Scatter-limited phototherapy: a model for laser treatment of skin

Optimized selection of neodymium laser parameters for successful enlarged veins treatment

Full clearance and no side effects method of treating enlarged veins was successfully accomplished by one laser session. This is the ambition and dream of both dermatologists and patients. Most vascularity treatment protocols had shown some unpleasant adverse effects. The purpose of the present work is to work out, in advance, the accurate dose of laser pulse duration and fluence in order to treat varicose veins in the face, arms and legs with no adverse effects. This mission required the calculation of the exact rise in temperature of the enlarged vein; prior to laser treatment. These pre-calculated temperature rise values were tested on 20 subjects in order to have the best clinical outcomes; using fundamental frequency (1064 nm) pulsed Nd: YAG laser. This work necessitated the use of pulse length (15-30 ms), spot size (3, 5 mm), fluence (110-190 J/cm2) and skin cooling temperature (3-18 °C). Cooling of the skin before and after the treatment was needed to guarantee ultimate impactful results without side effects.

Fluorescence imaging reversion using spatially variant deconvolution

Fluorescence imaging opens new possibilities for intraoperative guidance and early cancer detection, in particular when using agents that target specific disease features. Nevertheless, photon scattering in tissue degrades image quality and leads to ambiguity in fluorescence image interpretation and challenges clinical translation. We introduce the concept of capturing the spatially-dependent impulse response of an image and investigate Spatially Adaptive Impulse Response Correction (SAIRC), a method that is proposed for improving the accuracy and sensitivity achieved. Unlike classical methods that presume a homogeneous spatial distribution of optical properties in tissue, SAIRC explicitly measures the optical heterogeneity in tissues. This information allows, for the first time, the application of spatially-dependent deconvolution to correct the fluorescence images captured in relation to their modification by photon scatter. Using experimental measurements from phantoms and animals, we investigate the improvement in resolution and quantification over non-corrected images. We discuss how the proposed method is essential for maximizing the performance of fluorescence molecular imaging in the clinic.

In Vivo Investigation of the Safety and Efficacy of Pulsed Dye Laser with Two Spot Sizes in Port-Wine Stain Treatment: A Prospective Side-by-Side Comparison

OBJECTIVE

Pulsed dye laser (PDL) with 7 and 10 mm spot sizes is widely used on a regular basis for the treatment of port-wine stain (PWS).

BACKGROUND DATA

No studies have reported on the differences in efficacy outcomes resulting from the use of different laser spot sizes in the treatment of PWS by PDL. Thus, an in vivo investigation into the differences in safety and efficacy of treatment between two spot sizes (7 vs. 10 mm) of PWS by PDL was conducted.

MATERIALS AND METHODS

A total of 35 PWS patients underwent three treatment sessions by using a 595 nm wavelength PDL (Vbeam^®, Candela Corp) with two laser settings: (1) 7 mm spot size, radiant exposure of 12 J/cm² and (2) 10 mm spot size, radiant exposure of 10 J/cm². Cryogen spray cooling and 1.5 msec pulse duration were applied. Therapeutic outcomes were evaluated by visual and chromametric evaluation 3 months after the final treatment.

RESULTS

Average blanching rates were 34.03% and 36.51% at sites treated by PDL with 7 and 10 mm laser spot sizes, respectively (p < 0.05).

CONCLUSIONS

On the basis of the laser setting, the therapeutic outcomes of PDL with 7 and 10 mm spot sizes were similar. PDL with a 10 mm laser spot size is more efficacious with lower radiant exposure than PDL with a 7 mm spot size; it can also reduce the treatment time.

