The application field that attracted a great deal of attention has been the medicine since the birth of the laser. From the beginning it was considered as a very potential and promising tool for several different application in medicine. Nevertheless nobody could have imagined at that time the development and the enormous effect of its use in so many different sectors of medicine ranging from surgery to oncology, from urology to ophtalmology, from ginecology to dermatology, from physiotherapy to aesthetic medicine. Nowadays the use of laser has become a very common practice in all the medicine sectors and with different pathologies. These pathologies have been cured thanks to the use of different laser sources, selected as a function of both wavelengths and power, and to more and more sophisticated technologies. We can just think to very complicated surgery operation which are performed in a successful way with the help of laser-scalpel, or to skin tumours treated with coherent light, to operation with laser endoscopy which is now the common practice, to get up to aesthetic, ophtalmology, and dermatological operations, and so on. Dermatology is one of the medical field in which laser action has been succesfully employed. Deseases like skin melanoms and angioma are usually treated with laser theraphy. In this field, during the last decades, technology supplied laser sources with technical properties specifically designed in order to accomplish the specific requirements of several application. Nowadays dermatologists can rely on a wide range of lasers which vary in wavelengths (some of them out of the visible range) and thus they can be selectively employed according to the specific application and type of pathology. The activity of the doctor consists in applying the laser light for a specific time and with a fixed intensity in the area of interest of the skin of the patient. After, he verifies the effects induced by the light laser after one or two weeks time. The physician usually makes use of the laser on his patient in an empirical way. Basically, just according to his own experience he decides the duration of the application and the intensity of laser light on the skin according to some parameters such as the individual patient, the pathology and the skin phototype. In most of the treatments what happens is that the doctor has no possibility to directly evaluate the effect of the laser applied on line since the wavelength of it is not in the visible range or it is pulsed. This means flashes of few milliseconds too fast to be recorded by the eyes. This limits the operation of the doctor because the beam power chosen might be too low or too high on one side or the duration of the pulse too short or too long respectively. The information comes only after a few days or weeks later to the physician. And this seems to be the only remarkable limit in the application of laser in dermatology. It is important to underline that the doctor should always work under a safe regime for the patient. This means that he has to avoid damages like scars which might occur since he has no direct vision of the interaction light-treated tissues and so he usually prefers working with a lower intensity of light. This aspect, on one side means a safer situation for the patient but on the other side minimize the efficacy of the therapy making the cure time longer. The possibility to give to the doctor a tool which makes him able to monitor on-line the reaction of the skin during the laser application (and not just examining the post application effects) means: 1- To enhance the performances of the light effect enlarging remarkably the application fields 2- To optimize the action in itself in terms of both efficiency and curing times. In photothermal regime, since the effect of the application of laser light on skin is linked to the local temperature induced, it is possible to evaluate the effects of such an interaction studying the thermal dynamic and in general the thermal behaviour of the tissues. In this view infrared thermography seems to be the best solution. Thanks to this technique, it is possible to achieve information about thermal interaction of surface and subsurface structure of the target under investigation by analysis and images elaboration. In the laser therapy field, infrared imaging technology can be used for a real-time monitoring of the laser-biological tissue interaction. This technique makes possible the direct evaluation about the reaction of the tissue in the specific region treated. The equipment capable of performing such measures is the infrared camera since it supplies thermal images which represent the dynamic thermal evolution laser induced. In the research activity of this work-thesis, the main pathology monitored and studied by infrared technique has been the Plane Angioma known as Port Wine Stain (PWS) pathology. This pathology is a vascular malformation that consists of a blood vessels accumulation under the tissue. This accumulation form a subsurface plane of vessels of depth and thickness depending on the specific anatomic region and, in general, different from case to case. It's possible to obtain information about the specific plane of blood vessels under treatment monitoring the thermal reaction of the tissue under laser action by IR imaging technique. The main target of this study are: - To evaluate the support of the infrared imaging, in the dermtological field, as a tool for scientific investigation And in particular way - To evaluate the employment of this technique as a tool for the control and optimization of laser parameters in order to make the treatment safer and more efficient In this work a novel methodological approach for the laser parameters optimization in the treatment on plane angioma is proposed. In particular, with this approach, an active thermography model, present in the literature, is employed in order to find morphological information for a specific plane angioma. With this model from the temporal evolution of the temperature obtained on the tissue after a single laser pulse-test (heat souce), it is possible to get a local evaluation of the depth and thickness of the plane of blood vessels in the anatomic area that the physician wants to treat. This information permits a morphological reconstruction of the multilayer biological tissue under treatment. Subsequently, a 2D+1 numerical simulation based on a