Pub Date : 2001-11-11DOI: 10.1115/imece2001/htd-24427
L. P. Silver, P. Hamilton, Angela C. Ni, R. Aimi, M. Curley
Tissue charring during radio frequency (RF) therapy causes an impedance rise and prevents further tissue heating from occurring, thereby limiting the size of lesions that can be created. The ability to create very large lesions would provide minimally invasive treatment options for deep tissue left ventricular arrythmias and otherwise-untreatable large liver tumors. Adding convection as a method of heat transfer by injecting saline at the RF electrode site acts to both clamp the electrode/tissue interface temperature and carry energy deeper into the tissue. We have developed a RF system that uses both conduction and convection simultaneously to both enhance the amount of heat transfer and prevent or greatly delay the onset of charring. Here we confirm the heat transfer augmentation of convection with experimental results in skeletal muscle, liver, and myocardium.
{"title":"Use of Saline Injection to Create Large Thermal Lesions During Radio Frequency Ablation Therapy: 2. Experimental Results","authors":"L. P. Silver, P. Hamilton, Angela C. Ni, R. Aimi, M. Curley","doi":"10.1115/imece2001/htd-24427","DOIUrl":"https://doi.org/10.1115/imece2001/htd-24427","url":null,"abstract":"\u0000 Tissue charring during radio frequency (RF) therapy causes an impedance rise and prevents further tissue heating from occurring, thereby limiting the size of lesions that can be created. The ability to create very large lesions would provide minimally invasive treatment options for deep tissue left ventricular arrythmias and otherwise-untreatable large liver tumors. Adding convection as a method of heat transfer by injecting saline at the RF electrode site acts to both clamp the electrode/tissue interface temperature and carry energy deeper into the tissue. We have developed a RF system that uses both conduction and convection simultaneously to both enhance the amount of heat transfer and prevent or greatly delay the onset of charring. Here we confirm the heat transfer augmentation of convection with experimental results in skeletal muscle, liver, and myocardium.","PeriodicalId":219774,"journal":{"name":"Advances in Heat and Mass Transfer in Biotechnology","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116633256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/htd-24422
J. Pearce, A. Schmitz
The IR sensitive membrane of the Crotaline pit organ was modeled numerically to help interpret electrophysiologic measurements of the pit organ response to a calibrated infrared source simulating a biological target. The model results are compared to electrophysiologic measurements for an on-axis exposure (target normal to the pit organ axis, oriented for maximum response). Additional model studies were conducted to: 1) estimate the field of view of the pit organ and 2) estimate the expected temperature rise in the membrane from the target at varying distances. The pit organ model was based on detailed measurements of its geometry. The membrane illumination irradiance difference from background thermal radiation (in W/mm2) was calculated from a quasi-analytical solution for the radiation coupling factor, Fjj. The illumination function was used to estimate temperature rise neglecting infrared heat transfer between the membrane and surrounding pit organ tissues. That is, the membrane was assumed in thermal steady state with the snake body and the environment outside of the target. The mammalian target is thus assumed to represent a small perturbation to the thermal steady state condition. This matches the electrophysiologic data, and is reasonable since the snake is cold blooded and snake body temperature is very close to its surroundings. The membrane includes blood flow effects, but it turns out that the membrane blood flow is strictly capillary in nature and changes the effective lateral thermal conductivity rather than providing significant heat transfer. The membrane is “optically thin”, being only about 5 wavelengths in thickness, and the specific optical properties of the interior layers were estimated from relative water content.
