An overview of three promising mechanical, optical, and biochemical engineering approaches to improve selective photothermolysis of refractory port wine stains

Optical Microneedle-Lens Array for Selective Photothermolysis

Photothermolysis is the process that converts radiation energy into thermal energy, which results in the destruction of surrounding tissues or cells through thermal diffusion. Laser therapy that is based on photothermolysis has been a widely used treatment for various skin diseases such as skin cancers and port-wine stains. It offers several benefits such as non-invasiveness and selective treatment. However, the use of light, e.g., laser, for safe and effective photothermolysis becomes challenging due to the limited penetration of light into skin tissue as well as the presence of melanin, which absorbs this light. To solve the current issues, we propose an optical microneedle-lens array (OMLA) coated with gold in this work to directly deliver light to targeted skin layers without being absorbed by surrounding tissues as well as melanin, which results in the improvement of the efficiency of photothermal therapy. We developed a novel fabrication method, frame-guided micromolding, to prepare the OMLA by assembling two negative molds with simultaneous alignment. In addition, evaluations of the optical and heat transfer characteristics of the OMLA were performed. We expect our developed OMLA to play a crucial role in realizing more effective laser therapy by allowing the precise delivery of photons to the target area.

M-CSAFN: Multi-Color Space Adaptive Fusion Network for Automated Port-Wine Stains Segmentation

Automatic segmentation of port-wine stains (PWS) from clinical images is critical for accurate diagnosis and objective assessment of PWS. However, this is a challenging task due to the color heterogeneity, low contrast, and indistinguishable appearance of PWS lesions. To address such challenges, we propose a novel multi-color space adaptive fusion network (M-CSAFN) for PWS segmentation. First, a multi-branch detection model is constructed based on six typical color spaces, which utilizes rich color texture information to highlight the difference between lesions and surrounding tissues. Second, an adaptive fusion strategy is used to fuse complementary predictions, which address the significant differences within the lesions caused by color heterogeneity. Third, a structural similarity loss with color information is proposed to measure the detail error between predicted lesions and truth lesions. Additionally, a PWS clinical dataset consisting of 1413 image pairs was established for the development and evaluation of PWS segmentation algorithms. To verify the effectiveness and superiority of the proposed method, we compared it with other state-of-the-art methods on our collected dataset and four publicly available skin lesion datasets (ISIC 2016, ISIC 2017, ISIC 2018, and PH2). The experimental results show that our method achieves remarkable performance in comparison with other state-of-the-art methods on our collected dataset, achieving 92.29% and 86.14% on Dice and Jaccard metrics, respectively. Comparative experiments on other datasets also confirmed the reliability and potential capability of M-CSAFN in skin lesion segmentation.

Extended Application of Fractional Carbon Dioxide Laser in the Treatment of Port Wine Stain Birthmarks with Hypertrophy: A Case Report

Background: Conventional treatments of port wine stain birthmarks often do not achieve the desired outcome in patients with hypertrophy. Potential reasons include deeper and larger blood vessels, abnormal arrangement of blood vessels, and darker or thicker epidermis. However, these factors may not significantly limit the efficacy of fractional carbon dioxide (CO2) laser. The aim of this case report was to examine the extended application of fractional CO2 laser in treating patients with hypertrophic port wine stain birthmarks. Methods: Two cases with hypertrophic port wine stain birthmarks treated with fractional CO2 laser for 5 years are described in this case report. Results: When compared with conventional treatment, both cases reported better outcomes, including a reduced risk of infection, pigmentation, and scarring, a decrease of clinical erythema, and much less pain. Conclusions: The findings demonstrate that fractional CO2 laser has the potential to be an effective modality for the treatment of patients with hypertrophic port wine stains.

Experimental study of combined photodynamic and photothermal therapy in the treatment of port wine stain

Laser therapy has become the golden standard of port wine stain (PWS), but complete clearance of resistant PWSs is still difficult. The application of photodynamic therapy (PDT) in the treatment of PWS shows potential in clinical practice, especially for large-area and deep lesions. In this work, in vivo animal experimental investigation on the coupling effect of PDT with multi-pulse laser (MPL) irradiation on the treatment of PWS was conducted by using a dorsal skin window chamber model. Through visualization of the thermal response of blood vessels and damage evaluation, it is found that the combination of PDT with MPL results in 96.2% more vascular injury than PDT alone and 90% more than MPL alone, thus reducing side effects such as purpura after treatment. The combined therapy also has the benefit of large treatment area, uniform fading effect, shortened light duration, and reduced photosensitizer admit.

Vascular damage mechanism and parameter optimization under alexandrite laser irradiation: a theoretical study

The 755-nm Alexandrite Laser has a good clinical effect in treating resistant port wine stain, without causing thermal damage of normal tissue and side effects such as purpura. However, little is known about the mechanism of vascular damage induced by 755-nm laser irradiation, which restricts the optimization of laser parameters. In this work, the thermal damage model and the pressure damage model were used to study the damage mechanism of 755-nm laser irradiation on vessels, and the incident energy density and pulse width required for vascular damage were determined according to the damage mode. Under the irradiation of 755-nm laser, the vascular injury pattern was the co-occurrence of vessel rupture and vessel constriction, and the energy density required for the treatment of vessels with a diameter of 200 μm to reach the damage threshold was the lowest.

