The aim of this study is to assess the effects of Nd:YAG laser light on pancreatic tissue. The final goal is to investigate the feasibility of Laser Ablation (LA) for the removal of pancreatic cancer. Besides the high mortality and the poor diagnosis of pancreatic tumor, treatments for inoperable patients are limited, and consist mainly in palliative methods aimed to reduce the pain and to slightly improve the life quality of the patient. The social and economic impacts of the traditional surgery, the Whipple procedure, for pancreatic cancer removal is high, considering the strong invasivity and the reduced life expectancy, the use of many resources of the hospital (i.e., a expert surgeon, a complete and experienced team, the operating theatre available for many hours) and the long recovery times, among other factors. Since an adjuvant solution is desirable, the Endoscopic Ultrasound guided-LA represents a minimally-invasive solution for removal of pancreatic cancer: it is an alternative to the traditional surgery, and can be employed also in patients who cannot undergone operation. Laser light is carried inside the deep seated neoplasia through an optical fiber applicator, guided in the target site trough an endoscope, and images can be acquired by an ultrasound probe placed on the tip of the endoscope, avoiding percutaneous entry. Positive outcomes in EUS guided-LA in vivo procedure have been preliminary carried out in our Hospital (Endoscopy Unit of University Campus Bio-Medico di Roma) on human liver neoplasia and on pancreases of eight healthy pigs with a Nd:YAG laser. EUS guided-LA was applied on porcine pancreases, with different laser power settings, showing no post-procedure complications within 24 hours after treatment. The promising results of the first trials on animal models encourage to pursue the research on LA application on pancreas. In order to plan a safe and effective therapy, a mathematical model of the thermal effects caused by pancreas absorption of laser light is useful. The prediction of injured tissue volume size and temperature rise during treatment may allow to optimize the dosimetry of LA. In the present study, I implemented a theoretical model to predict the temperature distribution within pancreas undergoing LA, and several experimental trials have been performed, aiming to assess capability prediction of theoretical model and outcome on pancreas. The interaction between pancreatic tissue and Nd:YAG laser has been assessed from two perspectives: the measurement of temperature distribution within pancreas undergoing LA, and the estimation of optical properties of tissue. Thermometry trials have been carried out considering two modalities: invasive one, using temperature sensors (Fiber Bragg Gratings, thermocouples, Fluoroptic probes), and non-invasive one, based on CT-scan and MRI images. Although the drawback of invasivity, Fiber Bragg gratings have the advantages to be MRI compatible, and the small size (diameter of 250 µm) allows performing quasi-punctual measurement. Furthermore, they are not affected by measurement artifact, if compared with thermocouples and Fluoroptic probes, due to direct light absorption, and do not present artifacts on CT images during CT-thermometry. All these features make FBG the most appropriate sensors for LA thermometry. As far as it concerns non-invasive thermometry, images-based thermometry aims to provide real time images with acceptable temperature resolution: both CT-scan and MRI-based approach are suitable for temperature monitoring during LA on pancreas. Results obtained during trials show a thermal sensitivity of methods comparable with the results reported in current literature for other tissue (e.g., liver). Also the performances of Dual-Source CT (DSCT) scanner have been evaluated for thermotherapy purposes, in collaboration with Radiology Department in Klinikum of Goethe Universität (Frankfurt am Main, Germany). Three fusion factors, corresponding at three kVp settings (80 kV, 110 kVp and 140 kVp), have been analyzed, and their thermal sensitivity has been assessed. On the other hand, the investigation of laser-pancreas interaction included also the study of pancreas optical properties, absent in the currently literature, since this project represents the first study about laser irradiated pancreas. Biological tissue are highly scattering media, and the phenomenon of conversion of laser light into heat is related to the capability of tissue to absorb and to scatter laser light. Two experimental approaches have been employed to estimate tissue optical properties: the first one is based on a double integrating sphere system, and the second one on goniometric and spectrophotometric measurements, in collaboration with Biophysik Institute of Goethe Universität (Frankfurt am Main, Germany). Although still under investigation, preliminary results are comparable with data of other tissues: e.g., for native porcine liver at 850 nm I measured an anisotropy factor of 0.947, comparable with the range of values between 0.93 and 0.95 reported by some authors.

