In vivo measurement and imaging of ferrimagnetic particle concentrations in biological tissues

Heath Pardoe

Research output: ThesisDoctoral Thesis

106 Downloads (Pure)

Abstract

[Truncated abstract] Clinical magnetic resonance imaging (MRI) scanners were used to investigate the measurement and imaging of ferrimagnetic particle concentrations in biological tissues in vivo. The presence of ferrimagnetic particles tends to increase the proton transverse relaxation rate (R2) of water protons in tissue. A quantitative image of R2 can be generated using a series of single spin echo magnetic resonance images acquired using clinical MRI scanners and analysing the images using techniques based on that reported by Clark and St. Pierre (2000). If ferrimagnetic particles have a high enough concentration, there is a monotonic relationship between particle concentration and R2; therefore an image of R2 gives a map of the ferrimagnetic particle concentration in the tissue. These techniques were used to investigate the feasibility of in vivo measurement of the concentration and distribution of both synthetic and biogenic ferrimagnetic particles in tissue. Rabbit liver was loaded with ferrimagnetic particles of ?-Fe2O3 (designed for magnetic hyperthermia treatment of liver tumours) by injecting various doses of a suspension of the particles into the hepatic artery in vivo. R2 images of the livers in vivo, excised, and dissected were generated from a series of single spin-echo images. Mean R2 values for samples of ferrimagnetic-particle-loaded liver dissected into approximate 1 cm cubes were found to linearly correlate with tissue iron concentration over the range from approximately 0.1 to at least 2.7 mg Fe/g dry tissue when measured at room temperature. Changing the temperature of ferrimagnetic-particle-loaded samples of liver from 1?C to 37?C had no observable effect on tissue R2 values. However, a small but significant decrease in R2 was found for control samples containing no ferrimagnetic material on raising the temperature from 1?C to 37?C. Both chemically measured iron ii concentrations and mean R2 values for rabbit livers with implanted tumours tended to be higher than those measured for tumour-free liver. This study indicates that tissue R2 measurement and imaging by nuclear magnetic resonance may have a useful role in magnetic hyperthermia therapy protocols for the treatment of liver cancer. In order to investigate the use of clinical MRI scanners to measure biogenic ferrimagnetic particle concentrations in human brain tissue, agar gel based phantoms containing ferrimagnetic particles were made in order to determine the lower concentration detection limit for such particles in a homogenous medium. Magnetite/maghemite nanoparticles were synthesized in the presence of either dextran or polyvinyl alcohol, yielding cluster- and necklace-like aggregates, respectively. Magnetization, Mossbauer spectroscopy, and microscopy measurements indicated that the arrangement of the particles within the aggregates affects the magnetic properties of the particles resulting in smaller particles in the clusters having higher superparamagnetic blocking temperatures than larger particles in the necklaces.
Original languageEnglish
QualificationDoctor of Philosophy
Publication statusUnpublished - 2005

Fingerprint

liver
magnetic resonance
scanners
tumors
hyperthermia
rabbits
echoes
ferrimagnetic materials
iron
dextrans
protons
polyvinyl alcohol
arteries
magnetite
brain
temperature
low concentrations
therapy
alcohols
cancer