{"title":"Numerical Model Study of the Field of View and Temporal Response of the Infrared Sense Organ in Crotaline Pit Vipers","authors":"J. Pearce, A. Schmitz","doi":"10.1115/imece2001/htd-24422","DOIUrl":"https://doi.org/10.1115/imece2001/htd-24422","url":null,"abstract":"The IR sensitive membrane of the Crotaline pit organ was modeled numerically to help interpret electrophysiologic measurements of the pit organ response to a calibrated infrared source simulating a biological target. The model results are compared to electrophysiologic measurements for an on-axis exposure (target normal to the pit organ axis, oriented for maximum response). Additional model studies were conducted to: 1) estimate the field of view of the pit organ and 2) estimate the expected temperature rise in the membrane from the target at varying distances. The pit organ model was based on detailed measurements of its geometry. The membrane illumination irradiance difference from background thermal radiation (in W/mm2) was calculated from a quasi-analytical solution for the radiation coupling factor, Fjj. The illumination function was used to estimate temperature rise neglecting infrared heat transfer between the membrane and surrounding pit organ tissues. That is, the membrane was assumed in thermal steady state with the snake body and the environment outside of the target. The mammalian target is thus assumed to represent a small perturbation to the thermal steady state condition. This matches the electrophysiologic data, and is reasonable since the snake is cold blooded and snake body temperature is very close to its surroundings. The membrane includes blood flow effects, but it turns out that the membrane blood flow is strictly capillary in nature and changes the effective lateral thermal conductivity rather than providing significant heat transfer. The membrane is “optically thin”, being only about 5 wavelengths in thickness, and the specific optical properties of the interior layers were estimated from relative water content.","PeriodicalId":219774,"journal":{"name":"Advances in Heat and Mass Transfer in Biotechnology","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116241259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/htd-24417
O. Craciunescu, B. Raaymakers, A. Kotte, Shiva K. Das, T. Samulski, J. Lagendijk
One of the most important technical aspects in clinical hyperthermia is the ability to measure and/or simulate the 3D temperature fields. Related to that, an essential part is the way in which the complex heat transfer related to vasculature is described. We report here the results of a collaboration between the hyperthermia modeling groups from the UMC Utrecht, The Netherlands, and Duke UMC, USA. Utrecht’s hyperthermia group has developed a flexible, discrete vasculature thermal model (DIVA) (Kotte et al. 1996) that describes the heat transfer related to discrete vasculature. The vasculature was imaged using MR angiography. To account for the smaller vessels that are responsible for the significant bioheat transport, relative perfusion maps measured at Duke using dynamic enhanced-magnetic resonance imaging were used. Alternatively, the VAMP program (Van Leeuwen et al. 1998) was used to artificially generate smaller vasculature. The cases with discretized vasculature were compared to continuum models where either heterogeneous isotropic perfusion, or relative perfusion maps were used. All simulations were compared to MR thermometry data. The conclusion is that for tumors crossed by or near large vessels, a combination of large vessels discretization and perfusion maps yields temperatures that match very well the MR thermometry data.
临床热疗中最重要的技术方面之一是测量和/或模拟三维温度场的能力。与此相关的一个重要部分是描述与脉管系统有关的复杂传热的方式。我们在此报告来自荷兰乌得勒支UMC和美国杜克UMC的热疗模型组之间合作的结果。Utrecht的热疗小组开发了一种灵活的离散脉管热模型(DIVA) (Kotte et al. 1996)，描述了与离散脉管系统相关的热传递。血管造影采用MR血管造影。为了解释负责重要生物热传输的较小血管，使用杜克大学使用动态增强磁共振成像测量的相对灌注图。或者，使用VAMP程序(Van Leeuwen et al. 1998)人工生成更小的脉管系统。将离散化血管的病例与连续模型进行比较，在连续模型中，使用异质各向同性灌注或相对灌注图。所有模拟都与MR测温数据进行了比较。结论是，对于由大血管穿过或靠近大血管的肿瘤，大血管离散化和灌注图的结合产生的温度与MR测温数据非常吻合。
