title: Achieving high spatial resolution and high SNR in low-field MRI of hyperpolarised gases with Slow Low Angle SHot.
abstract: MRI of hyperpolarised gases is usually performed with fast data acquisition to achieve high spatial resolutions despite rapid diffusion-induced signal attenuation. We describe a double-cross k-space sampling scheme suitable for Slow Low Angle SHot (SLASH) acquisition and yielding an increased SNR. It consists of a series of anisotropic partial acquisitions with a reduced resolution in the read direction, which alleviates signal attenuation and still provides a high isotropic resolution. The advantages of SLASH imaging over conventional FLASH imaging are evaluated analytically, using numerical lattice calculations, and experimentally in phantom cells filled with hyperpolarised (3)He-N(2) gas mixtures. Low-field MRI is performed (here 2.7 mT), a necessary condition to obtain long T(2)(∗) values in lungs for slow acquisition. Two additional benefits of the SLASH scheme over FLASH imaging have been demonstrated: it is less sensitive to the artefacts due to concomitant gradients and it allows measuring apparent diffusion coefficients for an extended range of times.
authors: Laboratoire Kastler Brossel, ENS, UPMC, CNRS, Paris, France.
authors: Kajum
authors: K
authors: Safiullin
authors: Cavin
authors: C
authors: Talbot
authors: Pierre-Jean
authors: PJ
authors: Nacher
mesh_terms: D000465:Algorithms; D005740:Gases / Q000032:analysis* / Q000737:chemistry*; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D055672:Static Electricity
chemical_list: D005740:Gases