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Vanderbilt University
1.
West, Kathryn Louise.
Multi-exponential T2 Myelin Water Imaging in Ex-Vivo Rodent Brain at 7T and 15.2T.
Degree: MS, Biomedical Engineering, 2014, Vanderbilt University
URL: http://hdl.handle.net/1803/11313 
► To apply MWI techniques to excised, fixed rodent brains, multi-exponential T2 (MET2) data were acquired at high (7T) and ultra-high (15.2T) fields with and without…
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▼ To apply MWI techniques to excised, fixed rodent brains, multi-exponential T2 (MET2) data were acquired at high (7T) and ultra-high (15.2T) fields with and without tissue doping with Gadolinium to increase SNR efficiency. From relaxivity measurements, optimal scan parameters are found based on the minimal Cramér-Rao lower bounds (CRLB) of variance of myelin water fraction (MWF). Subsequently acquired MET2 data were analyzed to obtain myelin water fraction (MWF) maps with and without contrast agent at each field strength with various techniques, displaying the potential for MWI in rodent brain in the study of myelin content across whole brain.
Advisors/Committee Members: Daniel F. Gochberg (committee member), Mark D. Does (Committee Chair).
Subjects/Keywords: ultra-high field; Muliti-exponential T2; Myelin
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APA (6th Edition):
West, K. L. (2014). Multi-exponential T2 Myelin Water Imaging in Ex-Vivo Rodent Brain at 7T and 15.2T. (Thesis). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/11313
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
West, Kathryn Louise. “Multi-exponential T2 Myelin Water Imaging in Ex-Vivo Rodent Brain at 7T and 15.2T.” 2014. Thesis, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/11313.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
West, Kathryn Louise. “Multi-exponential T2 Myelin Water Imaging in Ex-Vivo Rodent Brain at 7T and 15.2T.” 2014. Web. 19 Jan 2021.
Vancouver:
West KL. Multi-exponential T2 Myelin Water Imaging in Ex-Vivo Rodent Brain at 7T and 15.2T. [Internet] [Thesis]. Vanderbilt University; 2014. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/11313.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
West KL. Multi-exponential T2 Myelin Water Imaging in Ex-Vivo Rodent Brain at 7T and 15.2T. [Thesis]. Vanderbilt University; 2014. Available from: http://hdl.handle.net/1803/11313
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Vanderbilt University
2.
Banks, Joshua Ian.
Development and Characterization of NMR and MRI Methods for Assessment of Tumor Oxygen Consumption.
Degree: MS, Physics, 2012, Vanderbilt University
URL: http://hdl.handle.net/1803/14280
► A common feature of invasive cancers is that they have an upregulation of glucose metabolism and reduced oxygen utilization. The overall goal of this research…
(more)
▼ A common feature of invasive cancers is that they have an upregulation of glucose metabolism and reduced oxygen utilization. The overall goal of this research was to develop a 17Oxygen MRI method to access this aberrant tumor metabolism using a T1ρ weighted pulse sequence on a Bruker NMR Spectrometer. An assessment of the reliability of this pulse sequence for quantifying the ratio of concentrations of H217O (necessary for measuring the metabolic rate in vivo) water in 4 pairs of phantoms was preformed. Specifically, we varied the pH and concentration of Gadopentetic acid (Gd-DTPA) (which modulated T1 and T2 profiles) in 4 different combinations to mimic conditions in the tumor microeviorment. We then used the signal decay data collected at a low and high spin lock power and inserted this data into an eqaution. This equation was then used to compute the ratio of concentration between an enriched and unenriched phantom in each of the 4 pairs.
The two -frequency method was able to quantify [H217O] successfully in the phantoms without Gd-DTPA using the fitted signal data but failed to yield the correct result for the raw data. Thus, to further evaluate these approaches we need employ studies at clinical field strengths. Nevertheless, our results suggest that the quantification of H217O is insensitive to pH but sensitive to changes in T1 and T2.
Advisors/Committee Members: Daniel F. Gochberg (committee member), C. Chad Quarles (Committee Chair).
Subjects/Keywords: Oxygen-17; Oxidative Phosphorylation; MRI; NMR
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APA (6th Edition):
Banks, J. I. (2012). Development and Characterization of NMR and MRI Methods for Assessment of Tumor Oxygen Consumption. (Thesis). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/14280
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Banks, Joshua Ian. “Development and Characterization of NMR and MRI Methods for Assessment of Tumor Oxygen Consumption.” 2012. Thesis, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/14280.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Banks, Joshua Ian. “Development and Characterization of NMR and MRI Methods for Assessment of Tumor Oxygen Consumption.” 2012. Web. 19 Jan 2021.
Vancouver:
Banks JI. Development and Characterization of NMR and MRI Methods for Assessment of Tumor Oxygen Consumption. [Internet] [Thesis]. Vanderbilt University; 2012. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/14280.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Banks JI. Development and Characterization of NMR and MRI Methods for Assessment of Tumor Oxygen Consumption. [Thesis]. Vanderbilt University; 2012. Available from: http://hdl.handle.net/1803/14280
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Vanderbilt University
3.
Lankford, Christopher Lynn.
Multiple Echo, Caesar Cipher Acquisition and Model-Based Reconstruction (ME-CAMBREC): a Novel Accelerated T2 Mapping Method.
