(The) oxygenation measurement by separation of In-flow effect in arterial blood with TRFGE technique in NMR

Abstract

Recently, the development of the dynamic functional NMR studies based on the $T_2\,^{\ast}$ effect by using gradient echo imaging brought about a new dimension in the functional imaging. However, these fast gradient echo imaging techniques are not only sensitive to $T_2\,^{\ast}$ effect but are also greatly related to the in-flow effect from the unsaturated arterial blood flowing into the imaging slice. The currently used gradient echo imaging techniques, therefore, that show the signal change is a mixture of the inflow effect due to the blood flow and susceptibility effect, not the susceptibility effect alone. In this thesis, a new functional activity model is proposed by the numerical simulation based on the published data in human brain activity, and by the repeated experiments using the TRFGE technique which enhances the signal affected by the susceptibility and suppresses the in-flow effect. As a result, the data due to the true oxygenation are obtained in the arterial blood vessel. The proposed model and TRFGE technique which enhances the susceptibility effect is shown to be useful for the definition of the activities in human brain and the more quantitative functional imaging in the near future.