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Purpose: Muscle groups within the tongue in healthy and diseased populations show different behaviors during speech. Visualizing and quantifying strain patterns of these muscle groups during tongue motion can provide insights into tongue motor control and adaptive behaviors of a patient. Method: We present a pipeline to estimate the strain along the muscle fiber directions in the deforming tongue during speech production. A deep convolutional network estimates the crossing muscle fiber directions in the tongue using diffusion-weighted magnetic resonance imaging (MRI) data acquired at rest. A phase-based registration algorithm is used to estimate motion of the tongue muscles from tagged MRI acquired during speech. After transforming both muscle fiber directions and motion fields into a common atlas space, strain tensors are computed and projected onto the muscle fiber directions, forming so-called strains in the line of actions (SLAs) throughout the tongue. SLAs are then averaged over individual muscles that have been manually labeled in the atlas space using high-resolution T2-weighted MRI. Data were acquired, and this pipeline was run on a cohort of eight healthy controls and two glossectomy patients. Results: The crossing muscle fibers reconstructed by the deep network show orthogonal patterns. The strain analysis results demonstrate consistency of muscle behaviors among some healthy controls during speech production. The patients show irregular muscle patterns, and their tongue muscles tend to show more extension than the healthy controls. Conclusions: The study showed visual evidence of correlation between two muscle groups during speech production. Patients tend to have different strain patterns compared to the controls. Analysis of variations in muscle strains can potentially help develop treatment strategies in oral diseases. [ABSTRACT FROM AUTHOR]

Purpose: The goal of this study is to validate the muscle architecture derived from both ex vivo and in vivo diffusion-weighted magnetic resonance imaging (dMRI) of the human tongue with histology of an ex vivo tongue. Method: dMRI was acquired with a 200-direction high angular resolution diffusion imaging (HARDI) diffusion scheme for both a postmortem head (imaged within 48 hr after death) and a healthy volunteer. After MRI, the postmortem head was fixed and the tongue excised for hematoxylin and eosin (H&E) staining and histology imaging. Structure tensor images were generated from the stained images to better demonstrate muscle fiber orientations. The tongue muscle fiber orientations, estimated from dMRI, were visualized using the tractogram, a novel representation of crossing fiber orientations, and compared against the histology images of the ex vivo tongue. Results: Muscle fibers identified in the tractograms showed good correspondence with those appearing in the histology images. We further demonstrated tongue muscle architecture in in vivo tractograms for the entire tongue. Conclusion: The study demonstrates that dMRI can accurately reveal the complex muscle architecture of the human tongue and may potentially benefit planning and evaluation of oral surgery and research on speech and swallowing. [ABSTRACT FROM AUTHOR]

Purpose: Anterior tongue shape during /s/ production is often described as "tip-up" or apical, versus "tip-down" or laminal. Typically, this is determined by observing the shape of the anterior midline tongue. The purpose of this study was to identify methods of curvature calculation that quantify the observed shape differences and to examine whether the shape differences were affected by palate shape. Previous work shows that palate height has some effect (Grimm et al., 2017). Method: Four curvature-based measures were applied to a series of points selected along the tongue surface in midsagittal cine magnetic resonance images during speech. The measures were minimal curvature, averaged largest curvature (ALC), normalized ALC, and interpolated normalized ALC. These measures were compared to visual judgments of apical and laminal /s/. Anterior palate shape was measured from dental casts. Results: The apical /s/ contained a flat or concave region in the anterior tongue, while the laminal /s/ had a convex shape along the entire tongue. Thus, the laminal shape was less complex than the apical. The last 2 metrics, based on averages of multiple normalized curvatures, captured this complexity difference. Subjects with a more steeply sloped anterior palate tended to use laminal /s/. Conclusions: The tongue shape for the 2 /s/ types was best defined by complexity of the shape, rather than local anterior shape. Statistical quantities that measured curvature in multiple locations, and normalized across subjects, were best at distinguishing the 2 /s/ shapes. Interpolating additional points between the manually selected ones did not improve the method. [ABSTRACT FROM AUTHOR]

Purpose: Intrinsic and extrinsic tongue muscles in healthy and diseased populations vary both in their intra- and intersubject behaviors during speech. Identifying coordination patterns among various tongue muscles can provide insights into speech motor control and help in developing new therapeutic and rehabilitative strategies. Method: We present a method to analyze multisubject tongue muscle correlation using motion patterns in speech sound production. Motion of muscles is captured using tagged magnetic resonance imaging and computed using a phasebased deformation extraction algorithm. After being assembled in a common atlas space, motions from multiple subjects are extracted at each individual muscle location based on a manually labeled mask using high-resolution magnetic resonance imaging and a vocal tract atlas. Motion correlation between each muscle pair is computed within each labeled region. The analysis is performed on a population of 16 control subjects and 3 post-partial glossectomy patients. Results: The floor-of-mouth (FOM) muscles show reduced correlation comparing to the internal tongue muscles. Patients present a higher amount of overall correlation between all muscles and exercise en bloc movements. Conclusions: Correlation matrices in the atlas space show the coordination of tongue muscles in speech sound production. The FOM muscles are weakly correlated with the internal tongue muscles. Patients tend to use FOM muscles more than controls to compensate for their postsurgery function loss. [ABSTRACT FROM AUTHOR]

