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.

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.

Treatment Planning for Transurethral and Interstitial Thermal Therapy for Benign Prostatic Hyperplasia

2009 ◽  
Author(s):  
Chandrasekhar Thamire ◽  
Rabee Zuberi ◽  
Charlie Choe ◽  
Prabhakar Pandey
Keyword(s):  
Benign Prostatic Hyperplasia ◽  
Treatment Planning ◽  
Thermal Damage ◽  
Treatment Time ◽  
Ex Vivo ◽  
Prostatic Hyperplasia ◽  
Bioheat Transfer ◽  
Temperature History ◽  
Target Tissue ◽  
Thermal Coagulation

The purpose of this study is to develop thermal-damage correlations for transurethral and interstitial thermotherapy to aid treatment planning for benign prostatic hyperplasia (BPH). Using an Alternating-direction implicit method, the Pennes bioheat transfer equation is solved for microwave and ultrasound hyperthermia applicators for a range of parameters, including the applicator power, treatment time, and coolant parameters. Thermal coagulation contours are developed by evaluating the temperature-history data against the thermal-damage data obtained in ex-vivo experiments for prostate tissue slices and cells. Treatment protocols are proposed for treatment planning purposes and developing an optimal hyperthermia applicator that can coagulate the target tissue effectively, without destroying the surrounding healthy tissue.

Design of Laser Treatment Protocols for Bacterial Disinfection in Root Canals Using Theoretical Modeling and MicroCT Imaging

2012 ◽  
Vol 4 (3) ◽  
Author(s):  
Jennifer Gill ◽  
Dwayne Arola ◽  
Ashraf F. Fouad ◽  
Liang Zhu
Keyword(s):  
Root Canal ◽  
Thermal Damage ◽  
Elevated Temperatures ◽  
Surrounding Tissue ◽  
Tooth Root ◽  
Bioheat Equation ◽  
Human Teeth ◽  
Treatment Protocols ◽  
Theoretical Simulations ◽  
Bacterial Disinfection

Theoretical simulations of temperature elevations in root dentin are performed to evaluate, how heating protocols affect the efficacy of using erbium, chromium; yttrium, scandium, gallium, garnet (Er,Cr;YSGG) pulsed lasers for bacterial disinfection during root canal treatments. The theoretical models are generated based on microcomputer tomography (microCT) scans of extracted human teeth. Heat transfer simulations are performed using the Pennes bioheat equation to determine temperature distributions in tooth roots and surrounding tissue during 500 mW pulsed Er,Cr;YSGG laser irradiation on the root canal for eradicating bacteria. The study not only determines the heat penetration within the deep dentin but also assesses potential thermal damage to the surrounding tissues. Thermal damage is assumed to occur when the tissue is subject to a temperature above at least 47 °C for a minimum duration of 10 s. Treatment protocols are identified for three representative tooth root sizes that are capable of maintaining elevated temperatures in deep dentin necessary to eradicate bacteria, while minimizing potential for collateral thermal tissue damage at the outer root surfaces. We believe that the study not only provides realistic laser heating protocols for various tooth root geometries but also demonstrates utility of theoretical simulations for designing individualized treatments in the future.

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.

The Effects of Large Blood Vessels on Three-Dimensional Tissue Temperature Distributions During Electromagnetic Induced Nano-Hyperthermia: Numerical Simulation

2008 ◽  
Author(s):  
Zhong-Shan Deng ◽  
Jing Liu
Keyword(s):  
Blood Vessels ◽  
Tumor Cells ◽  
Three Dimensional ◽  
The Body ◽  
Thermal Therapy ◽  
Tissue Temperature ◽  
Surrounding Tissue ◽  
Temperature Profiles ◽  
Hyperthermia Treatment ◽  
Tumor Hyperthermia

As is well known, the blood flowing through large blood vessels acts as a heat sink and plays an important role in affecting temperature profiles of heated tissues [1]. In hyperthermia, heating is usually limited to the tumor and a small margin of the surrounding tissue. Since the temperatures in the rest of the body remain normal, the blood that supplies the tumor will be relatively cold. Consequently, the blood flow inside a large vessel will represent a sink which cools the nearby heated tissues and then limits heating lesion during tumor hyperthermia. Under this adverse condition, a part of vital tumor cells may remain in the thermally lethal area and lead to recurrence of tumors after hyperthermia treatment. More specifically, tumor cell survival in the vicinity of large blood vessels is often correlated with tumor recurrence after thermal therapy. Therefore, it is difficult to implement an effective hyperthermia treatment when a tumor is contiguous to a large blood vessel or such vessel transits the tumor. How to totally destroy tumor cells in the vicinity of large blood vessels has been a major challenge in hyperthermia [2].

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.

Evaluation of Effectiveness of Er,Cr:YSGG Laser For Root Canal Disinfection: Theoretical Simulation of Temperature Elevations in Root Dentin

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
L. Zhu ◽  
M. Tolba ◽  
D. Arola ◽  
M. Salloum ◽  
F. Meza
Keyword(s):  
Alternative Treatment ◽  
Root Canal ◽  
Thermal Damage ◽  
Treatment Time ◽  
Treatment Protocol ◽  
Surrounding Tissue ◽  
Bioheat Equation ◽  
Canal Surface ◽  
Theoretical Simulation ◽  
Bacterial Disinfection

Erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) lasers are currently being investigated for disinfecting the root canal system. Prior to using laser therapy, it is important to understand the temperature distribution and to assess thermal damage to the surrounding tissue. In this study, a theoretical simulation using the Pennes bioheat equation is conducted to evaluate how heat spreads from the canal surface using an Er,Cr:YSGG laser. Results of the investigation show that some of the proposed treatment protocols for killing bacteria in the deep dentin are ineffective, even for long heating durations. Based on the simulation, an alternative treatment protocol is identified that has improved effectiveness and is less likely to introduce collateral damage to the surrounding tissue. The alternative protocol uses 350 mW laser power with repeating laser tip movement to achieve bacterial disinfection in the deep dentin (800 μm lateral from the canal surface), while avoiding thermal damage to the surrounding tissue (T<47°C). The alternative treatment protocol has the potential to not only achieve bacterial disinfection of deep dentin but also shorten the treatment time, thereby minimizing potential patient discomfort during laser procedures.

scholarly journals A new CEM₄₃ thermal dose model based on Vogel-Tammann-Fulcher behaviour in thermal damage processes

2021 ◽  
Author(s):  
Hisham Assi
Keyword(s):  
High Temperature ◽  
Thermal Damage ◽  
Ex Vivo ◽  
Current Model ◽  
Damage Threshold ◽  
Thermal Therapy ◽  
Published Data ◽  
Thermal Dose ◽  
Model Based ◽  
Dose Model

Thermal dose models are metrics that quantify thermal damage in tissues based on the temperature and the time of exposure. The validity and accuracy of one of the commonly used models (CEM₄₃) for high temperature thermal therapy applications (50-90 degree Celcius) is questionable. It was found to over-estimate the accumulation of thermal damage for high-temperature applications. A new CEM₄₃ dose model based on Arrhenius type Vogel-Tammann-Fulcher equation using published data is introduced in this work. The new dose values for the same damage threshold that was produced at different in-vivo skin experiments were in the same order of magnitude, while the current dose values were 2 orders of magnitude different. The new dose values for same damage threshold in 6 lessions in ex-vivo liver experiments were more consistent than the current dose values. Computer simulations of laser interstitial thermal therapy showed that the current model usually predicts bigger volume than the new model does. The deviation in damaged volume prediction can be significant. The contribution of this work is introducing methods that can lead to more robust thermal dosimetry which will result in improved therapy modelling, monitoring and control.

scholarly journals A new CEM₄₃ thermal dose model based on Vogel-Tammann-Fulcher behaviour in thermal damage processes

2021 ◽  
Author(s):  
Hisham Assi
Keyword(s):  
High Temperature ◽  
Thermal Damage ◽  
Ex Vivo ◽  
Current Model ◽  
Damage Threshold ◽  
Thermal Therapy ◽  
Published Data ◽  
Thermal Dose ◽  
Model Based ◽  
Dose Model

Thermal dose models are metrics that quantify thermal damage in tissues based on the temperature and the time of exposure. The validity and accuracy of one of the commonly used models (CEM₄₃) for high temperature thermal therapy applications (50-90 degree Celcius) is questionable. It was found to over-estimate the accumulation of thermal damage for high-temperature applications. A new CEM₄₃ dose model based on Arrhenius type Vogel-Tammann-Fulcher equation using published data is introduced in this work. The new dose values for the same damage threshold that was produced at different in-vivo skin experiments were in the same order of magnitude, while the current dose values were 2 orders of magnitude different. The new dose values for same damage threshold in 6 lessions in ex-vivo liver experiments were more consistent than the current dose values. Computer simulations of laser interstitial thermal therapy showed that the current model usually predicts bigger volume than the new model does. The deviation in damaged volume prediction can be significant. The contribution of this work is introducing methods that can lead to more robust thermal dosimetry which will result in improved therapy modelling, monitoring and control.

scholarly journals Prevention of Advanced Cancer by Vitamin D3 Supplementation: Interaction by Body Mass Index Revisited

Nutrients ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 1408
Author(s):  
Hermann Brenner ◽  
Sabine Kuznia ◽  
Clarissa Laetsch ◽  
Tobias Niedermaier ◽  
Ben Schöttker
Keyword(s):  
Body Mass Index ◽  
Vitamin D ◽  
Cancer Patients ◽  
Body Mass ◽  
Advanced Cancer ◽  
Vitamin D3 ◽  
Normal Weight ◽  
The Body ◽  
Published Data ◽  
Vitamin D3 Supplementation

Meta-analyses of randomized controlled trials (RCTs) have demonstrated a protective effect of vitamin D3 (cholecalciferol) supplementation against cancer mortality. In the VITAL study, a RCT including 25,871 men ≥ 50 years and women ≥ 55 years, protective effects of vitamin D3 supplementation (2000 IU/day over a median of 5.3 years) with respect to incidence of any cancer and of advanced cancer (metastatic cancer or cancer death) were seen for normal-weight participants but not for overweight or obese participants. We aimed to explore potential reasons for this apparent variation of vitamin D effects by body mass index. We conducted complementary analyses of published data from the VITAL study on the association of body weight with cancer outcomes, stratified by vitamin D3 supplementation. Significantly increased risks of any cancer and of advanced cancer were seen among normal-weight participants compared to obese participants in the control group (relative risk (RR), 1.27; 95% confidence interval (CI), 1.07–1.52, and RR, 1.44; 95% CI, 1.04–1.97, respectively). No such patterns were seen in the intervention group. Among those with incident cancer, vitamin D3 supplementation was associated with a significantly reduced risk of advanced cancer (RR, 0.86; 95% CI, 0.74–0.99). The observed patterns point to pre-diagnostic weight loss of cancer patients and preventive effects of vitamin D3 supplementation from cancer progression as plausible explanations for the body mass index (BMI)—intervention interactions. Further research, including RCTs more comprehensively exploring the potential of adjuvant vitamin D therapy for cancer patients, should be pursued with priority.

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