Showing papers in "Lasers in Surgery and Medicine in 2004"

Fractional Photothermolysis: A New Concept for Cutaneous Remodeling Using Microscopic Patterns of Thermal Injury

Abstract: Background and Objectives: We introduce and clinically examine a new concept of skin treatment called fractional photothermolysis (FP), achieved by applying an array of microscopic treatment zones (MTZ) of thermal injury to the skin. Study Design/Materials and Methods: Two prototype devices emitting at 1.5 mm wavelength provided a pattern of micro-exposures with variable MTZ density. Effects of different MTZ densities were tested on the forearms of 15 subjects. Clinical effects and histology were assessed up to 3 months after exposure. Treatment of photoaged skin on the periorbital area in an additional 30 subjects receiving four treatments over a period of 2–3 weeks was also tested. Tissue shrinkage and clinical effects were assessed up to 3 months after treatment. Results: Pattern densities with spacing of 250 mm or more were well tolerated. Typical MTZ had a diameter of 100 mm and penetrated 300 mm into the skin. Reepithelialization was complete within 1 day. Clinical effects were assessed over a 3-month period. Histology at 3 months revealed enhanced undulating rete ridges and increased mucin deposition within the superficial dermis. Periorbital treatments were well tolerated with minimal erythema and edema. Linear shrinkage of 2.1% was measured 3 months after the last treatment. The wrinkle score improved 18% (P < 0.001) 3 months after the last treatment. Conclusions: FP is a new concept for skin restoration treatment. Safety and efficacy were demonstrated with a prototype device. Further clinical studies are necessary to refine the optimum parameters and to explore further dermatological applications. Lasers Surg. Med. 34:426– 438, 2004. 2004 Wiley-Liss, Inc.

Selective electro-thermolysis in aesthetic medicine: a review.

Abstract: The use of radiofrequency (RF) for selective electro-thermolysis has been found to produce a highly efficient thermal effect on biological tissue. Different from optical energy, RF energy is dependent on the electrical properties of the tissue rather than on concentration of chromophores in the skin for selective thermal destruction of targeted sites. Good results have been obtained with systems that use RF current alone for skin resurfacing, with efficacy comparable to laser resurfacing but with potentially more rapid healing. A related adverse effect is pain accompanying the procedure, due to a high depth of penetration. Another technology integrates RF energy together with optical energy (using lower energies of both forms of energies). These systems have shown efficacy in hair removal for all hair colors and skin types, as well as wrinkle reduction; and may reduce the risk of side effects associated with either RF or optical treatments alone. This article discusses the properties of electrical current in medicine and reviews the studies to date that have evaluated RF energy for dermatological applications. Lasers Surg. Med. 34:91–97, 2004. © 2004 Wiley-Liss, Inc.

Bactericidal effect of different laser systems in the deep layers of dentin

Abstract: Background and Objectives: In recent years, various laser systems have gained importance in the field of laserassisted endodontics, namely the Nd:YAG, the diode, the Er:YAG, and the Er,Cr:YSGG laser. Individual studies have been carried out so far, focusing on the respective wavelength, its specific bactericidal capabilities, and potential usefulness is root-canal disinfection. The present in vitro investigation however, was performed to compare the microbicidal effect of these laser systems under standardized conditions and to draw a conclusion upon their relative effectiveness in the deep layers of dentin. Study Design/Materials and Methods: In total, 360 slices of root dentin with a thickness of 1 mm were obtained by longitudinal cuts of freshly extracted human premolars. The samples were steam sterilized and subsequently inoculated with a suspension of either Escherichia coli or Enterococcus faecalis. After the incubation, the samples were randomly assigned to the four different laser systems tested. Each laser group consisted of two different operational settings and a control. The dentinal samples underwent ‘‘indirect’’ laser irradiation through the dentin from the bacteria-free side and were then subjected to a classical quantitative microbiologic evaluation. To assess the temperature increase during the irradiation procedure, additional measurements were carried out using a thermocouple. Results: Microbiology indicated that all laser systems were capable of significant reductions in both test strains. At an effective output power of 1 W, E. coli was reduced by at least three log steps in most of the samples by the tested wavelengths, with the best results for the Er:YAG laser showing complete eradication of E. coli in 75% of the samples. E. faecalis, a stubborn invader of the root canal, showed minor changes in bacterial count at 1 W. Using the higher setting of 1.5 W, significant reductions of E. coli were again observed with all laser systems, where only the diode and the Er:YAG laser were capable of complete eradication of E. faecalis to a significant extent. There was no significant relation between the temperature increase and the bactericidal effect. Conclusions: The present study demonstrates that all the wavelengths investigated are suitable for the disinfection of even the deeper layers of dentin and may prove to constitute valuable tools in state-of-the-art endodontics. Lasers Surg. Med. 35:111–116, 2004. 2004 Wiley-Liss, Inc.

Effects of low-intensity laser therapy on the orthodontic movement velocity of human teeth: a preliminary study.

Abstract: Background and Objectives: Low-intensity laser therapy (LILT) has been studied in many fields of dentistry, but to our knowledge, this is the first time that its effects on orthodontic movement velocity in humans are investigated. Study Design/Patients and Methods: Eleven patients were recruited for this 2-month study. One half of the upper arcade was considered control group (CG) and received mechanical activation of the canine teeth every 30 days. The opposite half received the same mechanical activation and was also irradiated with a diode laser emitting light at 780 nm, during 10 seconds at 20 mW, 5 J/cm 2 , on 4 days of each month. Data of the biometrical progress of both groups were statistically compared. Results: All patients showed significant higher acceleration of the retraction of canines on the side treated with LILT when compared to the control. Conclusions: Our findings suggest that LILT does accelerate human teeth movement and could therefore considerably shorten the whole treatment duration. Lasers Surg. Med. 35:117–120, 2004. 2004 Wiley-Liss, Inc.

Efficacy of 904 nm gallium arsenide low level laser therapy in the management of chronic myofascial pain in the neck: a double-blind and randomize-controlled trial.

