Energy deposition profile in human skin upon irradiation with a 1,342 nm Nd:YAP laser

Background and Objectives

Nd:YAP laser emitting at 1,342 nm appears promising for nonablative skin rejuvenation treatment, based on favorable absorption properties of water and melanin in this part of the spectrum. A quantitative determination of energy deposition characteristics of Nd:YAP in normal human skin should enable design of a safe and effective treatment protocol for future human studies.

Study Design

Energy deposition profile of a prototype Nd:YAP laser was determined using pulsed photothermal radiometry. This technique involves time‐resolved measurement of mid‐infrared emission from a sample after pulsed laser irradiation. The laser‐induced temperature depth profile is reconstructed from the radiometric transients using a custom optimization algorithm, developed and tested earlier in our group. Measurements were performed on the extremities of four healthy volunteers at low radiant exposure (2.8 J/cm²). For the purpose of comparison, energy deposition characteristics of commercial Nd:YAG and KTP lasers (at 1,064 and 532 nm, respectively), were also determined at the same test sites.

Results

On average, the Nd:YAP laser deposits 50% of the absorbed energy within the top 0.36 mm of skin and 90% within 0.86 mm, which is significantly shallower than the Nd:YAG laser. The ratio between the dermal versus epidermal heating is more favorable and shows a smaller inter‐ and intra‐patient variance as compared to both Nd:YAG and KTP laser.

Conclusions

Energy deposition characteristics of the 1,342 nm Nd:YAP laser are very suitable for controlled heating of the upper dermis, as required for nonablative skin rejuvenation. The risks of overheating the epidermis or subcutis should be significantly reduced in comparison with the 1,064 nm Nd:YAG laser. Lasers Surg. Med. 45: 8–14, 2013. © 2012 Wiley Periodicals, Inc.     

倍频Nd:YAG激光治疗毛细血管扩张133例

目的:观察Versapulse可调长脉宽倍频Nd:YAG532nm激光(VPW532)治疗毛细血管扩张的疗效及安全性。方法:使用VPW532激光治疗毛细血管扩张133例,观察其疗效和不良反应。结果:133例患者中,应用VPW532激光治疗1～3次后,治愈104例,显效20例,有效9例,总有效率达93.2%。仅有6例出现暂时性色素沉着,均无瘢痕形成。结论:VPW532激光治疗毛细血管扩张疗效显著,副作用轻微。     

The Nd:YAG laser in neurological surgery

The Nd:YAG laser has been applied in microneuro-surgery and has been found to be quite effective in removing had and hemorrhagic tumors such as meningiomas, tumors of the deep skull base, or tumors deep in the ventricle. Another indication for the use of the Nd:YAG laser is to open the thick sellar floor in transsphenoidal operations.     

Nd:YAG laser excision of a giant gingival pyogenic granuloma of pregnancy

A 19-year-old Hispanic nullipara experienced the rapid growth of an oral lesion on the right lower gingiva which she had first noticed at 29 weeks gestation. The lesion interfered with oral hygiene and eating. At surgery, the lesion measured 3.5 × 2.5 × 2.0 cm. Biopsy confirmed a pyogenic granuloma (“granuloma gravidarum”). Panorex films showed no bony invasion. The lesion was excised using the Nd:YAG laser under general anesthesia when the patient had reached 36 3/7 weeks gestation. We chose the Nd:YAG laser over the CO₂ laser for the removal of this very vascular lesion, because of its superior coagulation characteristics. This technique results in removal of the lesion with less danger of bleeding than with any other surgical technique. The patient did well postoperatively, delivered a healthy 3,884 g infant at 40 6/7 weeks gestation, and has had no recurrence after 15 months of follow-up. © 1994 Wiley-Liss, Inc.     

Far-ultraviolet laser ablation of the cornea: photoacoustic studies

Wide bandwidth piezoelectric transducers made of thin (9 microns) polyvinylidene fluoride film have been used to make time-resolved measurements of the stress-wave generated by far-ultraviolet (193 nm) laser ablation in corneal tissue in vitro. At high fluence (approximately 250 mJ/cm2), ablation commences within 10 ns (+/- 5 ns) of the laser pulse and generates short acoustic impulses (approximately 30 ns). The time profile of the ablation, when coupled to the energy requirements for ablation from earlier work, allows the estimation of a temperature and a half-life for the thermal decomposition of the collagen in cornea. These values do not support a photothermal mechanism for the ablation under the experimental conditions.     