Degree: PhD, Biomedical Engineering, 2016, Vanderbilt University
URL: http://hdl.handle.net/1803/14384
► Due to the need to acquire a series of T2-weighted images, quantitative T2 mapping protocols in magnetic resonance imaging (MRI) suffer from long scan times.…
(more)
▼ Due to the need to acquire a series of T2-weighted images, quantitative T2 mapping protocols in magnetic resonance imaging (MRI) suffer from long scan times. In order to alleviate this problem, fast spin-echo (FSE) imaging protocols can be employed, but the resulting images contain errors in the form of smoothing and ghosting artifacts which propagate to T2 maps. This dissertation presents a new method, dubbed Multiple Echo, Caesar Cipher Acquisition and Model-Based Reconstruction (ME-CAMBREC), which explicitly accounts for k-space signal attenuation during the reconstruction step. T2 maps generated by ME-CAMBREC contained reduced artifact compared to those generated by FSE methods, while requiring only a fraction of the scan time of a multiple spin-echo protocol. For moderate-to-high acceleration factors, ME-CAMBREC outperformed parallel imaging and steady-state T2 mapping techniques. Data suitable for ME-CAMBREC can be acquired in multi-slice mode using pulse sequence interleafs, but a slice gap should be employed to limit T2 bias caused by radiofrequency profile effects. Although ME-CAMBREC can be used to generate accurate T2s in the presence of flip angle errors, it was shown that the use of an independent measure of the transmit field (B1+) will improve fitted T2 precision.
Advisors/Committee Members: Bruce M. Damon (committee member), Daniel F. Gochberg (committee member), William A. Grissom (committee member), E. Brian Welch (committee member), Mark D. Does (Committee Chair).
Subjects/Keywords: MRI; T2; fast imaging; model-based reconstruction; parametric constraint
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APA (6th Edition):
Lankford, C. L. (2016). Multiple Echo, Caesar Cipher Acquisition and Model-Based Reconstruction (ME-CAMBREC): a Novel Accelerated T2 Mapping Method. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/14384
Chicago Manual of Style (16th Edition):
Lankford, Christopher Lynn. “Multiple Echo, Caesar Cipher Acquisition and Model-Based Reconstruction (ME-CAMBREC): a Novel Accelerated T2 Mapping Method.” 2016. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/14384.
MLA Handbook (7th Edition):
Lankford, Christopher Lynn. “Multiple Echo, Caesar Cipher Acquisition and Model-Based Reconstruction (ME-CAMBREC): a Novel Accelerated T2 Mapping Method.” 2016. Web. 19 Jan 2021.
Vancouver:
Lankford CL. Multiple Echo, Caesar Cipher Acquisition and Model-Based Reconstruction (ME-CAMBREC): a Novel Accelerated T2 Mapping Method. [Internet] [Doctoral dissertation]. Vanderbilt University; 2016. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/14384.
Council of Science Editors:
Lankford CL. Multiple Echo, Caesar Cipher Acquisition and Model-Based Reconstruction (ME-CAMBREC): a Novel Accelerated T2 Mapping Method. [Doctoral Dissertation]. Vanderbilt University; 2016. Available from: http://hdl.handle.net/1803/14384
Vanderbilt University
4.
Li, Hua.
Towards quantitative measurements of tissue microstructure using temporal diffusion spectroscopy.
Degree: PhD, Physics, 2015, Vanderbilt University
URL: http://hdl.handle.net/1803/12743
► Diffusion MRI provides a non-invasive means to characterize tissue microstructure at varying length scales. Apparent diffusion coefficients (ADCs) of tissue water may be measured at…
(more)
▼ Diffusion MRI provides a non-invasive means to characterize tissue microstructure at varying length scales. Apparent diffusion coefficients (ADCs) of tissue water may be measured at relatively long diffusion times with conventional pulsed gradient spin echo (PGSE) methods, or at much shorter effective diffusion times using oscillating gradient spin echo (OGSE) methods. Besides the information provided by single ADC measurements, the manner in which ADC disperses with gradient frequency (or diffusion time) provides information on the characteristic dimensions of structures within the medium. However, despite increasing interest in applying frequency-dependent ADC to derive novel information on tissue, the interpretations of ADC spectra are not always clear. Meanwhile, to better characterize the tissue microstructure, the direct quantitation of restricting dimensions may be more helpful. The contrast and structural information provided by temporal diffusion spectroscopy are comprehensively studied in this thesis, including (1) the structural information revealed by the dispersion of ADC with frequency; (2) the influence of cell membrane permeability on MR diffusion measurements; and (3) the quantification of restricting size in simple one-pool and two-pool models. This work may help better understand the contrast by temporal diffusion spectroscopy and demonstrates its potential for quantitative measurements of tissue microstructure.
Advisors/Committee Members: Junzhong Xu (committee member), Mark D. Does (committee member), Adam W. Anderson (committee member), Daniel F. Gochberg (committee member), John C. Gore (Committee Chair).
Subjects/Keywords: diffusion; MRI
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APA (6th Edition):
Li, H. (2015). Towards quantitative measurements of tissue microstructure using temporal diffusion spectroscopy. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/12743
Chicago Manual of Style (16th Edition):
Li, Hua. “Towards quantitative measurements of tissue microstructure using temporal diffusion spectroscopy.” 2015. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/12743.