Purpose: The aims of this article were to determine the effects of hard palate morphology and glossectomy surgery on tongue position and shape during /s/ for patients with small tumors. The first expectation was that laminal /s/ would be more prevalent in patients, than apical, due to reduced tongue tip control after surgery. The second was that patients would hold the tongue more anteriorly than controls to compensate for reduced tongue mass. Method: Three-dimensional tongue volumes were calculated from magnetic resonance imaging for the whole tongue and the portion anterior to the first molar during the /s/ in /əsuk/ for 21 controls and 14 patients. These volumes were used to calculate tongue anteriority and cross-sectional shape. Dental casts were used to measure palate perimeter, height, and width of the hard palate. Results: Palate height correlated with tongue height in controls (p < .05), but not patients. In patients, tongue anteriority correlated negatively with canine width and cross-sectional tongue shape (p < .05). Controls with a high palate favored laminal /s/. Patients preferred laminal /s/ regardless of palate height (p < .01). Conclusions: For controls, hard palate height affected tongue height; a higher palate yielded a higher tongue. For patients, hard palate width affected tongue width; a narrower palate yielded a more anterior tongue. Tongue shape was unaffected by any palate features. Preference for /s/ showed an interaction effect between subject and palate height. Controls with high palates preferred a laminal /s/. All patients preferred a laminal /s/; glossectomy surgery may reduce tongue tip control. [ABSTRACT FROM AUTHOR]

Purpose: Measuring tongue deformation and internal muscle motion during speech has been a challenging task because the tongue deforms in 3 dimensions, contains interdigitated muscles, and is largely hidden within the vocal tract. In this article, a new method is proposed to analyze tagged and cine magnetic resonance images of the tongue during speech in order to estimate 3-dimensional tissue displacement and deformation over time. Method: The method involves computing 2-dimensional motion components using a standard tag-processing method called harmonic phase, constructing superresolution tongue volumes using cine magnetic resonance images, segmenting the tongue region using a random - walker algorithm, and estimating 3-dimensional tongue motion using an incompressible deformation estimation algorithm. Results: Evaluation of the method is presented with a control group and a group of people who had received a glossectomy carrying out a speech task. A 2-step principal-components analysis is then used to reveal the unique motion patterns of the subjects. Azimuth motion angles and motion on the mirrored hemi-tongues are analyzed. Conclusion: Tests of the method with a various collection of subjects show its capability of capturing patient motion patterns and indicate its potential value in future speech studies. [ABSTRACT FROM AUTHOR]

Purpose: In this study, the authors examined changes in tongue motion caused by glossectomy surgery. A speech task that involved subtle changes in tongue-tip positioning (the motion from /i/ to /s/ ) was measured. The hypothesis was that patients would have limited motion on the tumor (resected) side and would compensate with greater motion on the nontumor side in order to elevate the tongue tip and blade for /s/. Method: Velocity fields were extracted from tagged magnetic resonance images in the left, middle, and right tongue of 3 patients and 10 controls. Principal components (PCs) analysis quantified motion differences and distinguished between the subject groups. Results: PCs 1 and 2 represented variance in (a) size and independence of the tongue tip, and (b) direction of motion of the tip, body, or both. Patients and controls were correctly separated by a small number of PCs. Conclusions: Motion of the tumor slice was different between patients and controls, but the nontumor side of the patients’ tongues did not show excessive or adaptive motion. Both groups contained apical and laminal /s/ users, and 1 patient created apical /s/ in a highly unusual manner. [ABSTRACT FROM AUTHOR]

Purpose: Accurate tissue motion tracking within the tongue can help professionals diagnose and treat vocal tract-related disorders, evaluate speech quality before and after surgery, and conduct various scientific studies. The authors compared tissue tracking results from 4 widely used deformable registration (DR) methods applied to cine magnetic resonance imaging (MRI) with harmonic phase (HARP)-based tracking applied to tagged MRI. Method: Ten subjects repeated the phrase "a geese" multiple times while sagittal images of the head were collected at 26 Hz, first in a tagged MRI data set and then in a cine MRI data set. HARP tracked the motion of 8 specified tissue points in the tagged data set. Four DR methods including diffeomorphic demons and free-form deformations based on cubic B-spline with 3 different similarity measures were used to track the same 8 points in the cine MRI data set. Individual points were tracked and length changes of several muscles were calculated using the DR- and HARP-based tracking methods. Results: The results showed that the DR tracking errors were nonsystematic and varied in direction, amount, and timing across speakers and within speakers. Comparison of HARP and DR tracking with manual tracking showed better tracking results for HARP except at the tongue surface, where mistracking caused greater errors in HARP than DR. Conclusions: Tissue point tracking using DR tracking methods contains nonsystematic tracking errors within and across subjects, making it less successful than tagged MRI tracking within the tongue. However, HARP sometimes mistracks points at the tongue surface of tagged MRI because of its limited bandpass filter and tag pattern fading, so that DR has better success measuring surface tissue points on cine MRI than HARP does. Therefore, a hybrid method is being explored. [ABSTRACT FROM AUTHOR]