and the degree of irreversible tissue denaturation. The PID-controlled application constantly maintained the pre-determined temperature of 353 K (steady-state error = < 1 K). Due to constant energy delivery, coagulation volumes linearly increased up to 1.04 ± 0.02 cm(3) with irradiation time. Integration of temperature feedback with diffuser-assisted photothermal treatments can provide a feasible therapeutic modality to treat pancreatic tumors in an effective manner.

GreenLight laser vs diode laser vaporization of the prostate: 3-year results of a prospective nonrandomized study

BACKGROUND AND OBJECTIVE

Laser vaporization of the prostate is one of the alternatives to transurethral resection of the prostate. Short-term studies report a comparable outcome after laser vaporization with the 532 nm 120-W GreenLight high-performance system (HPS) laser and the 980 nm 200 W high-intensity diode (diode) laser. In this study, we analyzed the intermediate-term results of both techniques.

MATERIALS AND METHODS

From January 2007 to January 2008, 112 consecutive patients with symptomatic benign prostate enlargement were nonrandomly assigned to treatment with the GreenLight laser or the diode laser. Perioperative parameters, postoperative functional outcome, complications, and the reoperation rate at 3 years were analyzed.

RESULTS

Improvement of voiding symptoms (International Prostate Symptom Score, quality-of-life) and micturition parameters (maximum flow rate, postvoid residual volume) showed no significant difference between the HPS group and the diode group. A significantly higher reoperation rate was observed in the diode group in comparison to the HPS group (37.5% vs 8.9%, p=0.0003) due to obstructive necrotic tissue (16.1% vs 0%, p=0.0018), bladder neck stricture (16.1% vs 1.8%, p=0.008), and persisting or recurrent adenoma (5.4% vs 7.1%, p=0.70), respectively.

CONCLUSIONS

Both lasers lead to comparable improvement of voiding parameters and micturition symptoms. Treatment with the 200 W diode laser led to a significantly higher reoperation rate, which might be attributed to a higher degree of coagulation necrosis. Thus, a careful clinical application of this diode laser type is warranted.

Diode laser vaporisation of the prostate vs. diode laser under cold irrigation: A randomised control trial

Objective

To compare the perioperative morbidity and early follow-up after diode laser vaporisation of the prostate (LVP) and its modification, diode laser under cold irrigation (LUCI) in patients with symptomatic benign prostatic hyperplasia, as the main disadvantages of LVP are the postoperative pain, dysuria and storage urinary symptoms.

Patients and methods

This was a single-centre prospective randomised control trial in which 100 patients were randomised to receive LVP (50) or LUCI (50) from June 2011 until July 2012. LUCI is similar to LVP except that it is done under normal irrigation with saline at 4 °C instead of saline at room temperature. The primary outcome measures were the International Prostate Symptom Score (IPSS), IPSS-Dysuria, a pain scale (PS), maximum flow rate (Q_max), a quality-of-life (QoL) score and the postvoid residual urine volume (PVR) after 1 month, then the IPSS, Q_max, QoL, and PVR at 3 and 12 months. Secondary outcomes included intraoperative surgical variables, e.g., the decline in core temperature, bleeding, peri- and postoperative morbidity.

Results

The baseline characteristics of both groups were similar. For the primary outcome measures, there was a statistically significant difference between the groups in all variables except Q_max after 1 month, in favour of LUCI. The mean (SD) IPSS at 1 month in the LVP group was 8.97 (1.68), statistically significantly different from that after LUCI, of 6.89 (1.5) (P < 0.05). The mean IPSS-Dysuria at 1 month was also significantly, at −2.32 (0.91) for LVP and 3.54 (1.07) for LUCI (P < 0.05). The respective mean PS at 1 month was 7.84 (2.92) and 5.7 (2.1) (P < 0.05). The QoL and PVR at 1 month were also significantly different. Within the first month 17% of patients in the LVP group and 4% in the LUCI group complained of transient urgency or stress incontinence, and this difference was statistically significant (P < 0.05). There was no significant bleeding in either group. The mean operative time or applied energy of LVP was not statistically significant from that of LUCI, and there was no significant difference in the decline in core temperature between the groups (P > 0.05).

Conclusion

LUCI is a good modification for reducing the pain, dysuria and storage symptoms associated with LVP. The procedure appears to be safe, with no significant decrease in core temperature in either group.

