Purpose
To improve the spatiotemporal qualities of images and dynamics of speech MRI through an improved data sampling and image reconstruction approach.
Methods
For data acquisition, we used a ...Poisson‐disc random under sampling scheme that reduced the undersampling coherence. For image reconstruction, we proposed a novel locally higher‐rank partial separability model. This reconstruction model represented the oral and static regions using separate low‐rank subspaces, therefore, preserving their distinct temporal signal characteristics. Regional optimized temporal basis was determined from the regional‐optimized virtual coil approach. Overall, we achieved a better spatiotemporal image reconstruction quality with the potential of reducing total acquisition time by 50%.
Results
The proposed method was demonstrated through several 2‐mm isotropic, 64 mm total thickness, dynamic acquisitions with 40 frames per second and compared to the previous approach using a global subspace model along with other k‐space sampling patterns. Individual timeframe images and temporal profiles of speech samples were shown to illustrate the ability of the Poisson‐disc under sampling pattern in reducing total acquisition time. Temporal information of sagittal and coronal directions was also shown to illustrate the effectiveness of the locally higher‐rank operator and regional optimized temporal basis. To compare the reconstruction qualities of different regions, voxel‐wise temporal SNR analysis were performed.
Conclusion
Poisson‐disc sampling combined with a locally higher‐rank model and a regional‐optimized temporal basis can drastically improve the spatiotemporal image quality and provide a 50% reduction in overall acquisition time.
Travertine crystal growth ripples are used to reconstruct the early hydraulic history of the Anio Novus aqueduct of ancient Rome. These crystalline morphologies deposited within the aqueduct channel ...record the hydraulic history of gravity-driven turbulent flow at the time of Roman operation. The wavelength, amplitude, and steepness of these travertine crystal growth ripples indicate that large-scale sustained aqueduct flows scaled directly with the thickness of the aqueous viscous sublayer. Resulting critical shear Reynolds numbers are comparable with those reconstructed from heat/mass transfer crystalline ripples formed in other natural and engineered environments. This includes sediment transport in rivers, lakes, and oceans, chemical precipitation and dissolution in caves, and melting and freezing in ice. Where flow depth and perimeter could be reconstructed from the distribution and stratigraphy of the travertine within the Anio Novus aqueduct, flow velocity and rate have been quantified by deriving roughness-flow relationships that are independent of water temperature. More generally, under conditions of near-constant water temperature and kinematic viscosity within the Anio Novus aqueduct channel, the travertine crystal growth ripple wavelengths increased with decreasing flow velocity, indicating that systematic changes took place in flow rate during travertine deposition. This study establishes that travertine crystal growth ripples such as those preserved in the Anio Novus provide a sensitive record of past hydraulic conditions, which can be similarly reconstructed from travertine deposited in other ancient water conveyance and storage systems around the world.
Purpose
To enable a more comprehensive view of articulations during speech through near‐isotropic 3D dynamic MRI with high spatiotemporal resolution and large vocal‐tract coverage.
Methods
Using ...partial separability model‐based low‐rank reconstruction coupled with a sparse acquisition of both spatial and temporal models, we are able to achieve near‐isotropic resolution 3D imaging with a high frame rate. The total acquisition time of the speech acquisition is shortened by introducing a sparse temporal sampling that interleaves one temporal navigator with four randomized phase and slice‐encoded imaging samples. Memory and computation time are improved through compressing coils based on the region of interest for low‐rank constrained reconstruction with an edge‐preserving spatial penalty.
Results
The proposed method has been evaluated through experiments on several speech samples, including a standard reading passage. A near‐isotropic 1.875 × 1.875 × 2 mm3 spatial resolution, 64‐mm through‐plane coverage, and a 35.6‐fps temporal resolution are achieved. Investigations and analysis on specific speech samples support novel insights into nonsymmetric tongue movement, velum raising, and coarticulation events with adequate visualization of rapid articulatory movements.
Conclusion
Three‐dimensional dynamic images of the vocal tract structures during speech with high spatiotemporal resolution and axial coverage is capable of enhancing linguistic research, enabling visualization of soft tissue motions that are not possible with other modalities.
Magnetic resonance (MR) imaging is becoming an established tool in capturing articulatory and physiological motion of the structures and muscles throughout the vocal tract and enabling visual and ...quantitative assessment of real-time speech activities. Although motion capture speed has been regularly improved by the continual developments in high-speed MR technology, quantitative analysis of multi-subject group data remains challenging due to variations in speaking rate and imaging time among different subjects. In this paper, a workflow of post-processing methods that matches different MR image datasets within a study group is proposed. Each subject's recorded audio waveform during speech is used to extract temporal domain information and generate temporal alignment mappings from their matching pattern. The corresponding image data are resampled by deformable registration and interpolation of the deformation fields, achieving inter-subject temporal alignment between image sequences. A four-dimensional dynamic MR speech atlas is constructed using aligned volumes from four human subjects. Similarity tests between subject and target domains using the squared error, cross correlation, and mutual information measures all show an overall score increase after spatiotemporal alignment. The amount of image variability in atlas construction is reduced, indicating a quality increase in the multi-subject data for groupwise quantitative analysis.