MLA Handbook (7th Edition):
Li, Hua. “Towards quantitative measurements of tissue microstructure using temporal diffusion spectroscopy.” 2015. Web. 19 Jan 2021.
Vancouver:
Li H. Towards quantitative measurements of tissue microstructure using temporal diffusion spectroscopy. [Internet] [Doctoral dissertation]. Vanderbilt University; 2015. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/12743.
Council of Science Editors:
Li H. Towards quantitative measurements of tissue microstructure using temporal diffusion spectroscopy. [Doctoral Dissertation]. Vanderbilt University; 2015. Available from: http://hdl.handle.net/1803/12743
Vanderbilt University
5.
Spear, John Thomas.
Quantitative Characterization of Biological Tissues by NMR Relaxation in the Rotating Frame.
Degree: PhD, Physics, 2016, Vanderbilt University
URL: http://hdl.handle.net/1803/10867
► Measurements of the spin-lattice relaxation rate in the rotating frame, R1rho, using spin-locking techniques have long been exploited to investigate relatively slow molecular motions and,…
(more)
▼ Measurements of the spin-lattice relaxation rate in the rotating frame, R1rho, using spin-locking techniques have long been exploited to investigate relatively slow molecular motions and, more recently, to analyze chemical exchange. The variation of R1rho with spin-lock amplitude, or R1rho dispersion, provides the means to examine dynamic processes occurring on the time scale of the applied effective field, but corresponding techniques have been somewhat overlooked by the MRI community. Chemical exchange contributions to R1rho of protons in tissues are shown to dominate conventional dipole-dipole interactions at high fields, and R1rho dispersion depends on the exchange rate and chemical shift of the labile species. In addition, proton diffusion in the presence of intrinsic susceptibility gradients also contributes significantly to R1rho dispersion at low spin-lock amplitudes. Simulations and experiments performed in this work reveal these effects to largely be the dominant mechanisms influencing spin-locked relaxation at high static magnetic fields, and demonstrate the potential for using R1rho to characterize tissues across a variety of pathologies. Exchange-based R1rho methods are used to quantify exchange rates in solutions containing one or two solute pools and to produce images in which the contrast emphasizes the presence of metabolites exchanging at specific rates rather than with specific chemical shifts. A novel theory is derived that quantifies diffusion-based R1rho dispersion, which is subsequently applied to create parametric maps that reflect average sub-voxel microstructure and to calculate intrinsic gradient strengths in model systems of polystyrene microspheres and Red Blood Cells (RBC’s). This approach may further be used to estimate cell sizes and to emphasize vasculature of specific sizes in fMRI studies. Exchange and diffusion effects are also verified to be independent processes that may be analyzed simultaneously in biologically relevant applications. Collectively, R1rho dispersion methods provide a powerful alternative to traditional MRI methods and produce novel complementary information for quantitative tissue characterize.
Advisors/Committee Members: Daniel F. Gochberg (committee member), Michael S. Hutson (committee member), Erin C. Rericha (committee member), Thomas E. Yankeelov (committee member), John C. Gore (Committee Chair).
Subjects/Keywords: T1rho; diffusion; chemical exchange; spin-locking; NMR relaxation; tissue microstructure
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APA (6th Edition):
Spear, J. T. (2016). Quantitative Characterization of Biological Tissues by NMR Relaxation in the Rotating Frame. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/10867
Chicago Manual of Style (16th Edition):
Spear, John Thomas. “Quantitative Characterization of Biological Tissues by NMR Relaxation in the Rotating Frame.” 2016. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/10867.
MLA Handbook (7th Edition):
Spear, John Thomas. “Quantitative Characterization of Biological Tissues by NMR Relaxation in the Rotating Frame.” 2016. Web. 19 Jan 2021.
Vancouver:
Spear JT. Quantitative Characterization of Biological Tissues by NMR Relaxation in the Rotating Frame. [Internet] [Doctoral dissertation]. Vanderbilt University; 2016. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/10867.
Council of Science Editors:
Spear JT. Quantitative Characterization of Biological Tissues by NMR Relaxation in the Rotating Frame. [Doctoral Dissertation]. Vanderbilt University; 2016. Available from: http://hdl.handle.net/1803/10867
Vanderbilt University
6.
Cobb, Jared Guthrie.
Quantitative proton relaxometry in the rotating frame with magnetic resonance imaging.
Degree: PhD, Biomedical Engineering, 2011, Vanderbilt University
URL: http://hdl.handle.net/1803/14019
► Conventional magnetic resonance imaging (MRI) uses contrast that is weighted by the intrinsic tissue parameters T1, and T2. Contrast may also be generated in the…
(more)
▼ Conventional magnetic resonance imaging (MRI) uses contrast that is weighted by the intrinsic tissue parameters T1, and T2. Contrast may also be generated in the rotating frame with the analogous time constants T1ρ or T2ρ. Traditionally T1ρ measurements have been used to investigate low frequency dipolar interactions in the kHz range. However, other biological processes, such as chemical exchange, also occur on this time scale. Recently it has been shown that these processes dominate R1ρ (1/T1ρ) relaxation at high field, and these interactions are of interest as high field imaging systems become increasingly common. We have developed quantitative spin-locking (SL) techniques to probe rotating frame relaxation on clinical and pre-clinical imaging systems. Experiments were performed with these techniques to generate T1ρ maps of pediatric epiphyseal cartilage and mouse brain.