Clinical application of Nd:YAG laser for the treatment of small hepatocellular carcinoma with new shaped laser probe

BACKGROUND AND OBJECTIVES: Surgical resection of hepatocellular carcinoma (HCC) is not always regarded as the first choice of treatment, because most HCCs develop in cirrhotic liver. It becomes adaptation of minimally invasive treatments for HCC. In animal experiments, we previously reported that our newly developed neodymium:yttrium aluminum garnet (Nd:YAG) laser system could ablate liver tissue in short periods. STUDY DESIGN/PATIENTS AND METHODS: Six HCC cases (mean diameter; 16.3 +/- 3.50 mm) were enrolled. The Nd:YAG laser generator with a wavelength of 1,064 nm at 10 W of power emitted the laser in a forward fashion and in all patients the laser beam safely irradiated the target lesion. RESULTS: There was no recurrence of HCC in the laser-ablated area in six patients for duration of 21.8+/- 4.35 months. A local recurrence was found in only one patient. CONCLUSIONS: This study showed the clinical usefulness of laser ablation in the treatment of HCC.     

Laser resection technique and results of multiple lung metastasectomies using a new 1,318 nm Nd:YAG laser system

BACKGROUND AND OBJECTIVES: Advantages of a new 1,318 nm Nd:YAG laser based on multiple lung metastasectomies are shown. STUDY DESIGN/MATERIALS AND METHODS: Ninety-three percent of 328 patients with metastases (8/patient, range 1-124) had precision laser resections (lobectomy-rate reduced to 7%); this laser delivers 20 kW/cm(2) 1,318 nm power densities with 400 microm fibers, and a focussing handpiece. Absorption in water is tenfold higher. RESULTS AND CONCLUSIONS: Between 1/1996 and 12/2003 in 328 patients (164 males/females, 61 years) 3,267 nodules were removed. Pathologic examination revealed 2,546 metastases (range 3-80 mm) from kidney (n = 112), colorectal (n = 91), and breast cancers (n = 35). In 85% of patients where the complete resection was achieved the 5-year survival was 41%. For remaining 15% (incomplete resection) the 5-year survival was 7%. Five-year survival for patients with 10 (and more) metastases was 28%, for patients with 20 (and more) was 26%. No 30-day mortality was observed. CONCLUSION: This new laser system facilitates any kind of parenchymal lung resection in lobe-sparing manner and in case of complete resection improves significantly the survival.     

长脉宽1064nmNd：YAG激光治疗儿童皮肤血管瘤的疗效

目的探讨长脉宽1064nmNd：YAG激光治疗儿童皮肤血管瘤的疗效和不良反应。方法将207例血管瘤患者（164例为增生期,43例为静止期）分为两组：A组为皮损完全位于皮肤（142例）;B组为部分皮损位于皮下（65例）,使用长脉宽1064nmNd：YAG激光治疗。分别选择光斑直径2、6mm,能量50～90J／cm2和脉宽10、40、60ms进行治疗,治疗间歇期为1个月。结果207例经1～6次治疗后．两组总有效率均为100％。两组治疗有效率的差异无统计学意义（P〉0．05）。不良反应率为11．6％,均可以逐渐恢复。结论长脉宽1064nmNd：YAG激光治疗浅表型皮肤血管瘤疗效显著,不良反应少且短暂。     

Wavelength dependence of pulsed laser ablation of calcified tissue

Pulsed laser ablation of calcified biological tissue was studied at several wavelengths in the near-ultraviolet, visible, near- and mid-infrared regions of the spectrum. The primary tissue model was bovine shank bone, while human arterial calcified plaque and normal human artery wall were also studied at selected wavelengths for comparison. Laser irradiances were on the order of MW/mm², fluences ranged up to 1000 mJ/mm², and repetition rates varied between 0.3–10 Hz. Spot sizes on the tissue surface ranged from 150 to 850 μm. Laser craters made with wavelengths between λ=295 nm and λ=375 nm and in the λ =3 pm region exhibited the highest quality ablation with clean, sharp cuts following closely the spatial contour of the incident beam. Craters drilled with visible wavelengths between λ =450 nm and λ =590 nm were generally larger than the incident laser beam spot, irregular in shape and often surrounded by large flakes of tissue debris. Ablation fluence thresholds increased with wavelength through the visible wavelengths and into the mid-infrared, but dropped to their lowest values near λ=3 pm. Fluence thresholds obtained with the tissue under a 1 mm depth of saline were approximately twice air thresholds. Ablation yields also varied with wavelength, probably due to increased scattering in the visible region, and were the same under saline as in air.     