{"title":"A Case Study of Hyperthermia Induced Temperature Computations in Human Sarcomas Using Discrete Vasculature and Relative Perfusion Maps","authors":"O. Craciunescu, B. Raaymakers, A. Kotte, Shiva K. Das, T. Samulski, J. Lagendijk","doi":"10.1115/imece2001/htd-24417","DOIUrl":"https://doi.org/10.1115/imece2001/htd-24417","url":null,"abstract":"\u0000 One of the most important technical aspects in clinical hyperthermia is the ability to measure and/or simulate the 3D temperature fields. Related to that, an essential part is the way in which the complex heat transfer related to vasculature is described. We report here the results of a collaboration between the hyperthermia modeling groups from the UMC Utrecht, The Netherlands, and Duke UMC, USA. Utrecht’s hyperthermia group has developed a flexible, discrete vasculature thermal model (DIVA) (Kotte et al. 1996) that describes the heat transfer related to discrete vasculature. The vasculature was imaged using MR angiography. To account for the smaller vessels that are responsible for the significant bioheat transport, relative perfusion maps measured at Duke using dynamic enhanced-magnetic resonance imaging were used. Alternatively, the VAMP program (Van Leeuwen et al. 1998) was used to artificially generate smaller vasculature. The cases with discretized vasculature were compared to continuum models where either heterogeneous isotropic perfusion, or relative perfusion maps were used. All simulations were compared to MR thermometry data. The conclusion is that for tumors crossed by or near large vessels, a combination of large vessels discretization and perfusion maps yields temperatures that match very well the MR thermometry data.","PeriodicalId":219774,"journal":{"name":"Advances in Heat and Mass Transfer in Biotechnology","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122601044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/htd-24419
G. Aguilar, S. Valdes, J. Nelson, E. Lavernia
Port wine stain (PWS) birthmarks are a congenital and progressive vascular malformation of the dermis, involving capillaries, which occurs in approximately 0.7% of children. The objective of laser surgery for this and similar conditions is to cause selective thermal damage, thrombosis, and, eventually, permanent photocoagulation in the PWS vessels. To achieve this, the radiated laser light is set at a specific wavelength, which is highly absorbed by the blood vessels’ hemoglobin (the major chromophore in blood). Unfortunately, the PWS vessels do not absorb all energy radiated — a significant amount is also absorbed by hemoglobin in the ectatic capillaries of the upper dermis. This unwanted absorption causes two problems: firstly, insufficient heat generation within the targeted vessels leads to poor clinical results, and, secondly, there is an increased risk of damage to the overlying epidermis. In current PWS laser therapy, cryogen spray cooling (CSC) is used effectively to cool and protect selectively the epidermis (tens of micrometers thick) prior to the laser pulse, while minimally cooling the blood vessels. The thermal response of the system is characterized by time and/or temperature dependent boundary conditions. However, in many recent studies, the boundary conditions induced by CSC are regarded as constant. In the present work we study the effects of time-dependent boundary conditions on the overall epidermal thermal damage after PWS laser therapy. We use computer models to simulate the laser light distribution, heat diffusion, and tissue damage, and introduce experimentally determined time-dependent boundary conditions measured for custom-made and commercial atomizing nozzles. We show that time-dependent boundary conditions have a significant effect in the optimal laser dose required to induce photocoagulation of PWS blood vessels while preserving the epidermis.