If the power of the SL field is varied, the measured T1ρ values will change in a phenomenon known as T1ρ dispersion. These dispersion profiles vary with tissue properties such as pH and metabolite concentration, and the data may be fit with a model to extract unique parameters such as chemical exchange. Novel methods were developed to generate exchange rate based contrast using the contrast features of T1ρ dispersion profiles. A number of exogenous and endogenous contrast agents were quantitatively compared to chemical exchange saturation contrast (CEST) imaging. CEST and SL techniques were evaluated for their complementary features to determine the experimental conditions where each may be most appropriately used.
Diffusion processes were explored as an additional
contributor to T1ρ dispersion. Various spherical phantoms of different size and material properties were measured with SL techniques to observe their effects on contrast. Methods were developed to separate the effects of diffusion and chemical exchange.
The experiments reported here further elucidate the contributing factors to R1ρ relaxation in a variety of biologically relevant molecules and tissues. Finally, the methods resulting from these experiments are useful for generating novel contrast that is primarily dependent on exchange rates.
Advisors/Committee Members: Daniel F. Gochberg (committee member), Mark D. Does (committee member), Bruce M. Damon (committee member), J. Christopher Gatenby (committee member), John C. Gore (Committee Chair).
Subjects/Keywords: rotating frame; relaxometry; MRI; t1rho
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APA (6th Edition):
Cobb, J. G. (2011). Quantitative proton relaxometry in the rotating frame with magnetic resonance imaging. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/14019
Chicago Manual of Style (16th Edition):
Cobb, Jared Guthrie. “Quantitative proton relaxometry in the rotating frame with magnetic resonance imaging.” 2011. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/14019.
MLA Handbook (7th Edition):
Cobb, Jared Guthrie. “Quantitative proton relaxometry in the rotating frame with magnetic resonance imaging.” 2011. Web. 19 Jan 2021.
Vancouver:
Cobb JG. Quantitative proton relaxometry in the rotating frame with magnetic resonance imaging. [Internet] [Doctoral dissertation]. Vanderbilt University; 2011. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/14019.
Council of Science Editors:
Cobb JG. Quantitative proton relaxometry in the rotating frame with magnetic resonance imaging. [Doctoral Dissertation]. Vanderbilt University; 2011. Available from: http://hdl.handle.net/1803/14019
Vanderbilt University
7.
Horch, Robert Adam.
Studies Of Proton Nuclear Magnetic Resonance Relaxation In Human Cortical Bone: From Ex Vivo Spectroscopy To Clinical Imaging Methods.
Degree: PhD, Biomedical Engineering, 2011, Vanderbilt University
URL: http://hdl.handle.net/1803/14596
► Current clinical bone diagnostic measures rely predominantly on X-ray-based contrast and are primarily sensitive to bone mineral content. Since bone also contains collagen and water…
(more)
▼ Current clinical bone diagnostic measures rely predominantly on X-ray-based contrast and are primarily sensitive to bone mineral content. Since bone also contains collagen and water components, which are heavily implicated in fracture resistance, these X-ray measures are micro-anatomically incomplete and do not identify individuals who will fracture. This dissertation aims to improve clinical bone fracture risk assessment through the use of novel magnetic resonance imaging (MRI) methods, which provide quantitative measures of the non-mineral bone components. The overall goal is to advance our understanding of 1H nuclear magnetic resonance (NMR) relaxation in human cortical bone to the point that diagnostically-relevant parameters may be extracted from in vivo bone MRI measurements. To accomplish this, custom NMR hardware was first developed for a rigorous, NMR relaxation-based characterization of ex vivo cortical bone. Such characterization was used to identify the micro-anatomical origins of cortical bone NMR signal components, which included collagen, bound water, and pore water protons. These signal components correlated well with various bone mechanical properties, indicating diagnostic relevance. Using the well-characterized cortical bone relaxation characteristics, novel and clinically practical methods for quantitative, diagnostic bone MRI were developed and validated. Collectively, this work represents a biophysical basis for cortical bone MRI, which stands ready for translation to clinical and research studies.
Advisors/Committee Members: Bruce M. Damon (committee member), Jeffry S. Nyman (committee member), Daniel F. Gochberg (committee member), John C. Gore (committee member), Mark D. Does (Committee Chair).
Subjects/Keywords: MRI; NMR; cortical bone; T2; bound water; pore water
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APA (6th Edition):
Horch, R. A. (2011). Studies Of Proton Nuclear Magnetic Resonance Relaxation In Human Cortical Bone: From Ex Vivo Spectroscopy To Clinical Imaging Methods. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/14596
Chicago Manual of Style (16th Edition):
Horch, Robert Adam. “Studies Of Proton Nuclear Magnetic Resonance Relaxation In Human Cortical Bone: From Ex Vivo Spectroscopy To Clinical Imaging Methods.” 2011. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/14596.
MLA Handbook (7th Edition):
Horch, Robert Adam. “Studies Of Proton Nuclear Magnetic Resonance Relaxation In Human Cortical Bone: From Ex Vivo Spectroscopy To Clinical Imaging Methods.” 2011. Web. 19 Jan 2021.
Vancouver:
Horch RA. Studies Of Proton Nuclear Magnetic Resonance Relaxation In Human Cortical Bone: From Ex Vivo Spectroscopy To Clinical Imaging Methods. [Internet] [Doctoral dissertation]. Vanderbilt University; 2011. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/14596.
