Controlling diffusion of 3He by buffer gases: a structural contrast agent in lung MRI.

Purpose: To study the influence of admixing inert buffer gases to laser-polarized (3)He in terms of resulting diffusion coefficients and the consequences for image contrast and resolution.

Materials And Methods: The diffusion coefficient of (3)He was altered by admixing buffer gases of various molecular weights ((4)He, N(2), and SF(6)). The influence of the pulse sequence and the diffusion coefficient on the appearance of MRI of (laser-polarized) gases was analyzed by comparison of basic theoretical concepts with demonstrative experiments.

[Microstructure of the lung: diffusion measurement of hyperpolarized 3Helium].

Imaging methods to study the lung are traditionally based on x-ray or on radioactive contrast agents. Conventional magnetic resonance imaging (MRI) has only limited applications for lung imaging because of the low tissue density of protons concentration of hydrogen atoms, which are usually the basis for the imaging. The introduction of hyperpolarized noble gases as a contrast agent in MRI has opened new possibilities for lung diagnosis.

[Hyperpolarized (3)helium gas for functional magnetic resonance imaging of the lung].

Lung imaging is traditionally done using X-ray-based methods, since MRI is limited by low proton density as well as inherent magnetic field inhomogeneities of the lung tissue. After introduction of MRI using hyperpolarized noble gases, a totally new field of MRI of the chest has rapidly evolved. These techniques reveal new functional information of the lungs, which could not be obtained before.

Assessment of lung microstructure with magnetic resonance imaging of hyperpolarized Helium-3.

Magnetic resonance imaging of the apparent diffusion coefficient (ADC) of hyperpolarized Helium-3 is a new technique for probing pulmonary microstructure in vivo. The aim of this study was the assessment of potential sources of systematic errors of the ADC measurement. The influence of macroscopic motion was determined by measurements at two different delays after initiating the breath-hold, and before and after cardiac arrest.

Diffusion-weighted MRI of the lung with hyperpolarized helium-3: a study of reproducibility.

Purpose: To determine the reproducibility of several parameters of the ADC measurement by calculating the scan-to-scan intrasubject variability.

Materials And Methods: Measurements were performed using a gradient-echo sequence with a bipolar gradient for diffusion weighting (b=3.89 sec/cm2).

Functional evaluation of emphysema using diffusion-weighted 3Helium-magnetic resonance imaging, high-resolution computed tomography, and lung function tests.

Purpose: To assess the emphysematous enlargement of distal airspaces and concomitant large and small airway disease using diffusion-weighted Helium-magnetic resonance imaging (MRI), high-resolution computed tomography (HRCT), and lung function tests (LFT).

Methods: Seven patients were examined after single lung transplantation (LTx) and 1 before double LTx for various forms of emphysema. Five patients after double LTx served as controls.