Bojana Stefanovic1, John G Sled, G Bruce Pike. 1. McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Canada. bojana@bic.mni.mcgill.ca
Abstract
PURPOSE: To investigate the dependence of occipital gray and white matter T(2) on the Carr-Purcell-Meiboom-Gill (CPMG) refocusing interval, thereby testing the basis of a novel functional magnetic resonance imaging (fMRI) method for blood volume quantification, and addressing recent questions surrounding T(2) contrast in the occipital lobe. MATERIALS AND METHODS: A CPMG sequence with 1 x 1 x 5 mm(3) resolution was used to quantify T(2) in a single axial slice at the midlevel of the occipital lobe in 23 healthy adult volunteers. Refocusing intervals of 8, 11, and 22 msec were compared. A Bayesian classifier was used to classify a 1 x 1 x 1 mm(3) T(1)-weighted three-dimensional data set into gray matter, white matter, and cerebrospinal fluid, with an average 95% a posteriori probability used as the threshold for inclusion into a tissue-specific region of interest (ROI). RESULTS: The usual T(2) contrast between the gray and white matter (i.e., T(2GM) > T(2WM)) was observed, with a highly significant effect of tissue type on the estimated T(2) (P < 10(-5)). The observed T(2) gradually decreased with increasing refocusing interval, for a decrease of 3.3 +/- 1.5 msec in gray matter and 3.0 +/- 1.5 msec in white matter between the 8 and 22 msec refocusing interval acquisitions. CONCLUSION: The observed T(2) shortening is consistent with the effect of the dramatic decrease in T(2) of partly deoxygenated blood on this range of refocusing rates. Copyright 2003 Wiley-Liss, Inc.
PURPOSE: To investigate the dependence of occipital gray and white matter T(2) on the Carr-Purcell-Meiboom-Gill (CPMG) refocusing interval, thereby testing the basis of a novel functional magnetic resonance imaging (fMRI) method for blood volume quantification, and addressing recent questions surrounding T(2) contrast in the occipital lobe. MATERIALS AND METHODS: A CPMG sequence with 1 x 1 x 5 mm(3) resolution was used to quantify T(2) in a single axial slice at the midlevel of the occipital lobe in 23 healthy adult volunteers. Refocusing intervals of 8, 11, and 22 msec were compared. A Bayesian classifier was used to classify a 1 x 1 x 1 mm(3) T(1)-weighted three-dimensional data set into gray matter, white matter, and cerebrospinal fluid, with an average 95% a posteriori probability used as the threshold for inclusion into a tissue-specific region of interest (ROI). RESULTS: The usual T(2) contrast between the gray and white matter (i.e., T(2GM) > T(2WM)) was observed, with a highly significant effect of tissue type on the estimated T(2) (P < 10(-5)). The observed T(2) gradually decreased with increasing refocusing interval, for a decrease of 3.3 +/- 1.5 msec in gray matter and 3.0 +/- 1.5 msec in white matter between the 8 and 22 msec refocusing interval acquisitions. CONCLUSION: The observed T(2) shortening is consistent with the effect of the dramatic decrease in T(2) of partly deoxygenated blood on this range of refocusing rates. Copyright 2003 Wiley-Liss, Inc.
Authors: Pascal Sati; Afonso C Silva; Peter van Gelderen; Maria I Gaitan; Jillian E Wohler; Steven Jacobson; Jeff H Duyn; Daniel S Reich Journal: Neuroimage Date: 2011-08-27 Impact factor: 6.556
Authors: Ernesto Staroswiecki; Kristin L Granlund; Marcus T Alley; Garry E Gold; Brian A Hargreaves Journal: Magn Reson Med Date: 2011-12-16 Impact factor: 4.668