Council of Science Editors:
Horch RA. Studies Of Proton Nuclear Magnetic Resonance Relaxation In Human Cortical Bone: From Ex Vivo Spectroscopy To Clinical Imaging Methods. [Doctoral Dissertation]. Vanderbilt University; 2011. Available from: http://hdl.handle.net/1803/14596
Vanderbilt University
8.
Janve, Vaibhav Anil.
Myelin sensitivity in quantitative magnetization transfer and diffusion tensor imaging in an animal model of multiple sclerosis.
Degree: PhD, Physics, 2015, Vanderbilt University
URL: http://hdl.handle.net/1803/11234
► Conventional MRI is sensitive to detect brain abnormalities non-invasively through excellent contrast generated by variation in relaxation times and water proton density. However, conventional MRI…
(more)
▼ Conventional MRI is sensitive to detect brain abnormalities non-invasively through excellent contrast generated by variation in relaxation times and water proton density. However, conventional MRI lacks the specificity and quantitation to specific pathologies and tissue components such as myelin. Myelin is the major constituent of white matter ─an insulating macromolecular sleeve wrapped around axons of brain cells. Loss of white matter, specifically myelin leads to severe motor and cognitive deficits in diseases such as multiple sclerosis. Advanced quantitative MRI methods such as quantitative magnetization transfer (qMT) and diffusion tensor imaging (DTI) have emerged as putative biomarkers that improve sensitivity, specificity and provide quantitative metrics to measure myelin. qMT and DTI are model based quantitative techniques, which provide sub-voxel information of the underlying tissue architecture. qMT is sensitive to the tissue macromolecular content, whereas DTI is sensitive to tissue microstructure. Pool size ratio (PSR, a qMT parameter) and radial diffusivity (RD, a DTI parameter) provide an indirect quantitative measure of myelin. However, their relative sensitivities and specificities to myelin are unclear. qMT and DTI are based on different physical principles and may provide complementary information. While histology is the gold standard for myelin quantification, it can only be performed postmortem or through invasive biopsies. Thus, systematic quantitative MRI and histological validation studies are essential to determine the specific sensitivities of non-invasive quantitative metrics. Although, limited data is available on such studies due to their tedious, time intensive and complex nature. My thesis work addresses this gap by performing quantitative MRI and histological validation on a relatively new animal model of multiple sclerosis (MS), which recapitulates the inflammatory and non-inflammatory demyelinating phases seen in patients. The animal model was characterized using structural MRI, qMRI and histological methods. To enable quantitative comparisons amongst MRI and histological parameters, detailed processing protocol were designed and implemented including 3D qMT and DTI protocols and histological pipeline. In vivo and ex vivo studies were performed and qMT and DTI metrics were correlated with histology and among each other to determine their specific sensitivities. Furthermore, in an attempt to translate the animal work to clinical settings, a fast qMT sequence with GRASE readout was tested on human scanners. In conclusion, we found that PSR, and RD are sensitive to histological myelin content with PSR having the strongest correlation.
Advisors/Committee Members: Adam W. Anderson (committee member), David J. Ernst (committee member), Mark D. Does (committee member), John C. Gore (committee member), Daniel F. Gochberg (Committee Chair).
Subjects/Keywords: MRI; magnetization transfer; diffusion; multiple sclerosis; qMT; DTI; quantitative
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APA (6th Edition):
Janve, V. A. (2015). Myelin sensitivity in quantitative magnetization transfer and diffusion tensor imaging in an animal model of multiple sclerosis. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/11234
Chicago Manual of Style (16th Edition):
Janve, Vaibhav Anil. “Myelin sensitivity in quantitative magnetization transfer and diffusion tensor imaging in an animal model of multiple sclerosis.” 2015. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/11234.
MLA Handbook (7th Edition):
Janve, Vaibhav Anil. “Myelin sensitivity in quantitative magnetization transfer and diffusion tensor imaging in an animal model of multiple sclerosis.” 2015. Web. 19 Jan 2021.
Vancouver:
Janve VA. Myelin sensitivity in quantitative magnetization transfer and diffusion tensor imaging in an animal model of multiple sclerosis. [Internet] [Doctoral dissertation]. Vanderbilt University; 2015. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/11234.
Council of Science Editors:
Janve VA. Myelin sensitivity in quantitative magnetization transfer and diffusion tensor imaging in an animal model of multiple sclerosis. [Doctoral Dissertation]. Vanderbilt University; 2015. Available from: http://hdl.handle.net/1803/11234
Vanderbilt University
9.
West, Kathryn Louise.
Development and Evaluation of Relaxation-Based Measures of Myelin Content and Microstructure in Rodent Brains.
