70 vs 120 W thulium:yttrium‐aluminium‐garnet 2 µm continuous‐wave laser for the treatment of benign prostatic hyperplasia: a systematic ex‐vivo evaluation

Study Type – Aetiology (case series)
Level of Evidence 4

OBJECTIVE

To evaluate the ablative and haemostatic properties of the recently introduced 120‐W thulium:yttrium‐aluminium‐garnet (Tm‐YAG) laser and to assess these results against those of the previously introduced 70‐W Tm‐YAG laser.

MATERIALS AND METHODS

The ex‐vivo model of the isolated blood‐perfused porcine kidney was used to determine the ablation capacity, haemostatic properties and coagulation depth of a 2 µm continuous‐wave Tm‐YAG laser. The energy was delivered using a 550‐µm and an 800‐µm bare‐ended fibre. The results of the recently introduced 120‐W Tm‐YAG were compared to the established 70‐W device. Kidney tissue was embedded for histological evaluation. After staining (haematoxylin and eosin, H&E; and NADH) of the specimen, the coagulation zone and depth of the necrotic tissue layer were measured.

RESULTS

With increased power output, the mean (sd ) rate of vaporization of tissue increased, from 9.80 (3.03) g/10 min at 70 W to 16.41 (5.2) g/10 min at 120 W using the 550 µm fibre. The total amount of ablated tissue using the 800 µm fibre was lower than with the 550 µm fibre. With increasing power output the bleeding rate remained stable in either group. Tissue penetration remained shallow, even with increasing power output. In contrast to H&E staining, where the coagulation zone was measured, NADH staining showed an inner zone of necrotic tissue, again with no difference between the 70‐ and the 120‐W Tm‐YAG.

CONCLUSION

The 120‐W Tm‐YAG offers significantly higher ablation rates than the 70‐W device, and despite the increased rate of ablation with the 120‐W Tm‐YAG, the bleeding rate and depth of tissue penetration were comparable to those using the 70‐W device.     

High-power diode laser at 980 nm for the treatment of benign prostatic hyperplasia: ex vivo investigations on porcine kidneys and human cadaver prostates

Diode laser systems at 980 nm have been introduced for the treatment of lower-urinary-tract-symptoms (LUTS) suggestive of benign prostatic enlargement (BPE). However, the coagulation and vaporization properties are unknown. We therefore aimed to evaluate these properties in ex vivo models in comparison with the kalium-titanyl-phosphate-(KTP) laser. The diode laser treatment was applied to isolated, blood-perfused porcine kidneys and fresh human cadaver prostates (HCPs) at different generator settings. We performed histological examination to compare the depth of coagulation and vaporization. The diode laser showed larger ablation and coagulation characteristics than the KTP laser did. Ablation of the diode laser was found to be 1.79-times (120 W in porcine kidney, P < 0.0001) and 3.0–5 times (200 W in HCP, P < 0.0005) larger. The diode laser created a nine-times (120 W in porcine kidney, P < 0.0001) and seven-times (200 W in HCP, P < 0.0001) deeper necrosis zone. The diode laser vaporization was highly effective ex vivo. Owing to the laser’s deep coagulation zones, in vivo animal experiments are mandatory before the diode laser (980 nm) is applied in a clinical setting, so that damage to underlying structures is prevented.     

Der Diodenlaser

INTRODUCTION AND OBJECTIVES: Laser therapy of symptomatic benign prostatic hyperplasia (BPH) remains a challenge for most urologic surgeons. The main goal of laser surgery is to achieve a marked volume reduction and to decrease bladder outlet obstruction and lower urinary tract symptoms with minimal morbidity. Laser therapy encompasses a variety of techniques using different laser wavelengths, application systems, and surgical techniques to achieve contrasting tissue effects. In an in vitro animal model we compared the vaporization and coagulation effects of the potassium-titanyl-phosphate (KTP) laser, holmium:yttrium-aluminum-garnet (Ho:YAG) laser, and diode laser (980 nm). MATERIAL AND METHODS: In an in vitro model using isolated perfused porcine kidneys we investigated the vaporization, the coagulation effect, and the bleeding rate of the KTP, Ho:YAG, and diode lasers on five porcine kidneys each. The application of each laser type was standardized. The area of laser application was 1 cm x 1 cm. The KTP group received an application with 80 W, the Ho:YAG group an application with 10-30 W, and the diode group an application with 30, 60, and 100 W. Hemostasis was measured semiquantitatively. Ablation and coagulation were investigated macro- and microscopically. RESULTS: Concerning the ablation capacity, the diode laser is most effective (more than fivefold) compared to the KTP and Ho:YAG lasers but demonstrated a rather large coagulation zone of up to tenfold in comparison to the KTP and Ho:YAG lasers. Semiquantitatively, in terms of bleeding rate, all lasers were equivalent in this ex vivo model. CONCLUSIONS: Our very early and limited experience indicates that KTP (80 W) and Ho:YAG (30 W) laser application are equivalent in terms of tissue ablation capacity and coagulation in an experimental setting. The diode laser at 980 nm is superior in terms of ablation capacity but has a large coagulation zone. Concerning the bleeding rate all tested lasers are equivalent in this ex vivo model.     