{"title":"Effect of Time-Dependent Boundary Conditions on Epidermal Tissue Damage During Port Wine Stain Laser Surgery","authors":"G. Aguilar, S. Valdes, J. Nelson, E. Lavernia","doi":"10.1115/imece2001/htd-24419","DOIUrl":"https://doi.org/10.1115/imece2001/htd-24419","url":null,"abstract":"\u0000 Port wine stain (PWS) birthmarks are a congenital and progressive vascular malformation of the dermis, involving capillaries, which occurs in approximately 0.7% of children. The objective of laser surgery for this and similar conditions is to cause selective thermal damage, thrombosis, and, eventually, permanent photocoagulation in the PWS vessels. To achieve this, the radiated laser light is set at a specific wavelength, which is highly absorbed by the blood vessels’ hemoglobin (the major chromophore in blood). Unfortunately, the PWS vessels do not absorb all energy radiated — a significant amount is also absorbed by hemoglobin in the ectatic capillaries of the upper dermis. This unwanted absorption causes two problems: firstly, insufficient heat generation within the targeted vessels leads to poor clinical results, and, secondly, there is an increased risk of damage to the overlying epidermis.\u0000 In current PWS laser therapy, cryogen spray cooling (CSC) is used effectively to cool and protect selectively the epidermis (tens of micrometers thick) prior to the laser pulse, while minimally cooling the blood vessels. The thermal response of the system is characterized by time and/or temperature dependent boundary conditions. However, in many recent studies, the boundary conditions induced by CSC are regarded as constant. In the present work we study the effects of time-dependent boundary conditions on the overall epidermal thermal damage after PWS laser therapy. We use computer models to simulate the laser light distribution, heat diffusion, and tissue damage, and introduce experimentally determined time-dependent boundary conditions measured for custom-made and commercial atomizing nozzles. We show that time-dependent boundary conditions have a significant effect in the optimal laser dose required to induce photocoagulation of PWS blood vessels while preserving the epidermis.","PeriodicalId":219774,"journal":{"name":"Advances in Heat and Mass Transfer in Biotechnology","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128376009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/htd-24423
Saurin P. Purohit, Joshua Nelson, Jian X. Zhang, M. Clemens, Charles Y. Lee
Hypothermic machine perfusion preservation (MPP) has the potential to relieve the current donor shortage problem by providing superior preserved tissue and viable non-heart-beating donor tissue. For the liver, MPP has not improved preservation. Currently, the major cause of damage associated with MPP of livers is unknown. An intravital microscopy study was conducted to investigate the state of sinusoidal perfusion during 24-hour MPP. Fluorescein isothiocynate (FITC)-labeled albumin was utilized to mark the microvascular space while FITC-labeled red blood cells were used to determine the fluid velocity. The results showed that there was an increase in vascular resistance (> 275%) when the liver was perfused with a UW solution for 24 hours at 5°C and with a flow rate of 5 ml/min. This vascular resistance further increased (> 425%) during rewarming (for 1 hour, at 37°C and 15 ml/min). The mean flow velocities increased during initial MPP from 236 ±16 μm/s (mean ± standard error) to 434 ± 20 μm/s and the mean shear stress values increased from 5.3 ± 0.8 dynes/cm2 to 6.5 ± 0.8 dynes/cm2, after 24 hours of MPP the mean flow velocity values and shear stress values decreased (223 ± 13 μm/s and 3.3 ± 0.8 dynes/cm2) respectively. The reason for this was detected by the FITC-labeled albumin, in the tissue. It was evident that these areas (after 24 hours of MPP) also displayed increased blockage. It also appeared from the micrographs and the histology study that the blockage occurred as a result of endothelial cells rounding after 24 hours of MPP. The cells remained rounded even after rewarming the tissue. This could be a mechanism of damage to the liver during 24-hour of MPP.
{"title":"Flow Dynamics During Machine Perfusion Preservation of Livers","authors":"Saurin P. Purohit, Joshua Nelson, Jian X. Zhang, M. Clemens, Charles Y. Lee","doi":"10.1115/imece2001/htd-24423","DOIUrl":"https://doi.org/10.1115/imece2001/htd-24423","url":null,"abstract":"\u0000 Hypothermic machine perfusion preservation (MPP) has the potential to relieve the current donor shortage problem by providing superior preserved tissue and viable non-heart-beating donor tissue. For the liver, MPP has not improved preservation. Currently, the major cause of damage associated with MPP of livers is unknown. An intravital microscopy study was conducted to investigate the state of sinusoidal perfusion during 24-hour MPP. Fluorescein isothiocynate (FITC)-labeled albumin was utilized to mark the microvascular space while FITC-labeled red blood cells were used to determine the fluid velocity. The results showed that there was an increase in vascular resistance (> 275%) when the liver was perfused with a UW solution for 24 hours at 5°C and with a flow rate of 5 ml/min. This vascular resistance further increased (> 425%) during rewarming (for 1 hour, at 37°C and 15 ml/min). The mean flow velocities increased during initial MPP from 236 ±16 μm/s (mean ± standard error) to 434 ± 20 μm/s