Degree: PhD, Biomedical Engineering, 2016, Vanderbilt University
URL: http://hdl.handle.net/1803/14525
► Advanced neuroimaging techniques provide the possibility to non-invasively understand and monitor white matter during development and disease. While data from quantitative MRI techniques, such as…
(more)
▼ Advanced neuroimaging techniques provide the possibility to non-invasively understand and monitor white matter during development and disease. While data from quantitative MRI techniques, such as multiexponential T2 (MET2) and quantitative magnetization transfer (qMT), correlate with myelin content, neither provide an absolute measure of the myelin volume fraction (MVF). Additionally, in preclinical studies, despite time-intensity and small tissue samples, histology remains the gold standard for quantitatively assessing changes in myelin content and white matter microstructural properties, such as myelin thickness and the g-ratio (ratio of axon radius to myelinated fiber radius). Therefore, the work in this dissertation first established and validated methods for MVF imaging from MET2 and qMT against quantitative electron microscopy. We show strong agreement in adult, control mice along with three mouse models of white matter disease. Next, we applied MVF imaging in mice during normal development and observe good agreement between MET2 and qMT and with expected myelin development. To further investigate specific changes in myelin microstructure, recent methods proposed measuring the g-ratio from MRI (gMRI). We revised the model and displayed with quantitative histology that gMRI provides an axon-area-weighted g-ratio. Calculating gMRI requires an accurate measure of MVF; thus, we utilize our MVF imaging techniques to measure gMRI in mouse brain and detect changes in g-ratio with disease in agreement with quantitative histology. In short, we develop and validate measures of MVF and g-ratio from MRI which have the potential to non-invasively provide more specific and thorough assessment of white matter not obtainable with currently used methods.
Advisors/Committee Members: Adam W. Anderson (committee member), Kevin C. Ess (committee member), Daniel F. Gochberg (committee member), John C. Gore (committee member), Mark D. Does (Committee Chair).
Subjects/Keywords: magnetization transfer; multiexponential T2; myelin; MRI; neuroimaging; histology; g-ratio
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APA (6th Edition):
West, K. L. (2016). Development and Evaluation of Relaxation-Based Measures of Myelin Content and Microstructure in Rodent Brains. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/14525
Chicago Manual of Style (16th Edition):
West, Kathryn Louise. “Development and Evaluation of Relaxation-Based Measures of Myelin Content and Microstructure in Rodent Brains.” 2016. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/14525.
MLA Handbook (7th Edition):
West, Kathryn Louise. “Development and Evaluation of Relaxation-Based Measures of Myelin Content and Microstructure in Rodent Brains.” 2016. Web. 19 Jan 2021.
Vancouver:
West KL. Development and Evaluation of Relaxation-Based Measures of Myelin Content and Microstructure in Rodent Brains. [Internet] [Doctoral dissertation]. Vanderbilt University; 2016. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/14525.
Council of Science Editors:
West KL. Development and Evaluation of Relaxation-Based Measures of Myelin Content and Microstructure in Rodent Brains. [Doctoral Dissertation]. Vanderbilt University; 2016. Available from: http://hdl.handle.net/1803/14525
Vanderbilt University
10.
Semmineh, Natenael Berhanu.
Computational and Experimental Investigation of DSC-MRI Signal
Behavior in Magnetically Inhomogeneous Media.
Degree: PhD, Physics, 2014, Vanderbilt University
URL: http://hdl.handle.net/1803/12183
► The systematic investigation of susceptibility-induced contrast in MRI is important to improve our understanding of the influence of tissue microstructure on dynamic susceptibility contrast (DSC)-MRI…
(more)
▼ The systematic investigation of susceptibility-induced contrast in MRI is important to improve our understanding of the influence of tissue microstructure on dynamic susceptibility contrast (DSC)-MRI derived perfusion data. The Finite Perturber Method (FPM) has previously been used to investigate susceptibility contrast in MRI arising from arbitrarily shaped structures. However, the FPM has low computational efficiency in simulating water diffusion, especially for complex three-dimensional structures that mimic tissue. In this work, an improved computational approach that combines the FPM with a matrix-based finite difference method (FDM), termed the Finite Perturber Finite Difference Method (FPFDM), was developed to more efficiently investigate the biophysical basis of DSC-MRI data and its sensitivity to vascular geometry and contrast agent (CA) distribution within tissue. The application of the FPFDM to the physiological and physical conditions encountered in a typical DSC-MRI brain tumor study enabled the derivation of a new DSC-MRI metric, termed the Transverse Relaxivity at Tracer Equilibrium (TRATE), which we propose specifically reports on tumor cellular properties. Computational FPFDM studies revealed that TRATE depends on cellular density, size, shape and spatial distribution. To validate the in vivo sensitivity of TRATE it was evaluated in two animal brain tumor models, the 9L and C6, which have varying cellular characteristics. The TRATE values were also compared to measures of the apparent diffusion coefficient (ADC), the CA transfer constant (Ktrans), the extravascular extracellular volume fraction (ve) and histological data. The TRATE values in 9L tumors were significantly higher than those in C6 tumors, a finding that reflects the histologically confirmed higher cell density in 9L tumors and lower cellular density. A voxel-wise comparison of TRATE with ADC, ve, and Ktrans maps showed low spatial correlation, indicating it is providing unique and complementary information on tumor status. In summary, the studies described herein highlight the value of pairing computational and experimental advancements in order to enhance our characterization of DSC-MRI contrast mechanisms and how such mechanisms can be leveraged to derive new non-invasive metrics for evaluating brain tumors.
Advisors/Committee Members: Kalman Varga (committee member), David J. Ernst (committee member), John C. Gore (committee member), Daniel F. Gochberg (committee member), C. Chad Quarles (Committee Chair).
Subjects/Keywords: dynamic susceptibility contrast; transverse relaxation; vascular structures; cellular structures; contrast agent leakage; diffusion.