Femtosecond laser corneal ablation threshold: dependence on tissue depth and laser pulse width

BACKGROUND AND OBJECTIVE: Diode pumped, all-solid-state ultrafast lasers are now widely used to perform minimally invasive refractive surgery and keratoplasty procedures. Despite such use, a systematic study concerning ultrafast laser-tissue interactions is lacking. We determined the corneal ablation threshold as a function of the laser pulse width and stromal depth by simultaneous monitoring of the intensity of the laser-induced plasma and the second harmonic generation signals (SHG) from the collagen. STUDY DESIGN/MATERIALS AND METHODS: Ablation thresholds in porcine cornea samples were determined using three diode pumped all-solid-state ultrafast lasers (a Nd:glass femtosecond laser, a Yb:KYW femtosecond laser, and a Nd: YAG picosecond laser) over a range from 800 femtoseconds to 20 picoseconds. RESULTS: Corneal ablation threshold remained nearly constant within the first 200 microm of stroma and was consistent with previous findings with the threshold proportional to the square root of the laser pulse width. CONCLUSION: Corneal ablation thresholds can be precisely determined by simultaneous monitoring of the intensity of the laser-induced plasma and the SHG from the cornea.     

A model for thermal ablation of biological tissue using laser radiation

We present a theory of thermal laser ablation based on the heat equation and on an energy balance equation derived from it. Ablation is assumed to be brought about by the heating and evaporation of tissue water. The model is three-dimensional, and scattering and the water-steam phase transition are explicitly taken into account. The model predicts threshold parameters and a steady-state ablation velocity in terms of the optical and thermal properties of the tissue and the laser beam intensity and spot diameter.     

Selective ablation of surface enamel caries with a pulsed Nd:YAG dental laser

BACKGROUND AND OBJECTIVE: High intensity infrared light from the pulsed Nd:YAG dental laser is absorbed by carious enamel and not absorbed by healthy enamel. Consequently, this system has potential for selective removal of surface enamel caries. Safety and efficacy of the clinical procedure was evaluated in two sets of clinical trials at three dental schools. Selective ablation was evaluated with FTIR spectroscopy. STUDY DESIGN/MATERIALS AND METHODS: Carious lesions were randomized to drill or laser treatment. Pulp diagnosis, enamel surface condition, preparations, and restorations were evaluated by blinded evaluators. In Study I, surface caries were removed from 104 third molars scheduled for extraction. One-week post-treatment teeth were evaluated clinically, extracted, and the pulp was examined histologically. In Study II, 90 patients with 462 lesions on 374 teeth were randomized to laser or drill and followed for 6 months. RESULTS: Pulsed Nd:YAG laser removal of surface enamel caries was demonstrated to be both safe and effective. Caries were removed in all conditions. There were no adverse events and both clinical and histological evaluations of pulp vitality showed no abnormalities. A significantly greater number of preparations in the drill groups vs. laser groups entered dentin (drill = 11, laser = 1, P = 0.007). CONCLUSION: The more conservative laser treatment removed the caries but not the sound enamel below the lesion. The pulsed Nd:YAG dental laser was found to be both safe and effective for surface caries removal.     

Selective removal of residual composite from dental enamel surfaces using the third harmonic of a Q-switched Nd:YAG laser

BACKGROUND AND OBJECTIVE: Conventional methods of residual composite removal after the debonding of orthodontic brackets involve the use of abrasives that damage the underlying enamel. The objective of this study was to demonstrate that 355-nm laser pulses with a pulse width of 10 ns are well suited for the removal of composite through selective laser ablation. STUDY DESIGN/MATERIALS AND METHODS: The residual composite remaining on the surface of extracted human third molars and bovine incisors was removed using multiple laser pulses from the third harmonic (355-nm) of a Q-switched Nd:YAG laser. RESULTS: There is selective ablation of composite from the enamel surface without any discernable damage to the underlying enamel. CONCLUSION: This study demonstrates that 355-nm, 10 ns laser pulses can be used for the selective ablation of dental composite without thermal or mechanical damage to the underlying enamel.     