Strategy of boundary discretization in numerical simulation of laser propagation in skin tissue with vascular lesions

Understanding light propagation in skin tissues with complex blood vessels can help improve clinical efficacy in the laser treatment of cutaneous vascular lesions. The voxel-based Monte Carlo (VMC) algorithm with simple blood vessel geometry is commonly used in studying the law of light propagation in tissues. However, unavoidable errors are expected in VMC because of the zigzag polygonal interface. A tetrahedron-based Monte Carlo with extended boundary condition (TMCE) solver is developed to discretize complex tissue boundaries accurately. Tetrahedra are generated along the interface, resulting in a polyhedron approximation to match the real interface. A comparison between TMCE and VMC shows neglected differences in the overall distribution of energy deposition of different models, but poor adaptability of the curved tissue interface in VMC leads to a higher energy deposition error than TMCE in a mostly deposited region in blood vessels. Replacing the real blood vessel with a cylinder-shaped vessel shows an error lower than that caused by VMC. Statistical significance analysis of energy deposition by TMCE shows that mean curvature has stronger relationship with energy deposition than the Gaussian curvature, which indicates the importance of this geometric parameter in predicting photon behavior in vascular lesions.

Artificial red blood cells increase large vessel wall damage and decrease surrounding dermal tissue damage in a rabbit auricle model after subsequent flashlamp-pumped pulsed-dye laser treatment

Artificial red blood cells (i.e. hemoglobin [Hb] vesicles [Hb-Vs]) function effectively as photosensitizers in flashlamp-pumped pulsed-dye laser (PDL) treatment for port-wine stains in animal models. Hb-Vs deliver more Hb to the vicinity of the endothelial cells. Both Hb-Vs and red blood cells absorb the laser energy and generate heat, supporting the removal of very small blood vessels and deeper subcutaneous blood vessels with PDL irradiation in in vivo experiments. Here, we analyzed the photosensitizing effect of Hb-Vs in PDL irradiation on large blood vessels and surrounding soft tissues. We histopathologically analyzed markers of damage to the large vessels and surrounding dermal tissue in a rabbit auricle model following PDL irradiation alone or subsequent to the addition of intravenous Hb-V injection. Markers were graded on a five-point scale and statistically compared. The changes in laser light absorption and reflection in a human skin model caused by the administration of Hb-Vs were evaluated using Monte Carlo light-scattering programs. Histological markers of damage to blood vessels were significantly greater in Hb-V-injected arteries and veins measuring 1-3 mm in diameter as compared with the controls. However, Hb-V injection significantly reduced PDL-induced necrosis and hemorrhage in the surrounding tissues. During computer simulation, photon absorption increased within the vessel layer and decreased around the layer. Intravenous Hb-Vs increase the extent of damage in larger vessel walls but significantly reduce damage to the surrounding skin after subsequent PDL irradiation. These beneficial effects are the result of improving vessel selectivity by Hb-Vs in vessels. Hb-V administration prior to PDL irradiation therapy could mechanically improve the outcomes and safety profiles of port-wine stain treatment protocols.

Efficacy evaluation and treatment parameter optimization for laser surgery of Ota's nevus based on an advanced non-equilibrium bio-tissue heat transfer model

This study was performed to better understand the laser-tissue interaction mechanism and optimize the laser wavelength and pulse duration for the laser treatment of Ota's nevus, thereby providing the precise theoretical guidance for clinician to improve the therapeutic effect. A non-equilibrium bio-tissue heat transfer model coupled with thermo-mechanical effect for the explosive vaporization of melanin granule induced by laser heating was developed to investigate the temperature and thermal damage distribution using alexandrite (755 nm) and Nd:YAG (1064 nm) lasers with the pulse width of 10-120 ns. Cryogen spray cooling (CSC) was introduced to prevent the epidermal thermal damage due to competitive laser absorption between epidermal and dermal melanin. Thermal injury of the epidermis with temperature in the melanin zone reaching 132.3 °C was induced by alexandrite laser. The optimal pulse durations were 50 and 30 ns, and the corresponding incident laser fluence thresholds were 6.45 and 19.5 J·cm^-2 for alexandrite and Nd:YAG laser, respectively, with the pre-cooling of R32 spray. Using R32 spray cooling, the 1064-nm laser fluence threshold of melanin can be increased by 56.0%, resulting in an indirect increase (80.4%) of injury thickness. Nd:YAG laser (1064 nm) was highly suitable for the removal of melanin in the deep tissue owing to its deep penetration. Too short pulse duration should be avoided to prevent the epidermal thermal damage. The improvement of therapeutic effect by CSC demonstrates its high clinical application potential.

Monitoring perfusion and oxygen saturation in port-wine stains during vascular targeted photodynamic therapy

Background

Vascular targeted photodynamic therapy (V-PDT) is a safe and effective therapeutic modality for port-wine stains (PWS) by targetedly damaging the dilated and malformed blood vessels. This study aims to monitor and quantify the changes in oxygen saturation (StO₂), blood volume fraction (BVF) and perfusion in PWS lesions before and during V-PDT.

Methods

Microvascular parameters (i.e., StO₂ and BVF) and skin perfusion were measured noninvasively by using diffuse reflectance spectroscopy (DRS) and laser Doppler imaging (LDI), respectively. The change in StO₂, BVF and perfusion that occurred in the PWS lesions of 26 patients were monitored and investigated before and during V-PDT in vivo with the systematic administration of the porphyrin-based photosensitizer HiPorfin.

Results

The mean StO₂ (P<0.05), BVF (P<0.05), and perfusion (P<0.001) in PWS lesions of all subjects significantly increased by 6%, 34%, and 113%, respectively, 3 min after the initiation of V-PDT. The StO₂ increased first and fluctuated during V-PDT. The overall trend of BVF change was consistent with the perfusion change. The BVF and the perfusion of PWS lesions increased after the initiation of V-PDT, and then gradually decreased.