biometric heat transfer model is executed on this multilayer. With the simulations the thermal behaviour of the biological multilayers can be achieved for different set of laser parameters as input. By the evaluations obtained with this approach, the operator can adjust the laser parameters for each specific therapy in a proper way changing the intensity and the duration of the laser ligth according to the type of plane of vessels and to the skin phototype treated. This allows to specialists to employ laser systems in a more specific, well controlled and less empiric way. The research activity, theoretical and experimental, object of this thesis work, is described in four chapters. In the first chapter the foundamental theoretical concept of the laser-tissue interaction are presented. In particular, the main interaction mechanisms as the photothermal interaction, the photochemical interaction, the photoablation, the plasma-induced ablation and the photodisruption are described. The chapter conclude with the state of art of the laser application in medical field. In the second chapter the priciples and applications of the infrared imaging technique are reported. The passive and active approach are explained. The problems relative to atmospheric trasmittance and infrared detectors are treated. At the end of the chapter, our novel approach and , in particular, the new application of infrared imaging in medical science are discussed. The third chapter, is the reading key for the understanding of the experimental work presented in this thesis. A detailed description of the activity research is given. The novel approach proposed and realized, the pathology analized and computation instruments used are treated and discussed. Particularly, the pulsed thermography model and the numerical approach employed in the operative protocol performed are explained in detail. In the last chapter, the main experimental and numerical results found are reported and discussed. The main characteristic of the laser tool and the infrared cameras used in the monitoring are showed. Some preliminaries results are presented. Numerical and experimental results achieved with the novel approach proposed and relative to different multilayer biological tissues affected by plane angioma are illustrated and compared. In the conclusions of the chapter, some set of laser parameters optimized for treatment of specific clinical situations are proposed. The experimental research activity has been made in collaboration with the Department of Dermatology of the University II Policlinico in Naples, monitoring patients in the laser therpay and photodynamics ambulatory. The data analysis and imaging elaboration have been done in the LIRT (Lab of Infrared Imaging and Thermography) of the Cibernetic Institute of CNR "E. Caianiello" in Pozzuoli (Na), which funded my grant, under the supervision of Dr. P. Mormile and in collaboration with Dr. L. Petti to whom go my most sincere thanks. In addition I also want to thank Dr. A. Baldo and Dr. G. Monfregola of the Department of Dermatology of the University II Policlinico for their availability, support and courtesy.
Infrared Imaging for Laser-Therapy Monitoring
RIPPA MASSIMO
2010
Abstract
The application field that attracted a great deal of attention has been the medicine since the birth of the laser. From the beginning it was considered as a very potential and promising tool for several different application in medicine. Nevertheless nobody could have imagined at that time the development and the enormous effect of its use in so many different sectors of medicine ranging from surgery to oncology, from urology to ophtalmology, from ginecology to dermatology, from physiotherapy to aesthetic medicine. Nowadays the use of laser has become a very common practice in all the medicine sectors and with different pathologies. These pathologies have been cured thanks to the use of different laser sources, selected as a function of both wavelengths and power, and to more and more sophisticated technologies. We can just think to very complicated surgery operation which are performed in a successful way with the help of laser-scalpel, or to skin tumours treated with coherent light, to operation with laser endoscopy which is now the common practice, to get up to aesthetic, ophtalmology, and dermatological operations, and so on. Dermatology is one of the medical field in which laser action has been succesfully employed. Deseases like skin melanoms and angioma are usually treated with laser theraphy. In this field, during the last decades, technology supplied laser sources with technical properties specifically designed in order to accomplish the specific requirements of several application. Nowadays dermatologists can rely on a wide range of lasers which vary in wavelengths (some of them out of the visible range) and thus they can be selectively employed according to the specific application and type of pathology. The activity of the doctor consists in applying the laser light for a specific time and with a fixed intensity in the area of interest of the skin of the patient. After, he verifies the effects induced by the light laser after one or two weeks time. The physician usually makes use of the laser on his patient in an empirical way. Basically, just according to his own experience he decides the duration of the application and the intensity of laser light on the skin according to some parameters such as the individual patient, the pathology and the skin phototype. In most of the treatments what happens is that the doctor has no possibility to directly evaluate the effect of the laser applied on line since the wavelength of it is not in the visible range or it is pulsed. This means flashes of few milliseconds too fast to be recorded by the eyes. This limits the operation of the doctor because the beam power chosen might be too low or too high on one side or the duration of the pulse too short or too long respectively. The information comes only after a few days or weeks later to the physician. And this seems to be the only remarkable limit in the application of laser in dermatology. It is important to underline that the doctor should always work under a safe regime for the patient. This means that he has to avoid damages like scars which might occur since he has no direct vision of the interaction light-treated tissues and so he usually prefers working with