and the mean shear stress values increased from 5.3 ± 0.8 dynes/cm2 to 6.5 ± 0.8 dynes/cm2, after 24 hours of MPP the mean flow velocity values and shear stress values decreased (223 ± 13 μm/s and 3.3 ± 0.8 dynes/cm2) respectively. The reason for this was detected by the FITC-labeled albumin, in the tissue. It was evident that these areas (after 24 hours of MPP) also displayed increased blockage. It also appeared from the micrographs and the histology study that the blockage occurred as a result of endothelial cells rounding after 24 hours of MPP. The cells remained rounded even after rewarming the tissue. This could be a mechanism of damage to the liver during 24-hour of MPP.","PeriodicalId":219774,"journal":{"name":"Advances in Heat and Mass Transfer in Biotechnology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128484793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/htd-24433
A. Aksan, David S. Nielubowicz, J. Mcgrath
Application of sub-ablative levels of heat to collagenous tissues causes helix-to-coil transformation in the collagen microstructure resulting in overall tissue shrinkage. This phenomenon has important therapeutic applications in medicine, such as thermokeratoplasty, treatment of shoulder, knee and ankle instabilities and treatment of chronic discogenic lumbar pain associated with herniated discs. During the therapy, heat is applied arthroscopically by a laser or a radio-frequency probe (bipolar or monopolar). The amount and permanence of shrinkage established in the tissue is a function of the maximum temperature reached and the exposure time as well as the mechanical stress applied on the tissue during heating. Therefore, the thermal and mechanical history that the tissue experiences is a major factor determining its response and long-term mechanical stability. These are the defining factors for the success of the therapy. It is hypothesized in this study that there are significant differences between the thermal histories created in the tissue by different heating modalities owing to the differences between their modes of action. The solutions to the temperature distributions created by these different heating modalities — laser and radiofrequency applied with a bipolar and a monopolar probe — are compared and parameters of clinical significance are discussed.
{"title":"Modeling the Thermal Histories of Collagenous Tissues Subjected to Different Heating Modalities","authors":"A. Aksan, David S. Nielubowicz, J. Mcgrath","doi":"10.1115/imece2001/htd-24433","DOIUrl":"https://doi.org/10.1115/imece2001/htd-24433","url":null,"abstract":"Application of sub-ablative levels of heat to collagenous tissues causes helix-to-coil transformation in the collagen microstructure resulting in overall tissue shrinkage. This phenomenon has important therapeutic applications in medicine, such as thermokeratoplasty, treatment of shoulder, knee and ankle instabilities and treatment of chronic discogenic lumbar pain associated with herniated discs. During the therapy, heat is applied arthroscopically by a laser or a radio-frequency probe (bipolar or monopolar). The amount and permanence of shrinkage established in the tissue is a function of the maximum temperature reached and the exposure time as well as the mechanical stress applied on the tissue during heating. Therefore, the thermal and mechanical history that the tissue experiences is a major factor determining its response and long-term mechanical stability. These are the defining factors for the success of the therapy. It is hypothesized in this study that there are significant differences between the thermal histories created in the tissue by different heating modalities owing to the differences between their modes of action. The solutions to the temperature distributions created by these different heating modalities — laser and radiofrequency applied with a bipolar and a monopolar probe — are compared and parameters of clinical significance are discussed.","PeriodicalId":219774,"journal":{"name":"Advances in Heat and Mass Transfer in Biotechnology","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126992216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/htd-24418
Liang Zhu, Maithreyi Bommadevara
In this study a theoretical model was developed to evaluate the temperature difference between the body core and the arterial blood supplied to the brain. Several factors including the local blood perfusion rate, blood vessel bifurcation in the neck, and blood vessel pairs on both sides of the neck were considered in the model. The theoretical approach was used to estimate the potential for cooling of blood in the carotid artery on its way to the brain by heat exchange with its countercurrent jugular vein and by the radial heat conduction loss to the cool neck surface. It shows that blood temperature along the common and internal carotid arteries typically decreases up to 0.86°C during hyperthermia. Selectively cooling the neck surface during hypothermia increases the heat loss from the carotid arteries and results in approximately 1.2°C in the carotid arterial temperature. This research could provide indirect evidence of the existence of selective brain cooling (SBC) in humans during hyperthermia. The simulated results can also be used to evaluate the feasibility of lowering brain temperature effectively by selectively cooling the head and neck surface during hypothermia treatment for brain injury or multiple sclerosis.