Light and energy based therapeutics for genitourinary syndrome of menopause: Consensus and controversies

Gynecologist and plastic surgeons pioneered the application of lasers in medicine and surgery almost 5 decades ago, initially used to treat cervical and vaginal pathologies. Ever since, energy-based devices have been deployed to treat pelvic pathologies and improve fertility. Recent technological developments triggered an unprecedented wave of publications, assessing the efficacy of fractional laser, and radiofrequency on the vaginal wall in reversing natural aging processes. Studies have shown that a certain degree of thermal energy deposited on the vaginal wall stimulates proliferation of the glycogen-enriched epithelium, neovascularization, and collagen formation in the lamina propria, and improves natural lubrication and control of urination. This review aimed to review such data and to guide future research. A unique assembly of experts from around the globe, compiled and edited this manuscript based on a thorough literature review and personal experience. Lasers Surg. Med. 49:137-159, 2017. © 2017 Wiley Periodicals, Inc.

Selective photoantisepsis

BACKGROUND AND OBJECTIVE

Selective killing of pathogens by laser is possible due to the difference in absorption of photon energy by pathogens and host tissues. The optical properties of pathogenic microorganisms are used along with the known optical properties of soft tissues in calculations of the laser-induced thermal response of pathogen colonies embedded in a tissue model. The objective is to define the laser parameters that optimize pathogen destruction and depth of the bactericidal effect.

MATERIALS AND METHODS

The virtual periodontium is a computational model of the optical and time-dependent thermal properties of infected periodontal tissues. The model simulates the periodontal procedure: Laser Sulcular Debridement.¹ Virtual pathogen colonies are placed at different depths in the virtual periodontium to determine the depth for effective bactericidal effects given various laser parameters (wavelength, peak power, pulse duration, scan rate, fluence rate) and differences in pathogen sensitivities.

RESULTS

Accumulated background heat from multiple passes increases the depth of the bactericidal effect. In visible and near-IR wavelengths the large difference in absorption between normal soft tissue and Porphyromonas gingivalis (Pg) and Prevotella intermedia (Pi) results in selective destruction. Diode laser (810 nm) efficacy and depth of the bactericidal effect are variable and dependent on hemin availability. Both pulsed-Nd:YAG and the 810 nm diode lasers achieve a 2-3 mm deep damage zone for pigmented Pg and Pi in soft tissue without surface damage (selective photoantisepsis). The model predicts no selectivity for the Er:YAG laser (2,940 nm). Depth of the bactericidal effect is highly dependent on pathogen absorption coefficient. Highly sensitive pathogens may be destroyed as deep as 5-6 mm in soft tissue. Short pulse durations enable confinement of the thermal event to the target. Temporal selectivity is achieved by adjusting pulse duration based on target size.

CONCLUSION

The scatter-limited phototherapy model of the infected periodontium is applied to develop a proper dosimetry for selective photoantisepsis. Dosimetry planning is essential to the development of a new treatment modality. Lasers Surg. Med. 48:763-773, 2016. © 2016 Wiley Periodicals, Inc.

Why do port-wine stains (PWS) on the lateral face respond better to pulsed dye laser (PDL) than those located on the central face?

BACKGROUND

After pulsed dye laser (PDL) treatment, facial lateral port-wine stains (PWS) clear quicker and more completely than central PWS do.

OBJECTIVE

We sought to investigate whether the difference in the efficacy of the treatment between central and lateral facial PWS was related to different histologic manifestations.

METHOD

Thirteen patients with PWS had biopsies and underwent PDL treatments in both central and lateral areas of the face. The hypothesis was tested by correlating the PWS response to PDL with the depth and diameter of the PWS vessels. The clinical efficacy was assessed by chromameter 2 months after the final PDL treatment, whereas diameter and depth of PWS vessels were measured in biopsy specimens.

RESULTS

All patients were treated on central and lateral facial sites. The chromameter evaluation showed that the average blanching rate was 34.01% and 8.68% for lateral and central facial sites, respectively (P < .05), which suggests a better response to PDL treatment in the lateral than in the central area. Histologic manifestations showed that vessels in the lateral regions were primarily located in the papillary dermis, whereas in the central regions they were extensively distributed from the dermis into the subcutaneous tissue.

LIMITATIONS

The small number of cases included in this study and the lack of follow-up longer than 2 months constitute limitations.