Abstract: Background and Objectives: A prospective, doubleblind, randomized, and controlled trial was conducted in patients with chronic myofascial pain syndrome (MPS) in the neck to evaluate the effects of infrared low level 904 nm Gallium-Arsenide (Ga-As) laser therapy (LLLT) on clinical and quality of life (QoL). Study Design/Patients and Methods: The study group consisted of 60 MPS patients. Patients were randomly assigned to two treatment groups: Group I (actual laser; 30 patients) and Group II (placebo laser; 30 patients). LLLT continued daily for 2 weeks except weekends. Follow-up measures were evaluated at baseline, 2, 3, and 12 weeks. All patients were evaluated with respect to pain at rest, pain at movement, number of trigger points (TP), the Neck Pain and Disability Visual Analog Scale (NPAD), Beck depression Inventory (BDI), and the Nottingham Health Profile (NHP). Results: In active laser group, statistically significant improvements were detected in all outcome measures compared with baseline (P < 0.01) while in the placebo laser group, significant improvements were detected in only pain score at rest at the 1 week later of the end of treatment. The score for self-assessed improvement of pain was significantly different between the active and placebo laser groups (63 vs. 19%) (P < 0.01). Conclusion: This study revealed that short-period application of LLLT is effective in pain relief and in the improvement of functional ability and QoL in patients with MPS. Lasers Surg. Med. 35:229–235, 2004. 2004 Wiley-Liss, Inc.

MR thermometry-based feedback control of laser interstitial thermal therapy at 980 nm.

Abstract: Background and Objectives The goal of this study was to explore the feasibility of magnetic resonance thermal imaging (MRTI)-based feedback control of intracerebral laser interstitial thermal therapy (LITT), using a computer workstation and 980-nm diode laser interfaced to an MR scanner. Study Design/Materials and Methods A computer-controlled laser thermal therapy system was used to produce 12 ex vivo lesions in 3 canine and porcine brains and 16 in vivo lesions in 6 canines with diffusing tip fiberoptic applicators and energies from 54 to 900 J. MRTI predictions of thermal damage were correlated with histopathologic analysis. Results Under feedback control, no carbonization, vaporization, or applicator damage was observed. MRTI-based prediction of thermal dose was not significantly different from histological evaluation of achieved thermal necrosis. Conclusions The computer-controlled thermal therapy system was effective at regulating heating, eliminating carbonization and vaporization, and protecting fiberoptic applicators. MRTI estimation of thermal dose accurately predicted achieved thermal necrosis. Lasers Surg. Med. 34:48–55, 2004. © 2004 Wiley-Liss, Inc.

Histomorphometric study of the healing of human oral mucosa after gingivoplasty and low-level laser therapy.

Abstract: Background and objectives: The aim of the present study was to analyze the effects of diode laser irradiation on the healing of human oral mucosa. Materials and Methods: After gingivoplasty, the right hemi-arch (test group) of 16 patients was irradiated with a diode laser. The left side (control group) was not irradiated. Incisional biopsies were performed on both sides at 7, 14, 21, and 60 days after surgery and morphometrically analyzed by light microscopy. Results: Epithelium width ranged from 260.6 to 393.5 mm. Volume densities of basal (20.2%), prickle cell (55.6%), and cornified (24.2%) layers remained stable. The peak number of neutrophils were 6 cells/mm 2 and the mononuclear cells were 44 cells/mm 2 . Collagen fibers (80%) and fibroblasts (14%) occupied the main volume of connective tissue. The one-way ANOVA and the paired Student’s t-test were used for statistical analysis (P<0.05). Conclusion: Low-level laser therapy did not accelerate the healing of oral mucosa after gingivoplasty. Lasers Surg. Med. 35:377–384, 2004. 2004 Wiley-Liss, Inc.

Infrared imaging of subcutaneous veins

Abstract: Background and Objectives Imaging of subcutaneous veins is important in many applications, such as gaining venous access and vascular surgery. Despite a long history of medical infrared (IR) photography and imaging, this technique is not widely used for this purpose. Here we revisited and explored the capability of near-IR imaging to visualize subcutaneous structures, with a focus on diagnostics of superficial veins. Study Design/Materials and Methods An IR device comprising a head-mounted IR LED array (880 nm), a small conventional CCD camera (Toshiba Ik-mui, Tokyo, Japan), virtual-reality optics, polarizers, filters, and diffusers was used in vivo to obtain images of different subcutaneous structures. The same device was used to estimate the IR image quality as a function of wavelength produced by a tunable xenon lamp-based monochrometer in the range of 500–1,000 nm and continuous-wave Nd:YAG (1.06 μm) and diode (805 nm) lasers. Results The various modes of optical illumination were compared in vivo. Contrast of the IR images in the reflectance mode was measured in the near-IR spectral range of 650–1,060 nm. Using the LED array, various IR images were obtained in vivo, including images of vein structure in a pigmented, fatty forearm, varicose leg veins, and vascular lesions of the tongue. Conclusion Imaging in the near-IR range (880–930 nm) provides relatively good contrast of subcutaneous veins, underscoring its value for diagnosis. This technique has the potential for the diagnosis of varicose veins with a diameter of 0.5–2 mm at a depth of 1–3 mm, guidance of venous access, podiatry, phlebotomy, injection sclerotherapy, and control of laser interstitial therapy. Lasers Surg. Med. 34:56–61, 2004. © 2004 Wiley-Liss, Inc.

Effect of low-power laser irradiation on protein synthesis and ultrastructure of human gingival fibroblasts.

Abstract: Background and Objectives Low-power lasers improve wound healing. Cell proliferation and protein secretion are important steps of this process. The aim of this study was to analyze both protein synthesis and ultrastructural morphology of human gingival fibroblasts irradiated by a low-power laser. Study Design/Materials and Methods The cell line FMM1 was grown in nutritional deficit. Laser irradiation was carried out with a gallium–aluminum–arsenate (Ga–Al–As) diode laser (904 nm, 120 mW, energy density of 3 J/cm2). The protein synthesis analysis and ultrastructural morphology of control (non-irradiated) and irradiated cultures were obtained. Results There were changes in the structure of cytoplasm organelles of treated cells. The procollagen was not altered by the laser irradiation; however, there were a significant reduction of the amount of protein in the DMEM conditioned by irradiated cells. Conclusions Low-power laser irradiation causes ultrastructural changes in cultured fibroblasts. We suggest that these alterations may lead to disturbances in the collagen metabolism. Lasers Surg. Med. 34:260–265, 2004. © 2004 Wiley-Liss, Inc.

Dental bleaching efficacy with diode laser and LED irradiation: an in vitro study.