To introduce a highly innovative imaging method to study the complex velopharyngeal (VP) system and introduce the potential future clinical applications of a VP atlas in cleft care.
Four healthy ...adults participated in a 20-min dynamic magnetic resonance imaging scan that included a high-resolution T2-weighted turbo-spin-echo 3D structural scan and five custom dynamic speech imaging scans. Subjects repeated a variety of phrases when in the scanner as real-time audio was captured.
Multisite institution and clinical setting.
Four adult subjects with normal anatomy were recruited for this study.
Establishment of 4-D atlas constructed from dynamic VP MRI data.
Three-dimensional dynamic magnetic resonance imaging was successfully used to obtain high quality dynamic speech scans in an adult population. Scans were able to be re-sliced in various imaging planes. Subject-specific MR data were then reconstructed and time-aligned to create a velopharyngeal atlas representing the averaged physiological movements across the four subjects.
The current preliminary study examined the feasibility of developing a VP atlas for potential clinical applications in cleft care. Our results indicate excellent potential for the development and use of a VP atlas for assessing VP physiology during speech.
Hypernasality is one of the most detrimental speech disturbances that lead to declines of speech intelligibility. Velopharyngeal inadequacy, which is associated with anatomic defects such as cleft ...palate or neuromuscular disorders that affect velopharygneal function, is the primary cause of hypernasality. A simulation study by Rong and Kuehn J. Speech Lang. Hear. Res. 55(5), 1438-1448 (2012) demonstrated that properly adjusted oropharyngeal articulation can reduce nasality for vowels synthesized with an articulatory model Mermelstein, J. Acoust. Soc. Am. 53(4), 1070-1082 (1973). In this study, a speaker-adaptive articulatory model was developed to simulate speaker-customized oropharyngeal articulatory adaptation to compensate for the acoustic effects of nasalization on /a/, /i/, and /u/. The results demonstrated that (1) the oropharyngeal articulatory adaptation effectively counteracted the effects of nasalization on the second lowest formant frequency (F2) and partially compensated for the effects of nasalization on vowel space (e.g., shifting and constriction of vowel space) and (2) the articulatory adaptation strategies generated by the speaker-adaptive model might be more efficacious for counteracting the acoustic effects of nasalization compared to the adaptation strategies generated by the standard articulatory model in Rong and Kuehn. The findings of this study indicated the potential of using oropharyngeal articulatory adaptation as a means to correct maladaptive articulatory behaviors and to reduce nasality.
The distinction between underlying and excrescent stops in pairs like ‘mints’ and ‘mince’ was convincingly demonstrated by
Fourakis and Port (1986). Several subsequent studies have been unable to ...replicate the result for speakers of American English, or have done so only partially. These studies have largely dealt with the acoustic signal. This study presents an approach to stop excrescence that refers to both the aerodynamics and articulation of the phenomenon. The results confirm and expand on the original findings. Using nasal flow as an indirect measure of velopharyngeal aperture and electropalatography (EPG) to estimate the moment of oral release, the presence of occlusion, as well as the duration of nasal and oral occlusion were measured. Overall contact across the palate was also measured. Disyllabic and monosyllabic tokens with /ns/ and /nts/ in final position were pronounced by four male speakers of American English. Disyllabic tokens could be either stressed or unstressed on the final syllable. In Experiment I, speakers produced tokens in a standard carrier phrase; in Experiment II, they produced one of the items in contrastive focus to its ‘homophonous’ counterpart, e.g., ‘I said
mince not mints’. Underlying stops were significantly longer than excrescent stops, including in the contrastive-focus condition. A trading relation between nasal and oral stop duration was demonstrated when the stop was excrescent, but not when it was underlying. This suggests that the nasal–oral occlusion in epenethetic stops is divided proportionally between the underlying nasal and excrescent oral stop, but that the durations of the nasal and underlying oral stops are independent.
► Words like ‘mints’ and ‘mince’ may differ in the presence and length of t. ► Most studies of the pairs have dealt with the acoustic signal. ► This study uses articulation (EPG) and aerodynamics to measure the length of t. ► Underlying stops are shown to be longer than excrescent stops. ► For length of n and t, a trading relation is observed in excrescent stops.
The Maya Classroom in Diaspora Goti, Korinta Maldonado; Shosted, Ryan
Maya America,
01/2019, Letnik:
1, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Over the past ten years, professors and students from the University of Illinois have collaborated with the rapidly growing population of Maya residents in Champaign County, Illinois to develop ...opportunities to use, preserve, and pass on their linguistic and cultural skills. Our general goals are to support educators and school to better understand the linguistic and cultural heritage of the Maya students and to open up spaces and build support networks for the students to continue to use their language in diaspora.
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