Endoscopic Nd:YAG laser surgery on malignant and benign lesions of the trachea and carina

A total of 47 patients with malignant and benign lesions in the trachea and carina were used to demonstrate the effectiveness of endoscopic Nd:YAG laser surgery. The histology consisted of 37 malignant and 10 benign lesions, and 23 of the patients had severe symptoms with laser surgery being performed as a lifesaving emergency. Endoscopic Nd:YAG laser treatment was able to dilate the tracheal calibers from, 2.6±0.9 mm to 6.1±1.4 mm in the emergency cases with a remarkable effect and brought relief from wheezing and dyspnea, with an objective improvement of more than 25 per cent in peak expiratory flow rate being demonstrated. Furthermore, the tracheal diameters were able to be dilated from about 7 mm to 10 mm in the non-emergency cases. A remarkable effect was achieved in patients with intraluminal or mixed types of tumors among both the emergency and non-emergency cases. The survival rates of the emergency patients in whom a remarkable effect was achieved were definitely better than those in whom only fair or poor effects were achieved and, in the non-emergency cases, similar results were demonstrated. In conclusion, the application of endoscopic Nd:YAG laser surgery to tracheal stenotic diseases has an instantaneous and definite effect on luminal dilatation and shows significance as a lifesaving procedure. Moreover, the resultant improvement in the patients' general condition could make it possible for them to undergo other combined therapy and prolong their life span. Endoscopic Nd:YAG laser surgery is thus considered to be a very effective and established procedure for the treatment of tracheal stenotic lesions.     

无表皮剥脱1 320nm Nd:YAG激光治疗面颈部皱纹

目的:观察1320nmNd:YAG激光治疗面颈部皱纹临床效果。方法:采用1320nmNd:YAG激光对面颈部皱纹进行治疗,每5￣6次为一个疗程,治疗间隔时间3￣4周,随后建议每6￣12个月维持治疗1次,患者和医生共同对疗效进行评价。结果:65例患者,其中满意55例,满意率84.6%,有效率100%。结论:1320nmNd:YAG激光治疗面颈部皱纹安全、疗效肯定,效果满意,尤其适合于静态性皱纹的治疗。     

强脉冲光及Nd:YAG(1064nm)激光治疗皮肤血管瘤疗效观察

目的:评价应用强脉冲光及Nd:YAG(1064nm)激光治疗皮肤血管瘤的临床效果。方法:回顾并随访2006年1月～2010年12月在笔者科室采用强脉冲光及Nd:YAG(1064nm)激光治疗的476例皮肤血管瘤患者,对其疗效进行分析。结果:随访2年,皮肤浅表血管瘤治愈率为88.4%,有效率为10.7%,深浅混合血管瘤联合药物注射治疗的治愈率为78.4%、有效率为17.6%,副作用轻微。结论:强脉冲光及Nd:YAG(1064nm)激光治疗皮肤血管瘤疗效好、治疗次数少、安全性高,值得推广。     

Holmium:YAG laser ablation of vascular tissue

The ablation of atherosclerotic lesions without collateral thermal or shock wave damage is thought to be a key element for successful laser angioplasty. This study evaluated the effectiveness of pulsed holmium:YAG laser (2.1 microns wavelength) for this application. Fresh normal tissue (n = 139) and arteriosclerotic canine arteries (n = 21) as well as formalin-preserved normal canine (n = 31) and atherosclerotic human arteries (n = 177) were irradiated under saline via a 600 microns diameter fiber placed perpendicular to the intimal surface with 0-10 gm of force. The laser was operated in the free running mode (FRM; 250 microseconds pulsewidth, 5 Hz, 30-7,100 mJ/mm2) and in the Q-switched mode (QSM; 200 nsec pulsewidth, 6 Hz, 30-1,100 mJ/mm2). Following the experiments, the samples were prepared for histologic and morphometric analysis. Ablation thresholds in the FRM were 60 and 180 mJ/mm2 in fresh and preserved canine tissue, respectively. Ablation thresholds in the QSM for fresh and preserved canine tissues were 75 and 180 mJ/mm2, respectively. Thresholds for human atherosclerotic tissue were dependent on the amount of calcification. In the QSM and FRM, there were no samples that could not be penetrated at 1,100 mJ/mm2 and above. Histologic examination of the FRM samples revealed confined columns of tissue ablation, with approximately 55-250 microns and 70-140 microns zones of thermal effect being apparent in the fresh and formalin-preserved samples, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)