Cite this

@phdthesis{a8987857f8154219aba9578619382abb,
title = "In vivo measurement and imaging of ferrimagnetic particle concentrations in biological tissues",
abstract = "[Truncated abstract] Clinical magnetic resonance imaging (MRI) scanners were used to investigate the measurement and imaging of ferrimagnetic particle concentrations in biological tissues in vivo. The presence of ferrimagnetic particles tends to increase the proton transverse relaxation rate (R2) of water protons in tissue. A quantitative image of R2 can be generated using a series of single spin echo magnetic resonance images acquired using clinical MRI scanners and analysing the images using techniques based on that reported by Clark and St. Pierre (2000). If ferrimagnetic particles have a high enough concentration, there is a monotonic relationship between particle concentration and R2; therefore an image of R2 gives a map of the ferrimagnetic particle concentration in the tissue. These techniques were used to investigate the feasibility of in vivo measurement of the concentration and distribution of both synthetic and biogenic ferrimagnetic particles in tissue. Rabbit liver was loaded with ferrimagnetic particles of ?-Fe2O3 (designed for magnetic hyperthermia treatment of liver tumours) by injecting various doses of a suspension of the particles into the hepatic artery in vivo. R2 images of the livers in vivo, excised, and dissected were generated from a series of single spin-echo images. Mean R2 values for samples of ferrimagnetic-particle-loaded liver dissected into approximate 1 cm cubes were found to linearly correlate with tissue iron concentration over the range from approximately 0.1 to at least 2.7 mg Fe/g dry tissue when measured at room temperature. Changing the temperature of ferrimagnetic-particle-loaded samples of liver from 1?C to 37?C had no observable effect on tissue R2 values. However, a small but significant decrease in R2 was found for control samples containing no ferrimagnetic material on raising the temperature from 1?C to 37?C. Both chemically measured iron ii concentrations and mean R2 values for rabbit livers with implanted tumours tended to be higher than those measured for tumour-free liver. This study indicates that tissue R2 measurement and imaging by nuclear magnetic resonance may have a useful role in magnetic hyperthermia therapy protocols for the treatment of liver cancer. In order to investigate the use of clinical MRI scanners to measure biogenic ferrimagnetic particle concentrations in human brain tissue, agar gel based phantoms containing ferrimagnetic particles were made in order to determine the lower concentration detection limit for such particles in a homogenous medium. Magnetite/maghemite nanoparticles were synthesized in the presence of either dextran or polyvinyl alcohol, yielding cluster- and necklace-like aggregates, respectively. Magnetization, Mossbauer spectroscopy, and microscopy measurements indicated that the arrangement of the particles within the aggregates affects the magnetic properties of the particles resulting in smaller particles in the clusters having higher superparamagnetic blocking temperatures than larger particles in the necklaces.",
keywords = "Magnetic resonance imaging, Brain, Magnetite, Proton transverse relaxation rate imaging, Biomineralisation, Biogenic magnetite, Magnetic nanoparticles, Liver",
author = "Heath Pardoe",
year = "2005",
language = "English",

}

In vivo measurement and imaging of ferrimagnetic particle concentrations in biological tissues. / Pardoe, Heath.

2005.

Research output: ThesisDoctoral Thesis

TY - THES

T1 - In vivo measurement and imaging of ferrimagnetic particle concentrations in biological tissues

AU - Pardoe, Heath

PY - 2005

Y1 - 2005

N2 - [Truncated abstract] Clinical magnetic resonance imaging (MRI) scanners were used to investigate the measurement and imaging of ferrimagnetic particle concentrations in biological tissues in vivo. The presence of ferrimagnetic particles tends to increase the proton transverse relaxation rate (R2) of water protons in tissue. A quantitative image of R2 can be generated using a series of single spin echo magnetic resonance images acquired using clinical MRI scanners and analysing the images using techniques based on that reported by Clark and St. Pierre (2000). If ferrimagnetic particles have a high enough concentration, there is a monotonic relationship between particle concentration and R2; therefore an image of R2 gives a map of the ferrimagnetic particle concentration in the tissue. These techniques were used to investigate the feasibility of in vivo measurement of the concentration and distribution of both synthetic and biogenic ferrimagnetic particles in tissue. Rabbit liver was loaded with ferrimagnetic particles of ?-Fe2O3 (designed for magnetic hyperthermia treatment of liver tumours) by injecting various doses of a suspension of the particles into the hepatic artery in vivo. R2 images of the livers in vivo, excised, and dissected were generated from a series of single spin-echo images. Mean R2 values for samples of ferrimagnetic-particle-loaded liver dissected into approximate 1 cm cubes were found to linearly correlate with tissue iron concentration over the range from approximately 0.1 to at least 2.7 mg Fe/g dry tissue when measured at room temperature. Changing the temperature of ferrimagnetic-particle-loaded samples of liver from 1?C to 37?C had no observable effect on tissue R2 values. However, a small but significant decrease in R2 was found for control samples containing no ferrimagnetic material on raising the temperature from 1?C to 37?C. Both chemically measured iron ii concentrations and mean R2 values for rabbit livers with implanted tumours tended to be higher than those measured for tumour-free liver. This study indicates that tissue R2 measurement and imaging by nuclear magnetic resonance may have a useful role in magnetic hyperthermia therapy protocols for the treatment of liver cancer. In order to investigate the use of clinical MRI scanners to measure biogenic ferrimagnetic particle concentrations in human brain tissue, agar gel based phantoms containing ferrimagnetic particles were made in order to determine the lower concentration detection limit for such particles in a homogenous medium. Magnetite/maghemite nanoparticles were synthesized in the presence of either dextran or polyvinyl alcohol, yielding cluster- and necklace-like aggregates, respectively. Magnetization, Mossbauer spectroscopy, and microscopy measurements indicated that the arrangement of the particles within the aggregates affects the magnetic properties of the particles resulting in smaller particles in the clusters having higher superparamagnetic blocking temperatures than larger particles in the necklaces.

