Application of a stretched-exponential model for morphometric analysis of accelerated diffusion-weighted 129Xe MRI of the rat lung.

Objective: Diffusion-weighted, hyperpolarized Xe MRI is useful for the characterization of microstructural changes in the lung. A stretched exponential model was proposed for morphometric extraction of the mean chord length (L) from diffusion-weighted data. The stretched exponential model enables accelerated mapping of L in a single-breathhold using compressed sensing.

High spatial resolution hyperpolarized He MRI of the rodent lung using a single breath X-centric gradient-recalled echo approach.

Purpose: Hyperpolarized (HP) gas MRI of the rodent lung is of great interest because of the increasing need for novel biomarkers with which to develop new therapies for respiratory diseases. The use of fast gradient-recalled echo (FGRE) for high-resolution HP gas rodent lung MRI is challenging as a result of signal loss caused by significant diffusion weighting, particularly in the larger airways. In this work, a modified FGRE approach is described for HP He rodent lung MRI using a centric-out readout scheme (ie, x-centric), allowing high-resolution, density-weighted imaging.

Fractional ventilation mapping using inert fluorinated gas MRI in rat models of inflammation and fibrosis.

The purpose of this study was to extend established methods for fractional ventilation mapping using (19) F MRI of inert fluorinated gases to rat models of pulmonary inflammation and fibrosis. In this study, five rats were instilled with lipopolysaccharide (LPS) in the lungs two days prior to imaging, six rats were instilled with bleomycin in the lungs two weeks prior to imaging and an additional four rats were used as controls. (19) F MR lung imaging was performed at 3 T with rats continuously breathing a mixture of sulfur hexafluoride and O2 .

Hyperpolarized and inert gas MRI: the future.

Magnetic resonance imaging (MRI) is a potentially ideal imaging modality for noninvasive, nonionizing, and longitudinal assessment of disease. Hyperpolarized (HP) agents have been developed in the past 20 years for MR imaging, and they have the potential to vastly improve MRI sensitivity for the diagnosis and management of various diseases. The polarization of nuclear magnetic resonance (NMR)-sensitive nuclei other than (1)H (e.

In vivo regional ventilation mapping using fluorinated gas MRI with an x-centric FGRE method.

Purpose: Inert fluorinated gas lung MRI is a new and promising alternative to hyperpolarized gas lung MRI; it is less expensive and does not require expensive isotopes/polarizers. The thermally polarized nature of signal obtained from fluorinated gases makes it relatively easy to use for dynamic lung imaging and for obtaining lung ventilation maps. In this study, we propose that the sensitivity and resolution of fluorine-19 (19F) in vivo images can be improved using the x-centric pulse sequence, thereby achieving a short echo time/pulse repetition time.

Inert fluorinated gas MRI: a new pulmonary imaging modality.

Fluorine-19 ((19)F) MRI of the lungs using inhaled inert fluorinated gases can potentially provide high quality images of the lungs that are similar in quality to those from hyperpolarized (HP) noble gas MRI. Inert fluorinated gases have the advantages of being nontoxic, abundant, and inexpensive compared with HP gases. Due to the high gyromagnetic ratio of (19)F, there is sufficient thermally polarized signal for imaging, and averaging within a single breath-hold is possible due to short longitudinal relaxation times.

Comparison of hyperpolarized (3)He MRI rat lung volume measurement with micro-computed tomography.

In this study, the upper-limit volume (gas plus partial tissue volume) as well as absolute volume (gas only) of lungs measured with hyperpolarized (3)He-MR imaging is compared with that determined by micro-computed tomography (CT) under similar ventilation conditions in normal rats. Five Brown Norway rats (210-259 g) were ventilated with O(2), alternately with (3)He, using a computer-controlled ventilator, and 3D density-weighted images of the lungs were acquired during a breath hold after six wash-in breaths of (3)He. The rats were then transferred to a micro-CT scanner, and a similar experimental setup was used to obtain images of the lungs during a breath hold of air with an airway pressure equal to that of the MR imaging breath hold.

Rapid 3-D mapping of hyperpolarized 3He spin-lattice relaxation times using variable flip angle gradient echo imaging with application to alveolar oxygen partial pressure measurement in rat lungs.

Objective: The purpose of this work was to develop a rapid 3-D, variable flip angle (VFA) method for measurement of hyperpolarized (3)He T(1) which accounts for the effects of radiofrequency (RF) pulses without the need for additional flip angle information.

Materials And Methods: The 3-D, VFA method was validated in vitro over a range of oxygen partial pressures ranging from 0.04 to 0.

Membrane gas diffusion measurements with MRI.

Gas transport across polymeric membranes is fundamental to many filtering and separation technologies. To elucidate transport mechanisms, and understand the behaviors of membrane materials, accurate measurement of transport properties is required. We report a new magnetic resonance imaging (MRI) methodology to measure membrane gas phase diffusion coefficients.

Thin film MRI-high resolution depth imaging with a local surface coil and spin echo SPI.

A multiple echo, single point imaging technique, employing a local surface coil probe, is presented for examination of thin film samples. Depth images with a nominal resolution of 5 microm were acquired with acquisition times on the order of 10 min. The method may be used to observe dynamic phenomenon such as polymerization, wetting, and drying in thin film samples.