CONCLUSION

Lateral facial PWS respond better to PDL than PWS located in the central face. Differences in vessel location and diameter may be responsible for the variations in PWS response to PDL.

Low-level laser irradiation promotes the proliferation and maturation of keratinocytes during epithelial wound repair

Low-level laser therapy (LLLT) has been extensively employed to improve epithelial wound healing, though the exact response of epithelium maturation and stratification after LLLT is unknown. Thus, this study aimed to assess the in vitro growth and differentiation of keratinocytes (KCs) and in vivo wound healing response when treated with LLLT. Human KCs (HaCaT cells) showed an enhanced proliferation with all the employed laser energy densities (3, 6 and 12 J/cm(2) , 660 nm, 100 mW), together with an increased expression of Cyclin D1. Moreover, the immunoexpression of proteins related to epithelial proliferation and maturation (p63, CK10, CK14) all indicated a faster maturation of the migrating KCs in the LLLT-treated wounds. In that way, an improved epithelial healing was promoted by LLLT with the employed parameters; this improvement was confirmed by changes in the expression of several proteins related to epithelial proliferation and maturation. Immunofluorescent expression of cytokeratin 10 (red) and Cyclin D1 (green) in (A) Control keratinocytes and (B) Low-level laser irradiated cells. Blue color illustrates the nuclei of the cells (DAPI staining).

Laser acupuncture for the treatment of asthma in children: a systematic review of randomized controlled trials

BACKGROUND AND OBJECTIVES

Laser acupuncture has often been recommended as a treatment of asthma. The technique is noninvasive, and seems particularly suitable for children. However, the results from several clinical trials are contradictory. The objective of this review was to assess the effectiveness of laser acupuncture in the treatment of childhood asthma.

METHODS

Literature searches of electronic database were conducted in The Cochrane Library, Medline, EMBASE, AMED, CINAHL, and two Chinese literature databases (CNKI and VIP) up to February 2012. Randomized controlled trials (RCTs) testing laser acupuncture for asthma in children were included. No language restrictions were applied. Three authors independently selected articles, extracted data, and assessed trial quality.

RESULTS

Our searches identified 13 potential eligible studies, of which three with a total number of 176 patients met our inclusion criteria. The quality of included RCTs were low. One RCT with a parallel group design showed positive results, while two crossover RCTs generated negative results. There was variation in the type of patients, the interventions, and outcome measures. Because of the significant clinical and methodological heterogeneity, no meta-analysis was performed.

CONCLUSIONS

The number of RCTs and their total sample sizes are small; and their methodological quality is low. Therefore, no compelling evidence exists to suggest that laser acupuncture is not an effective treatment for childhood asthma. Further rigorous studies are warranted.

Removal of out-of-plane fluorescence for single cell visualization and quantification in cryo-imaging

We developed a cryo-imaging system, which alternates between sectioning (10-40 microm) and imaging bright field and fluorescence block-face image volumes with micron-scale-resolution. For applications requiring single-cell detection of fluorescently labeled cells anywhere in a mouse, we are developing software for reduction of out-of-plane fluorescence. In mouse experiments, we imaged GFP-labeled cancer and stem cells, and cell-sized fluorescent microspheres. To remove out-of-plane fluorescence, we used a simplified model of light-tissue interaction whereby the next-image was scaled, blurred, and subtracted from the current image. We estimated scaling and blurring parameters by minimizing an objective function on subtracted images. Tissue-specific attenuation parameters [micro(T): heart (267 +/- 47.6 cm(-1)), liver (218 +/- 27.1 cm(-1)), brain (161 +/- 27.4 cm(-1))] were found to be within the range of estimates in the literature. "Next-image" processing removed out-of-plane fluorescence equally well across multiple tissues (brain, kidney, liver, etc.), and analysis of 200 microsphere images gave 97 +/- 2% reduction of out-of-plane fluorescence. Next-image processing greatly improved axial-resolution, enabled high quality 3D volume renderings, and improved automated enumeration of single cells by up to 24%. The method has been used to identify metastatic cancer sites, determine homing of stem cells to injury sites, and show microsphere distribution correlated with blood flow patterns.

