Simultaneous functional MRI acquisition of distributed brain regions with high temporal resolution using a 2D-selective radiofrequency excitation

Abstract

Purpose: To perform simultaneous functional MRI of multiple, distributed brain regions at high temporal resolution using a 2D-selective radiofrequency (2DRF) excitation. Methods: A tailored 2DRF excitation is used to excite several, small regions-of-interest distributed in the brain. They are acquired in a single projection image with an appropriately chosen orientation such that the different regions-of-interest can be discriminated by their position in the projection plane. Thus, they are excited and acquired simultaneously with a temporal resolution comparable to that of a single-slice measurement. The feasibility of this approach for functional neuroimaging (in-plane resolution 2 x 2 mm2) at high temporal resolution (80 ms) is demonstrated in healthy volunteers for regions-of-interest in the visual and motor system using checkerboard and finger tapping block-design paradigms. Results: Task-related brain activation could be observed in both the visual and the motor system simultaneously with a high temporal resolution. For an onset shift of 240 ms for half of the checkerboard, a delay of the hemodynamic response in the corresponding hemisphere of the visual cortex could be detected. Conclusion: Limiting the excited magnetization to the desired target regions with a 2DRF excitation reduces the imaging sampling requirements which can improve the temporal resolution significantly.