Ex vivo and in vivo investigations of the novel 1,470 nm diode laser for potential treatment of benign prostatic enlargement

Perioperative haemorrhage is still the major complication of transurethral resection of the prostate (TURP) for benign enlargement of the prostate. Photoselective vaporisation of the prostate (PVP) with the potassium–titanyl–phosphate (KTP) laser has been shown to achieve instant tissue ablation with excellent haemostatic properties. Our aim was to determine the tissue removal capacity, coagulation and haemostatic property of the novel 1,470 nm diode laser, ex vivo and in vivo. We evaluated two prototype diode laser systems at 1,470 nm in an ex vivo, isolated, blood-perfused, porcine kidney model (n = 5; 10 W–50 W) and in an in vivo investigation of beagle prostate (n = 4; 100 W) to assess vaporisation capacities and coagulation properties at different generator settings. The diode laser evaluation was compared with an 80 W KTP laser in the porcine model. After the laser treatment we performed a histological examination to compare the depth of coagulation and vaporisation. The diode laser system (50 W) showed significantly lower (P < 0.0001) capacities for tissue removal than the 80 W KTP laser (0.96 mm ± 0.17 mm and 5.93 mm ± 0.25 mm, respectively, P < 0.0001), while coagulation zones were significantly (P < 0.001) larger in diode laser-treated kidneys (3,39 mm ± 0.93 mm and 1.27 mm ± 0.13 mm, respectively). In vivo, the diode laser displayed rapid ablation of prostatic tissue with no intraoperative haemorrhage. Histological examination revealed coagulation zones of 2.30 mm (±0.26) at 100 W in the diode laser-treated prostates.     

Comparison of the local effects of a 600-μm bare fibre at high laser power on lung parenchyma: Nd:YAG laser 1320 vs. 1064 nm

Lung metastases are often resected non-anatomically with a laser using a diode-pumped Nd:YAG laser at a wavelength of 1320 nm with a laser output of up to 60 W. Usually the removal of lesions is carried out in contact mode by means of a bare fibre. We compared the local effects of an Nd:YAG laser at a wavelength of 1064 nm with those at a wavelength of 1320 nm using a 600-μm bare fibre in contact mode in an experimental model. The investigations were carried out on porcine lungs freshly withdrawn at the abattoir. The 600-μm laser fibre was fixed vertically in contact with the lung surface on a fibre holder. The fibre holder was connected to a feeding device that advances the laser fibre at constant speeds (5, 10 or 20 mm/s). In each case, two laser powers were examined: 20 and 60 W. The lung lesions produced by the laser fibre were excised for histological examination. After haematoxylin–eosin staining, the depth of the vaporisation and coagulation zones (in μm) from the laser cuts was measured. For each setting, an average value was calculated. The individual groups were compared for significance using a non-parametric Mann–Whitney U test (p?<?0.05). At a low speed of the bare fibre of 5 mm/s and a laser output of 20 W, the average depth of the vaporisation zone was 858?±?3.3 μm (λ?=?1064 nm) compared to 766.0?±?7.5 μm (λ?=?1320 nm) (p?<?0.01). Upon faster movement (20 mm/s), the extension of the vaporisation zone decreased to 320.3?±?7.1 μm (λ?=?1064 nm). The depth of the vaporisation zone increased significantly at 60 W, both at λ?=?1064 and 1320 nm with 1517.0?±?1.7 μm and 1414.0?±?4.9 μm, respectively. The extent of the coagulation zone was significantly smaller at 20 W and the low speed of 5 mm/s, namely, 200.4?±?3.7 μm (λ?=?1064 nm) and 224.1?±?2.8 μm (1320-nm laser). Upon faster movement of the laser fibre at the same output, the extent of the coagulation zone decreased in both groups. At a laser power of 60 W, the extent of the coagulation zone was significantly less with the 1064-nm laser (110.3?±?2.4 μm) than with the 1320-nm laser (324.8?±?1.9 μm; p?<?0.001). When the laser fibre moves more rapidly, the extent of the coagulation zone decreases further. The Nd:YAG laser with a wavelength of 1320 nm still has the optimal ratio of cutting and coagulation capacity on the resection surface. With the 1064-nm Nd:YAG laser, a higher cutting capacity is associated with a decrease of the coagulation capacity.     