Abstract: Background and Objectives Bleaching techniques achieved significant advances with the use of coherent or incoherent radiation sources to activate the bleaching agents. This in vitro study compares the whitening efficacy of LED and diode laser irradiation using the two agents Opalescence X-tra and HP Whiteness. Study Design/Materials and Methods A total of 60 bovine incisors were randomly divided into six groups, three for each bleaching agent, receiving only agent, agent and LED (wavelength 470 nm), agent and 1.6 W diode laser (808 nm). The results of the irradiations were characterized using the CIEL*a*b* system. Results Significant differences in the chroma value are obtained for the two whitening agents and for the different light sources. In terms of lightness, the association of Laser and Whiteness HP bleaching gel showed significantly better results than when the same agent was used alone or in combination with LED. Conclusions Best overall results are obtained with the Whiteness HP and Laser association. Lasers Surg. Med. 35:254–258, 2004. © 2004 Wiley-Liss, Inc.

Methemoglobin formation during laser induced photothermolysis of vascular skin lesions.

Abstract: Background and Objective Monitoring dynamic changes during laser induced photothermolysis of vascular skin lesions is essential for obtaining an optimal therapeutic result. Rapid photoinduced thermal damage occurs at a threshold temperature of about 70°C. It is therefore, relevant to identify markers to indicate if this threshold temperature has been reached. Methemoglobin, which is formed by a photo-induced oxidation of hemoglobin, indicates that the temperature has reached this threshold value. This study presents a proof of concept of a method for monitoring the in vivo presence of methemoglobin immediately after laser exposure. Study Design/Materials and Methods The present study was designed to investigate the in vivo temperature dependence of hemoglobin absorption in the 450–800 nm spectrum range. In vivo diffuse reflectance measurements of port-wine stain (PWS) and telangiectasia were performed prior to, and immediately after, laser treatment with a pulsed dye laser (PDL) at 585 nm wavelength. Results In vivo measurements following laser treatment of vascular skin lesions showed an immediate increase in the optical absorption of blood. This effect, caused by thermal stress, is a result of an increased dermal blood volume fraction and methemoglobin formation. The effect is light dose dependent, and reflectance spectra revealed methemoglobin formation in patients treated with fluences above 5 J/cm2 at 585 nm wavelength. Conclusions It was proved that methemoglobin can be measured in vivo by reflectance spectroscopy. Measurements of the average methemoglobin concentrations immediately after laser exposure may be a valuable diagnostic tool to verify that the blood temperature has been sufficiently high to induce thermal damage to the vessel wall. Lasers Surg. Med. 34:414–419, 2004. © 2004 Wiley-Liss, Inc.

Optical clearing of in vivo human skin: Implications for light-based diagnostic imaging and therapeutics

Abstract: Lasers in Surgery and Medicine 34:83–85 (2004) Letter to the Editor Optical Clearing of In Vivo Human Skin: Implications for Light-Based Diagnostic Imaging and Therapeutics Misbah H. Khan, MD , Bernard Choi, PhD , Samuel Chess, BS , Kristen M. Kelly, MD , Jerry McCullough, and J. Stuart Nelson, MD , PhD * Beckman Laser Institute and Medical Clinic, University of California-Irvine, Irvine, CA 92612 The complex morphological nature of human skin provides a highly scattering medium for visible and near- infrared wavelengths due to variations in the indices of refraction of different components therein. Scattering diminishes the depth and clarity of images in light-based diagnostic imaging and attenuates the effective light dose that reaches targeted chromophores in laser therapeutics [1]. Light-based diagnostic techniques and therapeutics would likely be improved if scattering could be reduced, thereby enhancing light penetration into human skin. One method to enhance light penetration into skin is the use of hyperosmotic and biocompatible agents that induce an optical clearing effect [2]. Hyperosmotic agents result in refractive index matching between cells and ground substance in the dermis, which is believed to cause a reduction in optical scattering. Studies done by Vargas et al. [3] and Wang et al. [4], demonstrated that the injection of hyperosmotic agents into rat dermis could significantly reduce light scattering and thereby enhance the imaging depth of non-invasive techniques such as optical coherence tomography (OCT). If delivered by injection into the dermis, these hyperosmotic agents tend to dehydrate the skin and reduce the index mismatch between inter/in- tracellular components [5]. Although glycerol and polyethylene glycol (PEG) reduce optical scattering in human skin, their clinical utility has been very limited. Penetration of glycerol and PEG through intact skin is very minimal and extremely slow, because these agents are hydrophilic and penetrate the lipophilic stratum corneum poorly. In order to enhance skin penetra- tion, these agents need to be either injected into the dermis or the stratum corneum has to be removed, mechanically (e.g., tape stripping) or thermally (e.g., erbium: YAG laser ablation). Clinical utility would be improved if the clearing agent could be applied topically onto intact skin and there- after migrate across the stratum corneum and epidermis into the dermis. In this letter, we present our evaluation of the use of topically applied optical clearing agents in vitro as well as in vivo. Food and Drug Administration (FDA) approved lipophilic polypropylene glycol-based polymers (PPG) and hydrophilic PEG-based polymers, both with indices of refraction that closely match that of dermal collagen s 2004 Wiley-Liss, Inc. PhD , (1.47) were studied alone and in a combined pre-polymer mixture. To measure the optical properties (diffuse transmission and surface reflectance) of freshly excised in vitro human skin, an integrating sphere was used [6] with an inverse adding doubling algorithm [7] to estimate the reduced scattering coefficient ( s ’) of the samples. The optical clearing potential (OCP) was defined as the ratio of m s ’ immediately before and 24 hours after, agent application. Optical clearing agents including, glycerol and PPG- and PEG-based polymers compounds were applied alone, and in a PPG- and PEG-based combined pre-polymer mixture, topically on the epidermal side of the skin samples which were left undisturbed in an incubator at 378C for 24 hours. The OCP was found to be significantly higher for the lower molecular weight combined PPG- and PEG-based pre-polymer mixture as compared to glycerol or either pre-polymer alone. The combined PPG- and PEG-based pre-polymer mixture was also evaluated for its OCP in vivo. The volar forearm of a healthy volunteer was pre-cleaned, shaved and, divided into two areas, i.e., untreated control and where the combined pre-polymer mixture was topically applied onto the skin surface in the form of a thick layer under occlusion. After 2 hours, the mixture was removed and cross-polarized images of the hair shafts were obtained. Visualization of the intradermal portion of the hair shaft (approximately 1 mm deep) was enhanced on the area where the combined pre- polymer mixture was applied (Fig. 1). The combined PPG- and PEG-based pre-polymer mix- ture was topically applied to a 2 2 cm area on the leg of a healthy volunteer (that contained vascular telangiecta- sias). Cross-polarized images of the vessels before, and 2 hours after application under occlusion were obtained. Visibility of the telangiectasias was enhanced (approxi- mately 500 mm deep) and smaller telangiectatic branches *Correspondence to: J. Stuart Nelson, MD, PhD, Beckman Laser Institute, University of California, 1002 Health Sciences Road East Irvine, CA 92612-1475. E-mail: snelson@laser.bli.uci.edu Accepted 1 December 2003 Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/lsm.20014

In vivo optical coherence tomography for the diagnosis of oral malignancy.

