Transpupillar laser phototherapy for retinal and choroidal tumors: A rational approach

Rol, Pascal O.; Fankhauser, Franz; Giger, Hans; Dürr, U.; Kwasniewska, Sylwia

doi:10.1007/s004170050352

Cited by 25 publications

(8 citation statements)

References 108 publications

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“…Não foi considerada a ação focalizadora do cristalino; m) Uma condição de contorno de temperatura constante foi imposta para a superfície posterior da esclera; n) Uma condição de contorno convectiva foi imposta sobre a superfície anterior do olho com coeficiente de transferência de calor estimado por Lagendijk (Scott, 1988) considerando a evaporação do filme lacrimal e a troca de calor por radiação e convecção para o ambiente com h = (20 ± 2) W/m 2 °C; o) As temperaturas iniciais nas diferentes regiões do olho foram obtidas por meio de uma simulação preliminar em regime estacionário para o olho não exposto à radiação; e p) Os eixos pupilar, visual e óptico foram considerados como coincidentes devido à simetria do problema. Para determinar o valor do dano térmico causado ao tecido nas várias camadas do olho, será utilizado o modelo que Birngruber (Rol et al, 2000) desenvolveu para determinar a função dano na retina e na coroide durante tratamentos com termoterapia transpupilar a laser. O modelo descreve o efeito do calor na taxa de reação química, e considera a variação na concentração de moléculas não danificadas, utilizando a lei de Arrhenius.…”

Section: Nomenclaturaunclassified

Análise computacional do dano térmico no olho humano portador de um melanoma de coroide quando submetido à termoterapia transpupilar a laser

Silva

Lyra

Lima

2013

RBEB

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Resumo Este trabalho apresenta um modelo bidimensional do olho humano para investigar a evolução da temperatura em estado transitório e o dano térmico associado nas camadas do olho e, principalmente, no melanoma de coroide. A modelagem e simulação computacional foram executadas para um paciente portador de um melanoma de coroide, submetido a um tratamento por irradiação com laser. Para determinar o campo de temperaturas, foi desenvolvido um modelo que utiliza a equação da biotransferência de calor de Pennes (BHTE-Bioheat Transfer Equation) que possui um termo de fonte/sumidouro que responde pelo calor transferido através da perfusão sanguínea. O modelo de Birngruber foi utilizado para determinar a função dano térmico durante a termoterapia transpupilar a laser (TTT). A análise foi efetuada a partir de uma imagem de ultrassom do paciente. Este tipo de exame forneceu as dimensões do olho e do tumor. O software comercial de CFD (Computational Fluid Dynamics) FLUENT, que emprega o Método dos Volumes Finitos (MVF), foi utilizado nas análises do modelo. Foram calculadas as temperaturas em estado estacionário para o olho não irradiado e estes resultados foram utilizados como condição inicial para a simulação de estado transitório para o olho irradiado, durante 60 segundos, com um laser de diodo (810 nm e potências de saída de 178, 222, 400 e 500 mW) cujos feixes apresentavam diâmetros de 2,0 e 3,0 mm e intensidades de 56.588 W/m 2 e 70.736 W/m 2 sobre a córnea. Para validar o modelo, os resultados das temperaturas, em estado estacionário para o olho não exposto à radiação do laser, foram comparados com outros mostrando uma boa concordância entre eles. Os resultados das temperaturas e do dano térmico, estado transitório, para o olho irradiado com o laser estão, qualitativamente, em acordo com a literatura disponível. Palavras-chave Melanoma de coroide, Dano térmico, BHTE, Birngruber, TTT, Simulação computacional. Computational analysis of thermal damage in the human eye carrying a choroidal melanoma when exposed to laser transpupillary thermotherapy treatment Abstract This paper presents a two-dimensional model of the human eye to investigate the evolution of temperature in transient state and the associated thermal damage in the layers of the eye and, especially in the choroidal melanoma. The computer modeling and simulation were performed for a patient with a choroidal melanoma, undergoing treatment by laser irradiation. To determine the temperature field, we developed a model that uses the Pennes Bioheat Transfer Equation (BHTE) that has a term of source/sink that responds to the heat transferred through the blood perfusion. The Birngruber model was used to determine the function of thermal damage during the laser transpupillary thermotherapy (TTT). The analysis was carried out from an ultrasound image of the patient. This type of examination provided the dimensions of the eye and the tumor. The CFD (Computational Fluid Dynamics) commercial software FLUENT ® , which uses the Finite Volume Method (FVM) was used in the ...

