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Le
Zhang
Author
Materials Science Program
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI.
However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest.
At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
Summer 2017
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
Le
Zhang
Author
Materials Science Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI.
However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest.
At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
Summer 2017
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
Le
Zhang
Creator
Materials Science Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its
Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is
critical to a number of applications, including the monitoring of thermal therapy in
cancer patients. The resonance frequency of water protons is the most commonly used probe
to measure relative temperature changes with MRI. The water proton resonance frequency
(PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any
tissue type and is as a result suitable to measure relative temperature changes in vivo.
It has also been suggested that PRF could be used for absolute temperature measurements if
a temperature independent resonance frequency, like that of neighboring fat spins
(methylene protons), could be used to remove the effect of field drift and magnetic field
inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water
and fat spins have also been suggested as a possible means of correcting for the effect of
macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than
that typically probed by MRI. However water and fat do not mix and water and fat tissues
have very different magnetic susceptibilities. In this thesis we analyze the effect of
microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced
PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using
a combination of simulations and high-resolution spectroscopic measurements, we show that
by referencing the water resonance frequency to that of nearby methylene protons one could
obtain very inaccurate temperature measurements. We also show that the impact of
microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance
frequency, which probes into the difference in resonance frequencies between water and fat
spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility
gradients the strongest. At the same time we investigate the temperature dependence of the
chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient
of LDX resonance frequency is 20-fold higher than that of water and it is linear within
the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since
LDX and methylene protons reside in the same environment, the effect of both macro and
microscopic susceptibility gradients can be completely removed by referencing LDX to the
nearby methylene protons, providing the opportunity to measure absolute temperature. We
validated this method both in vitro and in vivo in rodents. We then applied this method in
humans to directly measure the temperature of brown adipose tissue, which is a type of
adipose tissue with clinical significance.
Summer 2017
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field,
Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting
institution
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
Le
Zhang
Creator
Materials Science Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
Summer 2017
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
Summer 2017
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
2017-08
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
2017-08
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
2017-08
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
2017-08
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
2017-08
University of North Carolina at Chapel Hill
Degree granting institution
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
2017-08
University of North Carolina at Chapel Hill
Degree granting institution
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
2017
Medical imaging
Biophysics
Brown Adipose Tissue; Distant Dipolar Field; Intermolecular Zero-quantum Coherences; MRI; MR Thermometry; Xenon-129
eng
Doctor of Philosophy
Dissertation
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
2017-08
University of North Carolina at Chapel Hill
Degree granting institution
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
University of North Carolina at Chapel Hill Graduate School
Degree granting institution
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
2017-08
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
2017
Medical imaging
Biophysics
Brown Adipose Tissue, Distant Dipolar Field, Intermolecular Zero-quantum Coherences, MRI, MR Thermometry, Xenon-129
eng
Doctor of Philosophy
Dissertation
Materials Science
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
2017-08
University of North Carolina at Chapel Hill
Degree granting institution
Le
Zhang
Creator
Materials Science Graduate Program
Department of Applied Physical Sciences
College of Arts and Sciences
Temperature Dependence of the Chemical Shift of Lipid-dissolved 129Xe and Its Applications in MR Thermometry
The ability to measure tissue temperature non invasively and in vivo is critical to a number of applications, including the monitoring of thermal therapy in cancer patients. The resonance frequency of water protons is the most commonly used probe to measure relative temperature changes with MRI. The water proton resonance frequency (PRF) shifts linearly with temperature with a coefficient of -0.01ppm/°C for almost any tissue type and is as a result suitable to measure relative temperature changes in vivo. It has also been suggested that PRF could be used for absolute temperature measurements if a temperature independent resonance frequency, like that of neighboring fat spins (methylene protons), could be used to remove the effect of field drift and magnetic field inhomogeneities. Similarly, intermolecular zero-quantum coherences (iZQCs) between water and fat spins have also been suggested as a possible means of correcting for the effect of macroscopic susceptibility gradients at the microscopic scale, a scale much smaller than that typically probed by MRI. However water and fat do not mix and water and fat tissues have very different magnetic susceptibilities. In this thesis we analyze the effect of microscopic susceptibility gradient gener- ated at water-fat interfaces on fat-referenced PRF thermometry methods and on iZQC water-fat thermometry methods. Specifically, by using a combination of simulations and high-resolution spectroscopic measurements, we show that by referencing the water resonance frequency to that of nearby methylene protons one could obtain very inaccurate temperature measurements. We also show that the impact of microscopic susceptibility gradients is even stronger on the iZQC water-fat resonance frequency, which probes into the difference in resonance frequencies between water and fat spins more heavily at water-fat interfaces, where microscopic magnetic susceptibility gradients the strongest. At the same time we investigate the temperature dependence of the chemical shift of lipid- dissolved 129Xe (LDX). We show that the temperature coefficient of LDX resonance frequency is 20-fold higher than that of water and it is linear within the most clinically-relevant temperature range (20∼45°C) used in thermotherapies. Since LDX and methylene protons reside in the same environment, the effect of both macro and microscopic susceptibility gradients can be completely removed by referencing LDX to the nearby methylene protons, providing the opportunity to measure absolute temperature. We validated this method both in vitro and in vivo in rodents. We then applied this method in humans to directly measure the temperature of brown adipose tissue, which is a type of adipose tissue with clinical significance.
2017
Medical imaging
Biophysics
Brown Adipose Tissue; Distant Dipolar Field; Intermolecular Zero-quantum Coherences; MRI; MR Thermometry; Xenon-129
eng
Doctor of Philosophy
Dissertation
Rosa Tamara
Branca
Thesis advisor
Sean
Washburn
Thesis advisor
Jianping
Lu
Thesis advisor
Yue
Wu
Thesis advisor
Hong
Yuan
Thesis advisor
text
2017-08
University of North Carolina at Chapel Hill
Degree granting institution
Zhang_unc_0153D_17268.pdf
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2017-07-24T22:01:18Z
2019-08-15T00:00:00
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