{"title":"Temperature Difference Between the Body Core and the Arterial Blood Supplied to the Brain During Hyperthermia or Hypothermia","authors":"Liang Zhu, Maithreyi Bommadevara","doi":"10.1115/imece2001/htd-24418","DOIUrl":"https://doi.org/10.1115/imece2001/htd-24418","url":null,"abstract":"\u0000 In this study a theoretical model was developed to evaluate the temperature difference between the body core and the arterial blood supplied to the brain. Several factors including the local blood perfusion rate, blood vessel bifurcation in the neck, and blood vessel pairs on both sides of the neck were considered in the model. The theoretical approach was used to estimate the potential for cooling of blood in the carotid artery on its way to the brain by heat exchange with its countercurrent jugular vein and by the radial heat conduction loss to the cool neck surface. It shows that blood temperature along the common and internal carotid arteries typically decreases up to 0.86°C during hyperthermia. Selectively cooling the neck surface during hypothermia increases the heat loss from the carotid arteries and results in approximately 1.2°C in the carotid arterial temperature. This research could provide indirect evidence of the existence of selective brain cooling (SBC) in humans during hyperthermia. The simulated results can also be used to evaluate the feasibility of lowering brain temperature effectively by selectively cooling the head and neck surface during hypothermia treatment for brain injury or multiple sclerosis.","PeriodicalId":219774,"journal":{"name":"Advances in Heat and Mass Transfer in Biotechnology","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127790190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/htd-24434
S. Bhowmick, P. Bhowmick, J. Coad, J. Bischof
Correlation between thermal history and tissue destruction is of considerable importance for successful management of BPH using minimally invasive thermal therapies such as radiofrequency or microwave probes. In order to accomplish this goal, the present in vitro study assesses the cellular viability of BPH tissue subjected to different temperature-times in an experimental matrix. Hyperplastic prostatic tissue was obtained from 8 patients after the surgical removal of the glands for other reasons (typically cancer). A piece of tissue was taken from the lateral lobe of the gland and was then sectioned into multiple thin strips (1mm thick), placed on a coverslip and heated on a thermally controlled copper block to various temperatures (45°C-70°C) for various times (1 minute–60 minutes). After heat treatment, the tissue slices were cultured for 72 hours and viability data was obtained using two independent assays: histology and dye uptake. Results indicate that the hyperplastic prostate tissue showed a progressive histologic increase in irreversible stromal tissue injury with increasing temperature-time severity. A small amount (∼5% or less) of stromal apoptosis was found in the control and mildly treated tissue. Dye uptake studies for stromal viability paralleled the histologic findings for the temperature-time combinations explored in the present study. In vitro thermal injury thresholds for 90% destruction of human BPH tissue were identified at 45°C-60min, 55°C-20min, 60°C-5min and 70°C-2 min. The Arrhenius model of injury was fit to the viability data after controlled heating to obtain parameters that will allow the prediction of injury under variable heating conditions. Arrhenius analysis of both assays showed a break point at 60°C based on 90% normalized survival. The activation energy (E) values for temperatures below and above the break point were 199.05 and 66.04 kJ/mole for the dye uptake study and 162.6 and 62.99 kJ/mole for histology. The corresponding frequency factor (A) values below and above the break point were 1.81 × 1030 and 1.82 × 109 s−1 for dye uptake study and 2.84 × 1024 and 6.64 × 108 s−1 for histology. This study is the first to report Arrhenius parameters for human BPH tissue for supraphysiological thermal therapy and will be useful for prediction of tissue destruction during thermal therapy of BPH in the clinic.
