ELECTRONIC POSTER - ismrm

exponential decay of only CSF signal using a non-selective T2 preparation scheme. CSF volume fractions in ventricles were found to
be about 1.0, while cortical volumes ranged from 0.05-0.5. The T2 of CSF was found to be 1654ms±389ms.
14:00 3421. Simultaneous BOLD and ASL for Characterizing Cerebrovascular Responses to
Hyperoxia in Normal Brain and in Glioblastoma
Heisoog Kim 1,2 , Ciprian Catana 1 , Grace Kim 1 , Ovidiu C. Andronesi 1 , Dominique L.
Jennings 1 , Divya S. Bolar 1,3 , Elizabeth R. Gerstner 4 , Tracy T. Batchelor 4 , Rakesh K.
Jain 5 , A Gregory Sorensen 1
1 A.A.Martinos center, Massachusetts General Hospotal, Charlestown, MA, United States; 2 NSE/HST,
Massachusetts Institute of Technology, Cambridge, MA, United States; 3 EECS/HST, Massachusetts Institute of
Technology, Cambridge, MA, United States; 4 Neurology, Massachusetts General Hospotal, Boston, MA,
United States; 5 Radiology, Massachusetts General Hospotal, Boston, MA, United States
In this study, simultaneous BOLD-ASL method was used to assess quantitatively the characteristic cerebral responses to 100% oxygen
exposure in normal brain and in glioblastoma (GB). BOLD and Flow effects in normal brain were detected primarily in the cortex
(increased BOLD and decreased CBF responses), which agreed with previously published data. Heterogeneous BOLD signal was
observed in GB. The enhancing tumor showed a larger increase in BOLD and a smaller decrease responses in CBF than contralateral
normal tissue did, which implies the characteristic properties of the tumor vasculature (i.e. tortuous, large vessels, inefficient blood
circulation).
14:30 3422. Detecting Focal Changes in CBF Independently from Tissue Content Using Arterial
Spin Labeling (ASL) FMRI
Ajna Borogovac 1 , Christian Habeck 2 , Joy Hirsch 3 , Iris Asllani 4
1 Biomedical Engineering, Columbia University, New York, NY, United States; 2 Neurology, Columbia
University; 3 Neuroscience & Psychiatry, Columbia University; 4 Radiology, Columbia University
Quantification of inter-subject differences in cerebral blood flow (CBF) separately from respective differences in tissue content
presents a known challenge in analysis of group data. Recently, our group has developed an algorithm which corrects for partial
volume effects (PVE) in arterial spin labeling (ASL) imaging and also yields tissue specific flow ‘density’ maps (CBFd) which are,
theoretically, independent of tissue content. The goals of the present work are to (1) optimize the PVEc algorithm for applications
where focal differences in CBFd occur (e.g. in functional imaging) and (2) demonstrate how segmentation can affect accuracy of CBF
and CBFd estimation.
15:00 3423. Left/right Asymmetry Measures in Somatosensory Cortex Using MEG, ASL and
BOLD FMRI.
Claire M. Stevenson 1 , Karen J. Mullinger 1 , Joanne R. Hale 1 , Peter G. Morris 1 , Susan T.
Francis 1
1 SPMMRC School of Physics and Astronomy, The University of Nottingham, Nottingham, Nottinghamshire,
United Kingdom
Functional asymmetry in the human brain, as measured by fMRI, has been well documented in motor regions but to a lesser extent in
the somatosensory cortex. Here we combine ultra-high field BOLD fMRI, CBF and modulations in electrical oscillatory activity as
measured by MEG to gain insight into mechanisms of cerebral lateralisation in the somatosensory cortex. fMRI results show an
increased response contra-laterally and suggest an increase in lateralisation with dominant hand stimulation. Beta power activity
appears to follow this trend reinforcing the importance of considering both phase locked and non-phase-locked neural activity when
describing the BOLD response.
Fluctuations & Noise
Hall B Monday 14:00-16:00 Computer 20
14:00 3424. Identification of Resting State Networks Using Whole-Brain CASL
Jingyi Xie 1 , Peter Jezzard 1 , Linqing Li 1 , Yazhuo Kong 1 , Christian F. Beckmann 1,2 , Karla
L. Miller 1 , Stephen M. Smith 1
1 Oxford Centre for Functional MRI of the Brain, Oxford, United Kingdom; 2 Department of Clinical
Neuroscience, Imperial College, London, United Kingdom
There is increasing interest in resting brain activity. However, to our knowledge, ASL has not yet been used to study RSNs across the
whole brain with single timeseries acquisitions. In this study, we implemented a novel true whole-brain CASL technique with EPI
readout to study dynamic characteristics of cerebral blood flow during the resting state. We extracted the major covarying networks in
the resting brain, as imaged in 8 subjects at rest. The major brain networks are highly similar to recent published results obtained using
BOLD fMRI. We also characterised very low-frequency RSN temporal behaviour for the first time.