Ex vivo efficacy evaluation of laser vaporization for treatment of benign prostatic hyperplasia using a 300-W high-power laser diode with a wavelength of 980 nm

BACKGROUND AND OBJECTIVE

Laser vaporization of the prostate is considered to be a promising treatment for benign prostatic hyperplasia (BPH), and efficiency of vaporization and hemostasis are both important parameters for such treatment. In this study, we used a high-power laser diode with a wavelength of 980 nm to obtain high vaporization efficiency with good hemostasis. The objective of this study is to evaluate the efficacy of laser vaporization for treatment of BPH in ex vivo experiments using a 300-W high-power laser diode with a wavelength of 980 nm quantitatively.

MATERIALS AND METHODS

An ex vivo experimental setup simulating clinical treatment situation was constructed. Bovine prostate tissue was used as a sample. The power setting was 100, 150, 200, 250, or 300 W, and the irradiation time was 0.5, 1, or 2 s. After laser irradiation, vaporized and coagulated depths were measured.

RESULTS

The vaporized depth increased with the laser power and irradiation time, and the results confirmed that the high-power laser diode could efficiently vaporize the prostate tissue. Coagulated depth increased as the laser power became higher.

CONCLUSIONS

Laser vaporization of prostate tissue using a high-power laser diode with a wavelength of 980 nm represents a promising treatment for BPH; this method exhibits high vaporization efficiency and good hemostasis. However, operators must be aware of the risk of postoperative perforation of the prostatic capsule caused by coagulation of deep regions that cannot be visualized by endoscopic observation.

Optical feedback-induced light modulation for fiber-based laser ablation

Optical fibers have been used as a minimally invasive tool in various medical fields. However, due to excessive heat accumulation, the distal end of a fiber often suffers from severe melting or devitrification, leading to the eventual fiber failure during laser treatment. In order to minimize thermal damage at the fiber tip, an optical feedback sensor was developed and tested ex vivo. Porcine kidney tissue was used to evaluate the feasibility of optical feedback in terms of signal activation, ablation performance, and light transmission. Testing various signal thresholds demonstrated that 3 V was relatively appropriate to trigger the feedback sensor and to prevent the fiber deterioration during kidney tissue ablation. Based upon the development of temporal signal signatures, full contact mode rapidly activated the optical feedback sensor possibly due to heat accumulation. Modulated light delivery induced by optical feedback diminished ablation efficiency by 30% in comparison with no feedback case. However, long-term transmission results validated that laser ablation assisted with optical feedback was able to almost consistently sustain light delivery to the tissue as well as ablation efficiency. Therefore, an optical feedback sensor can be a feasible tool to protect optical fiber tips by minimizing debris contamination and delaying thermal damage process and to ensure more efficient and safer laser-induced tissue ablation.

Diode laser-induced tissue effects: in vitro tissue model study and in vivo evaluation of wound healing following non-contact application

INTRODUCTION

The basic difference between the various common medical laser systems is the wavelength of the emitted light, leading to altered light-tissue interactions due to the optical parameters of the tissue. This study examines laser induced tissue effects in an in vitro tissue model using 1,470 nm diode laser compared to our standard practice for endonasal applications (940 nm diode laser) under standardised and reproducible conditions. Additionally, in vivo induced tissue effects following non-contact application with focus on mucosal healing were investigated in a controlled intra-individual design in patients treated for hypertrophy of nasal turbinate.

METHODS

A certified diode laser system emitting the light of λ = 1470 nm was evaluated with regards to its tissue effects (ablation, coagulation) in an in vitro setup on porcine liver and turkey muscle tissue model. To achieve comparable macroscopic tissue effects the laser fibres (600 µm core diameter) were fixed to a computer controlled stepper motor and the laser light was applied in a reproducible procedure under constant conditions. For the in vivo evaluation, 20 patients with nasal obstruction due to hyperplasia of inferior nasal turbinates were included in this prospective randomised double-blinded comparative trial. The endoscopic controlled endonasal application of λ = 1470 nm on the one and λ = 940 nm on the other side, both in 'non-contact' mode, was carried out as an outpatient procedure under local anaesthesia. The postoperative wound healing process (mucosal swelling, scab formation, bleeding, infection) was endoscopically documented and assessed by an independent physician.