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Semmineh, N. B. (2014). Computational and Experimental Investigation of DSC-MRI Signal
Behavior in Magnetically Inhomogeneous Media. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/12183
Chicago Manual of Style (16th Edition):
Semmineh, Natenael Berhanu. “Computational and Experimental Investigation of DSC-MRI Signal
Behavior in Magnetically Inhomogeneous Media.” 2014. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/12183.
MLA Handbook (7th Edition):
Semmineh, Natenael Berhanu. “Computational and Experimental Investigation of DSC-MRI Signal
Behavior in Magnetically Inhomogeneous Media.” 2014. Web. 19 Jan 2021.
Vancouver:
Semmineh NB. Computational and Experimental Investigation of DSC-MRI Signal
Behavior in Magnetically Inhomogeneous Media. [Internet] [Doctoral dissertation]. Vanderbilt University; 2014. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/12183.
Council of Science Editors:
Semmineh NB. Computational and Experimental Investigation of DSC-MRI Signal
Behavior in Magnetically Inhomogeneous Media. [Doctoral Dissertation]. Vanderbilt University; 2014. Available from: http://hdl.handle.net/1803/12183
Vanderbilt University
11.
Hong, Xin.
High angular resolution diffusion imaging of brain white matter and its application to schizophrenia.
Degree: PhD, Biomedical Engineering, 2010, Vanderbilt University
URL: http://hdl.handle.net/1803/11702
► By sampling the self-diffusion of water molecules, diffusion tensor imaging (DTI) is able to characterize the microstructure of brain white matter. Previous DTI studies in…
(more)
▼ By sampling the self-diffusion of water molecules, diffusion tensor imaging (DTI) is able to characterize the microstructure of brain white matter. Previous DTI studies in schizophrenia have reported white matter alterations as measured by changes in fractional anisotropy. However, DTI analysis is not capable of distinguishing between possible causes, such as a change in the fiber orientation coherence, a change in the intrinsic diffusivity of the fibers, or both. Compared with DTI, high angular resolution diffusion imaging (HARDI) provides more detailed structural information of underlying tissues. Fiber ORientation Estimated using Continuous Axially Symmetric Tensors (FORECAST) is a spherical deconvolution method to analyze HARDI data.
Based on Monte Carlo simulations, as well as bootstrap analysis of in vivo human data, the optimal imaging and processing parameters for conducting the FORECAST analysis within typical clinical constraints were determined, and the accuracy of the model was estimated.
In order to compare HARDI measurements between subjects, an algorithm was developed to transform the fiber orientation distribution (FOD) function, based on HARDI data, taking into account not only translation, but also rotation, scaling, and shearing effects of the spatial transformation. The algorithm was tested using simulated data, and intra-subject and inter-subject normalization of in vivo human data. All cases demonstrate reliable transformation of the FOD.
A voxel-based group comparison of the radial diffusivity and intravoxel fiber coherence was performed based on FORECAST analysis of the HARDI images from both healthy controls and patients with schizophrenia. Decreased FA and elevated radial diffusivity were found in a number of white matter regions in patients. Our results suggest that increased radial diffusivity is the major
contributor to the FA reduction, while decreased intravoxel fiber coherence also plays a role in the white matter alterations. This set of techniques, as a step forward from conventional DTI analysis, will likely be helpful in clinical studies of other white matter diseases as well.
Advisors/Committee Members: Zhaohua Ding (committee member), Mark D. Does (committee member), Daniel F. Gochberg (committee member), John C. Gore (committee member), Adam W. Anderson (Committee Chair).
Subjects/Keywords: optimization; FORECAST; spherical deconvolution; HARDI; Diffusion MRI; white matter; spatial normalization; schizophrenia
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MLA ·
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APA (6th Edition):
Hong, X. (2010). High angular resolution diffusion imaging of brain white matter and its application to schizophrenia. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/11702
Chicago Manual of Style (16th Edition):
Hong, Xin. “High angular resolution diffusion imaging of brain white matter and its application to schizophrenia.” 2010. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/11702.
MLA Handbook (7th Edition):
Hong, Xin. “High angular resolution diffusion imaging of brain white matter and its application to schizophrenia.” 2010. Web. 19 Jan 2021.
Vancouver:
Hong X. High angular resolution diffusion imaging of brain white matter and its application to schizophrenia. [Internet] [Doctoral dissertation]. Vanderbilt University; 2010. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/11702.
Council of Science Editors:
Hong X. High angular resolution diffusion imaging of brain white matter and its application to schizophrenia. [Doctoral Dissertation]. Vanderbilt University; 2010. Available from: http://hdl.handle.net/1803/11702
Vanderbilt University
12.
Kussainov, Arman Sainovitch.
Multiple quantum coherences experiment, simulations and applications.
Degree: PhD, Physics, 2008, Vanderbilt University
URL: http://hdl.handle.net/1803/14618
► MULTIPLE QUANTUM COHERENCES EXPERIMENT, SIMULATIONS AND APPLICATIONS ARMAN SAINOVITCH KUSSAINOV Dissertation under the direction of Professor Daniel F. Gochberg This dissertation discuses the intermolecular Multilpe…
(more)
▼ MULTIPLE QUANTUM COHERENCES EXPERIMENT, SIMULATIONS AND APPLICATIONS
ARMAN SAINOVITCH KUSSAINOV
Dissertation under the direction of Professor
Daniel F.