The Nd:YAG LIMAX® 120 high-output laser: local effects and resection capacity on liver parenchyma

Various technical options are available for the resection of liver metastases, including CUSA, Ultracision, water-jet, and stapler devices. It has been shown that new generation high-output lasers are suitable for the resection of lung metastases. The goal of the present study was to evaluate the local effects of laser application on liver parenchyma. Livers of freshly slaughtered pigs (N?=?6) were analyzed. The handheld laser was vertically held in the clamp of a hydraulic machine and sharply focused on the liver surface. The diode pumped Nd:YAG laser LIMAX® 120 (Gebrüder Martin GmbH & Co. KG, Tuttlingen, Germany) moved evenly over the liver surface at speeds of 5, 10, and 20 mm/s. Laser outputs of 60 and 120 W were applied at every speed. Histological sections (hematoxylin and eosin (HE) staining) of the extension area of vaporization and coagulation were analyzed by the use of the ImageJ software. In addition, the area of the liver parenchyma cut by the laser within 1 min was measured. The vaporized zone appeared wedge-shaped after histological section, whereas the area of coagulation appeared radiated outward. At 10 mm/s and 60 W, the mean vaporization of the measured zone was 356.6?±?3.9 μm in length. Superficial coagulation was observed at 20 mm/s laser speed, without effective resection. At 120 W and 5 mm/s working speed, the mean vaporization zone and the average width of coagulation were largest with 664.6?±?5.9 and 375.6?±?2.3 μm, respectively. The laser output power of 120 W allowed resection of an area of 6?±?0.4 cm² of liver parenchyma within 1 min. The Nd:YAG Laser LIMAX® 120 might be an effective tool for liver parenchyma dissection when it is applied at maximum output (120 W) and at a constant working speed of 5 mm/s.     

Endovenous Treatment of the Great Saphenous Vein Using a 1,320 nm Nd:YAG Laser Causes Fewer Side Effects than Using a 940 nm Diode Laser

BACKGROUND: Limited data are available about treatment-related side effects with respect to laser wavelength in endovenous laser treatment (ELT) of the great saphenous vein (GSV). OBJECTIVE: To compare the results and side effects of a 940 nm diode and a 1,320 nm neodymium:yttium-aluminum-garnet (Nd:YAG) laser. METHODS: Three patient cohorts (A, B, and C) received ELT of the GSV using a 940 nm diode laser at 15 W (group A) or 30 W (group B) or using a 1,320 nm laser at 8 W (group C). In all cases, energy was administered continuously with constant pullback of the laser fiber under perivenous tumescent local anesthesia. RESULTS: The GSVs of group A (n = 113), group B (n = 136), and group C (n = 33) received ELT. An average linear endovenous energy density of 24, 63, and 62 J/cm and an average endovenous fluence equivalent of 12, 30, and 33 J/cm2 were administered to the vein. Occlusion rates were 95% (group A), 100% (group B), and 100% (group C) at day 1 after ELT and 90.3% (group A), 100% (group B), and 97% (group C) at 3 months after ELT. With the 1,320 nm laser ELT (group C), treatment-related pain (50%) and the need for analgesics (36%) were significantly reduced (p < .005) in comparison with treatment-related pain (81%) and the need for analgesics (67%) after the 30 W 940 nm laser ELT (group B). Ecchymosis was also significantly reduced (p < .05) in group C (1,320 nm) compared with group B (30 W, 940 nm). CONCLUSION: ELT of the GSV using a 1,320 nm Nd:YAG laser causes fewer side effects compared with 940 nm diode laser ELT.     