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Section: Nomenclaturaunclassified

Análise computacional do dano térmico no olho humano portador de um melanoma de coroide quando submetido à termoterapia transpupilar a laser

Silva

Lyra

Lima

2013

RBEB

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“…The kinetics of the thermal denaturation, whose ABCM parameters are the activation energy and temperature, is represented by an integral damage, ΩD, that measures the produced physical damage. For a given damage, the denaturation is determined only by the temporal changes in tissue temperature (Rol et al, 2000).…”

Section: Physical-mathematical Modelmentioning

confidence: 99%

“…The heat generated by the electronic sensors can damage the adjacent neuronal tissue to the implant sites and also the implant. Furthermore, the increase in temperatures may foster an environment suitable to bacteria proliferation that could potentiate infections (Schwiebert et al, 2002). Energy dissipation and temperatures must be carefully controlled in order to avoid damage to the retina and adjacent tissues which in turn could disturb retinal capillary blood flow.…”

Section: Introductionmentioning

confidence: 99%

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The use of an axisymmetric formulation of the Finite Volume Method for the thermal analysis of the retina and ocular tissues following implantation of retinal prosthesis

Silva¹,

Lima²,

Lyra³

et al. 2012

J. Braz. Soc. Mech. Sci. & Eng.

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“…Photocoagulation of tissue occurs when light energy is transformed into thermal energy [5]. The argon lasers are used in a variety of ophthalmic surgeries (e.g., removal of conjunctival cysts, iridotomy, and trabeculoplasty) due to its convenience, effectiveness, and safety [6][7][8][9]. Also, Wohlrab et al [10] reported cases in which benign tumors of the eyelid were successfully removed with an argon laser.…”

Section: Introductionmentioning

confidence: 99%

Modified argon laser therapy for benign tumor of the eyelid

et al. 2022

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Background To report about the therapy of benign eyelid tumors with a modified argon laser technique as an alternative to surgery. Methods Nineteen benign tumors of the eyelid were included in this study. After staining the surface of the tumor with a violet marker, low-energy argon laser photoablation was performed. A mean number of 312 spots (spot size ranging from 150 to 500 μm) with a power of 200 to 400 mW, and a duration between 0.1 and 0.2 s were applied. Results The eyelid tumors were located mainly in the lower eyelid (58%). Dermal nevi and papilloma were the most frequently treated lesions. Over a mean follow-up period of 10.5 months (range 6–18 months), all eyelid tumors were successfully treated by a single session of laser therapy. All patients were satisfied with the laser therapy and the cosmetic result. No postoperative complications were observed. No relapses occurred during follow-up. Conclusions Our modified method of argon laser therapy utilizes the staining of the surface of the eyelid tumor to increase the amount of thermal laser energy absorbed by the target. This novel technique is simple and effective for treating benign eyelid tumors.

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Transpupillar laser phototherapy for retinal and choroidal tumors: A rational approach

Abstract: Photothermotherapy is not without risk unless the temperature field can be well adapted to the tumorous structure, as temperature elevations outside a small therapeutic range that affect vital structures are considered to be a risk factor.

Cited by 25 publications

References 108 publications

Análise computacional do dano térmico no olho humano portador de um melanoma de coroide quando submetido à termoterapia transpupilar a laser

Análise computacional do dano térmico no olho humano portador de um melanoma de coroide quando submetido à termoterapia transpupilar a laser

The use of an axisymmetric formulation of the Finite Volume Method for the thermal analysis of the retina and ocular tissues following implantation of retinal prosthesis

Modified argon laser therapy for benign tumor of the eyelid

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