Erin B Macdonald1, Gregory P Barton1, Benjamin L Cox1,2,3, Kevin M Johnson1,4, Roberta M Strigel1,4,5, Sean B Fain1,4,6. 1. Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin. 2. Morgridge Institute for Research, University of Wisconsin-Madison, Madison, Wisconsin. 3. Laboratory for Optical and Computational Instrumentation, University of Wisconsin-Madison, Madison, Wisconsin. 4. Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin. 5. Carbone Cancer Center, University of Wisconsin-Madison, Madison, Wisconsin. 6. Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin.
Abstract
PURPOSE: A multiecho, field of view (FOV)-oversampled k-t spiral acquisition and direct iterative decomposition of water and fat with echo asymmetry and least-squares estimation reconstruction is demonstrated to improve the stability of hyperpolarized 13 C magnetic resonance spectroscopic imaging (MRSI) in the presence of signal ambiguities attributed to low-SNR (signal-to-noise-ratio) species, local uncertainties in metabolite peaks, and echo-to-echo signal inconsistencies. THEORY: k-t spiral acquisitions redistribute readout points to be more densely spaced radially in k-space by acquiring an FOV and matrix that are oversampled by η. These more densely spaced spiral turns constitute effective intraspiral echoes and can supplement conventional interspiral echoes to improve spectral separation and reduce spectral cross-talk to better resolve 13 C-labeled species for spectroscopic imaging. METHODS: Digital simulations and imaging phantom experiments were performed for a range of interspiral echo spacings and η using multiecho, k-t spiral acquisitions. Image spectral cross-talk artifacts were evaluated both qualitatively and quantitatively as the percent error in measured metabolite ratios. In vivo murine experiments evaluated the feasibility of multiecho, k-t spiral [1-13 C]pyruvate MRSI to reduce spectral cross-talk for 3 scenarios of different expected reconstruction stability. RESULTS: Digital simulations and imaging phantom experiments both demonstrated reduced or comparable image spectral cross-talk and percent errors in measured metabolite ratios with increasing η and better choices of echo spacings. In vivo images displayed markedly reduced spectral cross-talk in lactate images acquired with η = 7 versus η = 1. CONCLUSION: The precision of hyperpolarized 13 C metabolic imaging and quantification in the presence of low-SNR species, local uncertainties in metabolite resonances, and echo-to-echo signal inconsistencies can be improved with the use of FOV-oversampled k-t spiral acquisitions.
PURPOSE: A multiecho, field of view (FOV)-oversampled k-t spiral acquisition and direct iterative decomposition of water and fat with echo asymmetry and least-squares estimation reconstruction is demonstrated to improve the stability of hyperpolarized 13 C magnetic resonance spectroscopic imaging (MRSI) in the presence of signal ambiguities attributed to low-SNR (signal-to-noise-ratio) species, local uncertainties in metabolite peaks, and echo-to-echo signal inconsistencies. THEORY: k-t spiral acquisitions redistribute readout points to be more densely spaced radially in k-space by acquiring an FOV and matrix that are oversampled by η. These more densely spaced spiral turns constitute effective intraspiral echoes and can supplement conventional interspiral echoes to improve spectral separation and reduce spectral cross-talk to better resolve 13 C-labeled species for spectroscopic imaging. METHODS: Digital simulations and imaging phantom experiments were performed for a range of interspiral echo spacings and η using multiecho, k-t spiral acquisitions. Image spectral cross-talk artifacts were evaluated both qualitatively and quantitatively as the percent error in measured metabolite ratios. In vivo murine experiments evaluated the feasibility of multiecho, k-t spiral [1-13 C]pyruvate MRSI to reduce spectral cross-talk for 3 scenarios of different expected reconstruction stability. RESULTS: Digital simulations and imaging phantom experiments both demonstrated reduced or comparable image spectral cross-talk and percent errors in measured metabolite ratios with increasing η and better choices of echo spacings. In vivo images displayed markedly reduced spectral cross-talk in lactate images acquired with η = 7 versus η = 1. CONCLUSION: The precision of hyperpolarized 13 C metabolic imaging and quantification in the presence of low-SNR species, local uncertainties in metabolite resonances, and echo-to-echo signal inconsistencies can be improved with the use of FOV-oversampled k-t spiral acquisitions.
Authors: Jan H Ardenkjaer-Larsen; Andrew M Leach; Neil Clarke; John Urbahn; Denise Anderson; Timothy W Skloss Journal: NMR Biomed Date: 2011-03-18 Impact factor: 4.044
Authors: Florian Wiesinger; Eliane Weidl; Marion I Menzel; Martin A Janich; Oleksandr Khegai; Steffen J Glaser; Axel Haase; Markus Schwaiger; Rolf F Schulte Journal: Magn Reson Med Date: 2011-11-29 Impact factor: 4.668
Authors: Jan H Ardenkjaer-Larsen; Björn Fridlund; Andreas Gram; Georg Hansson; Lennart Hansson; Mathilde H Lerche; Rolf Servin; Mikkel Thaning; Klaes Golman Journal: Proc Natl Acad Sci U S A Date: 2003-08-20 Impact factor: 11.205