Focal laser interstitial thermotherapy (LITT) at 980 nm for prostate cancer: treatment feasibility in Dunning R3327-AT2 rat prostate tumour

What's known on the subject? and What does the study add? Focal ablation of prostate cancer by laser interstitial thermotherapy (LITT) consists of including a tissue necrosis by thermotherapy using diffusing laser fitres located in the prostate. Because of its compatibility with magnetic resonance imaging, LITT offers the advantage in terms of lesion targeting and real‐time monitoring processing over other minimally invasive techniques using transrectal ultrasound. Moreover, the feasibility of MRI thermometry allows real‐time monitoring of LITT treatment. Our study proves reproducibility of laser interstitial thermotherapy at 980 nm in homogenous prostate cancer model.

OBJECTIVE

• ? To examine the feasibility and reproducibility of laser interstitial thermotherapy (LITT) as a minimally invasive method for the treatment of prostate cancer.

MATERIALS AND METHODS

• ? Heterotopic tumours of prostatic adenocarcinoma (Dunning R3327‐AT2) were induced in 10 male Copenhagen rats.
• ? After preoperative magnetic resonance imaging (MRI), a 10‐mm cylindrical diffusing fibre developed by our research department was inserted under ultrasonographic guidanceinto the tumour.
• ? LITT was performed with a 980‐nm diode laser (power 5 W) for75 s (fluence rate of 1145 J/cm²).
• ? Non‐enhanced T2‐weighted and dynamic gadolinium‐enhanced T1‐weighted MRI examinations were performed at baseline, 1 and 48 h after the procedure and correlated with histological findings.

RESULTS

• ? The necrosis lesions induced by LITT were visible on MRI.
• ? The mean (SD) ellipsoid necrosis volumes were 0.748 (0.075) mL at 1 h and 0.982 (0.052) mL at 48 h after the LITT procedure, and significantly different (P < 0.001).
• ? Histological analysis showed a strong correlation (r = 0.87) with the mean necrosis volume obtained by MRI at 48 h after LITT.

CONCLUSIONS

• ? In a prostatic adenocarcinoma model, 980‐nm LITT induces reproducible necrosis volumes.
• ? Further characterization of the response to LITT in an animal model and in human tissues will be important in establishing the efficacy of the procedure for prostate cancer focal therapy.

     

Photocoagulation with a copper vapour laser in rabbit liver: A comparative study between the 510 nm and the 578 nm wavelengths

The coagulation effect, penetration depth and healing process of the 510.6 nm (green) and 578.2 nm (yellow) wavelengths of copper vapour laser (CVL) were compared in vivo in rabbit liver (n=15). A pulsed CVL, the Cu 15 from Oxford Laser—pulse repetition 10 kHz, peak-power 70 kW, pulse width 25 ns, and average maximal power 16W—was used connected to a dichroic system. The beam was transmitted through a 1000 μm quartz fibre and focused with a handpiece providing a 2 mm diameter spot size. By means of this delivery system 270 focused lesions are achieved at a power output of 2.65 W (power density 80 W cm⁻²) with irradiation times of 3, 5 and 10 s. The operative and microscopic verifications were achieved at 0 hour, and on days 3, 10, 20 and 30. Immediately after laser application, the lesions were triangular, well demarcated, and characterized by a central vaporization surrounded by four peripheral zones: carbonization; coagulation; oedema; and transition. The penetration depth was noticeably bigger in the yellow wavelength than with green wavelength, evidenced on day 10 by superior size of yellow wavelength photocoagulations and coagulation necrosis. Fibrosis appeared by day 3 and was gaining ground quickly and intensively after yellow wavelength while the fibrotic reaction was delayed on day 10 after green wavelength. The more penetrating effect of yellow wavelength advocates for its use in liver tumour destruction and photoradiation therapy while the green wavelength, inducing less aggressive effect on the surrounding tissue, seems more suitable for liver resection.     

High‐power potassium‐titanyl‐phosphate laser fibres for endovaporization of benign prostatic hyperplasia: how much do they deteriorate during the procedure?

Study Type – Therapy (case series) Level of Evidence 4

OBJECTIVE

? To assess the residual power delivered at the tip of a high‐power (80 W) potassium‐titanyl‐phosphate (KTP) laser (80 W Green Light PV^TM, Laserscope®; American Medical Systems, Minnetonka, MN, USA) at the end of a photoselective vaporization of the prostate (PVP) procedure, as well as the deflection angle of the laser beam.

MATERIALS AND METHODS

? In total, 65 laser fibres were collected at the end of PVP procedures indicated for symptomatic benign prostatic hyperplasia over a period of 17 months. PVP was performed by two senior urologists. ? The power of laser beam at tip exit was measured for each fibre at the end of the procedures using a photodiode whose signal was amplified, and then quantified by a volt multimeter. ? The deflection angle was measured using a graduated sphere.