CO2 laser cryptolysis by coagulation for the treatment of halitosis

OBJECTIVE

The aim of this study was to evaluate the impact of CO(2) laser cryptolysis by coagulation (LCC) treatment in the volatile sulphur compounds (VSC) halitometry in patients with chronic caseous tonsillitis (CCT).

BACKGROUND DATA

Caseum retention and halitosis characterize CCT. Failure of clinical treatment indicated tonsillectomy. Recently, a conservative new treatment, CO(2 )LCC, has been introduced. It is painless and opens the crypt ostium, thus avoiding caseum retention. Halitometry is an objective new method for halitosis diagnosis. It measures VSC in parts per billion (ppb) in breathed air.

METHODS

Thirty-eight patients with CCT and complaints of halitosis were selected, underwent physical examination and halitometry measurements, and then received four sessions of LCC. The laser technique consisted of 6-W applications, in scanned and unfocused mode, around crypts, following the shape of their openings (fluence 54.5 joules/cm(2)) and, afterwards, over the entire tonsillar surface (fluence 18 joules/cm(2)). Halitometries were done before each LCC session.

RESULTS

LCC was well tolerated by all patients, and all patients showed improvement in halitosis after LCC treatment. Eight patients (21%) had abnormal halitometry (>150 ppb) before treatment, but after LCC sessions their halitometry values became normal. These patients had caseum at examination. VSC measurement was reduced by 30.1%, and caseum retention was significantly decreased in this group.

CONCLUSION

Abnormal halitometry in this population is related to the presence of caseum. LCC is safe, well tolerated, and improves complaints of halitosis in patients with CCT. Improvement was related to a decrease in caseum retention. Patients with abnormal halitometry had VSC halitometry improvement of approximately 30%.

Repetitive Er:YAG laser irradiation of human skin: a histological evaluation

BACKGROUND AND OBJECTIVE

Deep coagulation of skin collagen by Er:YAG laser repetitive pulses has been predicted by previous theoretical models and later demonstrated on animal skin. The goal of this study was to determine the effect of repetitive Er:YAG laser pulses on human skin and its response to this treatment.

STUDY DESIGN/MATERIALS AND METHODS

Lid skin of six female volunteers with blepharochalasis has been treated with laser at day 0, 7, and 21 before elective surgery-blepharoplasty. The treated skin was excised as part of the procedure and prepared for further histological examination. We used a 2,940 nm Er:YAG laser (Fidelis M320A by Fotona) with 'smooth' mode parameters: fluence from 0.50 to 2.00 J/cm2; six pulses per packet; 550 microsecond/pulse, 250 millisecond/packet; single pass, no overlapping; spot size 5 mm; repetition rate 20 Hz.

RESULTS

We observed deep collagen denaturation at laser fluences of 1.25 J/cm2 and over; epidermal damage was proportional to fluence with total coagulation of the epidermal layer at fluences of 1.75 J/cm2 and over. At day 7 after laser treatment we observed a complete regeneration of the epidermal layer and a regeneration zone within the dermis with prominent infiltration of CD68+ monocytes/macrophages. At day 21 after laser treatment we observed collagen remodeling and (myo-)fibroblast proliferation at tissue depths of up to 240 microm.

CONCLUSIONS

Repetitive Er:YAG laser irradiation is effective in deep denaturation and remodeling of human skin collagen in vivo, with less epidermal damage compared to standard Er:YAG laser skin resurfacing.

Laser acupuncture: past, present, and future

Laser acupuncture is defined as the stimulation of traditional acupuncture points with low-intensity, nonthermal laser irradiation. Although the therapeutic use of laser acupuncture is rapidly gaining in popularity, objective evaluation of its efficacy in published studies is difficult because treatment parameters such as wavelength, irradiance, and beam profile are seldom fully described. The depth of laser energy transmission, likely an important determinant of efficacy, is governed not only by these parameters, but also by skin properties such as thickness, age, and pigmentation-factors which have also received little consideration in laser acupuncture. Despite the frequently equivocal nature of the published laser studies, recent evidence of visual cortex activation by laser acupuncture of foot points, together with the known ability of laser irradiation to induce cellular effects at subthermal thresholds, provides impetus for further research.

