Magnetic Resonance Imaging of Lungs at Ultra-low Magnetic Field Strength Using Hyperpolarized ↑1↑2↑9Xe Gas [microform] PDF Download

Author: Juan Miguel Parra Robles
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780612978393
Category : Imaging systems in medicine
Languages : en
Pages : 236

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Author: Krzysztof Wawryzn
Publisher:
ISBN:
Category :
Languages : en
Pages : 210

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Background: Early diagnosis of radiation-induced lung injury (RILI) following radiation therapy is critical for prevention of permanent lung damage. Pulmonary imaging using magnetic resonance imaging (MRI) of the apparent diffusion coefficient (ADC) of hyperpolarized xenon (129Xe) gas shows promise for early measurement of RILI. Methods: An ultra-short echo time imaging sequence based on a pseudo-Cartesian kspace trajectory, known as Sectoral, is implemented at low magnetic field (0.07 T) for efficient use of the non-renewable magnetization of hyperpolarized 129Xe gas. A pilot study was performed to demonstrate the feasibility of ADC mapping using the Sectoral sequence on healthy and 2-weeks post irradiated rats. Results: A significant (p

Author: Hans-Ulrich Kauczor
Publisher: Springer Science & Business Media
ISBN: 354034618X
Category : Medical
Languages : en
Pages : 315

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During the past decade significant developments have been achieved in the field of magnetic resonance imaging (MRI), enabling MRI to enter the clinical arena of chest imaging. Standard protocols can now be implemented on up-to-date scanners, allowing MRI to be used as a first-line imaging modality for various lung diseases, including cystic fibrosis, pulmonary hypertension and even lung cancer. The diagnostic benefits stem from the ability of MRI to visualize changes in lung structure while simultaneously imaging different aspects of lung function, such as perfusion, respiratory motion, ventilation and gas exchange. On this basis, novel quantitative surrogates for lung function can be obtained. This book provides a comprehensive overview of how to use MRI for imaging of lung disease. Special emphasis is placed on benign diseases requiring regular monitoring, given that it is patients with these diseases who derive the greatest benefit from the avoidance of ionizing radiation.

Author: Ozkan Doganay
Publisher:
ISBN:
Category :
Languages : en
Pages : 302

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Lung cancer is the largest contributor to cancer-related mortality worldwide. Only 20% of stage III non-small cell lung cancer patients survive after 5-years post radiation therapy (RT). Although RT is an important treatment modality for lung cancer, it is limited by Radiation-Induced Lung Injury (RILI). RILI develops in two phases: (i) the early phase (days-weeks) referred to radiation pneumonitis (RP), and (ii) the late phase (months). There is a strong interest in early detection of RP using imaging to improve outcomes of RT for lung cancer. This thesis describes a promising approach based on 129Xe gas as a contrast agent for Magnetic Resonance Imaging (MRI) of the lung airspace due to the large increase in signal possible by spin exchange optical pumping, or hyperpolarization (Hp). Additionally, 129Xe provides unique functional information due to its relatively high solubility and significant chemical shift in pulmonary tissue (PT) and red blood cell (RBC) compartments. In this thesis, a specialized Hp 129Xe MRI method was developed for detection of gas exchange abnormalities in the lungs associated with thoracic RT. In particular, the feasibility of quantifying the early phase of RILI is demonstrated in a rat model of RILI two weeks post-irradiation with a single fraction dose of 18 Gy. The challenge of low signal-to-noise ratio (SNR) in the dissolved phases was addressed in this work by development and construction of a Transmit-Only/Receive-Only radiofrequency coil. Another challenge addressed in the thesis was the lack of imaging techniques that provide sufficient spatial and temporal information for gas exchange. Therefore, a novel Hp 129Xe MRI technique was developed based on the multi-point IDEAL pulse sequence. The combination of these two developments enabled investigation of regional gas exchange changes associated with RP in the rat lung two weeks post-irradiation to assess the feasibility of early detection of RILI. Theoretical analysis of the gas exchange curves enabled measurements of average PT thickness (LPT) increases consistent with histology and relative blood volume (VRBC) reductions in the irradiated animal cohort compared to a non-irradiated cohort, and between irradiated right lungs compared to unirradiated left lungs in the irradiated cohort.