Conclusions

V-PDT is an effective therapeutic modality in treating PWS. Results showed that LDI and DRS permitted the noninvasive monitoring of the changes in StO₂, BVF, and perfusion in PWS lesions during V-PDT, and these methods can be useful in facilitating our understanding of the basic physiological mechanisms during V-PDT.

Capillaroscopy and reflectance confocal microscopy characterization of refractory port-wine stains

Port-wine stains (PWS) are frequently refractory to laser treatments. Although previous data highlight prognostic factors and biological events related to poor outcomes, no previous publications correlate their capillaroscopic and architectural features. The aim of the present study is to describe refractory port-wine stains performing capillaroscopy and reflectance confocal microscopy (RCM) to describe their morphological and microscopic aspects. This is a prospective cohort study. All the consecutive patients with PWS poor responsive to previous treatment were included. Clinical assessment, capillaroscopy, and reflectance confocal microscopy were performed. A total of 65 patients were included, 12 with a capillaroscopic Type II pattern patients and 53 with Type III. At RCM examination, PWS with a capillaroscopic Type III pattern showed deeper-located blood vessels (p < 0.001) with a higher diameter (p < 0.042) compared with Type II. At the dynamic evaluation, 3 RCM patterns can be distinguished: Subset A, characterized by linear vessels with reduced diameter; Subset B, formed by enlarged vessels; and Subset C, characterized by deep and large aneurysmatic dilatation connected to small vessels. We defined 3 RCM patterns of refractory PWS.

In Vivo Assessment of Thermosensitive Liposomes for the Treatment of Port Wine Stains by Antifibrinolytic Site-Specific Pharmaco-Laser Therapy

Antifibrinolytic site-specific pharmaco-laser therapy (SSPLT) is an experimental treatment modality for refractory port wine stains (PWS). Conceptually, antifibrinolytic drugs encapsulated in thermosensitive liposomes are delivered to thrombi that form in semi-photocoagulated PWS blood vessels after conventional laser treatment. Local release of antifibrinolytics is induced by mild hyperthermia, resulting in hyperthrombosis and complete occlusion of the target blood vessel (clinical endpoint). In this study, 20 thermosensitive liposomal formulations containing tranexamic acid (TA) were assayed for physicochemical properties, TA:lipid ratio, encapsulation efficiency, and endovesicular TA concentration. Two candidate formulations (DPPC:DSPE-PEG, DPPC:MPPC:DSPE-PEG) were selected based on optimal properties and analyzed for heat-induced TA release at body temperature (T), phase transition temperature (T_m), and at T > T_m. The effect of plasma on liposomal stability at 37 °C was determined, and the association of liposomes with platelets was examined by flow cytometry. The accumulation of PEGylated phosphocholine liposomes in laser-induced thrombi was investigated in a hamster dorsal skinfold model and intravital fluorescence microscopy. Both formulations did not release TA at 37 °C. Near-complete TA release was achieved at T_m within 2.0–2.5 min of heating, which was accelerated at T > T_m. Plasma exerted a stabilizing effect on both formulations. Liposomes showed mild association with platelets. Despite positive in vitro results, fluorescently labeled liposomes did not sufficiently accumulate in laser-induced thrombi in hamsters to warrant their use in antifibrinolytic SSPLT, which can be solved by coupling thrombus-targeting ligands to the liposomes.

Theoretical Study on Pressure Damage Based on Clinical Purpura during the Laser Irradiation of Port Wine Stains with Real Complex Vessels

Port wine stains (PWSs) are congenital dermal vascular lesions composed of a hyperdilated vasculature. Purpura represented by local hemorrhage from water vaporization in blood during laser therapy of PWS is typically considered a clinical feedback, but with a low cure rate. In this study, light propagation and heat deposition in skin and PWSs is simulated by a tetrahedron-based Monte Carlo method fitted to curved bio-tissues. A curvature-corrected pressure damage model was established to accurately evaluate the relationship between purpura-bleeding area (rate) and laser therapy strategy for real complex vessels. Results showed that the standard deviation of Gaussian curvature of the vessel wall has negative relation with the fluence threshold of vessel rupture, but has positive relation with the effective laser fluence of vessel damage. This finding indicated the probable reason for the poor treatment of PWS, that is, considering purpura formation as a treatment end point (TEP) only leads to partial removal of vascular lesions. Instead, appropriate purpura area ratio with marked effects or rehabilitation should be adopted as TEP. The quantitative correlation between the fluence of a pulsed dye laser and the characteristics of vascular lesions can provide personalized and precise guidance for clinical treatments.

Microvascular Effects of Pulsed Dye Laser in Combination With Oxymetazoline

BACKGROUND AND OBJECTIVE

Oxymetazoline, an α-1A agonist, is approved by the United States Food and Drug Administration (FDA) for treatment of persistent facial erythema associated with rosacea and induces vasoconstriction by interacting with α receptors. The objective of our study was to study the microvascular effects of oxymetazoline and pulsed dye laser (PDL).

MATERIALS AND METHODS

A dorsal window chamber was surgically installed on 20 mice. Each animal was assigned to one of four experimental groups: saline alone, oxymetazoline alone (10 μl applied once daily × 7 days), saline + PDL (saline applied 5 minutes before PDL irradiation [10 mm spot, 1.5 ms pulse duration, 7 J/cm² delivered to epidermis]), or oxymetazoline + PDL (10 μl oxymetazoline applied 5 minutes before PDL and then once daily × 7 days). Brightfield and laser speckle imaging were performed for 7 days to monitor vascular architectural and functional changes.

