Vocal tract cross-distance estimation from real-time MRI using region-of-interest analysis

Real-Time Magnetic Resonance Imaging affords speech articu-lation data with good spatial and temporal resolution and com-plete midsagittal views of the moving vocal tract, but also brings many challenges in the domain of image processing and analy-sis. Region-of-interest analysis has previously been proposed for simple, efficient and robust extraction of linguistically-meaningful constriction degree information. However, the ac-curacy of such methods has not been rigorously evaluated, and no method has been proposed to calibrate the pixel intensity values or convert them into absolute measurements of length. This work provides such an evaluation, as well as insights into the placement of regions in the image plane and calibration of the resultant pixel intensity measurements. Measurement errors are shown to be generally at or below the spatial resolution of the imaging protocol with a high degree of consistency across time and overall vocal tract configuration, validating the utility of this method of image analysis. Index Terms: speech production data, real-time mri, analysis tools, vocal tract area functions