AB - [Truncated abstract] Clinical magnetic resonance imaging (MRI) scanners were used to investigate the measurement and imaging of ferrimagnetic particle concentrations in biological tissues in vivo. The presence of ferrimagnetic particles tends to increase the proton transverse relaxation rate (R2) of water protons in tissue. A quantitative image of R2 can be generated using a series of single spin echo magnetic resonance images acquired using clinical MRI scanners and analysing the images using techniques based on that reported by Clark and St. Pierre (2000). If ferrimagnetic particles have a high enough concentration, there is a monotonic relationship between particle concentration and R2; therefore an image of R2 gives a map of the ferrimagnetic particle concentration in the tissue. These techniques were used to investigate the feasibility of in vivo measurement of the concentration and distribution of both synthetic and biogenic ferrimagnetic particles in tissue. Rabbit liver was loaded with ferrimagnetic particles of ?-Fe2O3 (designed for magnetic hyperthermia treatment of liver tumours) by injecting various doses of a suspension of the particles into the hepatic artery in vivo. R2 images of the livers in vivo, excised, and dissected were generated from a series of single spin-echo images. Mean R2 values for samples of ferrimagnetic-particle-loaded liver dissected into approximate 1 cm cubes were found to linearly correlate with tissue iron concentration over the range from approximately 0.1 to at least 2.7 mg Fe/g dry tissue when measured at room temperature. Changing the temperature of ferrimagnetic-particle-loaded samples of liver from 1?C to 37?C had no observable effect on tissue R2 values. However, a small but significant decrease in R2 was found for control samples containing no ferrimagnetic material on raising the temperature from 1?C to 37?C. Both chemically measured iron ii concentrations and mean R2 values for rabbit livers with implanted tumours tended to be higher than those measured for tumour-free liver. This study indicates that tissue R2 measurement and imaging by nuclear magnetic resonance may have a useful role in magnetic hyperthermia therapy protocols for the treatment of liver cancer. In order to investigate the use of clinical MRI scanners to measure biogenic ferrimagnetic particle concentrations in human brain tissue, agar gel based phantoms containing ferrimagnetic particles were made in order to determine the lower concentration detection limit for such particles in a homogenous medium. Magnetite/maghemite nanoparticles were synthesized in the presence of either dextran or polyvinyl alcohol, yielding cluster- and necklace-like aggregates, respectively. Magnetization, Mossbauer spectroscopy, and microscopy measurements indicated that the arrangement of the particles within the aggregates affects the magnetic properties of the particles resulting in smaller particles in the clusters having higher superparamagnetic blocking temperatures than larger particles in the necklaces.

KW - Magnetic resonance imaging

KW - Brain

KW - Magnetite

KW - Proton transverse relaxation rate imaging

KW - Biomineralisation

KW - Biogenic magnetite

KW - Magnetic nanoparticles

KW - Liver

M3 - Doctoral Thesis

ER -