Abstract: Background and Objective: Oral cancer results in 10,000 U.S. deaths annually. Improved highly sensitive diagnostics allowing early detection of oral cancer would benefit patient survival and quality of life. Objective was to investigate in vivo non-invasive optical coherence tomography (OCT) techniques for imaging and diagnosing neoplasia-related epithelial, sub-epithelial changes throughout carcinogenesis. Study Design/Materials and Methods: In the standard hamster cheek pouch model for oral carcinogenesis (n ¼ 36), in vivo OCT was used to image epithelial and sub-epithelial change. OCT- and histopathology-based diagnoses on a scale of 0 (healthy) to 6 (squamous cell carcinoma, SCC) were performed at all stages throughout carcinogenesis by two blinded investigators. Results: Epithelial, sub-epithelial structures were clearly discernible using OCT. OCT diagnosis agreed with the histopathological gold standard in 80% of readings. Conclusion: In vivo OCT demonstrates excellent potential as a diagnostic tool in the oral cavity. Lasers Surg. Med. 35:269–275, 2004. 2004 Wiley-Liss, Inc.

Comparison of the effects of laser, ultrasound, and combined laser + ultrasound treatments in experimental tendon healing.

Abstract: Background and Objective Therapeutic ultrasound (US) and laser (L) treatments accelerate and facilitate wound healing, and also have beneficial effects on tendon healing. This randomized control study was designed to evaluate the effects of low-intensity US and low-level laser therapy (LLLT) on tendon healing in rats. Study Design/Materials and Methods Eighty-four healthy male Swiss-Albino rats were divided into three groups consisting of 28 rats, the left Achilles tendons were used as treatment and the right Achilles tendons as controls. The right and left Achilles tendons of rats were traumatized longitudinally. The treatment was started on postinjury day one. We applied the treatment protocols including low-intensity US treatment in Group I (US Group), Sham US in Group II (SUS Group), LLLT in Group III (L Group), Sham L in Group IV (SL Group), US and LLLT in Group V (US + L Group), and Sham US and Sham L in Group VI (SUS + SL Group). The US treatment was applied with a power of 0.5 W/cm2, a frequency of 1 MHz, continuously, 5 minutes daily. A low-level Ga–As laser was applied with a 904 nm wavelength, 6 mW average power, 1 J/ cm2 dosage, 16 Hz frequency, for 1 minute duration, continuously. In the control groups, the similar procedures as in the corresponding treatment groups were applied with no current (Sham method). The treatment duration was planned for 9 days (sessions) in all groups, except the rats used for biochemical evaluation on the 4th day of treatment, which were treated for 4 days. We measured the levels of the tissue hydroxyproline for biochemical evaluation on the 4th, 10th, and 21st days following the beginning of treatment and the tendon breaking strength on the 21st day following the beginning of treatment for biomechanical evaluation. Seven rats in each group were killed on the 4th, 10th, and 21st days for biochemical evaluation and on the 21st day for biomechanical evaluation. Results The hydroxyproline levels were found to be significantly increased in the treatment groups on the 10th and 21st days compared to their control groups (P 0.05). In comparison of the tendon breaking strengths, it was found as significantly increased in the treatment groups compared with their control groups (P < 0.05), although there was no significant difference between the treatment groups. Conclusions Although US, L, and combined US + L treatments increased tendon healing biochemically and biomechanically more than the control groups, no statistically significant difference was found between them. Also we did not find significantly more cumulative positive effects of combined treatment. As a result, both of these physical modalities can be used successfully in the treatment of tendon healing. Lasers Surg. Med. 35:84–89, 2004. © 2004 Wiley-Liss, Inc.

Thermal therapy of canine cerebral tumors using a 980 nm diode laser with MR temperature-sensitive imaging feedback.

Abstract: Background and Purpose The laser-induced thermal therapy (LITT) of cerebral tumors has conventionally been performed using Nd:YAG lasers and is associated with a risk of high focal temperatures potentially followed by cavitation that could result in boiling and/or explosive char. We have developed small diffusing laser fiber tips to better distribute the energy deposition and a computer controlled feedback system to monitor therapy and prevent excess temperature buildup. In this study, we evaluated the feasibility of using magnetic resonance temperature imaging (MRTI)-based feedback system for the thermal treatment of experimental intracerebral tumors using 980 nm laser irradiation delivered through these diffusing tips. Study Design/Materials and Methods Transmissible venereal tumors (TVTs) were grown via inoculation in the right cerebral hemisphere of seven canines. The laser fiber tips were inserted into a total of 10 independent TVT-suspected regions in the seven animals. Margins for the target area in each animal were prescribed on the basis of pretreatment MR images. MRTI-based feedback software was used to measure and regulate both temperature and the delivered thermal dose to achieve the desired thermal ablation and prevent excess heating. The effects of treatment were verified by results of histologic analyses. Results Treatments resulted in contiguous areas of thermal necrosis in tumors and adjacent brain margin. The feedback software successfully cut off the laser power once the desired treatment volume was achieved, and prevented focal temperatures from exceeding predefined thresholds. Follow-up MRI studies showed 1.4- to 2.9-fold LITT-induced lesion expansion within 1–6 days after treatment. Conclusions Targeted thermal coagulation of small intracerebral tumors is feasible using MRTI-based feedback and diffused 980 nm diode laser light. Lasers Surg. Med. 35:41–50, 2004. © 2004 Wiley-Liss, Inc.

In vivo targeted gene transfer in skin by the use of laser-induced stress waves.

Abstract: Background and Objectives Much interest has been shown in the use of lasers for nonviral targeted gene transfer, since the spatial characteristics of laser light are quite well defined. The aim of this study was to demonstrate in vivo gene transfer by the use of laser-induced stress waves (LISWs). Study Design/Materials and Methods After reporter genes had been intradermally injected to rat skin in vivo, a laser target was placed on the gene-injected skin. LISWs were generated by the irradiation of an elastic laser target with 532-nm nanosecond laser pulses of a Q-switched Nd:YAG laser. Results Levels of luciferase activities for the skin exposed to LISWs were two orders of magnitude higher than those for the skin injected with naked DNA. Expressions of enhanced green fluorescent protein (EGFP) and β-galactosidase were observed only in the area that was exposed to LISWs, and in addition, epidermal cells were selectively transfected. No major side effects were observed, and luciferase activity levels as high as 105 RLU per mg of protein were sustained even 5 days after gene transfer. Conclusion Highly efficient and site-specific gene transfer can be achieved by applying a few pulses of nanosecond pulsed LISWs to rat skin in vivo. Lasers Surg. Med. 34:242–248, 2004. © 2004 Wiley-Liss, Inc.

