Lasers in Surgery and Medicine

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.

Two prototype devices emitting at 1.5 μm 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.

Pattern densities with spacing of 250 μm or more were well tolerated. Typical MTZ had a diameter of 100 μm and penetrated 300 μm 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.

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.

Photodynamic therapy (PDT) appears to be endowed with several favorable features for the treatment of infections originated by microbial pathogens, including a broad spectrum of action, the efficient inactivation of antibiotic‐resistant strains, the low mutagenic potential, and the lack of selection of photoresistant microbial cells. Therefore, intensive studies are being pursued in order to define the scope and field of application of this approach.

Optimal cytocidal activity against a large variety of bacterial, fungal, and protozoan pathogens has been found to be typical of photosensitizers that are positively charged at physiological pH values (e.g., for the presence of quaternarized amino groups or the association with polylysine moieties) and are characterized by a moderate hydrophobicity (n‐octanol/water partition coefficient around 10). These photosensitizers in a micromolar concentration can induce a >4–5 log decrease in the microbial population after incubation times as short as 5–10 minutes and irradiation under mild experimental conditions, such as fluence‐rates around 50 mW/cm² and irradiation times shorter than 15 minutes.

PDT appears to represent an efficacious alternative modality for the treatment of localized microbial infections through the in situ application of the photosensitizer followed by irradiation of the photosensitizer‐loaded infected area. Proposed clinical fields of interest of antimicrobial PDT include the treatment of chronic ulcers, infected burns, acne vulgaris, and a variety of oral infections. Lasers Surg. Med. 38:468–481, 2006. © 2006 Wiley‐Liss, Inc.

We report the final results of a pilot clinical trial exploring the safety and feasibility of real‐time magnetic resonance‐guided laser‐induced thermal therapy (MRgLITT) for treatment of resistant focal metastatic intracranial tumors.

In patients with chemotherapy, whole‐brain radiation, and radiosurgery resistant metastatic intracranial tumors, minimally invasive stereotaxic placement of a saline‐cooled interstitial fiberoptic laser applicator under local anesthesia was followed by laser irradiation during continuous magnetic resonance imaging (MRI) scanning. A computer workstation extracted real‐time temperature‐sensitive information for feedback control over laser delivery. A total of 15 metastatic tumors were treated in 7 patients. Patients were followed with physical exam and imaging for 30 months.

In all cases, the procedure was well tolerated, and patients were discharged home within 24 hours. Follow‐up imaging at up to 30 months showed an acute increase in apparent lesion volume followed by a gradual and steady decrease. No tumor recurrence within thermal ablation zones was noted. Kaplan–Meier analysis indicated that the median survival was 19.8 months.

Real‐time magnetic resonance (MR) guidance of laser‐induced thermal therapy (LITT) offers a high level of control. This tool therefore enables a minimally invasive option for destruction and treatment of resistant focal metastatic intracranial tumors. MR‐guided LITT appears to provide a safe and potentially effective treatment for recurrent focal metastatic brain disease. A larger phase II and III series would be of interest to quantify potential median survival advantage. Lasers Surg. Med. 43:943–950, 2011. © 2011 Wiley Periodicals, Inc.

Phototherapy with low intensity laser irradiation has shown to be effective in promoting the proliferation of different cells. The aim of this in vitro study was to evaluate the potential effect of laser phototherapy (660 nm) on human dental pulp stem cell (hDPSC) proliferation.

The hDPSC cell strain was used. Cells cultured under nutritional deficit (10% FBS) were either irradiated or not (control) using two different power settings (20 mW/6 seconds to 40 mW/3 seconds), with an InGaAIP diode laser. The cell growth was indirectly assessed by measuring the cell mitochondrial activity through the MTT reduction‐based cytotoxicity assay.

The group irradiated with the 20 mW setting presented significantly higher MTT activity at 72 hours than the other two groups (negative control—10% FBS—and lased 40 mW with 3 seconds exposure time). After 24 hours of the first irradiation, cultures grown under nutritional deficit (10% FBS) and irradiated presented significantly higher viable cells than the non‐irradiated cultures grown under the same nutritional conditions.

Under the conditions of this study it was possible to conclude that the cell strain hDPSC responds positively to laser phototherapy by improving the cell growth when cultured under nutritional deficit conditions. Thus, the association of laser phototherapy and hDPSC cells could be of importance for future tissue engineering and regenerative medicine. Moreover, it opens the possibility of using laser phototherapy for improving the cell growth of other types of stem cells. Lesers Surg. Med. 40:433–438, 2008. © 2008 Wiley‐Liss, Inc.

Laser‐induced thermal therapy (LITT), coupled with magnetic resonance thermal imaging (MRTI) guidance, provides a minimally invasive and safe approach to treat brain tumors, especially metastases. We report here our experience using this treatment for recurrent glioblastomas.

Four patients, from 40 to 58 years old, were diagnosed with glioblastoma. After total resection, chemotherapy and radiation therapy, recurrence occurred. As each was ineligible for a second surgery, LITT was proposed as salvage therapy. Under stereotactic guidance, a fiberoptic applicator was inserted within the tumor LITT was performed under continuous MRTI. Real‐time feedback control based on MRTI was employed to assess the quality of local tissue destruction and to prevent unwanted damage to nearby structures.

The procedure was well tolerated with no peroperative neurological deterioration. In the short‐term follow‐up, one transient supplementary motor area syndrome, one epileptic seizure, and one cerebrospinal fluid leakage occurred. All were successfully managed. Post‐procedure MRI showed no complication, satisfying treatment volume, and a decrease in size of the treated tumor. For all patients, recurrence was observed with a mean/median progression free survival of 37/30 days. Mean/median overall survival after LITT was 10.5/10 months.

