MR microscopy of the rat lung using projection reconstruction

Abstract

Projection reconstruction has been implemented with self-refocused selection pulses on a small bore, 2.0 T MR microscope, to allow imaging of lung parenchyma. Scan synchronous ventilation and cardiac gating have been integrated with the sequence to minimize motion artifacts. A systematic survey of the pulse sequence parameters has been undertaken in conjunction with the biological gating parameters to optimize resolution and signal-to-noise (SNR). The resulting projection images with effective echo time of < 300 microseconds allow definition of lung parenchyma with an SNR improvement of approximately 15 x over a more conventional 2DFT short echo gradient sequence.

Imaging alveolar–capillary gas transfer using hyperpolarized 129 Xe MRI

“…In radial imaging, such off-resonant artifacts manifest themselves as a halo around the primary image (20), and no such halo is observed. Second, we note the absence of the major extrapulmonary airways from the dissolved-phase images.…”

“…129 Xe Imaging. The dissolved 129 Xe was imaged by using radial encoding (20,21) to overcome its short T* 2 . To differentiate 129 Xe in the barrier and RBC compartments, we use a variant of the Dixon technique originally developed to separate fat and water MR images (22).…”

Mechanical Ventilation for Imaging the Small Animal Lung

“…This image was acquired during end-expiration lung volume using cardiac gating and a very short echo delay time (345 sec) projection sequence (Gewalt et al 1993) that captures the very weak, short-lived signal from the lungs. The very rapid decay of the MR signal that occurs in the lungs, and not in other organs, is due to the lung's high susceptibility resulting from the extensive network of gastissue interfaces.…”

High-resolution diffusion imaging with DIFRAD-FSE (Diffusion-Weighted Radial Acquisition of Data With Fast Spin-Echo) MRI

“…Two attributes largely explain the insensitivity of RAD methods to motion in DW-MRI. First, the large phase errors associated with motion during the diffusion weighting can be removed in the image reconstruction process by employing a magnitude-only FBPR algorithm (22,25,26). This also removes the effects of Fourier data shifts when they are in the direction of the read-out gradient.…”

“…Because there are many ways to reconstruct images from radially acquired data, we will refer to these methods herein as Radial Acquisition of Data (RAD) methods. While Cartesian MRI is the standard today, there has been renewed interest in RAD methods due to their insensitivity to motion and flow (22)(23)(24)(25)(26) and novel properties for rapid data acquisition (27)(28)(29).…”