A Theoretical Comparison of the Efficacy of Microwave and Ultrasound Applicators Used in Transurethral Thermal Therapy

2005 ◽  
Author(s):  
Chandrasekhar Thamire ◽  
Rao L. Divi ◽  
Mukesh Verma
Keyword(s):  
Thermal Damage ◽  
Thermal Therapy ◽  
Accurate Estimation ◽  
Transient Temperature ◽  
Thermal Lesion ◽  
Thermal Coagulation ◽  
External Cooling ◽  
Alternating Direction ◽  
Damage Data ◽  
Prostate Tumor Cells

Microwave and ultrasound energy sources are commonly used in minimally invasive thermal therapy for benign prostatic hyperplasia. Successful management of the therapy using either of these methods requires an accurate estimation of the thermal dosage. The purpose of this study is to evaluate, theoretically, the thermal damage caused by typical transurethral microwave and ultrasound applicators for different thermal doses and compare the efficacy of the two methods. Using an Alternating-direction implicit method, the Pennes bio-heat transfer equation is solved for different levels of power and heating times. Internal and external cooling is applied to preserve the urethral and rectal lining and to control the temperatures within the tissue. The extent of thermal coagulation is determined from the resulting temperature histories, using the existing experimental thermal damage data for prostate tumor cells. The temperatures and damage contours calculated are validated using an Arrhenius analysis of the temperature and thermal-lesion data from the available experimental results. Results show that the calculated damage zones are in good agreement with those observed in the experiments. Results from calculations for different combinations of the parameters are presented in terms of the transient temperature histories and radial and axial extent of the lesion shapes. These results suggest that both methods can yield comparable thermal damage, though ultrasound appears to possess an improved control of directional heating.

Ultrasound Hyperthermia: Dose Estimation and Device Design for Intraluminal and External Delivery

2012 ◽  
Author(s):  
Danica Gordon ◽  
Chandrasekhar Thamire
Keyword(s):  
Thermal Damage ◽  
Treatment Time ◽  
The Body ◽  
Thermal Therapy ◽  
Surrounding Tissue ◽  
Temperature History ◽  
Published Data ◽  
Device Design ◽  
Treatment Protocols ◽  
Thermal Coagulation

Thermal ablation in the context of this study refers to destroying cancer cells by heating them to supraphysiological temperatures for appropriate times. Once the tumor cells and a small layer of surrounding tissue cells are killed, they are absorbed by the body over time. Compared to open surgery, radiation, and chemotherapy, thermal therapy can be less expensive and pose less risk of harmful post-procedural complications, while possessing the potential to be effective [1]. Currently microwave and radiofrequency ablation are in use for local hyperthermia; however, they lack the ability to focus heat into the target zones effectively or treat larger tumors without affecting the surrounding healthy tissue. In the current study, high frequency ultrasound (US) ablation is examined as a treatment modality because of its ability to focus and control heat effectively. Objectives of this study are to 1) develop thermal-damage correlations for US thermal therapy and 2) design delivery devices and associated treatment planning protocols. To achieve these goals, thermal damage information is first evaluated for a variety of cells and tissues from published data or pilot experiments. Required US dose levels are determined next through numerical experiments, followed by device design and estimation of thermal coagulation contours by comparing the temperature-history data against the thermal-damage data. Based on the analysis of the results for a range of parameters, namely, the applicator power, geometry, frequency, coolant parameters, treatment time, and tissue perfusion, treatment protocols are developed. Intraluminal, external, and interstitial modes of delivery are considered for focal sites in a variety of target areas. In the following sections, methods followed and sample results obtained are presented.

Thermal Therapy Protocols for Benign Prostatic Hyperplasia

2007 ◽  
Author(s):  
Daniel Chinn ◽  
Elvis Nditafon ◽  
Alvin Yew ◽  
Chandrasekhar Thamire
Keyword(s):  
Benign Prostatic Hyperplasia ◽  
Thermal Damage ◽  
Prostatic Hyperplasia ◽  
Operating Conditions ◽  
Thermal Therapy ◽  
Bioheat Transfer ◽  
Surrounding Tissue ◽  
Accurate Estimation ◽  
Transfer Model ◽  
Porous Media Model