RESULTS

We observed persistent blood flow in all of the saline-only and oxymetazoline-only experiments. A higher rate of vascular shutdown was observed with oxymetazoline + PDL (66.7%) compared with saline + PDL alone (16.7%). Oxymetazoline application increased venule diameter at 5 minutes post-application and decreased both arteriole and venule diameters at 60 minutes post-application.

CONCLUSION

The combination protocol of oxymetazoline + PDL induces persistent vascular shutdown observed 7 days after irradiation. This result may be associated with the acute vascular effects of oxymetazoline. Oxymetazoline + PDL should be evaluated as a treatment for cutaneous vascular disease, including rosacea and port wine birthmarks. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Port wine stain treatment outcomes have not improved over the past three decades

BACKGROUND

Since the early '80s, the pulsed dye laser has been the standard treatment tool for non-invasive port wine stain (PWS) removal. In the last three decades, a considerable amount of research has been conducted to improve clinical outcomes, given that a fraction of PWS patients proved recalcitrant to laser treatment. Whether this research actually led to increased therapeutic efficacy has not been systematically investigated.

OBJECTIVE

To analyse therapeutic efficacy in PWS patients globally from 1986 to date.

METHODS

PubMed was searched for all available PWS trials. Studies with a quartile percentage improvement scale were included, analysed and plotted chronologically. Treatment and patient characteristics were extracted. A mean clearance per study was calculated and plotted. A 5-study simple moving average was co-plotted to portray the trend in mean clearance over time. The data were separately analysed for multiple treatment sessions in previously untreated patients.

RESULTS

Sixty-five studies were included (24.3% of eligible studies) comprising 6207 PWS patients. Of all patients, 21% achieved 75-100% clearance. Although a few studies reported remarkably good outcomes in a subset of carefully selected patients, there was no upward trend over time in mean clearance.

CONCLUSION

The efficacy of PWS therapy has not improved in the past decades, despite numerous technical innovations and pharmacological interventions. With an unwavering patient demand for better outcomes, the need for development and implementation of novel therapeutic strategies to clear all PWS is as valid today as it was 30 years ago.

Site-specific pharmaco-laser therapy: A novel treatment modality for refractory port wine stains

Despite extensive efforts to optimize laser therapy, i.e., the current gold standard treatment, a majority of port wine stain (PWS) patients responds suboptimally to laser therapy. This paper describes the niceties of a novel PWS treatment modality termed site-specific pharmaco-laser therapy (SSPLT). In contrast to the classic approach of enhancing the extent of intravascular photocoagulation (the photothermal response), SSPLT focuses on optimization of post-irradiation thrombus formation (i.e., the hemodynamic response) by combining conventional laser therapy with the administration of thermosensitive drug delivery systems that encapsulate prothrombotic and antifibrinolytic drugs. The aim of SSPLT is to instill complete lumenal occlusion in target vessels, which has been linked to optimal PWS blanching.

RELEVANCE FOR PATIENTS

The current treatment options for PWS patients are limited in efficacy. Novel therapeutic modalities are needed to more effectively treat patients with recalcitrant PWSs. SSPLT is an experimental-stage treatment modality that could serve as an adjuvant to pulsed dye laser therapy for a selected group of patients whose PWS is ill-responsive to standard treatment. The expected clinical result of SSPLT is improved lesional blanching.

Tranexamic Acid-Encapsulating Thermosensitive Liposomes for Site-Specific Pharmaco-Laser Therapy of Port Wine Stains

Site-specific pharmaco-laser therapy (SSPLT) is a developmental stage treatment modality designed to non-invasively remove superficial vascular pathologies such as port wine stains (PWS) by combining conventional laser therapy with the prior administration of a prothrombotic and/or antifibrinolytic pharmaceutical-containing drug delivery system. For the antifibrinolytic SSPLT component, six different PEGylated thermosensitive liposomal formulations encapsulating tranexamic acid (TA), a potent antifibrinolytic lysine analogue, were characterized for drug:lipid ratio, encapsulation efficiency, size, endovesicular TA concentration (C TA), phase transition temperature (T m), and assayed for heat-induced TA release. Assays were developed for the quantification of liposomal TA and heat-induced TA release from two candidate formulations. The outcome parameters were then combined with a 3D histological reconstruction of a port wine stain biopsy to extrapolate in vivo posologies for SSPLT. The prime formulation, DPPC:DSPE-PEG2000 (96:4 molar ratio), had a drug:lipid molar ratio of 0.82, an encapsulation efficiency of 1.29%, a diameter of 155 nm, and a C TA of 214 mM. The peak TA release from this formulation (T m = 42.3 °C) comprised 96% within 2.5 min, whereas this was 94% in 2 min for DPPC:MPPC:DSPE-PEG2000 (86:10:4) liposomes (T m = 41.5 °C). Computational analysis revealed that < 400 DPPC:DSPE-PEG2000 (96:4 molar ratio) liposomes are needed to treat a PWS of 40 cm2, compared to a three-fold greater quantity of DPPC:MPPC:DSPE-PEG2000 (86:10:4) liposomes, indicating that, in light of the assayed parameters and endovascular laser-tissue interactions, the former formulation is most suitable for antifibrinolytic SSPLT. This was further confirmed with experiments involving ex vivo and in vivo liposome-platelet and liposome-red blood cell association as well as uptake and toxicity assays with cultured endothelial cells (HUVECs), macrophages (RAW 264.7), and hepatocytes (HepG2).

