Improved Real-time MRI of Oral-Velar Coordination Using a Golden-ratio Spiral View Order

In speech research using real-time magnetic resonance imaging (RT-MRI), frame reconstruction is typically performed with a constant temporal resolution. However, a flexible selection of temporal resolution is desirable because of natural variations in speaking rate and variations in the speed of different articulators. In this work, a novel spiral golden-ratio temporal view order was applied to nasal RT-MRI studies in imaging a mid-sagittal slice of the upper airway. Compared to conventional spiral bit-reversed temporal view order scheme, the proposed golden-ratio scheme provides less temporal blurring in the depiction of rapid tongue tip motion with a selection of high temporal resolution. It also provides higher signal-to-noise ratio (SNR) in the depiction of relatively slow velar motion with a selection of low temporal resolution. Index Terms: speech production, vocal tract shaping, real-time MRI, golden ratio, spiral trajector