0000000000170545
AUTHOR
J. Rivoire
Flip-angle measurement by magnetization inversion: Calibration of magnetization nutation angle in hyperpolarized 3 He magnetic resonance imaging lung experiments
The aim of this work was to establish a new, fast, and robust method of flip-angle calibration for magnetic resonance imaging of hyperpolarized 3He. The method called flip-angle measurement with magnetization inversion is based on acquiring images from periodically inverted longitudinal magnetization created using the spatial modulation of magnetization technique. By measuring the width of the area where the magnetization was inverted by the spatial modulation of magnetization preparation in phase images, the flip angle can be generated using a simple equation. To validate and establish the limits of the proposed method, flip-angle measurement with magnetization inversion acquisitions were …
Pushing the Limit – MRI of the Lung Using Hyperpolarized 3-Helium in Conjunction with Parallel Imaging
Imaging of the lung with hyperpolarized 3He became a well known technique in the last decade. Being able to image ventilation and the microstructure of the lung an increase of SNR and a shortage of scan time is eligible. By using a 32-channel phased array the sensitivity was increased dramatically. High resolution 2D-images with a resolution of 1 × 1 mm2 having a 3 mm slice was realized, showing highly detailed images of the lung. By applying parallel imaging techniques the SNR could be increased and scan time was reduced drastically by using a 2D acceleration of R = 4 × 2 with a 3D-protocol covering the whole lung.
Realization of administration unit for3He with gas recycling
Hyperpolarized (HP) noble gases (3He,129Xe) are used for MR-imaging of the lung. In the majority of case the HP gas is filled in Tedlarbags and directly inhaled by the patients. Starting from an earlier pilot device, an administration unit was built respectively to the Medical Devices Law to administer patients HP noble gas boli in defined quantities and at a predefined time during inspiration with high reproducibility and reliability without reducing MR-quality. The patient's airflows are monitored and recorded. It is possible to use gas admixtures, measure the polarization on-line and collect the exhaled gas for later recycling. The first images with healthy volunteers were taken with thi…
Magnetic Resonance Imaging and Computational Fluid Dynamics of High Frequency Oscillatory Ventilation (HFOV)
In order to better understand the mechanisms of gas transport during High Frequency Oscillatory Ventilation (HFOV) Magnetic Resonance Imaging (MRI) with contrast gases and numerical flow simulations based on Computational Fluid Dynamics(CFD) methods are performed.
Measurement of gas transport kinetics in high-frequency oscillatory ventilation (HFOV) of the lung using hyperpolarized 3He magnetic resonance imaging
PURPOSE: To protect the patient with acute respiratory distress syndrome from ventilator associated lung injury (VALI) high-frequency oscillatory ventilation (HFOV) is used. Clinical experience has proven that HFOV is an efficient therapy when conventional artificial ventilation is insufficient. However, the optimal settings of HFOV parameters, eg, tidal volumes, pressure amplitudes and frequency for maximal lung protection, and efficient gas exchange are not established unambiguously. METHODS: In this work magnetic resonance imaging (MRI) with hyperpolarized (3)He was employed to visualize the redistribution of gas within the cadaver pig lung during HFOV. The saturated slice method was use…
Design and evaluation of a 32-channel phased-array coil for lung imaging with hyperpolarized 3-helium
Imaging with hyperpolarized 3-helium is becoming an increasingly important technique for MRI diagnostics of the lung but is hampered by long breath holds (>20 sec), which are not always applicable in patients with severe lung disease like chronic obstructive pulmonary disease (COPD) or α-1-anti-trypsin deficiency. Additionally, oxygen-induced depolarization decay during the long breath holds complicates interpretation of functional data such as apparent diffusion coefficients. To address these issues, we describe and validate a 1.5-T, 32-channel array coil for accelerated 3He lung imaging and demonstrate its ability to speed up imaging 3He. A signal-to-noise ratio increase of up to a factor…
Application unit for the administration of contrast gases for pulmonary magnetic resonance imaging: optimization of ventilation distribution for3He-MRI
Purpose MRI of lung airspaces using gases with MR-active nuclei (3He, 129Xe, and 19F) is an important area of research in pulmonary imaging. The volume-controlled administration of gas mixtures is important for obtaining quantitative information from MR images. State-of-the-art gas administration using plastic bags (PBs) does not allow for a precise determination of both the volume and timing of a 3He bolus. Methods A novel application unit (AU) was built according to the requirements of the German medical devices law. Integrated spirometers enable the monitoring of the inhaled gas flow. The device is particularly suited for hyperpolarized (HP) gases (e.g., storage and administration with m…
Three-dimensional mapping of the B 1 field using an optimized phase-based method: Application to hyperpolarized 3 He in lungs
A novel method is presented for the three-dimensional mapping of the B1-field of a transmit radio-frequency MR coil. The method is based on the acquisition of phase images, where the effective flip angle is encoded in the phase of the nonselective hard pulse excitation. The method involves the application of a rectangular composite pulse as excitation in a three-dimensional gradient recall echo to produce measurable phase angle variation. However, such a pulse may significantly increase the radio-frequency power deposition in excess of the standard acceptable SAR limits, imposing extremely long TRs (>100 msec), which would result in acquisition times significantly greater than a single brea…
Lung ventilation- and perfusion-weighted Fourier decomposition magnetic resonance imaging: In vivo validation with hyperpolarized3He and dynamic contrast-enhanced MRI
The purpose of this work was to validate ventilation-weighted (VW) and perfusion-weighted (QW) Fourier decomposition (FD) magnetic resonance imaging (MRI) with hyperpolarized (3)He MRI and dynamic contrast-enhanced perfusion (DCE) MRI in a controlled animal experiment. Three healthy pigs were studied on 1.5-T MR scanner. For FD MRI, the VW and QW images were obtained by postprocessing of time-resolved lung image sets. DCE acquisitions were performed immediately after contrast agent injection. (3)He MRI data were acquired following the administration of hyperpolarized helium and nitrogen mixture. After baseline MR scans, pulmonary embolism was artificially produced. FD MRI and DCE MRI perfus…