a lower intensity of light. This aspect, on one side means a safer situation for the patient but on the other side minimize the efficacy of the therapy making the cure time longer. The possibility to give to the doctor a tool which makes him able to monitor on-line the reaction of the skin during the laser application (and not just examining the post application effects) means: 1- To enhance the performances of the light effect enlarging remarkably the application fields 2- To optimize the action in itself in terms of both efficiency and curing times. In photothermal regime, since the effect of the application of laser light on skin is linked to the local temperature induced, it is possible to evaluate the effects of such an interaction studying the thermal dynamic and in general the thermal behaviour of the tissues. In this view infrared thermography seems to be the best solution. Thanks to this technique, it is possible to achieve information about thermal interaction of surface and subsurface structure of the target under investigation by analysis and images elaboration. In the laser therapy field, infrared imaging technology can be used for a real-time monitoring of the laser-biological tissue interaction. This technique makes possible the direct evaluation about the reaction of the tissue in the specific region treated. The equipment capable of performing such measures is the infrared camera since it supplies thermal images which represent the dynamic thermal evolution laser induced. In the research activity of this work-thesis, the main pathology monitored and studied by infrared technique has been the Plane Angioma known as Port Wine Stain (PWS) pathology. This pathology is a vascular malformation that consists of a blood vessels accumulation under the tissue. This accumulation form a subsurface plane of vessels of depth and thickness depending on the specific anatomic region and, in general, different from case to case. It's possible to obtain information about the specific plane of blood vessels under treatment monitoring the thermal reaction of the tissue under laser action by IR imaging technique. The main target of this study are: - To evaluate the support of the infrared imaging, in the dermtological field, as a tool for scientific investigation And in particular way - To evaluate the employment of this technique as a tool for the control and optimization of laser parameters in order to make the treatment safer and more efficient In this work a novel methodological approach for the laser parameters optimization in the treatment on plane angioma is proposed. In particular, with this approach, an active thermography model, present in the literature, is employed in order to find morphological information for a specific plane angioma. With this model from the temporal evolution of the temperature obtained on the tissue after a single laser pulse-test (heat souce), it is possible to get a local evaluation of the depth and thickness of the plane of blood vessels in the anatomic area that the physician wants to treat. This information permits a morphological reconstruction of the multilayer biological tissue under treatment. Subsequently, a 2D+1 numerical simulation based on a biometric heat transfer model is executed on this multilayer. With the simulations the thermal behaviour of the biological multilayers can be achieved for different set of laser parameters as input. By the evaluations obtained with this approach, the operator can adjust the laser parameters for each specific therapy in a proper way changing the intensity and the duration of the laser ligth according to the type of plane of vessels and to the skin phototype treated. This allows to specialists to employ laser systems in a more specific, well controlled and less empiric way. The research activity, theoretical and experimental, object of this thesis work, is described in four chapters. In the first chapter the foundamental theoretical concept of the laser-tissue interaction are presented. In particular, the main interaction mechanisms as the photothermal interaction, the photochemical interaction, the photoablation, the plasma-induced ablation and the photodisruption are described. The chapter conclude with the state of art of the laser application in medical field. In the second chapter the priciples and applications of the infrared imaging technique are reported. The passive and active approach are explained. The problems relative to atmospheric trasmittance and infrared detectors are treated. At the end of the chapter, our novel approach and , in particular, the new application of infrared imaging in medical science are discussed. The third chapter, is the reading key for the understanding of the experimental work presented in this thesis. A detailed description of the activity research is given. The novel approach proposed and realized, the pathology analized and computation instruments used are treated and discussed. Particularly, the pulsed thermography model and the numerical approach employed in the operative protocol performed are explained in detail. In the last chapter, the main experimental and numerical results found are reported and discussed. The main characteristic of the laser tool and the infrared cameras used in the monitoring are showed. Some preliminaries results are presented. Numerical and experimental results achieved with the novel approach proposed and relative to different multilayer biological tissues affected by plane angioma are illustrated and compared. In the conclusions of the chapter, some set of laser parameters optimized for treatment of specific clinical situations are proposed. The experimental research activity has been made in collaboration with the Department of Dermatology of the University II Policlinico in Naples, monitoring patients in the laser therpay and photodynamics ambulatory. The data analysis and imaging elaboration have been done in the LIRT (Lab of Infrared Imaging and Thermography) of the Cibernetic Institute of CNR "E. Caianiello" in Pozzuoli (Na), which funded my grant, under the supervision of Dr. P. Mormile and in collaboration with Dr. L. Petti to whom go my most sincere thanks. In addition I also want to thank Dr. A. Baldo and Dr. G. Monfregola of the Department of Dermatology of the University II Policlinico for their availability, support and courtesy.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