Author: William Dominguez-Viqueira
Publisher:
ISBN:
Category :
Languages : en
Pages : 368

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Author: Xiaojun Xu
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Nara Savoye Higano
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 222

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Magnetic resonance imaging (MRI) is a modality that utilizes the phenomenon of nuclear magnetic resonance (NMR) to yield tomographic images of the body. Proton (1H) MRI has historically been successful in soft tissues but has suffered in the lung due to a variety of technical challenges, such as the low proton-density, rapid T2* relaxation time of the lung parenchymal tissue, and inherent physiological motion in the chest. Recent developments in radial ultrashort echo time (UTE) MRI have in part overcome these issues. In addition, there has been much progress in techniques for hyperpolarization of noble gases (3He and 129Xe) out of thermal equilibrium via spin exchange optical pumping, which can greatly enhance the gas NMR signal such that it is detectable within the airspaces of the lung on MRI.The lung is a unique organ due to its complex structural and functional dynamics, and its early development through the neonatal (newborn) period is not yet well understood in normal or abnormal conditions. Pulmonary morbidities are relatively common in infants and are present in a majority of patients admitted to the neonatal intensive care unit, often stemming from preterm birth and/or congenital defects. Current clinical lung imaging in these patients is typically limited to chest x-ray radiography, which does not provide tomographic information and so has lowered sensitivity. More rarely, x-ray computed tomography (CT) is used but exposes infants to ionizing radiation and typically requires sedation, both of which pose increased risks to pediatric patients. Thus the opportunity is ripe for application of novel pulmonary MRI techniques to the infant population. However, MR imaging of very small pulmonary structure and microstructure requires fundamental changes in the imaging theory of both 1H UTE MRI and hyperpolarized gas diffusion MRI. Furthermore, such young patients are often non-compliant, yielding a need for new and innovative techniques for monitoring respiratory and bulk motion.This dissertation describes methodology development and provides experimental results in both 1H UTE MRI and hyperpolarized 3He and 129Xe gas diffusion MRI, with investigation into the structure and function of infant lungs at both the macrostructural and microstructural level. In particular, anisotropically restricted gas diffusion within infant alveolar microstructure is investigated as a measurement of airspace size and geometry. Additionally, the phenomenon of respiratory and bulk motion-tracking via modulation of the k-space center's magnitude and phase is explored and applied via UTE MRI in various neonatal pulmonary conditions to extract imaging-based metrics of diagnostic value. Further, the proton-density regime of pulmonary UTE MRI is validated in translational applications. These techniques are applied in infants with various pulmonary conditions, including patients diagnosed with bronchopulmonary dysplasia, congenital diaphragmatic hernia, esophageal atresia/tracheoesophageal fistula, tracheomalacia, and no suspected lung disease. In addition, explanted lung specimens from both infants with and without lung disease are examined.Development and implementation of these techniques involves a strong understanding of the physics-based theory of NMR, hyperpolarization, and MR imaging, in addition to foundations in hardware, software, and image analysis techniques. This thesis first outlines the theory and background of NMR, MRI, and pulmonary physiology and development (Part I), then proceeds into the theory, equipment, and imaging experiments for hyperpolarized gas diffusion MRI in infant lung airspaces (Part II), and finally details the theory, data processing methods, and applications of pulmonary UTE MRI in infant patients (Part III). The potential for clinical translation of the neonatal pulmonary MRI methods presented in this dissertation is very high, with the foundations of these techniques firmly rooted in the laws of physics.

Author: Agilo Luitger Kern
Publisher:
ISBN:
Category :
Languages : de
Pages :

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Author: Adelaide Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 136

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Author: Brandon Zanette
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Hyperpolarized (HP) 129Xe Magnetic Resonance Imaging (MRI) of the lungs allows for the visualization of the spatial distribution of gas in the pulmonary airspaces upon inhalation by taking advantage of the 100,000 fold increase in signal. This technique yields high quality anatomical and functional images of the lungs that is otherwise difficult with conventional MRI. Direct imaging of lung ventilation is useful for the detection and quantification of obstructive lung diseases such as cystic fibrosis, chronic obstructive pulmonary disorder, and asthma. An added advantage of 129Xe is its solubility in bodily tissues such as the lung parenchyma and red blood cells, allowing for the detection of signals from beyond the airspaces. This property of 129Xe may be exploited to probe gas exchange upon inhalation, making HP 129Xe MRI a powerful tool for the investigation of terminal airway dysfunction in a variety of pulmonary diseases. However, the inherent challenges associated with dissolved 129Xe MRI has caused development of these techniques to lag ventilation (gas-phase) HP 129Xe MRI. The work in this thesis is focused on the technical development of dissolved 129Xe imaging techniques for use in both human and rodent experiments. A particular focus is given to radiation-induced lung injury (RILI), a serious and debilitating consequence of radiotherapy that affects a subset of patients. A new rat model of RILI that better represents regional injury is developed and tested. Temporally-resolved dissolved 129Xe imaging techniques for gas exchange mapping are developed and applied to the study of RILI in this model. Changes in lung physiology associated with radiation injury are quantified by parametrically mapping gas exchange. Finally, the techniques developed preclinically are modified and improved for clinical use. Parametric gas exchange mapping is demonstrated in humans. Accelerated dissolved 129Xe MRI with parallel imaging is also demonstrated. The results of this work will aid in the translations of dissolved 129Xe MRI into a clinically useful technique for a variety of lung diseases affecting gas exchange in the lungs, such as RILI.