RESULTS

? Approximately 70% of fibres delivered less than 40 W at the end of the procedure, which is less than the vaporization threshold. ? Some 9% of fibres had lost their diffraction capacity with a significant alteration of laser beam angulation. These values were not operator dependent.

CONCLUSIONS

? The data show that a large proportion of laser fibers deliver a significantly underpowered beam at the end of the procedures. ? This seems to be caused by peroperative destruction of the fibers, which results in a progressive loss of efficacy of PVP during procedures.     

Ablation of porcine ligamentum flavum with Ho:YAG,q‐switched Ho:YAG,and quadrupled Nd:YAG lasers

Background and Objectives

Ligamentum flavum (LF) is a tough, rubbery connective tissue providing a portion of the ligamentous stability to the spinal column, and in its hypertrophied state forms a significant compressive pathology in degenerative spinal stenosis. The interaction of lasers and this biological tissue have not been thoroughly studied. Technological advances improving endoscopic surgical access to the spinal canal makes selective removal of LF using small, flexible tools such as laser‐coupled fiber optics increasingly attractive for treatment of debilitating spinal stenosis. Testing was performed to assess the effect of Ho:YAG, Q‐switched Ho:YAG, and frequency quadrupled Nd:YAG lasers on samples of porcine LF. The objective was to evaluate the suitability of these lasers for surgical removal of LF.

Study Design/Materials and Methods

LF was resected from porcine spine within 2 hours of sacrifice and stored in saline until immediately prior to laser irradiation, which occurred within an additional 2 hours. The optical absorbance of a sample was measured over the spectral band from 190 to 2,360 nm both before and after dehydration. For the experiments using the Ho:YAG (λ = 2,080 nm, t_p = 140 µs, FWHM) and Q‐Switched Ho:YAG (λ = 2,080 nm, t_p = 260 ns, FWHM) lasers, energy was delivered to the LF through a laser‐fiber optic with 600 µm core and NA = 0.39. For the experiment using the frequency quadrupled Nd:YAG laser (λ = 266 nm, t_p = 5 ns FWHM), rather than applying the laser energy through a laser‐fiber, the energy was focused through an aperture and lens directly onto the LF. Five experiments were conducted to evaluate the effect of the given lasers on LF. First, using the Ho:YAG laser, the single‐pulse laser‐hole depth versus laser fluence was measured with the laser‐fiber in direct contact with the LF (1 g force) and with a standoff distance of 1 mm between the laser‐fiber face and the LF. Second, with the LF remaining in situ and the spine bisected along the coronal plane, the surface temperature of the LF was measured with an IR camera during irradiation with the Ho:YAG laser, with and without constant saline flush. Third, the mass loss was measured over the course of 450 Ho:YAG pulses. Fourth, hole depth and temperature were measured over 30 pulses of fixed fluence from the Ho:YAG and Q‐Switched Ho:YAG lasers. Fifth, the ablation rate and surface temperature were measured as a function of fluence from the Nd:YAG laser. Several LF staining and hole‐depth measurement techniques were also explored.