Histopathological evaluation in biopsies of palatine tonsils submitted to cryptolysis by coagulation with CO2 laser for treatment of chronic caseous tonsillitis

OBJECTIVE

To perform histopathological evaluation in biopsies of palatine tonsils in a group of patients, with symptoms of chronic caseous tonsillitis, treated with an innovative and conservative method, using CO(2) laser.

BACKGROUND DATA

In general, the treatment of chronic caseous tonsillitis with CO(2) laser, as described in the literature, refers to the clinical experience of the authors and, the technique used for criptolysis encourages tissue vaporization, which leads to the consequent reduction of the tonsillar parenchyma.

MATERIALS AND METHODS

The individuals were submitted to cryptolysis coagulation with only 6 W of CW, CO(2) laser power, in scanned and unfocused mode, over a mean area of 2.2 mm diameter, leading to energy doses from 18 to 54.5 joules/cm(2). Biopsies were performed at the beginning and end of each treatment. A comparative analysis was performed between the initial and final biopsies taking into consideration possible alterations in the following: germinal centers, lymphoid tissue, sub-epithelial fibrosis, and parenchyma fibrosis.

RESULTS

The histopathological analysis of these biopsies showed that the laser, used at a specific energy density, could relieve the symptoms of the disease causing neither increase of the fibrotic content nor decrease of the lymphoid structure. The action of the laser, following the proposed technique, is superficial, causing only epithelial coagulation, which enables a weakening of the tension forces in the crypt borders, causing them to open. This effect results in the reduction and even disappearance of caseous retention.

CONCLUSION

We, therefore, conclude that the proposed method of treatment with CO(2) laser, called laser cryptolysis by coagulation (LCC) is an effective and conservative method, causing no significant morphological alterations to the tonsils.

Can thermal lasers promote skin wound healing?

Lasers are now widely used for treating numerous cutaneous lesions, for scar revision (hypertrophic and keloid scars), for tissue welding, and for skin resurfacing and remodeling (wrinkle removal). In these procedures lasers are used to generate heat. The modulation of the effect (volatilization, coagulation, hyperthermia) of the laser is obtained by using different wavelengths and laser parameters. The heat source obtained by conversion of light into heat can be very superficial, yet intense, if the laser light is well absorbed (far-infrared:CO(2) or Erbium:Yttrium Aluminum Garnet [Er:YAG] lasers), or it can be much deeper and less intense if the laser light is less absorbed by the skin (visible or near-infrared). Lasers transfer energy, in the form of heat, to surrounding tissues and, regardless of the laser used, a 45-50 degrees C temperature gradient will be obtained in the surrounding skin. If a wound healing process exists, it is a result of live cells reacting to this low temperature increase. The generated supraphysiologic level of heat is able to induce a heat shock response (HSR), which can be defined as the temporary changes in cellular metabolism. These changes are rapid and transient, and are characterized by the production of a small family of proteins termed the heat shock proteins (HSP). Recent experimental studies have clearly demonstrated that HSP 70, which is over-expressed following laser irradiation, could play a role with a coordinated expression of other growth factors such as transforming growth factor (TGF)-beta. TGF-beta is known to be a key element in the inflammatory response and the fibrogenic process. In this process, the fibroblasts are the key cells since they produce collagen and extracellular matrix. In conclusion, the analysis of the literature, and the fundamental considerations concerning the healing process when using thermal lasers, are in favor of a modification of the growth factors synthesis after laser irradiation, induced by an HSR. An extensive review of the different techniques and several clinical studies confirm that thermal lasers could effectively promote skin wound healing, if they are used in a controlled manner.