2022 年 39 巻 4 号 p. 604-607
The magnetic field strength meant by ultra–high field magnetic resonance imaging (MRI) has been changing with the development of MRI, and in recent years, it is commonly used to refer to scanners with a magnet of 7 tesla (7T) or higher. The resolution of MRI depends on tissue relaxation time and contrast, as well as the signal–to–noise ratio (SNR). Increasing the magnetic field strength not only improves SNR, but also enhancing the tissue contrast. 7T MRI has significant advantages over conventional 3T MRI, including practical sub–millimeter order spatial resolution and improved sensitivity in functional MRI (fMRI). 7T MRI enhances intra–tissue (within gray and white matter) susceptibility contrast. In addition, high resolution of fMRI at 7T provides the opportunity for the separation of input and output information based on layer specific analysis in local brain regions. With the recent development of post–processing techniques, a paradigm shift from conventional macroscopic mapping (gyrus and sulcus) to analysis of function–structure relationships at the individual level is anticipated.