{"title":"In Vitro Assessment of the Efficacy of Thermal Therapy in Human Benign Prostatic Hyperplasia Tissue","authors":"S. Bhowmick, P. Bhowmick, J. Coad, J. Bischof","doi":"10.1115/imece2001/htd-24434","DOIUrl":"https://doi.org/10.1115/imece2001/htd-24434","url":null,"abstract":"\u0000 Correlation between thermal history and tissue destruction is of considerable importance for successful management of BPH using minimally invasive thermal therapies such as radiofrequency or microwave probes. In order to accomplish this goal, the present in vitro study assesses the cellular viability of BPH tissue subjected to different temperature-times in an experimental matrix. Hyperplastic prostatic tissue was obtained from 8 patients after the surgical removal of the glands for other reasons (typically cancer). A piece of tissue was taken from the lateral lobe of the gland and was then sectioned into multiple thin strips (1mm thick), placed on a coverslip and heated on a thermally controlled copper block to various temperatures (45°C-70°C) for various times (1 minute–60 minutes). After heat treatment, the tissue slices were cultured for 72 hours and viability data was obtained using two independent assays: histology and dye uptake. Results indicate that the hyperplastic prostate tissue showed a progressive histologic increase in irreversible stromal tissue injury with increasing temperature-time severity. A small amount (∼5% or less) of stromal apoptosis was found in the control and mildly treated tissue. Dye uptake studies for stromal viability paralleled the histologic findings for the temperature-time combinations explored in the present study. In vitro thermal injury thresholds for 90% destruction of human BPH tissue were identified at 45°C-60min, 55°C-20min, 60°C-5min and 70°C-2 min. The Arrhenius model of injury was fit to the viability data after controlled heating to obtain parameters that will allow the prediction of injury under variable heating conditions. Arrhenius analysis of both assays showed a break point at 60°C based on 90% normalized survival. The activation energy (E) values for temperatures below and above the break point were 199.05 and 66.04 kJ/mole for the dye uptake study and 162.6 and 62.99 kJ/mole for histology. The corresponding frequency factor (A) values below and above the break point were 1.81 × 1030 and 1.82 × 109 s−1 for dye uptake study and 2.84 × 1024 and 6.64 × 108 s−1 for histology. This study is the first to report Arrhenius parameters for human BPH tissue for supraphysiological thermal therapy and will be useful for prediction of tissue destruction during thermal therapy of BPH in the clinic.","PeriodicalId":219774,"journal":{"name":"Advances in Heat and Mass Transfer in Biotechnology","volume":"477 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130738121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/htd-24431
R. Devireddy, M. Neidert, J. Bischof, R. Tranquille
The effect of freezing on the viability and mechanical strength of bioartificial tissues was determined under a variety of cooling conditions, with the ultimate aim of optimizing the cryopreservation process. Bioartificial tissues (i.e. tissue-equivalents or TEs) were prepared by incubating entrapped human foreskin fibroblasts in collagen gels for a period of 2 weeks. The bioartificial tissues were frozen using a controlled rate freezer at various cooling rates (0.5, 2, 5, 20, 40 and > 1000°C/min or slam freezing). The viability (< 60 min after thawing) of the fibroblasts in the bioartificial tissue was assessed using the Ethidium Homodimer (dead cells stain red) and Hoechst Give cells stain blue) assay. Uniaxial tension experiments were performed on an MTS Microbionix System (Eden Prairie, MN) to assess the post-thaw mechanical properties (Maximum Stiffness; Ultimate Tensile Stress; and Strain to Failure) of the frozen-thawed bioartificial tissue (≤ 3 hours after thawing). The results suggest that cooling rates of either 2 or 5°C/min are optimal for preserving both the cell viability and mechanical properties of the bioartificial tissues, post-freeze. Bioartificial tissues were also frozen using a directional solidification stage at 5°C/min. The post-thaw viability results are comparable in both the directionally cooled and the controlled rate freezer samples. However, the mechanical properties of the directionally cooled samples are significantly different (with a higher maximum stiffness and a lower strain to failure) than those obtained for samples frozen using a controlled rate freezer. This suggests that the directionality of ice propagation into the sample affects the measured mechanical properties.
