Miller Karla L, Hargreaves Brian A, Lee Jongho, Ress David, deCharms R Christopher, Pauly John M
Department of Electrical Engineering, Stanford University, Stanford, California 94305-9510, USA.
Magn Reson Med. 2003 Oct;50(4):675-83. doi: 10.1002/mrm.10602.
Blood oxygenation level dependent (BOLD) functional MRI (fMRI) is an important method for functional neuroimaging that is sensitive to changes in blood oxygenation related to brain activation. While BOLD imaging has good spatial coverage and resolution relative to other neuroimaging methods (such as positron emission tomography (PET)), it has significant limitations relative to other MRI techniques, including poor spatial resolution, low signal levels, limited contrast, and image artifacts. These limitations derive from the coupling of BOLD functional contrast to sources of image degradation. This work presents an alternative method for fMRI that may over-come these limitations by establishing a blood oxygenation sensitive steady-state (BOSS) that inverts the signal from deoxygenated blood relative to the water signal. BOSS fMRI allows the imaging parameters to be optimized independently of the functional contrast, resulting in fewer image artifacts and higher signal-to-noise ratio (SNR). In addition, BOSS fMRI has greater functional contrast than BOLD. BOSS fMRI requires careful shimming and multiple acquisitions to obtain a precise alignment of the magnetization to the SSFP frequency response.
血氧水平依赖（BOLD）功能磁共振成像（fMRI）是一种重要的功能神经成像方法，对与脑激活相关的血氧变化敏感。虽然相对于其他神经成像方法（如正电子发射断层扫描（PET）），BOLD成像具有良好的空间覆盖范围和分辨率，但相对于其他MRI技术，它有显著局限性，包括空间分辨率差、信号水平低、对比度有限和图像伪影。这些局限性源于BOLD功能对比度与图像退化源的耦合。这项工作提出了一种fMRI的替代方法，该方法可以通过建立一个血氧敏感稳态（BOSS）来克服这些局限性，BOSS会反转相对于水信号的脱氧血液信号。BOSS fMRI允许独立于功能对比度优化成像参数，从而减少图像伪影并提高信噪比（SNR）。此外，BOSS fMRI比BOLD具有更大的功能对比度。BOSS fMRI需要仔细匀场和多次采集，以获得磁化与稳态自由感应衰减（SSFP）频率响应的精确对准。