Prospective analysis of the port-wine stain patient population in the Netherlands in light of novel treatment modalities

BACKGROUND

Pulsed dye laser is the gold standard for port-wine stain (PWS) treatment. However, pulsed dye lasers achieve suboptimal clinical results in a majority of patients. Patient demand for novel therapies and willingness to participate in clinical studies is currently unknown, yet, imperative for steering R&D activity. The objective of this study was to evaluate these two factors in relation to PWS patient demographics.

METHODS

A questionnaire was used to assess patient and PWS characteristics, treatment history, efficacy, and satisfaction, stress level, willingness to travel and pay for an effective treatment, participation in clinical studies, and amenability to intravenous drug administration. Descriptive statistics and correlation analysis were performed.

RESULTS

Of the respondents (N = 108), 65% would participate in clinical studies and 49% would accept intravenous drugs. For an effective treatment, 58% was prepared to pay over €2,000 and 48% would travel more than 6 h. Travel time was inversely correlated with age, clearance rate, and satisfaction. Facial PWS patients had undergone more treatments, were less satisfied, and less willing to participate in studies or accept intravenous drugs. Stress levels were higher in females.

CONCLUSION

There is considerable demand for new PWS therapies, and a substantial proportion of patients are willing to participate in clinical studies.

Nd:YAG laser combined with gold nanorods for potential application in port-wine stains: an in vivo study

Neodymium:yttrium aluminum garnet (Nd:YAG) lasers exhibit considerable potential for treating deeply buried port-wine stains. However, the application of Nd:YAG laser is limited by its weak absorption to blood. This in vivo study tested the efficacy and safety of utilizing thiol-terminated methoxypolyethylene glycol-modified gold nanorods (PEG-GNRs) to enhance the absorption of Nd:YAG laser to blood. Mouse mesentery and dorsal skinfold chamber (DSC) model were prepared to analyze the thermal responses of a single venule without anatomic structures, as well as blood vessels in the complex structure of the skin, to laser light. After the injection of 0.44 mg of PEG-GNRs, the required threshold density of laser energy for blood coagulation and complete vasoconstriction decreased from 24 to 18  J/cm2 in the mesentery model and from 36 to 31  J/cm2 in the DSC model. The laser pulse required for blood coagulation and complete vasoconstriction decreased by 67.75% and 62.25% on average in the mesentery model and by 67.55% and 54.45% on average in the DSC model. Histological and histochemical results confirmed that PEG-GNRs are nontoxic in the entire mouse life span. Therefore, combining PEG-GNRs with Nd:YAG laser may be effective and safe for inducing an obvious thermal response of blood vessels under low energy density and minimal pulse conditions.

Histologic changes associated with talaporfin sodium-mediated photodynamic therapy in rat skin

BACKGROUND AND OBJECTIVE

Alternative treatments are needed to achieve consistent and more complete port wine stain (PWS) removal, especially in darker skin types; photodynamic therapy (PDT) is a promising alternative treatment. To this end, we previously reported on Talaporfin Sodium (TS)-mediated PDT. It is essential to understand treatment tissue effects to design a protocol that will achieve selective vascular injury without ulceration and scarring. The objective of this work is to assess skin changes associated with TS-mediated PDT with clinically relevant treatment parameters.

STUDY DESIGN/MATERIALS AND METHODS

We performed TS (0.75 mg/kg)-mediated PDT (664 nm) on Sprague Dawley rats. Radiant exposures were varied between 15 and 100 J/cm² . We took skin biopsies from subjects at 9 hours following PDT. We assessed the degree and depth of vascular and surrounding tissue injury using histology and immunohistochemical staining.

RESULTS

TS-mediated PDT at 0.75 mg/kg combined with 15 and 25 J/cm² light doses resulted in vascular injury with minimal epidermal damage. At light dose of 50 J/cm² , epidermal damage was noted with vascular injury. At light doses >50 J/cm² , both vascular and surrounding tissue injury were observed in the forms of vasculitis, extravasated red blood cells, and coagulative necrosis. Extensive coagulative necrosis involving deeper adnexal structures was observed for 75 and 100 J/cm² light doses. Observed depth of injury increased with increasing radiant exposure, although this relationship was not linear.

CONCLUSION

TS-mediated PDT can cause selective vascular injury; however, at higher light doses, significant extra-vascular injury was observed. This information can be used to contribute to design of safe protocols to be used for treatment of cutaneous vascular lesions. Lasers Surg. Med. 49:767-772, 2017. © 2017 Wiley Periodicals, Inc.

Quantitative long-term measurements of burns in a rat model using Spatial Frequency Domain Imaging (SFDI) and Laser Speckle Imaging (LSI)

BACKGROUND AND OJECTIVES

The current standard for diagnosis of burn severity and subsequent wound healing is through clinical examination, which is highly subjective. Several new technologies are shifting focus to burn care in an attempt to help quantify not only burn depth but also the progress of healing. While accurate early assessment of partial thickness burns is critical for dictating the course of treatment, the ability to quantitatively monitor wound status over time is critical for understanding treatment efficacy. SFDI and LSI are both non-invasive imaging modalities that have been shown to have great diagnostic value for burn severity, but have yet to be tested over the course of wound healing.

METHODS

In this study, a hairless rat model (n = 6, 300-450 g) was used with a four pronged comb to create four identical partial thickness burns (superficial n = 3 and deep n = 3) that were used to monitor wound healing over a 28 days period. Weekly biopsies were taken for histological analysis to verify wound progression. Both SFDI and LSI were performed weekly to track the evolution of hemodynamic (blood flow and oxygen saturation) and structural (reduced scattering coefficient) properties for the burns.

