A technique to reduce motion artifact for externally triggered cine-MRI(EC-MRI) based on detecting the onset of the articulated word with spectral analysis.

One issue in externally triggered cine-magnetic resonance imaging (EC-MRI) for the dynamic observation of speech organs is motion artifact in the phase-encoding direction caused by unstable repetitions of speech during data acquisition. We propose a technique to reduce such artifact by rearranging the k-space data used to reconstruct MR images based on the analysis of recorded speech sounds. We recorded the subject's speech sounds during EC-MRI and used post hoc acoustical processing to reduce scanning noise and detect the onset of each utterance based on analysis of the recorded sounds.

Visualisation of hypopharyngeal cavities and vocal-tract acoustic modelling.

The hypopharyngeal cavities consist of the laryngeal cavity and bilateral piriform fossa, constituting the bottom part of the vocal tract near the larynx. Visualisation of these cavities with magnetic resonance imaging (MRI) techniques reveals that during speech, the laryngeal cavity takes the form of a long-neck flask and the piriform fossa takes the form of a goblet of varying shapes: the former diminishes greatly in whispering and the latter disappears during deep inhalation. These cavities have been shown to exert significant acoustic effects at higher frequency spectra.

Effect of fat-saturation pulse on EPI time series in the presence of B0 drift.

Purpose: We examined the hypothesis that the fat-saturation pulse in a global off-resonance state caused by magnetic field (B(0)) drift produced signal fluctuation in echo planar imaging (EPI) time series.

Methods: We performed 3 experiments using 2 types of phantoms, one of which was homemade and contained water and a well emulsified fat source.

Results: We found that B(0) drift was approximately +30 Hz in the first 30-min EPI time series and +15 Hz in the second series.

System stability of a 3T-MRI during continuous EPI scan.

The purpose of this study is to evaluate the general stability and image properties of a 3T MRI system newly installed at the ATR-Brain Activity Imaging Center (ATR-BAIC), in addition to a conventional 1.5T system. In this study, we focused on the echo planar imaging (EPI) sequence since continuous EPI with a relatively long duration of up to 30 min is routinely used, and the stabilization of EPI is always a concern.

Measurement of temporal changes in vocal tract area function from 3D cine-MRI data.

A 3D cine-MRI technique was developed based on a synchronized sampling method [Masaki et al., J. Acoust.

When meaningless symbols become letters: neural activity change in learning new phonograms.

Left fusiform gyrus and left angular gyrus are considered to be respectively involved with visual form processing and associating visual and auditory (phonological) information in reading. However, there are a number of studies that fail to show the contribution of these regions in carrying out these aspects of reading. Considerable differences in the type of stimuli and tasks used in the various studies may account for the discrepancy in results.

Dynamic analysis of articulatory movement using magnetic resonance imaging movies: methods and implications in cleft lip and palate.

Objectives: To visualize articulatory movement using a magnetic resonance imaging (MRI) movie of a subject with cleft lip and palate (clp) and to demonstrate the usefulness of this method for studying oropharyngeal function.

Material And Methods: Dynamic changes in oropharyngeal structures were assessed with an MRI movie of a man with cleft lip and palate and in a normal adult male volunteer during the articulation of /pa/, /ta/, and /ka/.

Results And Conclusions: Different movement patterns were observed during articulation in the subject with CLP compared with the normal volunteer.

Learning-induced neural plasticity associated with improved identification performance after training of a difficult second-language phonetic contrast.

Adult native Japanese speakers have difficulty perceiving the English /r-l/ phonetic contrast even after years of exposure. However, after extensive perceptual identification training, long-lasting improvement in identification performance can be attained. This fMRI study investigates localized changes in brain activity associated with 1 month of extensive feedback-based perceptual identification training by native Japanese speakers learning the English /r-l/ phonetic contrast.

[4D-MRI using the synchronized sampling method (SSM)].

A synchronized sampling method (SSM) was developed for the study of voluntary movements by combining the electrocardiographic (ECG) gating method with an external triggering device, and four-dimensional magnetic resonance imaging (4D-MRI) at a rate of 30 frames per second was accomplished by volumetric imaging with the SSM. This method was first applied to the motion imaging of articulatory organs during repetitions of a Japanese five-vowel sequence, and the dynamic change in vocal tract area function was demonstrated with sufficient temporal resolution. This paper describes the methodology, applicability, and limitations of 4D-MRI with the SSM.