Functional magnetic resonance imaging (fMRI) has the ability to monitor the vascular response to neuronal activity. The vascular response, changes in local blood flow, blood volume and oxygen consumption, is measured by the corresponding changes in oxygenation levels The paramagnetic nature of deoxygenated hemoglobin serves as a contrast agent for monitoring hemodynamic changes accompanying neural activity. Blood oxygen level dependent (BOLD) contrast has been widely utilized and the method of choice for non-invasive imaging of brain function, specifically in humans. With the application of BOLD fMRl to high spatial resolution mapping of brain function, it is becoming increasingly important to understand the specificity limitations of the vascular response and how to exploit these limits of specificity when using BOLD fMRI. BOLD fMRI may be performed using either T2 or T2' weighted images, both of which have sensitivity, although different, to BOLD effects. Our long-range goal is to realize the limitations of BOLD signals for the purpose of increasing the accuracy of mapping high resolution functional structures in the human brain. The central hypothesis of the proposed research is that T2 weighted BOLD fMRl can be efficiently implemented for high spatial resolution applications in humans and at high magnetic fields maximizes the specificity of the BOLD response. This hypothesis has been formdated from a substantial amount of preliminary data, which suggest feasibility of high resolution T2 weighted BOLD fMRl in humans, and theoretical considerations which predict advantages in specificity and sensitivity for T2 weighted BOLD signals at high magnetic fields. The central hypothesis will be tested and the objective of the application will be accomplished by pursuing three specific aims: 1) Develop a high-resolution T2 weighted imaging sequence for use in the human brain, 2) assess the vascular nature of the T2 response as it changes with fields strength, and 3) to determine whether or not T2 weighted BOLD fMRl is more suited, than conventional T2' weighted BOLD fMRl, for high spatial resolution applicants in humans. The rationale for the proposed research is: T2 weighted BOLD fMRl can provide more detailed and more specific information on microvascufar and hemodynamic changes associated with functional brain activation. As an advanced MR center, we are uniquely positioned to undertake the proposed research. Our laboratory has well-established expertise in functional imaging, advanced hardware and software development, and specialized RF coil design. The proposed research is innovative as high resolution T2 weighted BOLD fMRl in the human brain at submillimeter resolutions has not been feasible to date. We expect that T2 weighted BOLD fMRI will be the imaging method of choice for high spatial resolution applications. This is significant because of the increasing demands to reliably map high resolution functional structures in the human brain. It will advance the field of non-invasive brain mapping to unmatched levels of specificity and sensitivity to neuronal activity.
| Yacoub, Essa; Van De Moortele, Pierre-Francois; Shmuel, Amir et al. (2005) Signal and noise characteristics of Hahn SE and GE BOLD fMRI at 7 T in humans. Neuroimage 24:738-50 |
| Yacoub, Essa; Duong, Timothy Q; Van De Moortele, Pierre-Francois et al. (2003) Spin-echo fMRI in humans using high spatial resolutions and high magnetic fields. Magn Reson Med 49:655-64 |