Low level laser irradiation stimulates mitochondrial membrane potential and disperses subnuclear promyelocytic leukemia protein

Abstract: Background and Objectives: Low level laser irradiation (LLLI) is used to promote wound healing. Molecularly it is known to stimulate mitochondrial membrane potential (MMP), cytokine secretion, and cell proliferation. This study was designed to determine the influence of LLLI on the kinetics of MMP stimulation and decay, specific cytokine gene expression, and subcellular localization of promyelocytic leukemia (PML) protein on HaCaT human keratinocytes. Study Design/Material and Methods: The cells were irradiated by a 780 nm titanium–sapphire (Ti–Sa) laser with 2 J/cm 2 energy density. MMP was monitored with Mitotracker, a mitochondrial voltage-sensitive fluorescent dye. Cytokine gene expression was carried out using semiquantitative-reverse transcription polymerase chain reaction. Subcellular localization of PML protein, a cell-cycle checkpoint protein, was determined using immunofluorescent staining. Results: The fluorescence intensity of MMP was increased immediately after the end of LLLI by 148� 6% over control (P<0.001). Subsequently it decayed, reaching 51� 14% of the control level (P<0.01) within 200 minutes. This decay was characterized by an exponential curve (R¼ 0.96) with a lifetime of 79� 36 minutes (P<0.05). Following irradiation, the expression of interleukin-1a, interleukin-6, and keratinocyte growth factor (KGF) genes were transiently upregulated; but the expression of the proinflammatory gene interleukin-1b, was suppressed. The subnuclear distribution of PML was altered from discrete domains to its dispersed form within less than 1 hour after LLLI. Conclusions: These changes reflect a biostimulative boost that causes a shift of the cell from a quiescent to an activated stage in the cell cycle heralding proliferation and suppression of inflammation. Further characterization of MMP kinetics may provide a quantitative basis for assessment of the effect of LLLI in the clinical setting. Lasers Surg. Med. 35:369–376, 2004. 2004 Wiley-Liss, Inc.

A new mathematical approach to the diffusion approximation theory for selective photothermolysis modeling and its implication in laser treatment of port-wine stains.

Abstract: Background and Objectives Monte Carlo (MC) simulations of light–tissue interactions and analytical solutions for the diffusion approximation theory have been used to determine the optimal laser wavelength and radiant exposure to treat port-wine stains (PWS). Both approaches suggest that optimal parameters are a wavelength of 585 or 595-nm with pulse times of 0.45–20 milliseconds. However, which parameters are optimal is still unclear. As differences in vessel size and in temperature distribution within vessels appeared to be the main reasons for the varied responses to the same laser treatments, we sought to develop a solution to the diffusion approximation in order to calculate temperature distribution and the resulting coagulation pattern within specific blood vessels. Study Design/Materials and Methods The light and heat diffusion equations were simultaneously solved with the finite element method (FEM). The latent heat of evaporation was included in the thermal analysis. The temperature and coagulation patterns across specific blood vessels, within a heterogeneous medium, were calculated for laser wavelengths of 585 and 595-nm with clinical parameters. Results At 1.2 mm deep, the calculations predicted that vessels ranging from 50 to 100 μm in diameter would be coagulated from top to bottom, small vessels (10 μm) would be spared, and vessels larger than 150 μm would be partially coagulated. Coagulation across vessels was more uniform for the 595-nm than for the 585-nm wavelength. Maximal temperatures did not exceed 100°C because of the inclusion of latent heat in the thermal calculations. Conclusions To study laser treatments of PWS with the diffusion approximation, FEM is an effective method to calculate the coagulation patterns within specific blood vessels. To improve coagulation efficacy at 585 and 595-nm wavelengths, the radiant exposure should be increased without increasing the irradiance. Lasers Surg. Med. 34:335–347, 2004. © 2004 Wiley-Liss, Inc.

Investigation of fiber-optic probe designs for optical spectroscopic diagnosis of epithelial pre-cancers.

Abstract: Background and Objectives The first objective of this study was to evaluate the performance of fluorescence spectroscopy for diagnosing pre-cancers in stratified squamous epithelial tissues in vivo using two different probe geometries with (1) overlapping versus (2) non-overlapping illumination and collection areas on the tissue surface. Probe (1) and probe (2) are preferentially sensitive to the fluorescence originating from the tissue surface and sub-surface tissue depths, respectively. The second objective was to design a novel, angled illumination fiber-optic probe to maximally exploit the depth-dependent fluorescence properties of epithelial tissues. Study Design/Materials and Methods In the first study, spectra were measured from epithelial pre-cancers and normal tissues in the hamster cheek pouch and analyzed with a non-parametric classification algorithm. In the second study, Monte Carlo modeling was used to simulate fluorescence measurements from an epithelial tissue model with the angled illumination probe. Results An unbiased classification algorithm based on spectra measured with probes (1) and (2), classified pre-cancerous and normal tissues with 78 and 94% accuracy, respectively. The angled illumination probe design provides the capability to detect fluorescence from a wide range of tissue depths in an epithelial tissue model. Conclusions The first study demonstrates that fluorescence originating from sub-surface tissue depths (probe (2)) is more diagnostic than fluorescence originating from the tissue surface (probe (1)) in the hamster cheek pouch model. However in general, it is difficult to know a priori the optimal probe geometry for pre-cancer detection in a particular epithelial tissue model. The angled illumination probe provides the capability to measure tissue fluorescence selectively from different depths within epithelial tissues, thus obviating the need to select a single optimal probe design for the fluorescence-based diagnosis of epithelial pre-cancers. Lasers Surg. Med. 34:25–38, 2004. © 2004 Wiley-Liss, Inc.

Influence of pulse duration and pulse number in selective RPE laser treatment.

