BOLD techniques have been used in a vast range of applications including functional MRI (fMRI) and clinical MR venography of brain vasculature. Despite the immense success of BOLD fMRI applications, our understanding of complex neuronal and hemodynamic processes associated with BOLD techniques is limited. An experimental investigation with BOLD MR venography may allow us to expand our knowledge in hemodynamic process involved in BOLD fMRI. BOLD techniques are also clinically useful. In clinical brain imaging studies, imaging both time-of-flight (TOF) MR angiogram (MRA) and BOLD MR venogram (MRV) is often desirable, because they complement the depiction of vascular pathologies. Nevertheless, MRV is usually not acquired to minimize the image acquisition time. It will be highly beneficial if we can acquire MRV while imaging MRA without increasing scan time. Thus, the objective of our study was to develop and assess BOLD MRV techniques for both functional and clinical applications. For the experimental evaluation of BOLD MRV, we used a rat brain model at 9.4T. The scan condition for BOLD MRV was optimized and the venous origin of hypointense vasculature was investigated with modulation of oxygenation. Detailed venules of ˜16-30μm diameter were detected in the resulting in vivo images with 78μm isotropic scan resolution, verified with in vivo two-photon microscopy and computer simulation data. Activation foci of high-resolution BOLD fMRI maps were correlated with relatively large intracortical veins detected with high-resolution BOLD MRV, indicating that detectability of conventional BOLD fMRI is limited by density of these intracortical veins (˜1.5 vessels/mm²). For the clinical application of BOLD MRV, we developed and tested a compatible dual-echo arteriovenography (CODEA) technique for simultaneous acquisition of TOF MRA and BOLD MRV at a 3T human system. Image quality of the CODEA technique acquired in a single session was comparable to conventional TOF MRA and BOLD MRV separately acquired in two sessions. The CODEA technique was applied to chronic stroke studies. Detailed vascular structures including arterial occlusions and venous abnormalities were depicted. The CODEA technique appears valuable to other clinical applications, particularly for those requiring efficient MRA/MRV imaging with limited scan time such as acute stroke studies.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-04132009-150558 |
| Date | 25 September 2009 |
| Creators | Park, Sung-Hong |
| Contributors | Quihong He, George Stetten, Edwin M Nemoto, Kyongtae Ty Bae |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-04132009-150558/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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