Results

Aside from the expected absorbance peaks corresponding to the water in the LF, the most significant peaks in absorbance were located in the spectral band from 190 to 290 nm and persisted after the tissue was dehydrated. In the first experiment, using the Ho:YAG laser and with the laser‐fiber in direct contact with the LF, the lowest single‐pulse fluence for which LF was visibly removed was 35 J/cm². Testing was conducted at 6 fluences between 35 and 354 J/cm². Over this range the single‐pulse hole depth was shown to be near linear (R² = 0.9374, M = 1.6), ranging from 40 to 639 µm (N = 3). For the case where the laser‐fiber face was displaced 1 mm from the LF surface, the lowest single‐pulse fluence for which tissue was visibly removed was 72 J/cm². Testing was conducted at 4 energy densities between 72 and 180 J/cm². Over this range the single‐pulse hole depth was shown to be near linear (R² = 0.8951, M = 1.4), ranging from 31 to 220 µm (N = 3). In the second experiment, with LF in situ, constant flushing with room temperature saline was shown to drastically reduce surface temperature during exposure to Ho:YAG at 5 Hz with the laser‐fiber in direct contact with the LF. Without saline, over 1 minute of treatment with a per‐pulse fluence of 141 mJ/cm², the average maximum surface temperature measured 110°C. With 10 cc's of saline flushed over 1 minute and a per‐pulse laser fluence of 212 mJ/cm², the average maximum surface temperature was 35°C. In the third experiment, mass loss was shown to be linear over 450 pulses of 600 mJ from the Ho:YAG laser (212 J/cm², direct contact, N = 4; 108 J/cm², 1 mm standoff, N = 4). With the laser‐fiber in direct contact, an average of 53 mg was removed (R² = 0.996, M = 0.117) and with 1 mm laser‐fiber standoff, an average of 44 mg was removed (R² = 0.9988, M = 0.097). In the fourth experiment, 30 pulses of the Ho:YAG and Q‐Switched Ho:YAG lasers at 1 mm standoff, and 5 Hz produced similar hole depths for the tested fluences of 9 J/cm² (151 and 154 µm, respectively) and 18 J/cm² (470 and 442 µm, respectively), though the Ho:YAG laser produced significantly more carbonization around the rim of the laser‐hole. The increased carbonization was corroborated by higher measured LF temperature. In all tests with the Ho:YAG and Q‐Switched Ho:YAG, an audible photo‐acoustic affect coincided with the laser pulse. In the fifth experiment, with the frequency quadrupled Nd:YAG laser at 15 Hz for 450 pulses, ablation depth per pulse was shown to be linear for the fluence range of 0.18 – 0.73 J/cm² (R² = 0.989, M = 2.4). There was no noticeable photo‐acoustic effect nor charring around the rim of the laser‐hole.

Conclusion

The Ho:YAG, Q‐Switched Ho:YAG, and frequency quadrupled Nd:YAG lasers were shown to remove ligamentum flavum (LF). A single pulse of the Ho:YAG laser was shown to cause tearing of the tissue and a large zone of necrosis surrounding the laser‐hole. Multiple pulses of the Ho:YAG and Q‐Switched Ho:YAG lasers caused charring around the rim of the laser‐hole, though the extent of charring was more extensive with the Ho:YAG laser. Charring caused by the Ho:YAG laser was shown to be mitigated by continuously flushing the affected LF with saline during irradiation. The Nd:YAG laser was shown to ablate LF with no gross visible indication of thermal damage to surrounding LF. Lasers Surg. Med. 47:839–851, 2015. © 2015 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.     

Enhancement of tissue lesion depth by dual wavelength irradiation with the Nd-YAG/KTP laser: Perspectives for laser prostatectomy

The Nd-YAG/KTP laser coagulates and vaporizes prostate tissue. The objective of this study was to investigate the combined effects of both wavelengths and to determine the irradiation parameters allowing the largest lesion volume. Chicken breast tissue was irradiated ex vivo. Consecutive 1064 and 532 nm Nd-YAG/KTP laser irradiations were performed for different combinations (30 W/10 W, 20 W/20 W, 10 W/30 W) with variable total fluence (1200 J, 2400 J, 3600 J) and compared to isofluent single wavelengths at 40 W irradiation. The depths, diameters and volumes of the total lesion as well as the vaporization effects of the 532 nm wavelength on normal and on priorly coagulated tissue were analysed. Maximum total lesion depths (p< 0.001) were found under combined Nd-YAG/KTP (20 W/20 W) irradiation conditions. Ablation efficacy of the 532 nm wavelength was reduced after prior 1064 nm irradiation, but crater depths were increased. Dual wavelength irradiation with the Nd-YAG/KTP laser induces a specific denaturation process. This may represent a new approach to increase the depth of coagulation necrosis, and thus the treated volume, thereby improving long-term results.     

New alternatives for laser vaporization of the prostate: experimental evaluation of a 980-, 1,318- and 1,470-nm diode laser device

Purpose  

Several diode laser systems were introduced in recent years for the minimal-invasive surgical therapy of benign prostate enlargement. We investigated the ablation capacities, hemostatic properties and extend of tissue necrosis of different diode lasers at wavelengths of 980, 1,318 and 1,470 nm and compared the results to the 120 W GreenLight™ HPS laser.     

Characterization of a novel standardized human three‐dimensional skin wound healing model using non‐sequential fractional ultrapulsed CO2 laser treatments

Background and Objective

At present, there is no standardized in vitro human skin model for wound healing. Therefore, our aim was to establish and characterize an in vitro/ex vivo three‐dimensional (3D) wound healing model, which we employed to analyze the effects of dexpanthenol on wound healing and gene regulation.