RESULTS

LSI showed significant changes in blood flow from baseline to 220% in superficial and 165% in deep burns by day 7. In superficial burns, blood flow returned to baseline levels by day 28, but not for deep burns where blood flow remained elevated. Smaller increases in blood flow were also observed in the surrounding tissue over the same time period. Oxygen saturation values measured with SFDI showed a progressive increase from baseline values of 66-74% in superficial burns and 72% in deep burns by day 28. Additionally, SFDI showed significant decreases in the reduced scattering coefficient shortly after the burns were created. The scattering coefficient progressively decreased in the wound area, but returned towards baseline conditions at the end of the 28 days period. Scattering changes in the surrounding tissue remained constant despite the presence of hemodynamic changes.

CONCLUSIONS

Here, we show that LSI and SFDI are capable of monitoring changes in hemodynamic and scattering properties in burn wounds over a 28 days period. These results highlight the potential insights that can be gained by using non-invasive imaging technologies to study wound healing. Further development of these technologies could be revolutionary for wound monitoring and studying the efficacy of different treatments. Lasers Surg. Med. 49:293-304, 2017. © 2017 Wiley Periodicals, Inc.

The Role of Laser Speckle Imaging in Port-Wine Stain Research: Recent Advances and Opportunities

Here, we review our current knowledge on the etiology and treatment of port-wine stain (PWS) birthmarks. Current treatment options have significant limitations in terms of efficacy. With the combination of 1) a suitable preclinical microvascular model, 2) laser speckle imaging (LSI) to evaluate blood-flow dynamics, and 3) a longitudinal experimental design, rapid preclinical assessment of new phototherapies can be translated from the lab to the clinic. The combination of photodynamic therapy (PDT) and pulsed-dye laser (PDL) irradiation achieves a synergistic effect that reduces the required radiant exposures of the individual phototherapies to achieve persistent vascular shutdown. PDL combined with anti-angiogenic agents is a promising strategy to achieve persistent vascular shutdown by preventing reformation and reperfusion of photocoagulated blood vessels. Integration of LSI into the clinical workflow may lead to surgical image guidance that maximizes acute photocoagulation, is expected to improve PWS therapeutic outcome. Continued integration of noninvasive optical imaging technologies and biochemical analysis collectively are expected to lead to more robust treatment strategies.

Intraoperative monitoring of blood perfusion in port wine stains by laser Doppler imaging during vascular targeted photodynamic therapy: A preliminary study

OBJECTIVE

The objective of this study was to monitor blood perfusion dynamics of port wine stains (PWS) during vascular targeted photodynamic therapy (V-PDT) with laser Doppler imaging (LDI).

METHODS

The PWS lesions of 30 facial PWS patients received V-PDT, while the normal skins on the forearm of 5 healthy subjects were treated as light-only controls for comparison. Furthermore, two different PWS lesions in the same individual from each of 3 PWS patients successively received laser irradiation only and V-PDT, respectively. LDI was used to monitor intraoperative blood perfusion dynamics.

RESULTS

During V-PDT, the blood perfusion (278±96 PU) in PWS lesions for 31 of 33 PWS patients significantly increased after the initiation of V-PDT treatment, then reached a peak (638±105 PU) within 10min, followed by a slow decrease to a relatively lower level (515±100 PU). Furthermore, the time for reaching peak and the subsequent magnitude of decrease in blood perfusion varied with different patients. For light-only controls, an initial perfusion peak at 3min followed by a nadir and a secondary increase were found not only in normal skin, but also in PWS lesions.

CONCLUSION

The preliminary results showed that the LDI permits non-invasive monitoring blood perfusion changes of PWS lesions during V-PDT. There was a clear trend in blood perfusion responses during V-PDT and laser irradiation. The blood perfusion changes during treatment were due to V-PDT effects as well as local temperature increase induced by laser irradiation.

Intraoperative, real-time monitoring of blood flow dynamics associated with laser surgery of port wine stain birthmarks

BACKGROUND AND OBJECTIVE

Port-wine stain (PWS) birthmarks affect ∼22 million people worldwide. After several treatment sessions, complete disappearance of the PWS occurs in only ∼10% of treated patients. There is a need to develop a new strategy to improve the efficacy of each treatment session and the overall treatment outcome. The study objective was to determine how intraoperative measurements of blood flow correlate with treatment response assessed several weeks post treatment.

STUDY DESIGN/MATERIALS AND METHODS

We employed Laser Speckle Imaging (LSI) to measure intraoperative blood-flow dynamics. We collected data from 24 subjects undergoing laser therapy for facial PWS birthmarks. Photographs were taken before treatment and at a follow-up visit, and analyzed by two expert observers.

RESULTS

Intraoperative LSI enables real-time monitoring of blood-flow dynamics in response to laser treatment and can inform clinicians on the need for focused re-treatment. The degree of PWS blanching achieved is positively correlated with the log-transformed acute blood-flow reduction (P = 0.022).

CONCLUSION

LSI is a simple, intraoperative monitoring tool during laser therapy of PWS birthmarks. LSI provides a single value for blood flow that correlates well with the degree of blanching achieved with laser therapy.

Utility of spatial frequency domain imaging (SFDI) and laser speckle imaging (LSI) to non-invasively diagnose burn depth in a porcine model

Surgical intervention of second degree burns is often delayed because of the difficulty in visual diagnosis, which increases the risk of scarring and infection. Non-invasive metrics have shown promise in accurately assessing burn depth. Here, we examine the use of spatial frequency domain imaging (SFDI) and laser speckle imaging (LSI) for predicting burn depth. Contact burn wounds of increasing severity were created on the dorsum of a Yorkshire pig, and wounds were imaged with SFDI/LSI starting immediately after-burn and then daily for the next 4 days. In addition, on each day the burn wounds were biopsied for histological analysis of burn depth, defined by collagen coagulation, apoptosis, and adnexal/vascular necrosis. Histological results show that collagen coagulation progressed from day 0 to day 1, and then stabilized. Results of burn wound imaging using non-invasive techniques were able to produce metrics that correlate to different predictors of burn depth. Collagen coagulation and apoptosis correlated with SFDI scattering coefficient parameter [Formula: see text] and adnexal/vascular necrosis on the day of burn correlated with blood flow determined by LSI. Therefore, incorporation of SFDI scattering coefficient and blood flow determined by LSI may provide an algorithm for accurate assessment of the severity of burn wounds in real time.