Abstract: Background and Objectives: The therapeutic effect of laser treatment for macular diseases is related to the damage to the retinal pigment epithelium (RPE) and the subsequent restoration of the defect due to RPE proliferation. In contrast to conventional laser treatment, it is possible to damage the RPE selectively and to spare the photoreceptors by using repetitive microsecond laser pulses. It was the aim of the study to investigate the influence of pulse duration and number of pulses on angiographically and ophthalmoscopically visible retinal damage thresholds in order to optimize treatment modalities. Study Design/Materials and Methods: In total, 625 laser lesions with various parameters were applied to the retina in 11 eyes of 6 Chinchilla breed rabbits using an experimental laser system (Nd:YLF at 527 nm). Pulse duration (1.7 microseconds and 200 nanoseconds) and number of pulses (100, 10, and 1 pulses) were varied at a constant repetition rate of 100 Hz. Damage thresholds were determined in terms of ophthalmoscopic and fluorescein angiographic visibility, and the therapeutic window (TW; angiographic ED50 vs. ophthalmoscopic ED50) as well as the safety range (SR; angiographic ED84 vs. ophthalmoscopic ED16) between both thresholds were calculated. Selected laser lesions were evaluated by histology. Results: Generally, the ED50 radiant exposure for angiographic visibility decreases for shorter laser pulses and with an increase in the number of pulses. The TW for both pulse durations (1.7 microseconds and 200 nanoseconds) was wider with 100 pulses than with single pulses. The widest TW was found for 100 pulses at 200 nanoseconds pulse duration (5.9-fold above the angiographic threshold), and the smallest TW with a factor of 1.6 was found for 1.7 microseconds single pulses. In terms of SR, only irradiation with 100 pulses at 200 nanoseconds pulse duration was associated with a ratio > 2. Independently of pulse duration, histological examination of laser sites 1 hour after irradiation revealed widely intact photoreceptors, while the underlying RPE was damaged. Conclusions: Pulse duration and number of pulses have a significant influence on RPE damage thresholds and consecutively on TW and SR. Because fundus pigmentation in humans may vary intra- and interindividually by a factor of 2, a large TW and ideally also a large SR should be ensured in a clinical treatment context. In rabbits, the safety range with 200 nanoseconds pulses is higher than with the pulse duration of 1.7 microseconds currently in clinical use. These findings suggest the need for clinical pilot studies to prove whether these results can be transposed to the situation in humans. Lasers Surg. Med. 34:206–215, 2004. 2004 Wiley-Liss, Inc.

Full face laser resurfacing: therapy and prophylaxis for actinic keratoses and non-melanoma skin cancer.

Abstract: Background Although there are many effective treatment modalities for individual actinic keratoses (AKs), widespread lesions on the photoaged face pose a challenge due to inefficient and ineffective therapy resulting in high rates of recurrence after local destruction. Full face laser resurfacing offers an effective and efficient treatment option that successfully reduces the number of AK's on diffusely damaged skin and may show a prophylactic benefit for preventing non-melanoma skin cancers. Objective To assess the efficacy of full face laser resurfacing in reducing the number of facial AK's by comparing preoperative and postoperative numbers of lesions present and to observe the incidence of non-melanoma skin cancer after full face laser resurfacing. Study Design A retrospective chart review of 24 patients with widespread facial AK's (greater than 30) treated with full face UPCO2 and/or Er:Yag laser resurfacing was performed. All patients were a minimum of 1 year post-operative following facial laser resurfacing. The recurrence of AK's and the occurrence of facial non-melanoma skin cancers in these patients was assessed through chart analysis. Results Widespread AK's were effectively eliminated in all patients. Twenty-one patients (87%) remained lesion free for at least 1 year. Fourteen of the 24 patients (58.3%) showed no new lesions during a 2-year follow-up. There was an overall 94% reduction in total number of AK's. Adverse effects included transient perioral scarring in one patient, S. aureus infection in two patients, and dyschromia in two patients. Conclusions Full face laser resurfacing provides long-term effective prophylaxis against AKs and may reduce the incidence of AK related squamous cell carcinoma. Lasers Surg. Med. 34:114–119, 2004. © 2004 Wiley-Liss, Inc.

Increased brain tumor resection using fluorescence image guidance in a preclinical model

Abstract: Division of Pathology, St. Michael’s Hospital, Toronto, Ontario, Canada M5B 1W8Background and Objectives: Fluorescence image-guided brain tumor resection is thought to assist neuro-surgeons by visualizing those tumor margins that mergeimperceptibly into normal brain tissue and, hence, aredifficult to identify. We compared resection completenessand residual tumor, determined by histopathology, afterwhite light resection (WLR) using an operating microscopeversus additional fluorescence guided resection (FGR).StudyDesign/MaterialsandMethods:Weemployedanintracranial VX2 tumor in a preclinical rabbit model and afluorescence imaging/spectroscopy system, exciting anddetecting the fluorescence of protoporphyrin IX (PpIX)induced endogenously by administering 5-aminolevulinicacid (ALA) at 4 hours before surgery.Results: Using FGR in addition to WLR significantly in-creased resection completeness by a factor 1.4 from 68 38to 98 3.5%, and decreased the amount of residual tumorpost-resection by a factor 16 from 32 38 to 2.0 3.5% ofthe initial tumor volume.Conclusions: Additional FGR increased completeness ofresection and enabled more consistent resections betweencases. Lasers Surg. Med. 35:181–190, 2004. 2004 Wiley-Liss, Inc.Key words: malignant glioma; VX2; 5-aminolevulinicacid; protoporphyrin IX; fluorescence imaging and spectro-scopyINTRODUCTIONThe treatment of patients with high-grade gliomasremainsamajorchallenge.Theprognosisforthesepatientsis poor, with a median survival time after diagnosis andtreatment of less than 1 year [1,2]. It has been suggestedthat the prognosis is linked to the completeness of tumorremoval [3–6]. A recent [7] study of 416 patients withglioblastoma multiforme indicated that resection of 89% ofthe tumor volume is necessary to improve survival, whileresection of 98% or more resulted in a significant survivaladvantage of 4.2 months compared with a resection of lessthan 98%. However, such a high degree of tumor resectionis often limited by the surgeon’s ability to distinguishresidual tumortissue from surrounding braintissue underconventional white light microscope illumination [8].Hence,methodsenablingbetterintraoperativediscrimina-tion of viable tumor borders should be valuable.Fluorescence imaging and spectroscopy using 5-amino-levulinic acid (ALA)-induced protoporphyrin IX (PpIX) is apotential technique to enhance contrast of viable tumorborders.Althoughadministrationoffluorescentmarkerstoenhance contrast of malignant gliomas is not new [9–13],marking tumors with ALA is conceptually different fromearlier investigations, since ALA is not itself fluorescentbut is metabolized into fluorescent PpIX by a number ofmalignant tumors in situ through enzymes of the heme-biosynthesis pathway [14]. ALA-PpIX has been usedwidely,bothforfluorescencediagnosticsandphotodynamictherapy [15]. It may avoid problems that arise when afluorescent marker is administered directly, such as leak-age from the tumor into surrounding normal brain tissue[16]. We have shown previously [17–20] that ALA-inducedPpIXlevelsinnormalbraintissue,especiallywhitematter,are very low. Clinical and preclinical studies suggest thatthe resulting selectivity of ALA-PpIX in certain braintumors [14,17–25] is a result of various factors. The lowpermeability of ALA at the blood–brain barrier (BBB)[17,26] reduces uptake in normal brain, whereas thecompromised BBB in certain brain tumors is thought topermit selective ALA transport. Different activities ofenzymes in the heme pathway have also been observedbetween tumor and normal tissues, which subsequentlyenable selective production of PpIX [27,28].