Materials and Methods

The novel human 3D skin wound healing model using scaffold and collagen 3D organotypic skin equivalents was irradiated with a non‐sequential fractional ultrapulsed CO₂ laser. These standardized injured full‐thickness skin equivalents enable qRT–PCR, microarray, and histological studies analyzing the effect of topically or systemically applied compounds on skin wound healing.

Results

These human laser‐irradiated skin models were found to be appropriate for in vitro wound healing analysis. Topical treatment of skin wounds with a 5% dexpanthenol water‐in‐oil emulsion or two different 5% dexpanthenol oil‐in‐water emulsions clearly enhanced wound closure compared to laser‐irradiated untreated control models. To find out whether this positive effect is caused by the active substance dexpanthenol, laser‐irradiated skin models were cultured in calciumpantothenate containing medium (20 μg/ml) compared to skin equivalents cultured without calciumpantothenate. 3D models cultured in calciumpantothenate revealed considerably faster wound closure compared to the control models. Quantitative RT–PCR studies showed enhanced mRNA expression of MMP3, IL1α, keratin‐associated protein 4–12 (KRTAP4–12), and decreased expression of S100A7 in laser‐irradiated skin models cultured in medium containing calciumpantothenate.

Conclusion

This novel standardized human 3D skin wound healing model proves useful for topical pharmacological studies on wound healing and reveals new insights into molecular mechanisms of dexpanthenol‐mediated effects on wound healing. In addition, these novel 3D model systems can be used to monitor ex vivo effects of various laser systems on gene expression and morphology of human skin. Lasers Surg. Med. 47:257–265, 2015. © 2015 Wiley Periodicals, Inc.     

Dependence of laser photocoagulation on interstitial delivery parameters

Photocoagulation was performed ex vivo between tissue slabs by delivering continuous-wave laser energy from an optical fiber either directly, or by depositing the energy into a 2.4 mm diameter steel sphere at the fiber tip. The dependence of photocoagulation lesions on the following variables was assessed: (1) energy source: Nd:YAG-532 nm, 1,064 nm ± steel sphere, (2) tissue type: porcine muscle (light), bovine muscle (dark), (3) delivered power: P = 1.5–3.0 W (porcine), 1.0–2.5 W (bovine), (4) exposure duration: T = 300–1500 s. The resulting cross-sectional photocoagulation lesions are summarized as follows: 532 nm: elongated; central charring in all cases; 1,064 nm: circular; central charring only in bovine for P ? 2.0 W, T ? 500 s; sphere: circular; central charring in bovine for P ? 1.5 W and porcine for P ? 2.0 W. These experiments suggest photocoagulation lesion size decreases as optical penetration increases. The results indicate that interstitial laser photocoagulation lesions >10 mm diameter can be made without charring in both lightly and heavily pigmented tissues ex vivo by delivering 1,064 nm laser energy at sufficiently low power for at least 1,000 s from well-polished optical fibers. © 1994 Wiley-Liss, Inc.     

Transcranial laser stimulation improves human cerebral oxygenation

Background and Objective

Transcranial laser stimulation of the brain with near‐infrared light is a novel form of non‐invasive photobiomodulation or low‐level laser therapy (LLLT) that has shown therapeutic potential in a variety of neurological and psychological conditions. Understanding of its neurophysiological effects is essential for mechanistic study and treatment evaluation. This study investigated how transcranial laser stimulation influences cerebral hemodynamics and oxygenation in the human brain in vivo using functional near‐infrared spectroscopy (fNIRS).

Materials and Methods

Two separate experiments were conducted in which 1,064‐nm laser stimulation was administered at (1) the center and (2) the right side of the forehead, respectively. The laser emitted at a power of 3.4 W and in an area of 13.6 cm², corresponding to 0.25 W/cm² irradiance. Stimulation duration was 10 minutes. Nine healthy male and female human participants of any ethnic background, in an age range of 18–40 years old were included in each experiment.

Results

In both experiments, transcranial laser stimulation induced an increase of oxygenated hemoglobin concentration (Δ[HbO₂]) and a decrease of deoxygenated hemoglobin concentration (Δ[Hb]) in both cerebral hemispheres. Improvements in cerebral oxygenation were indicated by a significant increase of differential hemoglobin concentration (Δ[HbD] = Δ[HbO₂] ? Δ[Hb]). These effects increased in a dose‐dependent manner over time during laser stimulation (10 minutes) and persisted after laser stimulation (6 minutes). The total hemoglobin concentration (Δ[HbT] = Δ[HbO2] + Δ[Hb]) remained nearly unchanged in most cases.

