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Inflow‐based vascular‐space‐occupancy (iVASO) MRI
Author(s) -
Hua Jun,
Qin Qin,
Donahue Manus J.,
Zhou Jinyuan,
Pekar James J.,
van Zijl Peter C.M.
Publication year - 2011
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.22775
Subject(s) - cerebral blood volume , blood volume , perfusion , cerebral blood flow , hemodynamics , blood flow , inflow , magnetic resonance imaging , nuclear magnetic resonance , nuclear medicine , chemistry , medicine , biomedical engineering , cardiology , physics , radiology , mechanics
Vascular‐space‐occupancy (VASO) MRI, a blood nulling approach for assessing changes in cerebral blood volume (CBV), is hampered by low signal‐to‐noise ratio (SNR) because only 10–20% of tissue signal is recovered when using nonselective inversion for blood nulling. A new approach, called inflow‐VASO ( iVASO ), is introduced in which only blood flowing into the slice has experienced inversion, thereby keeping tissue and cerebrospinal fluid (CSF) signal in the slice maximal and reducing CSF partial volume effects. SNR increases of 198% ± 12% and 334% ± 9% (mean ± SD, n = 7) with respect to VASO were found at TR values of 5s and 2s, respectively. When using inflow approaches, data interpretation is complicated by the fact that signal changes are affected by vascular transit times. An optimal TR ‐range (1.5–2.5s) was derived in which the iVASO response during activation predominantly reflects arterial/arteriolar CBV (CBV a ) changes. In this TR ‐range, perfusion contributions to the signal change are negligible because arterial label has not yet undergone capillary exchange, and arterial and precapillary blood signals are nulled. For TR = 2s, the iVASO signal change upon visual stimulation corresponded to a CBV a increase of 58% ± 7%, in agreement with arteriolar CBV changes previously reported. The onset of the hemodynamic response for iVASO occurred 1.2 ± 0.5s ( n = 7) faster than for conventional VASO. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.