Gochberg
This dissertation discuses the intermolecular Multilpe Quantum Coherence (iMQC) phenomenon in nuclear magnetic resonance (NMR). This effect originates from the coherent long range dipole-dipole interaction between spins. A short introduction to nuclear magnetic resonance and the CRAZED experiment (the primary method to observe and study iMQC) is given. We perform numerical simulations of the CRAZED experiment, including relaxation processes, instantaneous radio frequency pulses and gradients, as well as phase cycling, phantom positioning, and sample rotation. The signal dependence on the sample
orientation, applied gradient strength and direction, and the underlying sample structure length scale has been determined experimentally and by numerical simulations for two biological tissues: rat sciatic nerve and mice fibrotic liver. The results indicate that the CRAZED signal may provide a unique means for elucidating sample structures at the hundreds of micrometers distance scale.
Advisors/Committee Members: Volker E. Oberacker (committee member), Sait A. Umar (committee member), Adam W. Anderson (committee member), John C. Gore (committee member), Daniel F. Gochberg (Committee Chair).
Subjects/Keywords: multiple quantum; dipolar field; coherences
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APA (6th Edition):
Kussainov, A. S. (2008). Multiple quantum coherences experiment, simulations and applications. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/14618
Chicago Manual of Style (16th Edition):
Kussainov, Arman Sainovitch. “Multiple quantum coherences experiment, simulations and applications.” 2008. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/14618.
MLA Handbook (7th Edition):
Kussainov, Arman Sainovitch. “Multiple quantum coherences experiment, simulations and applications.” 2008. Web. 19 Jan 2021.
Vancouver:
Kussainov AS. Multiple quantum coherences experiment, simulations and applications. [Internet] [Doctoral dissertation]. Vanderbilt University; 2008. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/14618.
Council of Science Editors:
Kussainov AS. Multiple quantum coherences experiment, simulations and applications. [Doctoral Dissertation]. Vanderbilt University; 2008. Available from: http://hdl.handle.net/1803/14618
Vanderbilt University
13.
Whitney, Heather Marie.
Studies of the design, use, and characteristics of methacrylic acid-based polymer gel dosimeters.
Degree: PhD, Physics, 2009, Vanderbilt University
URL: http://hdl.handle.net/1803/10517
► Polymer gel dosimeters are three-dimensional radiation-sensitive materials comprised of monomers and other chemicals distributed in an aqueous gelatin matrix. Upon irradiation by high energy X…
(more)
▼ Polymer gel dosimeters are three-dimensional radiation-sensitive materials comprised of monomers and other chemicals distributed in an aqueous gelatin matrix. Upon irradiation by high energy X or gamma rays, free radicals formed within the water initiate polymerization of the monomers, resulting in distributions of polymer that reflect the distribution of radiation dose. The polymers in turn affect the local nuclear magnetic resonance (NMR) properties of water, so that complex, integrated radiation dose distributions can be measured with high spatial resolution using magnetic resonance imaging. Previous studies have demonstrated the use of polymer gels for applications in dosimetry for clinical radiation therapy. However, there are several aspects of polymer gel dosimetry that remain unresolved. In this thesis some of these problems are addressed. In particular, the design and composition of gels for optimal dose response, the characterization of their dose responses for different NMR properties, the development of improved imaging methods, and the underlying mechanisms of dose response, are each considered. Methacrylic acid-based dosimeters have been optimized for measurements of dose based on transverse relaxation rates. In addition, measurements of other NMR parameters, such as the rates that govern magnetization transfer, are made, are considered and a new magnetization transfer parameter, the magnetization transfer proportion, is introduced as a simplified measure of dose response that is less susceptible to imaging errors than more traditional measures. A simple model is introduced to explain the dose response in terms of an increase in the number of efficiently relaxing protons through a chemical exchange relaxation mechanism, and the parameters of this model are derived from a series of appropriate NMR experiments.
Advisors/Committee Members: Todd E. Peterson (committee member), Richard F. Haglund (committee member), Daniel F. Gochberg (committee member), Malcolm J. Avison (committee member), John C. Gore (Committee Chair).
Subjects/Keywords: magnetic resonance imaging; polymer gel dosimetry
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Whitney, H. M. (2009). Studies of the design, use, and characteristics of methacrylic acid-based polymer gel dosimeters. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://hdl.handle.net/1803/10517
Chicago Manual of Style (16th Edition):
Whitney, Heather Marie. “Studies of the design, use, and characteristics of methacrylic acid-based polymer gel dosimeters.” 2009. Doctoral Dissertation, Vanderbilt University. Accessed January 19, 2021.
http://hdl.handle.net/1803/10517.
MLA Handbook (7th Edition):
Whitney, Heather Marie. “Studies of the design, use, and characteristics of methacrylic acid-based polymer gel dosimeters.” 2009. Web. 19 Jan 2021.
Vancouver:
Whitney HM. Studies of the design, use, and characteristics of methacrylic acid-based polymer gel dosimeters. [Internet] [Doctoral dissertation]. Vanderbilt University; 2009. [cited 2021 Jan 19].
Available from: http://hdl.handle.net/1803/10517.
Council of Science Editors:
Whitney HM. Studies of the design, use, and characteristics of methacrylic acid-based polymer gel dosimeters. [Doctoral Dissertation]. Vanderbilt University; 2009. Available from: http://hdl.handle.net/1803/10517
. 
Open Access Theses and Dissertations