Focal tumor control was performed safely using minimally invasive LITT with real‐time MRTI control. LITT could be considered as salvage therapy for high‐grade recurrent gliomas if a 1‐day treatment is considered useful for a few weeks gain in survival. Larger experience will be required to define indications for such infiltrative disease and accurately determine a potentially significant survival gain in good neurological condition associated with this 1‐day procedure. Lasers Surg. Med. 44: 361–368, 2012. © 2012 Wiley Periodicals, Inc.

This study was designed to examine modes of cell death after photodynamic therapy (PDT).

Murine leukemia L1210 cells and human prostate Bax‐deficient DU145 cells were examined after PDT‐induced photodamage to the endoplasmic reticulum (ER). Phase contrast, fluorescence and electron microscopy were used to identify changes in cellular morphology, chromatin condensation, loss of mitochondrial membrane potential, and formation of phagolysosomes. Western blots were used to assess the processing of LC3‐I to LC3‐II, a marker for autophagy. Inhibitors of apoptosis and/or autophagy were used to delineate the contributions of the two pathways to the effects of PDT.

Both apoptosis and autophagy occurred in L1210 after ER photodamage with the latter predominating after 24 hours. In DU145 cells, PDT conditions causing comparable cytotoxicity only initiated autophagy. PI3‐kinase inhibitors suppressed autophagy in both cell lines as indicated by inhibition of vacuolization and LC3 processing.

Both autophagy and apoptosis were observed in L1210 cells following ER photodamage. In the Bax‐deficient DU145 cell line only autophagy was observed. Current information suggests that autophagy can function as either a survival or death pathway. We propose that in the context of PDT, this may also be true. Lasers Surg. Med. © 2006 Wiley‐Liss, Inc.

It has been shown previously that low‐level laser therapy (LLLT) significantly reduces infarct size following induction of myocardial infarction in rats and dogs. The aim of the present study was to investigate the effect of LLLT on the expression of vascular endothelial growth factor (VEGF) and inducible nitric oxide synthase (iNOS).

Myocardial infarction was induced by occlusion of the left descending artery in 87 rats. LLLT was applied to intact and post‐infarction. VEGF, iNOS, and angiogenesis were determined.

Both the laser‐irradiated rat hearts post‐infarction and intact hearts demonstrated a significant increase in VEGF and iNOS expression compared to non‐laser‐irradiated hearts. LLLT also caused a significant elevation in angiogenesis.

It is concluded that VEGF and iNOS expression in the infarcted rat heart is markedly upregulated by LLLT and is associated with enhanced angiogenesis and cardioprotection. Lasers Surg. Med. © 2006 Wiley‐Liss, Inc.

Low‐level laser therapy (LLLT) has been shown to have beneficial effects on ischemic skeletal and heart muscles tissues. The aim of the present study was to approve the effectiveness of LLLT treatment at different locations on the brain in acute stroked rats.

Stroke was induced in 169 rats that were divided into four groups: control non‐laser and three laser‐treated groups where laser was employed ipsilateral, contralateral, and both to the side of the induced stroke. Rats were tested for neurological function.

In all three laser‐treated groups, a marked and significant improvement in neurological deficits was evident at 14, 21, and 28 days post stroke relative to the non‐treated group.

These observations suggest that LLLT applied at different locations in the skull and in a rather delayed‐phase post stroke effectively improves neurological function after acute stroke in rats. Lasers Surg. Med. 38:70–73, 2006. © 2006 Wiley‐Liss, Inc.

In the classic model of pleurisy there is little evidence about the anti‐inflammatory effects of low‐level laser therapy (LLLT) as well the dosage characteristics, such as wavelength, total energy, number and pattern of treatment. In this study we investigated the potential effects of LLLT on modulating the pro‐inflammatory and anti‐inflammatory mediators of acute inflammation in a rat pleurisy model.

A sample of 48 female Wistar rats were divided into control and experiential groups. An inflammation was induced by carrageenan (0.2 ml) injected into the pleural cavity. At 1, 2, and 3 hours after induction a continuous wave (20 mW) diode laser of the InGaAlP (660 nm) type was used in the four laser groups with different doses and treatment patterns. One group received a single dose of 2.1 J and the other three groups received a total energy of 0.9, 2.1, and 4.2 J. Four hours later the exudate volume, total and differential leukocytes, protein concentration, NO, IL‐6, IL‐10, TNF‐α, and MCP‐1 were measured from the aspirated liquid.

All the treatment patterns and quantity of energy studied show significant reduction of the exudate volume (P<0.05). Using energy of 0.9 J only NO, IL‐6, MCP‐1 and IL‐10 are significantly reduced (P<0.05). On the other hand, higher energies (2.1 and 4.2 J) significantly reduce all variables independently of the treatment pattern. The neutrophil migration has a straight correlation with the TNF‐α (r = 0.551) and NO (r = 0.549) concentration.

LLLT—660 nm induced an anti‐inflammatory effect characterized by inhibition of either total or differential leukocyte influx, exudation, total protein, NO, IL‐6, MCP‐1, IL‐10, and TNF‐α, in a dose‐dependent manner. Under these conditions, laser treatment with 2.1 J was more effective than 0.9 and 4.2 J. Lesers Surg. Med. 40:500–508, 2008. © 2008 Wiley‐Liss, Inc.