Thermal therapy for treatment of benign prostatic hyperplasia (BPH) is becoming increasingly popular due to the minimally invasive nature of the treatment. Successful management of such therapy requires accurate estimation of thermal dosage. The purpose of this study is to provide correlations for the thermal damage caused by ultrasound, microwave, and infrared devices under a range of operating conditions. A boundary-fitting finite difference method is used to examine the heat transfer in the prostate gland and surrounding tissue. The Pennes bioheat transfer model and a porous media model were utilized to calculate temperature histories. Necrosis zones were determined using published necrosis data for prostatic tissue and cells. Thermal damage correlations for the three different hyperthermia sources along with sample temperature contours and necrosis zones are presented. Results indicate that the applicator power level and heating time are the most important parameters in achieving the desired necrosis zones, while coolant parameters strongly affect the temperatures of the sensitive urethra and serve as constraints for protocol parameters. Out of the three sources evaluated, ultrasound modality appears to be the most capable of causing necrosis in the target zones, with least damage to the surrounding healthy tissues.

scholarly journals THERMAL LESION FORMATION AND DETERMINATION FOR EXTERNAL ULTRASOUND THERMAL THERAPY

2003 ◽  
Vol 15 (03) ◽  
pp. 124-132 ◽  
Author(s):  
HAO-LI LIU ◽  
YUNG-YAW CHEN ◽  
JIA-YUSH YEN ◽  
WIN-LI LIN
Keyword(s):  
Blood Perfusion ◽  
Heating System ◽  
Target Volume ◽  
Thermal Therapy ◽  
Bioheat Transfer ◽  
Heating Process ◽  
Thermal Lesion ◽  
Feedback Information ◽  
Temperature Feedback ◽  
Heating Pattern

The purpose of this paper is to investigate the relationship between the formation of the thermal lesion and the major parameters of the external ultrasound heating systems, and to propose a useful thermal lesion determination procedure, which is capable of specifying the range of a thermal lesion by temperature feedback in external ultrasound thermal therapy. This work is based on an ideal ultrasound power deposition formed by an external ultrasound heating system and the temperature distribution is calculated by the transient bioheat transfer equation. A simplified model was employed to determine the heating pattern for four most important parameters. Through the simplified power expression, the property of a new parameter, T300, which is defined as the maximal temperature corresponding to the thermal dose of 300 minutes, is also investigated. When the target volume is large enough such that the thermal conduction effect becomes negligible, the T300 value is almost independent of the system parameters and the heating strategies, and is dominated by the blood perfusion rate with a monotonic correlation. The method enables us to use feedback information in the ultrasound heating process and to pre-determine the heating range of the thermal lesion, which will be very useful in ultrasound treatment planning.

Optical-Thermal Response and Dynamic Thermal Damage of Bio-Tissue During Laser Thermotherapy

2003 ◽  
Author(s):  
G. M. Zhu ◽  
W. Liu ◽  
T. F. Zeng ◽  
K. Yang
Keyword(s):  
Thermal Injury ◽  
Thermal Damage ◽  
Tumor Tissue ◽  
Local Heating ◽  
Damage Model ◽  
Thermal Response ◽  
Tumor Treatment ◽  
Thermal Coagulation ◽  
Laser Head ◽  
Temperature Damage

Laser thermotherapy is a technique used for tumor treatment. It generates a local heating, causes thermal coagulation of living tissue and eliminates the tumor. Precise heating of tumor tissue with healthy minimum thermal injury to adjacent tissue is essential to thermotherapy. Understanding of heat transfer and optical-thermal interaction is important for control of temperature and design of thermotherapy. This study applies the Arrhenius damage model to describe the heat-induced change of optical properties. It calculates the distribution temperature, damage and optical-thermal response of bio-tissue during the laser treatment, and shows how these factors affect the effectiveness of laser thermotherapy. Similar research has been performed by Kim and coworkers [1996], Iizuka and coworkers [2000], and Whelan and coworkers [2000]. This study relaxes some conditions in previous investigations. It reveals the importance and the effect of size of the laser head.

Ultrasound Hyperthermia: Dose Estimation and Device Design

2012 ◽  
Author(s):  
Danica Gordon ◽  
Chandrasekhar Thamire
Keyword(s):  
Cancer Treatment ◽  
Treatment Modality ◽  
Thermal Damage ◽  
Operating Parameter ◽  
Cell Types ◽  
Temperature History ◽  
Device Design ◽  
High Frequency Ultrasound ◽  
Treatment Protocols ◽  
Thermal Coagulation

As a cancer treatment modality, thermal ablation offers the advantages of being less invasive and posing fewer post-procedural complications compared to traditional cancer therapies. It involves destroying cancerous cells by subjecting them to the appropriate amount of heat dose. In the present study, high frequency ultrasound (US) ablation is theoretically examined for effectiveness as a treatment modality for intraluminal and extracorporeal cancer treatment. Objectives of this study are to 1) develop thermal-damage correlations for a variety of cancer cells and 2) design US treatment devices, based on thermal damage correlations developed, and treatment planning protocols. To achieve these goals, thermal damage information for different cell types is first determined from earlier studies or pilot experiments. Required US doses for specific tissues are determined next through numerical experiments. Device design and estimation of thermal coagulation contours is then performed by comparing temperature-history data against the thermal-damage data for a range of device parameters. Treatment protocols are finally developed based on the analysis of the results for a range of applicable device parameters. Results are presented in terms of correlations for the volume and location of ablated tissue corresponding to a range of operating parameter values.