Interaction between pancreatic tissue and Nd:YAG laser for ablation purpose: thermometry and optical characterization / Paola Saccomandi - : . , 2014 Mar 26. ((26. ciclo

Interaction between pancreatic tissue and Nd:YAG laser for ablation purpose: thermometry and optical characterization

2014-03-26

Abstract

The aim of this study is to assess the effects of Nd:YAG laser light on pancreatic tissue. The final goal is to investigate the feasibility of Laser Ablation (LA) for the removal of pancreatic cancer. Besides the high mortality and the poor diagnosis of pancreatic tumor, treatments for inoperable patients are limited, and consist mainly in palliative methods aimed to reduce the pain and to slightly improve the life quality of the patient. The social and economic impacts of the traditional surgery, the Whipple procedure, for pancreatic cancer removal is high, considering the strong invasivity and the reduced life expectancy, the use of many resources of the hospital (i.e., a expert surgeon, a complete and experienced team, the operating theatre available for many hours) and the long recovery times, among other factors. Since an adjuvant solution is desirable, the Endoscopic Ultrasound guided-LA represents a minimally-invasive solution for removal of pancreatic cancer: it is an alternative to the traditional surgery, and can be employed also in patients who cannot undergone operation. Laser light is carried inside the deep seated neoplasia through an optical fiber applicator, guided in the target site trough an endoscope, and images can be acquired by an ultrasound probe placed on the tip of the endoscope, avoiding percutaneous entry. Positive outcomes in EUS guided-LA in vivo procedure have been preliminary carried out in our Hospital (Endoscopy Unit of University Campus Bio-Medico di Roma) on human liver neoplasia and on pancreases of eight healthy pigs with a Nd:YAG laser. EUS guided-LA was applied on porcine pancreases, with different laser power settings, showing no post-procedure complications within 24 hours after treatment. The promising results of the first trials on animal models encourage to pursue the research on LA application on pancreas. In order to plan a safe and effective therapy, a mathematical model of the thermal effects caused by pancreas absorption of laser light is useful. The prediction of injured tissue volume size and temperature rise during treatment may allow to optimize the dosimetry of LA. In the present study, I implemented a theoretical model to predict the temperature distribution within pancreas undergoing LA, and several experimental trials have been performed, aiming to assess capability prediction of theoretical model and outcome on pancreas. The interaction between pancreatic tissue and Nd:YAG laser has been assessed from two perspectives: the measurement of temperature distribution within pancreas undergoing LA, and the estimation of optical properties of tissue. Thermometry trials have been carried out considering two modalities: invasive one, using temperature sensors (Fiber Bragg Gratings, thermocouples, Fluoroptic probes), and non-invasive one, based on CT-scan and MRI images. Although the drawback of invasivity, Fiber Bragg gratings have the advantages to be MRI compatible, and the small size (diameter of 250 µm) allows performing quasi-punctual measurement. Furthermore, they are not affected by measurement artifact, if compared with thermocouples and Fluoroptic probes, due to direct light absorption, and do not present artifacts on CT images during CT-thermometry. All these features make FBG the most appropriate sensors for LA thermometry. As far as it concerns non-invasive thermometry, images-based thermometry aims to provide real time images with acceptable temperature resolution: both CT-scan and MRI-based approach are suitable for temperature monitoring during LA on pancreas. Results obtained during trials show a thermal sensitivity of methods comparable with the results reported in current literature for other tissue (e.g., liver). Also the performances of Dual-Source CT (DSCT) scanner have been evaluated for thermotherapy purposes, in collaboration with Radiology Department in Klinikum of Goethe Universität (Frankfurt am Main, Germany). Three fusion factors, corresponding at three kVp settings (80 kV, 110 kVp and 140 kVp), have been analyzed, and their thermal sensitivity has been assessed. On the other hand, the investigation of laser-pancreas interaction included also the study of pancreas optical properties, absent in the currently literature, since this project represents the first study about laser irradiated pancreas. Biological tissue are highly scattering media, and the phenomenon of conversion of laser light into heat is related to the capability of tissue to absorb and to scatter laser light. Two experimental approaches have been employed to estimate tissue optical properties: the first one is based on a double integrating sphere system, and the second one on goniometric and spectrophotometric measurements, in collaboration with Biophysik Institute of Goethe Universität (Frankfurt am Main, Germany). Although still under investigation, preliminary results are comparable with data of other tissues: e.g., for native porcine liver at 850 nm I measured an anisotropy factor of 0.947, comparable with the range of values between 0.93 and 0.95 reported by some authors.
Interaction between pancreatic tissue and Nd:YAG laser for ablation purpose: thermometry and optical characterization / Paola Saccomandi - : . , 2014 Mar 26. ((26. ciclo
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12610/68450
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