Use of 1,320 nm Nd:YAG laser for wrinkle reduction and the treatment of atrophic acne scarring in Asians.

Abstract: Background and objectives The role of 1,320 Nd:YAG in non-ablative skin rejuvenation in Asians is has not been established. Furthermore, no study has investigated the effectiveness of 1,320 Nd:YAG laser in the treatment of atrophic scarring in Asians. The objective of our study was to investigate the effectiveness of 1,320 Nd:YAG laser in wrinkle reduction and the treatment of atrophic acne scarring in Asians. Study Design/Materials and Methods Twenty-seven female patients were included in the study: seven were treated for acne scarring and the others for wrinkle reduction. A 1,320 nm Nd:YAG laser (Cooltouch II, Roseville, CA) was used to treat both the cheeks and forehead for the patients with wrinkles, and both cheeks only for patients with atrophic acne scarring. All patients received treatment in the post-auricular areas. A spot size of 10 mm was used, and three passes were performed (two pre-cooling and one post-cooling). Patients were treated monthly for 6 months. All patients were subjectively assessed before and after their last treatment sessions using a structured questionnaire, and objectively assessed by the use of clinical photographs for by independent observers. A cutometer was used to assess viscoelasticity, and biopsies were taken at the post-auricular site for assessment by a pathologist. Results The overall degree of patients' satisfaction was rated as 4.9 (range 0–9.8) for wrinkle reduction and 4 (range 0–10) for acne scarring. In terms of objective assessment by independent observers, the degree of improvement was considered to be mild or no change in most cases. The independent pathologist who assessed the degree of improvement in terms of increased collagen production detected no change in 8 patients, mild improvement in 9, and moderate improvement in 10.There was also improvement in term of epidermal thickness in 13 cases. Assessment by viscoelasticity indicated a significant degree of improvement in most parameters in both groups of patients. Blistering occurred in five cases, all in the central facial areas, and post-inflammatory hyperpigmentation occurred in three cases. All cases of PIH resolved after the use of 4% hydroquinoine. There was no scarring or hypopigmentation. Conclusions The 1,320 nm Nd:YAG laser is effective for wrinkle reduction and atrophic acne scar improvement, but to further enhance the clinical outcome a combination approach with another device such as IPL and a surgical technique such as subcision is necessary. Lasers Surg. Med. 34:98–103, 2004. © 2004 Wiley-Liss, Inc.

Flashlamp pulsed dye laser (PDL) suppression of keloid proliferation through down‐regulation of TGF‐β1 expression and extracellular matrix expression

Abstract: Background and Objectives Keloids have been treated with flashlamp pulsed dye lasers (PDLs) with good results. We investigated whether PDL treatments induced keloid regression by decreasing growth factor-β1 (TGF-β1) induction, thereby reducing fibroblast proliferation and collagen deposition. Study Design/Materials and Methods Clinical evaluation and photography documented keloid height/texture, erythema, and pliability before and after PDL treatments scheduled at 2-month intervals in 30 patients. Fluence per pulse was 10–18 J/cm2 (mean 14.0 J/cm2). Immunohistochemical (IHC) staining of TGF-β1, proliferating cell nuclear antigen (PCNA), and collagen (types I and III) in extra-cellular matrix was performed on 10 intra-lesional or punch biopsies obtained before and 7 days after PDL treatments. Results Twelve months after final PDL treatments, keloid regression ( ≥ 50%) had occurred in 26/30 patients in whom erythema and surface irregularities had been reduced and pliability had been increased. In 4/30 patients, no changes in keloids had occurred after 12 months. Multiple treatments ( > 6) yielded better results than fewer treatments: 79% versus 50%, respectively. Marked keloid regression ( ≥ 90%) occurred in two patients who had received more than 10 treatments. IHC staining indicated that expression of TGF-β1, PCNA and collagen type III, but not type I, was significantly reduced in keloid fibroblasts after PDL irradiation. Conclusions Keloids regressed following PDL-induced reduction in TGF-β1 expression, fibroblast proliferation, and collagen type III deposition. More than six PDL treatments at 2-month intervals provided the best results. Lasers Surg. Med. 34:104–108, 2004. © 2004 Wiley-Liss, Inc.

Treatment of vitiligo by 308-nm excimer laser: an evaluation of variables affecting treatment response.

Abstract: Background and Objectives To determine the true efficacy of the 308-nm excimer laser for the treatment of vitiligo, while taking into account confounding factors such as anatomic site of treatment, age, sex, skin type, MED, and duration of evolution of the vitiligo. Study Design/Materials and Methods Thirty-five patients with vitiligo were included. Each lesion was treated twice a week by the 308-nm excimer laser for a maximum of 24 sessions. Efficacy was blindly evaluated by two independent physicians. Results Repigmentation was noted in 46 plaques/52 (88.5%). Repigmentation rate (75%) was obtained in 14 (26.9%). In “UV sensitive” areas (face, neck, trunk), 8/14 lesions (57.1%) had a repigmentation rate, 75% versus 6/38 (15.8%) in “UV resistant” areas (bony prominences and extremities) (P = 0.031). No relationship could be established between response to the treatment and the following variables: age, sex, skin type, MED, and duration of evolution of the vitiligo (respectively, P = 1, 0.666, 0.566, 0.628, 0.521). Conclusions An aesthetically reasonable result is achieved essentially in “UV sensitive” areas, thus appearing to be the appropriate places of choice for this treatment. Lasers Surg. Med. 35:152–156, 2004. © 2004 Wiley-Liss, Inc.

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

Abstract: 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/cm 2 ; six pulses per packet; 550 msecond/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/cm 2 and over; epidermal damage was proportional to fluence with total coagulation of the epidermal layer at fluences of 1.75 J/cm 2 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 CD68þ monocytes/macrophages. At day 21 after laser treatment we observed collagen remodeling and (myo-)fibroblast proliferation at tissue depths of up to 240 mm. 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. Lasers Surg. Med. 35:146–151, 2004. 2004 Wiley-Liss, Inc.