RESULTS

In the experimental setup, the 1,470 nm laser diode system proved to be efficient in inducing tissue effects in non-contact mode with a reduced energy factor of 5-10 for highly perfused liver tissue to 10-20 for muscle tissue as compared to the 940 nm diode laser system. In the in vivo evaluation scab formation following laser surgery as assessed clinically on endonasal endoscopy was significantly reduced on 1,470 nm treated site compared to 940 nm diode laser treated site.

CONCLUSIONS

Diode laser system (1,470 nm) induces efficient tissue effects compared to 940 nm diode laser system as shown in the tissue model experiment. From the clinical point of view, the healing process following non-contact diode laser application revealed to be improved using 1,470 nm diode laser compared to our standard diode laser practise with 940 nm.

Characterization on ablation performance of various surgical fibers

Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia (BPH). Various surgical parameters still need to be tested and optimized to accomplish better clinical outcomes. The purpose of the current study is to investigate the effect of fiber core size on ablation performance at various laser power levels. Three optical fibers (600, 775, and 850 μm) were tested in vitro with a customized 532-nm laser system with power ranging from 120 to 180 W. Ablation performance was evaluated in light of total energy, irradiance, and volumetric energy density. Irrespective fiber size, crater dimension, and ablation volume linearly increased with the incident irradiance. However, each fiber created different geometry of ablation craters (i.e., deep columnar shape for 600 μm vs. shallow funnel shape for 850 μm). Smaller fiber size demonstrated the efficient energy usage for tissue removal. In-depth comprehension of fiber performance can help accomplish predictable and efficient surgical procedures for BPH therapy.

Tissue effects resulting from eraser laser enucleation of the prostate: in vivo investigation

BACKGROUND/AIMS/OBJECTIVES: To describe the depth of the laser coagulation zone in vivo based on histological examinations and the functional outcome of a 1,318-nm diode laser for enucleation in benign prostatic enlargement (BPE).

METHODS

A total of 20 patients with BPE were treated by laser Eraser® enucleation of the prostate (ELEP). Prostatic tissue wedges were evaluated to assess the depth of the ELEP coagulation zones. Additionally, patients were assessed preoperatively and 12 months postoperatively.

RESULTS

The coagulation zones were 0.36 ± 0.17 mm in epithelial tissue, 0.28 ± 0.15 mm in stromal tissue, and 0.25 ± 0.12 mm in mixed tissue. The coagulation area at the cutting edge completely sealed capillary vessels, reaching a depth of 0.35 ± 0.15 mm. The diameter of the coagulated vessels measured 1.75 ± 0.83 mm. Mean blood loss was 115.54 ± 93.12 ml, catheter time 1.35 ± 0.33 days, and hospital stay 1.89 ± 0.52 days. The International Prostate Symptom Score, maximal flow rate, and quality of life significantly improved 12 months after the procedure.

CONCLUSIONS

ELEP is safe and effective for BPE treatment and yields good results at a follow-up of 1 year. Because of the limited penetration depth, damage to the urinary sphincter is not expected.

[Laservaporization of the prostate: current status of the greenlight and diode laser]

In the last decade laser vaporization of the prostate has emerged as a safe and effective alternative to transurethral resection of the prostate (TURP). This was facilitated in particular by the introduction of photoselective vaporization of the prostate (PVP) with a 532 nm 80 W KTP laser in 2002. Prospective randomized trials comparing PVP and TURP with a maximum follow-up of 3 years mostly demonstrated comparable functional results. Cohort studies showed a safe application of PVP in patients under oral anticoagulation and with large prostates. Systems from various manufacturers with different maximum power output and wavelengths are now available for diode laser vaporization of the prostate. Prospective randomized trials comparing diode lasers and TURP are not yet available. In cohort studies and comparative studies PVP diode lasers are characterized by excellent hemostatic properties but functional results vary greatly with some studies reporting high reoperation rates.

[European Association of Urology guidelines on laser technologies]

CONTEXT

The European Association of Urology (EAU) Guidelines Office has set up a guideline working panel to analyse the scientific evidence published in the world literature on lasers in urologic practice.

OBJECTIVE

Review the physical background and physiologic and technical aspects of the use of lasers in urology, as well as current clinical results from these new and evolving technologies, together with recommendations for the application of lasers in urology. The primary objective of this structured presentation of the current evidence base in this area is to assist clinicians in making informed choices regarding the use of lasers in their practice.

EVIDENCE ACQUISITION

Structured literature searches using an expert consultant were designed for each section of this document. Searches were carried out in the Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, and Medline and Embase on the Dialog/DataStar platform. The controlled terminology of the respective databases was used, and both Medical Subject Headings and EMTREE were analysed for relevant entry terms. One Cochrane review was identified.

