SimulScan and Partial Least Squares: Visualizing Swallowing Through Functional and Dynamic Imaging Correlations

Swallowing involves the precise coordination of muscles and brain areas and can be disrupted in a variety of neurological conditions. Current methods to visualize swallowing cannot examine both the biomechanics and brain activity associated with specific swallowing events. An updated version of a pulse sequence that simultaneously samples BOLD-based fMRI and dynamic imaging (called SimulScan) is introduced that provides higher quality and faster dynamic imaging, enabling data-driven analysis of swallowing function through a partial least squares (PLS) analysis.

Integrating updated dynamic imaging approaches, SimulScan achieved dynamic MRI at 23.75 frames per second with a 30 cm field of view with BOLD fMRI at a 1.6 s TR. Five subjects were scanned with SimulScan twice and with videofluoroscopy to compare the preliminary reliability of measuring swallowing biomechanics using computational analysis of swallowing mechanics (CASM) and the test-retest relationship in correlated functional and dynamic components of PLS.

High reliability of biomechanical measures of swallowing was achieved across the two SimulScan runs with CASM (r = 0.891; p < 0.0001) and between SimulScan and videofluoroscopy (r = 0.686; p < 0.0001). Correlations between dynamic and functional imaging across runs also showed high reliability (mean correlation of first 3 latent variable timeseries was 0.49 (p < 0.001) within a run and 0.17 (p < 0.001) across runs), indicating that SimulScan with PLS can extract reliable maps of linked correlations between the brain and the oropharyngeal dynamics.

The updated SimulScan with PLS analysis enables the study of central control of swallowing, providing simultaneous biomechanical visualization of the swallow along with brain functional signals.