Intraoperative, real-time monitoring of blood flow dynamics associated with laser surgery of port wine stain birthmarks

BACKGROUND AND OBJECTIVE

Port-wine stain (PWS) birthmarks affect ∼22 million people worldwide. After several treatment sessions, complete disappearance of the PWS occurs in only ∼10% of treated patients. There is a need to develop a new strategy to improve the efficacy of each treatment session and the overall treatment outcome. The study objective was to determine how intraoperative measurements of blood flow correlate with treatment response assessed several weeks post treatment.

STUDY DESIGN/MATERIALS AND METHODS

We employed Laser Speckle Imaging (LSI) to measure intraoperative blood-flow dynamics. We collected data from 24 subjects undergoing laser therapy for facial PWS birthmarks. Photographs were taken before treatment and at a follow-up visit, and analyzed by two expert observers.

RESULTS

Intraoperative LSI enables real-time monitoring of blood-flow dynamics in response to laser treatment and can inform clinicians on the need for focused re-treatment. The degree of PWS blanching achieved is positively correlated with the log-transformed acute blood-flow reduction (P = 0.022).

CONCLUSION

LSI is a simple, intraoperative monitoring tool during laser therapy of PWS birthmarks. LSI provides a single value for blood flow that correlates well with the degree of blanching achieved with laser therapy.

Treatment of port wine stains with pulsed dye laser: a retrospective study of 848 cases in Shandong Province, People's Republic of China

Background

Currently, 595 nm pulsed dye laser (PDL) therapy is offered as one of the effective treatments of port wine stains (PWSs). However, the efficacy of PDL differs in different populations.

Objective

The purpose of the study was to investigate the efficacy, and related factors, of 595 nm PDL in the treatment of PWSs in Chinese patients with skin type III to IV.

Methods

A total of 848 cases that were treated with PDL were enrolled and analyzed in this study. An independent dermatologist evaluated these lesions according to the before and after photographs.

Results

The response rate (RR) of all the 848 PWS patients was 69.9%, within which the cure rate was 6.3%. The patients aged ≤1 year had the highest RR (93.9%), whereas those treated after age 50 reacted the worst (RR =25%). We analyzed the anatomical distribution of the lesion and found that the temporal region had the highest lesion clearance (RR =75.3%), while the extremities had the lowest clearance (RR =44.5%). Compared with the patients whose lesion size was larger than 80 cm², the patients with small lesion size, of 0–20 cm², had better clinical effect (RR =73.8% vs 53.2%). The reactions of the patients with hyperplastic lesion were worse than those with red patches (RR =36.4% vs 71.7%). As well, increasing treatment numbers could achieve higher clearance rates (P=0.005).

Conclusion

The PDL had a relatively high RR but a low clearance rate in Chinese patients with PWS, although the earlier the intervention, the better was the efficacy. The response of PDL was, not only related to the anatomical area, but also, to the lesion size, type of lesion (ie, the presence of existing hyperplastic lesions), and the number of treatment, all of which are essential for the evaluation of therapeutic effect and acquisition of patients consent before treatment.

Quantitative assessment of graded burn wounds in a porcine model using spatial frequency domain imaging (SFDI) and laser speckle imaging (LSI)

Accurate and timely assessment of burn wound severity is a critical component of wound management and has implications related to course of treatment. While most superficial burns and full thickness burns are easily diagnosed through visual inspection, burns that fall between these extremes are challenging to classify based on clinical appearance. Because of this, appropriate burn management may be delayed, increasing the risk of scarring and infection. Here we present an investigation that employs spatial frequency domain imaging (SFDI) and laser speckle imaging (LSI) as non-invasive technologies to characterize in-vivo burn severity. We used SFDI and LSI to investigate controlled burn wounds of graded severity in a Yorkshire pig model. Burn wounds were imaged starting at one hour after the initial injury and daily at approximately 24, 48 and 72 hours post burn. Biopsies were taken on each day in order to correlate the imaging data to the extent of burn damage as indicated via histological analysis. Changes in reduced scattering coefficient and blood flow could be used to categorize burn severity as soon as one hour after the burn injury. The results of this study suggest that SFDI and LSI information have the potential to provide useful metrics for quantifying the extent and severity of burn injuries.

Vascular anomalies: classification, imaging characteristics and implications for interventional radiology treatment approaches

The term vascular anomaly represents a broad spectrum of vascular pathology, including proliferating vascular tumours and vascular malformations. While the treatment of most vascular anomalies is multifactorial, interventional radiology procedures, including embolic therapy, sclerotherapy and laser coagulation among others, are playing an increasingly important role in vascular anomaly management. This review discusses the diagnosis and treatment of common vascular malformations, with emphasis on the technique, efficacy and complications of different interventional radiology procedures.