{"title":"Effect of Freezing on Cell Viability and Mechanical Strength of Bioartificial Tissues","authors":"R. Devireddy, M. Neidert, J. Bischof, R. Tranquille","doi":"10.1115/imece2001/htd-24431","DOIUrl":"https://doi.org/10.1115/imece2001/htd-24431","url":null,"abstract":"\u0000 The effect of freezing on the viability and mechanical strength of bioartificial tissues was determined under a variety of cooling conditions, with the ultimate aim of optimizing the cryopreservation process. Bioartificial tissues (i.e. tissue-equivalents or TEs) were prepared by incubating entrapped human foreskin fibroblasts in collagen gels for a period of 2 weeks. The bioartificial tissues were frozen using a controlled rate freezer at various cooling rates (0.5, 2, 5, 20, 40 and > 1000°C/min or slam freezing). The viability (< 60 min after thawing) of the fibroblasts in the bioartificial tissue was assessed using the Ethidium Homodimer (dead cells stain red) and Hoechst Give cells stain blue) assay. Uniaxial tension experiments were performed on an MTS Microbionix System (Eden Prairie, MN) to assess the post-thaw mechanical properties (Maximum Stiffness; Ultimate Tensile Stress; and Strain to Failure) of the frozen-thawed bioartificial tissue (≤ 3 hours after thawing). The results suggest that cooling rates of either 2 or 5°C/min are optimal for preserving both the cell viability and mechanical properties of the bioartificial tissues, post-freeze. Bioartificial tissues were also frozen using a directional solidification stage at 5°C/min. The post-thaw viability results are comparable in both the directionally cooled and the controlled rate freezer samples. However, the mechanical properties of the directionally cooled samples are significantly different (with a higher maximum stiffness and a lower strain to failure) than those obtained for samples frozen using a controlled rate freezer. This suggests that the directionality of ice propagation into the sample affects the measured mechanical properties.","PeriodicalId":219774,"journal":{"name":"Advances in Heat and Mass Transfer in Biotechnology","volume":"216 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134367708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/htd-24415
P. Vadasz, A. S. Vadasz
A neoclassical model is proposed for the growth of cell and other populations in a homogeneous habitat. The model extends on the Logistic Growth Model (LGM) in a non-trivial way in order to address the cases where the Logistic Growth Model (LGM) fails short in recovering qualitative as well as quantitative features that appear in experimental data. These features include in some cases overshooting and oscillations, in others the existence of a “Lag Phase” at the initial growth stages, as well as an inflection point in the “In curve” of the population size. The proposed neoclassical model recovers also the Logistic Growth Curve as a special case. Comparisons of the solutions obtained from the proposed neoclassical model with experimental data confirm its quantitative validity, as well as its ability to recover a wide range of qualitative features captured in experiments.
{"title":"A Neoclassical Growth Model for Population Dynamics in a Homogeneous Habitat","authors":"P. Vadasz, A. S. Vadasz","doi":"10.1115/imece2001/htd-24415","DOIUrl":"https://doi.org/10.1115/imece2001/htd-24415","url":null,"abstract":"\u0000 A neoclassical model is proposed for the growth of cell and other populations in a homogeneous habitat. The model extends on the Logistic Growth Model (LGM) in a non-trivial way in order to address the cases where the Logistic Growth Model (LGM) fails short in recovering qualitative as well as quantitative features that appear in experimental data. These features include in some cases overshooting and oscillations, in others the existence of a “Lag Phase” at the initial growth stages, as well as an inflection point in the “In curve” of the population size. The proposed neoclassical model recovers also the Logistic Growth Curve as a special case. Comparisons of the solutions obtained from the proposed neoclassical model with experimental data confirm its quantitative validity, as well as its ability to recover a wide range of qualitative features captured in experiments.","PeriodicalId":219774,"journal":{"name":"Advances in Heat and Mass Transfer in Biotechnology","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134383190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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