Conclusion

Near‐infrared laser stimulation applied to the forehead can transcranially improve cerebral oxygenation in healthy humans. Lasers Surg. Med. 48:343–349, 2016. © 2016 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

     

Doppler-guided hemorrhoidal laser procedure for the treatment of symptomatic hemorrhoids: experimental background and short-term clinical results of a new mini-invasive treatment

Background  

According to the “vascular” theory, arterial overflow in the superior hemorrhoidal arteries would lead to dilatation of the hemorrhoidal venous plexus. A 980-nm diode laser-pulsed shot causes shrinkage of tissue. The depth of shrinkage can be regulated by the power and duration of the laser beam. Through a 1000-micron conic fiber, five laser shots generated at a power of 13 W with duration of 1.2 s each and a pause of 0.6 s caused shrinkage of tissues to the depth of approximately 5 mm. Terminal branches of the superior hemorrhoidal artery in the anal canal, if precisely identified through a Doppler signal, can be closed with the use of this laser.     

Erratum: Fiberoptic microneedles: Novel optical diffusers for interstitial delivery of therapeutic light

Background and Objectives

Photothermal therapies have limited efficacy and application due to the poor penetration depth of light inside tissue. In earlier work, we described the development of novel fiberoptic microneedles to provide a means to mechanically penetrate dermal tissue and deliver light directly into a localized target area. This paper presents an alternate fiberoptic microneedle design with the capability of delivering more diffuse, but therapeutically useful photothermal energy. Laser lipolysis is envisioned as a future clinical application for this design.

Materials and Methods

A novel fiberoptic microneedle was developed using hydrofluoric acid etching of optical fiber to permit diffuse optical delivery. Microneedles etched for 10, 30, and 50 minutes, and an optical fiber control were compared with three techniques. First, red light delivery from the microneedles was evaluated by imaging the reflectance of the light from a white paper. Second, spatial temperature distribution of the paper in response to near‐IR light (1,064 nm, 1 W CW) was recorded using infrared thermography. Third, ex vivo adipose tissue response during 1,064 nm, (5 W CW) irradiation was recorded with bright field microscopy.

Results

Acid etching exposed a 3 mm length of the fiber core, allowing circumferential delivery of light along this length. Increasing etching time decreased microneedle diameter, resulting in increased uniformity of red and 1,064 nm light delivery along the microneedle axis. For equivalent total energy delivery, thinner microneedles reduced carbonization in the adipose tissue experiments.

Conclusions

We developed novel microscale optical diffusers that provided a more homogeneous light distribution from their surfaces, and compared performance to a flat‐cleaved fiber, a device currently utilized in clinical practice. These fiberoptic microneedles can potentially enhance clinical laser procedures by providing direct delivery of diffuse light to target chromophores, while minimizing undesirable photothermal damage in adjacent, non‐target tissue. Lasers Surg. Med. 43:914‐920, 2011. © 2011 Wiley Periodicals, Inc.     

Comparison of two diode lasers on bactericidity in root canals—an in vitro study

This in vitro study compares two 810-nm and 940-nm diode lasers on bacterial kill in root canals of extracted human teeth and shows the clinical relevance of different treatment modalities. Ninety root canals of single-rooted human teeth were prepared up to ISO 70, steam sterilized, and assigned to two test groups (810 nm, 940 nm) and one control group. Following an initiatory experiment in which access opening of root canals and surrounding cavity were excluded from irradiation in the main experiment, 60 teeth were inoculated with 2 μl of either Escherichia coli or Enterococcus faecalis suspension. Laser irradiation was performed, additionally including access opening of root canals and surrounding cavity in the laser treatment. Excluding access opening of root canals and surrounding cavity from the laser treatment, the diode laser achieved an average bacterial reduction of Escherichia coli of 76.06% (810 nm) and 68.15% (940 nm), while including access cavities showed an average bacterial reduction of Escherichia coli of 97.84% (810 nm) and 98.83% (940 nm) and an average bacterial reduction of Enterococcus faecalis of 98.8% (810 nm) and 98.66% (940 nm). Diode laser wavelengths are effective in endodontic therapy. It seems to be clinically relevant that additional irradiation of the access cavity produces significantly better bactericidal results.