Conductive interstitial thermal therapy (CITT) device evaluation in VX2 rabbit model.

We have developed a conductive interstitial thermal therapy (CITT) device to precisely and reliably deliver controlled thermal doses to the surgical margins at the cavity site following tumor resection, intraoperatively. The temperature field created by CITT ablation of a perfused tissue was modeled with a finite element package Femlab. The modeling suggested that a maximum probe temperature of 120 degrees C and an ablation time of 20 minutes were required to ablate highly perfused tissue such as the VX2 carcinoma. Deployable pins enable faster and more reliable thermal ablation. The model predictions were tested by thermal ablation of VX2 carcinoma tumors implanted in adult New Zealand rabbits. The size of the ablated region was confirmed with a viability stain, triphenyltetrazolium chloride (TTC). Histopathological examination revealed 3 regions in the ablated area: a carbonized region (1-3 mm); a region that contained thermally fixed cells; and an area of coagulated necrosis cells. Cells in the thermally fixed region stained for PCNA (proliferating cell nuclear antigen) and were bounded by the carbonized layer at the cavity wall, and by necrotic cells that exhibit nuclear fragmentation and cell dissociation, 5 to 10 mm away from the CITT probe. Adjacent tissue outside the target region was spared with a clear demarcation between ablated and normal viable tissue. It is suggested that the CITT device can be used, clinically, to inhibit local recurrence by creating negative surgical margins following the resection of a primary tumor in non-metastatic early staged tumors.

Nd:YAG lasers (1,064 nm) in the treatment of venous malformations of the face and neck: challenges and benefits.

Neodymium:yttrium aluminum garnet (Nd:YAG) laser therapy for venous malformations (VMs) of the head and neck is a rather new therapeutical option in addition to sclerotherapy and surgery. One hundred forty-six patients (age 2 months to 77.5 years) with VMs in the head/neck (localized, diffuse, and multifocal) were retrospectively analyzed with regard to number and quality of treatments and laser parameters used. Of these patients, 72 had no prior treatment of any kind, and 74 were pretreated. Laser treatment of mucosa and tongue was done with a mean fluence of 103.1 J/cm(2), of skin with 90.7 J/cm(2), and of glomuvenous malformations with 81.2 J/cm(2). Complex VM can mostly be controlled but rarely cured. Initial Nd:YAG laser therapy is important in the treatment of VMs regarding shrinkage of the tissue, discoloration, and induction of the desired dermal fibrosis that facilitates the surgical handling of the skin and reduces the risk of skin loss in surgery and sclerotherapy.

Mathematical modeling of selective photothermolysis to aid the treatment of vascular malformations and hemangioma with pulsed dye laser.

Pulsed dye lasers (PDL) are the standard of care in the treatment of cutaneous vascular disorders such as the port-wine strains or hemangiomas of infancy. Nonetheless, there is still uncertainty regarding the specific laser parameters that are likely to yield optimal clinical outcomes. Using mathematical modeling, we explain and associate clinical outcomes with laser wavelength, radiant exposure, and pulse time and shape. The model's prediction that a continuous PDL pulse of 0.45 ms with a radiant exposure of 6 J/cm(2) is equivalent to delivering a 1.5-ms pulse consisting of three pulses with a radiant exposure of 12 J/cm(2) is in agreement with clinical studies. The model also suggests that for vascular malformations involving vessel diameters in the range of 150-500 microm, one should use a PDL at a wavelength of 595 nm with a radiant exposure of at least 12 J/cm(2) and pulse time of 1.5 ms, delivered in three pulses. Whereas it is calculated that malformations with vessels smaller than 50 microm will not respond to PDL in any clinical setting, an excellent response to PDL treatment at either a 585- or 595-nm wavelength can be expected for malformations with vessel diameters of 50-150 microm. Epidermal cooling is highly recommended for all settings to minimize pain and the risk of side effects. Finally, the model is used to generate a reference table that suggests specific PDL parameters for the treatment of various malformations and hemangiomas. The table cannot replace a clinician's experience with respect to which and how parameters should be changed, but provides a defined window of parameters that should be tried to improve clinical response.

Complications following pulsed dye laser treatment of superficial hemangiomas.

BACKGROUND AND OBJECTIVE: Pulsed dye laser (PDL) has been reported to be safe and effective in the management of superficial hemangiomas of infancy. We report 12 patients with hemangiomas with complications following PDL. STUDY DESIGN/MATERIALS AND METHODS: Records of patients with hemangiomas and a known adverse outcome following PDL were reviewed. RESULTS: All were treated early (age range: 5 days to 4 months), and all hemangiomas were facial with a superficial component. Eleven were treated with a 585 nm wavelength, fluence range of 4.7-7 J/cm(2), without dynamic cooling. One patient received 7-12 J/cm(2) utilizing a 595 nm wavelength with dynamic cooling. In eight cases, treatment led to severe ulceration with subsequent pain, scarring, and in one instance, life-threatening hemorrhage. In four, permanent atrophic scarring was noted without ulceration. CONCLUSIONS: PDL treatment of superficial hemangiomas may rarely lead to significant complications including atrophic scarring and severe ulceration.

Reticulate erythema following diode laser-assisted hair removal: a new side effect of a common procedure.

The popularity of laser-assisted hair removal has grown rapidly since April 3, 1995 when the Food and Drug Administration approved the introduction of the first hair removal laser system. Lasers with wavelengths in the red and infrared portion of the electromagnetic spectrum are most often used for hair removal because they effectively target melanin in the hair follicle and can potentially penetrate to the appropriate depth of the dermis. Despite all efforts to protect the skin from damage, photoepilation may result in clinically significant adverse reactions. The most common and known side effects of laser hair removal include transient erythema, perifollicular edema, pain, folliculitis, hyper-pigmentation, hypopigmentation, crusting, purpura, erosions and scarring. The present report describes the appearance of a reticulate erythema after diode laser treatment for hair removal, encountered in 10 patients in our clinics in London and Israel. To the best of our knowledge, this is the first report of this side effect. The aim of this work is to detail the clinical manifestations, histological findings, and follow-up of these patients in order to expand the clinical spectrum of laser-assisted hair removal side effects and to alert dermatologists to the possibility of this type of net-like erythema.

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

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 microm in diameter would be coagulated from top to bottom, small vessels (10 microm) would be spared, and vessels larger than 150 microm 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 degrees 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.