Photodynamic Therapy of oral dysplasia with topical 5‐aminolevulinic acid and light‐emitting diode array

Abstract: Background and Objectives: In Taiwan, more than two million people have the betel quid (BQ) chewing habit which is a risk factor related to premalignant lesion and squamous cell carcinoma of oral cavity. We developed a light-emitting diode (LED) array combined with topical 5aminolevulinic acid (ALA) for photodynamic therapy (PDT) and evaluated its effectiveness for the treatment of oral lesions. Study Design/Materials and Methods: We compared the ALA-PDT effect of the homemade LED array to that of a commercial light source on cultured Ca9-22 human gingival carcinoma cells and the DMBA-induced hamster buccal pouch carcinoma model. Furthermore, we treated several patients having an oral lesion using a topical ALA delivery system and the LED array. Results: The LED array light source was as effective as the commercial light source for ALA-PDT in cultured Ca9-22 cells with LD50 of 4.5 and 4.3 J/cm 2 , respectively, using an MTT assay. This light source was also effective in the DMBA-induced hamster buccal pouch carcinoma model, and in the patients of oral leukoplakia. Conclusions: ALA-PDT is effective for premalignant lesions such as mucosal dysplasia and carcinoma in situ of oral cavity. Good results could be obtained by using the homemade LED array as light source. The LED array has the advantages of low cost, high reliability, and portability. It is safe, convenient and easy to use for the treatment of oral dysplasia. Lasers Surg. Med. 34:18–24, 2004. 2004 Wiley-Liss, Inc.

Combined photodynamic and photothermal induced injury enhances damage to in vivo model blood vessels.

Abstract: Author(s): Kelly, Kristen M; Kimel, Sol; Smith, Tia; Stacy, Amy; Hammer-Wilson, Marie J; Svaasand, Lars O; Nelson, J Stuart | Abstract: Background and objectivesThe degree of port wine stain (PWS) blanching following pulsed dye laser (PDL) therapy remains variable and unpredictable. Because of the limitations of current PDL therapy, alternative treatment approaches should be explored. The objective was to evaluate a novel methodology for selective vascular damage, combined photodynamic (PDT) and photothermal (PDL) treatment, using the in vivo chick chorioallantoic membrane (CAM) model.Study design/materials and methodsThirty microliters of benzoporphyrin derivative monoacid ring A (BPD) solution was administered intraperitoneally into chick embryos at day 12 of development. Study groups were: (1) control (no BPD, no light); (2) BPD alone; (3) continuous wave irradiation (CW) alone (576 nm, 60 mW/cm2, 125 seconds); (4) CW + PDL; (5) BPD+PDL; (6) PDT (BPD+CW); (7) PDL alone (585 nm, 4 J/cm(2)); and (8) PDT+PDL (BPD + CW followed immediately by PDL). Vessels were videotaped prior to, and at 1 hour post-intervention and then assessed for damage based on the following scale: 0, no damage; 1, coagulation; 1.5, vasoconstriction; 2.0, coagulation+vasoconstriction; 2.5, angiostasis; 3.0, hemorrhage. Damage scores were weighted by vessel "order."ResultsPDT + PDL resulted in significantly (P l 0.01) more severe vascular damage than was observed in any other study group: 127% more than PDT, 47% more than PDL alone.ConclusionsPDT + PDL is a novel and promising approach for selective vascular damage and may offer a more effective method for treatment of PWS and other vascular skin lesions.

Effect of 5-aminolevulinic acid-mediated photodynamic therapy on MCF-7 and MCF-7/ADR cells

Abstract: Graduate Institute of Oral Biology, College of Medicine, National Taiwan University; Taipei 100, TaiwanBackground and Objectives: Photodynamic therapy(PDT) has been proposed as an alternative approach inovercoming multidrug resistance (MDR) phenotype. Toverify whether 5-aminolevulinic acid (ALA)-mediated PDTis effective in MDR cells, we studied the protoporphyrin IX(PpIX)content,intracellularlocalization,andphototoxicityin human breast cancer cells MCF-7 and derived MDRsubline, MCF-7/ADR.Study Design/Materials and Methods: The fluores-cence kinetics of ALA-induced PpIX was evaluated byspectrofluorometer. The phototoxicity of MCF-7 and MCF-7/ADR cells was determined by tetrazolium (MTT) assaysand clonogenic assay. Furthermore, Annexin V and pro-pidium iodide (PI) binding assays were performed toanalyze the characteristics of cell death after ALA–PDT.Results:MCF-7/ADRaccumulatedalowerlevelofPpIXascompared to parental MCF-7 cells. Significant phototoxi-city was observed in MCF-7 and increased in a fluence-dependentmannerwithLD

Therapeutic ratio quantifies laser antisepsis: ablation of Porphyromonas gingivalis with dental lasers.

Abstract: Background and Objectives: It is established that both pulsed Nd:YAG (1,064 nm) and continuous diode (810 nm) dental lasers kill pathogenic bacteria (laser antisepsis), but a quantitative method for determining clinical dosimetry does not exist. The purpose of this study was to develop a method to quantify the efficacy of ablation of Porphyromonas gingivalis (Pg) in vitro for two different lasers. Study Design/Materials and Methods: The ablation thresholds for the two lasers were compared in the following manner. The energy density was measured as a function of distance from the output of the fiber-optic delivery system. Pg cultures were grown on blood agar plates under standard anaerobic conditions. Blood agar provides an approximation of gingival tissue for the wavelengths tested in having hemoglobin as a primary absorber. Single pulses of laser energy were delivered to Pg colonies and the energy density was increased until the appearance of a small plume was observed coincident with a laser pulse. The energy density at this point defines the ablation threshold. Ablation thresholds to a single pulse were determined for both Pg and for blood agar alone. Results: The large difference in ablation thresholds between the pigmented pathogen and the host matrix for pulsed-Nd:YAG represented a significant therapeutic ratio andPg was ablated without visible effect on the blood agar. Near threshold the 810-nm diode laser destroyed both the pathogen and the gel. Conclusions: Clinically, the pulsed Nd:YAG may selectively destroy pigmented pathogens leaving the surrounding tissue intact. The 810-nm diode laser may not demonstrate this selectivity due to its greater absorption by hemoglobin and/or longer pulse duration. Lasers Surg. Med. 35:206–213, 2004. 2004 Wiley-Liss, Inc.