EVIDENCE SYNTHESIS

Depending on the date of publication, the evidence for different laser treatments is heterogeneous. The available evidence allows treatments to be classified as safe alternatives for the treatment of bladder outlet obstruction in different clinical scenarios, such as refractory urinary retention, anticoagulation, and antiplatelet medication. Laser treatment for bladder cancer should only be used in a clinical trial setting or for patients who are not suitable for conventional treatment due to comorbidities or other complications. For the treatment of urinary stones and retrograde endoureterotomy, lasers provide a standard tool to augment the endourologic procedure.

CONCLUSIONS

In benign prostatic obstruction (BPO), laser vaporisation, resection, or enucleation are alternative treatment options. The standard treatment for BPO remains transurethral resection of the prostate for small to moderate size prostates and open prostatectomy for large prostates. Laser energy is an optimal treatment method for disintegrating urinary stones. The use of lasers to treat bladder tumours and in laparoscopy remains investigational.

Laser prostatectomy of lower urinary tract symptoms due to benign prostate enlargement: a critical review of evidence

PURPOSE OF REVIEW

Different transurethral prostatic laser systems are available. In 2011, new Oxford evidence levels (LoEs) were published with significant changes compared with the former version. They are easier to use and incorporate more clinical aspects. Randomized trials of laser systems used before 2002, except Holmium laser, were not included in this critical evidence analysis, as these techniques are not in clinical use any more.

RECENT FINDINGS

Twenty-five [18 Holmium enucleation of the prostate (HoLEP) and seven photoselective vaporization of the prostate (PVP)] randomized trials covering transurethral electroresection of the prostate or HoLEP, PVP or Thulium laser enucleation were identified. According to evidence levels, there is a large gap in terms of long-term follow-up. The majority of randomised controlled trials are of low quality. Typically with HoLEP, many articles were published covering the same patient population (LoE II). Only one randomised controlled trial was published with Tm:YAG prostatectomy (LoE II) and none with diode lasers (980-1340 nm, LoE IV-V). Large cohort studies (LoE III-IV) provide additional evidence for PVP and HoLEP, typically for subgroups.

SUMMARY

In 2011, higher evidence on HoLEP and PVP has been published. Evidence levels for HoLEP and PVP are comparable with meta-analysis (LoE II). However, evidence that laser prostatectomy is better than transurethral electroresection of the prostate in terms of efficacy is lacking (LoE II). All lasers are safer in terms of perioperative bleeding (LoE II).

EAU guidelines on laser technologies

CONTEXT

The European Association of Urology (EAU) Guidelines Office has set up a guideline working panel to analyse the scientific evidence published in the world literature on lasers in urologic practice.

OBJECTIVE

Review the physical background and physiologic and technical aspects of the use of lasers in urology, as well as current clinical results from these new and evolving technologies, together with recommendations for the application of lasers in urology. The primary objective of this structured presentation of the current evidence base in this area is to assist clinicians in making informed choices regarding the use of lasers in their practice.

EVIDENCE ACQUISITION

Structured literature searches using an expert consultant were designed for each section of this document. Searches were carried out in the Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, and Medline and Embase on the Dialog/DataStar platform. The controlled terminology of the respective databases was used, and both Medical Subject Headings and EMTREE were analysed for relevant entry terms. One Cochrane review was identified.

EVIDENCE SYNTHESIS

Depending on the date of publication, the evidence for different laser treatments is heterogeneous. The available evidence allows treatments to be classified as safe alternatives for the treatment of bladder outlet obstruction in different clinical scenarios, such as refractory urinary retention, anticoagulation, and antiplatelet medication. Laser treatment for bladder cancer should only be used in a clinical trial setting or for patients who are not suitable for conventional treatment due to comorbidities or other complications. For the treatment of urinary stones and retrograde endoureterotomy, lasers provide a standard tool to augment the endourologic procedure.

CONCLUSIONS

In benign prostatic obstruction (BPO), laser vaporisation, resection, or enucleation are alternative treatment options. The standard treatment for BPO remains transurethral resection of the prostate for small to moderate size prostates and open prostatectomy for large prostates. Laser energy is an optimal treatment method for disintegrating urinary stones. The use of lasers to treat bladder tumours and in laparoscopy remains investigational.