Optical clearing agent perfusion enhancement via combination of microneedle poration, heating and pneumatic pressure

BACKGROUND AND OBJECTIVE

Optical clearing agents (OCAs) have shown promise for increasing the penetration depth of biomedical lasers by temporarily decreasing optical scattering within the skin. However, their translation to the clinic has been constrained by lack of practical means for effectively perfusing OCA within target tissues in vivo. The objective of this study was to address this limitation through combination of a variety of techniques to enhance OCA perfusion, including heating of OCA, microneedling and/or application of pneumatic pressure over the skin surface being treated (vacuum and/or positive pressure). While some of these techniques have been explored by others independently, the current study represents the first to explore their use together.

STUDY DESIGN/MATERIALS AND METHODS

Propylene glycol (PG) OCA, either at room-temperature or heated to 45°C, was topically applied to hydrated, body temperature ex vivo porcine skin, in conjunction with various combinations of microneedling pre-treatment (0.2 mm length microneedles, performed prior to OCA application), vacuum pre-treatment (17-50 kPa, performed prior to OCA application), and positive pressure post-treatment (35-172 kPa, performed after OCA application). The effectiveness of OCA perfusion was characterized via measurements of transmittance, reduced scattering coefficient, and penetration depth at a number of medically-relevant laser wavelengths across the visible spectrum.

RESULTS

Topical application of room-temperature (RT) PG led to an increase in transmittance across the visible spectrum of up to 21% relative to untreated skin. However, only modest increases were observed with addition of various combinations of microneedling pre-treatment, vacuum pre-treatment, and positive pressure post-treatment. Conversely, when heated PG was used in conjunction with these techniques, we observed significant increases in transmittance. Using an optimal PG perfusion enhancement protocol consisting of 45°C heated PG + microneedle pre-treatment + 35 kPa vacuum pre-treatment + 103 kPa positive pressure post-treatment, we observed up to 68% increase in transmittance relative to untreated skin, and up to 46% increase relative to topical RT PG application alone. Using the optimal PG perfusion enhancement protocol, we also observed up to 30% decrease in reduced scattering coefficient relative to untreated skin, and up to 20% decrease relative to topical RT PG alone. Finally, using the optimal protocol, we observed up to 25% increase in penetration depth relative to untreated skin, and up to 23% increase relative to topical RT PG alone.

CONCLUSIONS

The combination of heated PG, microneedling pre-treatment, vacuum pre-treatment, and positive pressure-post treatment were observed to significantly enhance the perfusion of topically applied PG. Although further studies are required to evaluate the efficacy of combined perfusion enhancement techniques in vivo, the current results suggest promise for facilitating the translation of OCAs to the clinic.

Pulsed dye laser-resistant port-wine stains: mechanisms of resistance and implications for treatment

Port-wine stains (PWS) are among the most common congenital vascular malformations. Unlike capillary haemangiomas, these lesions do not involute spontaneously but rather become progressively more disfiguring as the patient ages. While benign in nature, the cosmetic deformity and attendant psychological and emotional distress prompt the majority of those afflicted to seek treatment. The pulsed dye laser (PDL) has long been considered the treatment of choice for these vascular lesions; however, very few patients achieve total clearance with PDL therapy and a significant number of lesions fail to respond at all. In order to address these recalcitrant cases, the mechanisms that contribute to treatment resistance must be understood and novel laser and light therapies must be employed. This review will address what is currently known about lesion-specific characteristics of PDL-resistant PWS as well as discuss current and future treatment options.

The sensitivity in the IR spectrum of the intact and pathological tissues by laser biophotometry

In this paper, we use the laser biophotometry for in vivo investigations, searching the most sensitive interactions of the near-infrared spectrum with different tissues. The experimental methods are based on the average reflection coefficient (ARC) measurements. For healthy persons, ARC is the average of five values provided by the biophotometer. The probe is applied on dry skin with minimum pilosity, in five regions: left-right shank, left-right forearm, and epigastrium. For the pathological tissues, the emitting terminal is moved over the suspected area, controlling the reflection coefficient level, till a minimum value occurs, as ARC-Pathological. Then, the probe is moved on the symmetrical healthy region of the body to read the complementary coefficient from intact tissue, ARC-Intact, from the same patient. The experimental results show an ARC range between 67 and 59 mW for intact tissues and a lower range, up to 58-42 mW, for pathological tissues. The method is efficient only in those pathological processes accompanied by variable skin depigmentation, water retention, inflammation, thrombosis, or swelling. Frequently, the ARC ranges are overlapping for some diseases. This induces uncertain diagnosis. Therefore, a statistical algorithm is adopted for a differential diagnosis. The laser biophotometry provides a quantitative biometric parameter, ARC, suitable for fast diagnosis in the internal and emergency medicine. These laser biophotometry measurements are representatives for the Romanian clinical trials.

An overview of clinical and experimental treatment modalities for port wine stains

Port wine stains (PWS) are the most common vascular malformation of the skin, occurring in 0.3% to 0.5% of the population. Noninvasive laser irradiation with flashlamp-pumped pulsed dye lasers (selective photothermolysis) currently comprises the gold standard treatment of PWS; however, the majority of PWS fail to clear completely after selective photothermolysis. In this review, the clinically used PWS treatment modalities (pulsed dye lasers, alexandrite lasers, neodymium:yttrium-aluminum-garnet lasers, and intense pulsed light) and techniques (combination approaches, multiple passes, and epidermal cooling) are discussed. Retrospective analysis of clinical studies published between 1990 and 2011 was performed to determine therapeutic efficacies for each clinically used modality/technique. In addition, factors that have resulted in the high degree of therapeutic recalcitrance are identified, and emerging experimental treatment strategies are addressed, including the use of photodynamic therapy, immunomodulators, angiogenesis inhibitors, hypobaric pressure, and site-specific pharmaco-laser therapy.