RESEARCH ARTICLE


Cerebral Blood Volume Measurements – Gd_DTPA vs. VASO - and Their Relationship with Cerebral Blood Flow in Activated Human Visual Cortex



Ai-Ling Lin*, 1, 3, Hanzhang Lu2, Peter T Fox1, 3, 4, 5, 7, Timothy Q Duon1, 4, 5, 6, 7
1 Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX 78229, USA
2 Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
3 Departments of Psychiatry, University of Texas Health Science Center, San Antonio, TX 78229, USA
4 Departments of Radiology, University of Texas Health Science Center, San Antonio, TX 78229, USA
5 Departments of Physiology, University of Texas Health Science Center, San Antonio, TX 78229, USA
6 Departments of Ophthalmology, University of Texas Health Science Center, San Antonio, TX 78229, USA
7 South Texas Veterans Health Care System, Department of Veterans Affairs, San Antonio, Texas 78229


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© Lin et al; Licensee Bentham Open

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Research Imaging Institute, Department of Psychiatry, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr., Sam Antonio, TX 78229, USA; Tel: +1-210-567-8216; Fax: +1-210-567-8152; E-mail: lina3@uthscsa.edu


Abstract

Measurements of task-induced changes in cerebral blood volume (CBV) have been demonstrated using VAscular Space Occupancy (VASO) techniques (noninvasive and newly developed) and a contrast agent-based (Gd- DTPA) method (invasive but well-established) with functional magnetic resonance imaging (fMRI). We compared the two methods in determining CBV changes during multi-frequency visual stimulation (4 and 8 Hz). Specifically, we aimed to assess the impact of repetition time (TR) on CBV changes determination using VASO. With additional measurements of cerebral blood flow (CBF), the flow-volume coupling relationship (α value) and cerebral metabolic rate of oxygen were further determined. The results showed that i) using VASO, short TR (2s) caused overestimation of CBV changes, while long TR (6s) generated consistent CBV results, by comparison to the GD-DTPA method; ii) overestimation of CBV changes caused underestimated CMRO2 changes, but did not alter the frequency-related pattern, i.e., CMRO2 changes at 4 Hz were greater than those at 8 Hz regardless of the TR; and iii) the tasked-induced CBF-CBV coupling was stimulus frequency-dependent, i.e., α = 0.35-0.38 at 4 Hz and α = 0.51-0.53 at 8 Hz. Our data demonstrated that, with carefully chosen TRs, CBV measurements can be achieved non-invasively with VASO techniques.

Keywords: CBV, CBF, CMRO2, VASO, flow-metabolism coupling.