Two-Dimensional Transient Temperature Distribution in Cylindrical Bodies With Pulsating Time and Space-Dependent Boundary Conditions

1974 ◽  
Vol 96 (3) ◽  
pp. 300-306 ◽  
Author(s):  
J. A. Copley ◽  
W. C. Thomas
Keyword(s):  
Heat Flux ◽  
Boundary Conditions ◽  
Analytical Techniques ◽  
Transient Temperature ◽  
Two Dimensional ◽  
Transient Temperature Distribution ◽  
Gun Barrel ◽  
External Cooling ◽  
Periodic Heat ◽  
Good Agreement

The two-dimensional conduction equation is solved for a hollow cylinder subjected to a series of heat flux pulses on the inner boundary. The periodic heat flux is represented by an exponentially decreasing pulse with a spatial distribution of peak magnitude. The analytical techniques and representation of the boundary conditions apply to different situations involving pulsating boundary conditions. An application to the gun barrel heating problem is given. Calculated bore surface and internal temperature histories are in good agreement with experimental data. During the actual firing time in rapidly-firing guns, results show that external cooling is generally ineffective for controlling barrel bore surface temperature.

Tissue-Light Interaction During Monitoring of Thermal Lesion Using Quantum Dot Mediated Fluorescence Thermometry

2011 ◽  
Author(s):  
Willard Hanson ◽  
Najma Abdollahzadeh ◽  
Bumsoo Han
Keyword(s):  
Diffusion Approximation ◽  
Treatment Options ◽  
Thermal Therapy ◽  
Temperature Dependent ◽  
Thermal Lesion ◽  
Tissue Phantom ◽  
Localized Heating ◽  
Light Interaction

Thermal therapy, destroying tumor in situ by localized heating, is emerging as one of the treatment options for benign and localized tumors. Despite many advantages of thermal therapy, its clinical application is still limited due to the lack of a reliable intraoperative monitoring technique of the thermal lesion. To address this challenge, an intraoperative thermometry technique has been proposed using the temperature-dependent fluorescence of quantum dots (QDs). Its feasibility is recently demonstrated by monitoring the spatiotemporal temperature during gold nanoshell-mediated heating. In the present study, the effects of tissue-light interaction on the QD-mediated thermometry were investigated both experimentally and theoretically so that the technique can be extended to in vivo applications. As for experimental investigation, the QD fluorescence through tissue phantom was characterized with varying the thickness of the phantom over a temperature range relevant to thermal therapy. The results showed that the QD fluorescence through tissue phantom was still linearly correlated to the local temperature, but the slope of the correlations decreased with the phantom thickness. As for theoretical investigation, the radiative transfer equation was reduced to the diffusion approximation, and the QD fluorescence through tissue phantom was predicted by numerically solving the diffusion approximation. The results confirmed that the diffusion approximation could describe the tissue-light interaction for the QD-mediated thermometry but further research is still required to improve the accuracy of the prediction.

Treatment Protocols for Managing Transurethral Thermal Therapy for Benign Prostatic Hyperplasia

2005 ◽  
Author(s):  
Lara Paolini ◽  
Chandrasekhar Thamire
Keyword(s):  
Benign Prostatic Hyperplasia ◽  
Power Level ◽  
Heating Time ◽  
Prostatic Hyperplasia ◽  
Thermal Therapy ◽  
Accurate Estimation ◽  
Operating Parameters ◽  
Invasive Treatment ◽  
Treatment Protocols ◽  
Finite Differences Method

Application of thermal therapy using microwave or ultrasound applicators is becoming increasingly popular as a minimally invasive treatment for benign prostatic hyperplasia (BPH). Successful management of the therapy using such methods requires an accurate estimation of the thermal dosage. The purpose of this study is to theoretically evaluate the thermal damage caused by different heating sources for different values of thermal doses and operating parameters. Using a 3-D finite differences method, the Pennes bio-heat transfer equation is solved for selected operating parameters. Necrosis zones are then determined from published necrosis data for prostatic tumor cells. Sample results are presented in terms of the temperature contours and necrosis zones. Results indicate that heating time and power level are the most important parameters in creating the desired necrosis zones, while coolant parameters strongly affect the temperatures of the sensitive urethra and serve as constraints for protocol parameters.

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