Biomedical subjects

Maureen Stone

Publications and source records attributed to Maureen Stone.

8 recordsLinked to original sources

PubMed2006

Recording high quality speech during tagged cine-MRI studies using a fiber optic microphone.

PURPOSE: To investigate the feasibility of obtaining high quality speech recordings during cine imaging of tongue movement using a fiber optic microphone. MATERIALS AND METHODS: A Complementary Spatial Modulation of Magnetization (C-SPAMM) tagged cine sequence triggered by an electrocardiogram (ECG) simulator was used to image a volunteer while speaking the syllable pairs /a/-/u/, /i/-/u/, and the words "golly" and "Tamil" in sync with the imaging sequence. A noise-canceling, optical microphone was fastened approximately 1-2 inches above the mouth of the volunteer. The microphone was attached via optical fiber to a laptop computer, where the speech was sampled at 44.1 kHz. A reference recording of gradient activity with no speech was subtracted from target recordings. RESULTS: Good quality speech was discernible above the background gradient sound using the fiber optic microphone without reference subtraction. The audio waveform of gradient activity was extremely stable and reproducible. Subtraction of the reference gradient recording further reduced gradient noise by roughly 21 dB, resulting in exceptionally high quality speech waveforms. CONCLUSION: It is possible to obtain high quality speech recordings using an optical microphone even during exceptionally loud cine imaging sequences. This opens up the possibility of more elaborate MRI studies of speech including spectral analysis of the speech signal in all types of MRI.

Acoustics↗

PubMed2005

The tongue stops here: ultrasound imaging of the palate (L).

This letter presents a method for imaging the palate and extracting the palate contour from ultrasound images. Ultrasound does not usually capture the palate because the air at the tongue surface reflects the ultrasound beam back to the transducer. However, when the tongue touches the palate during a swallow, the ultrasound beam is transmitted through the soft tissue until it reaches and is reflected by the palate. In combination with tongue contours, the palate contour has the potential for disambiguation of the tongue surface, registration of images within and across subjects, and calculation of phonetically important measures.

Adolescent↗

PubMedDate not supplied

Functional segments in tongue movement.

The tongue is a deformable object, and moves by compressing or expanding local functional segments. For any single phoneme, these functional tongue segments may move in similar or opposite directions, and may reach target maximum synchronously or not. This paper will discuss the independence of five proposed segments in the production of speech. Three studies used ultrasound and tagged Cine-MRI to explore the independence of the tongue segments. High correlations between tongue segments would suggest passive biomechanical constraints and low correlations would suggest active independent control. Both physiological and higher level linguistic constraints were seen in the correlation patterns. Physiological constraints were supported by high correlations between adjacent segments (positive) and distant segments (negative). Linguistic constraints were supported by segmental correlations that changed with the phonemic content of the task.

Adult↗

PubMedDate not supplied

A guide to analysing tongue motion from ultrasound images.

This paper is meant to be an introduction to and general reference for ultrasound imaging for new and moderately experienced users of the instrument. The paper consists of eight sections. The first explains how ultrasound works, including beam properties, scan types and machine features. The second section discusses image quality, including the interpretation of anatomical features and artefacts seen in the image. The third section discusses the validity of the data collection procedures, including the effects of stabilizing the transducer and head position, and discusses some methods for stabilization. Section four discusses validation of the ultrasound and stabilization systems. The fifth section presents a sample recording set-up, supplemental information, and normalization strategies for sessions and subjects. In section six are methods of extracting contours from ultrasound images, displaying them, and analysing them. The seventh section considers the tracking of pellets on the tongue surface and the differences between tracking tissue points and continuous surfaces. The last section presents methods, challenges and results of 3D, computerized reconstruction of tongue surfaces. An outline of the paper can be found in Appendix I.

Biomechanical Phenomena↗

PubMedDate not supplied

Automatic contour tracking in ultrasound images.

In this paper, a new automatic contour tracking system, EdgeTrak, for the ultrasound image sequences of human tongue is presented. The images are produced by a head and transducer support system (HATS). The noise and unrelated high-contrast edges in ultrasound images make it very difficult to automatically detect the correct tongue surfaces. In our tracking system, a novel active contour model is developed. Unlike the classical active contour models which only use gradient of the image as the image force, the proposed model incorporates the edge gradient and intensity information in local regions around each snake element. Different from other active contour models that use homogeneity of intensity in a region as the constraint and thus are only applied to closed contours, the proposed model applies local region information to open contours and can be used to track partial tongue surfaces in ultrasound images. The contour orientation is also taken into account so that any unnecessary edges in ultrasound images will be discarded. Dynamic programming is used as the optimisation method in our implementation. The proposed active contour model has been applied to human tongue tracking and its robustness and accuracy have been verified by quantitative comparison analysis to the tracking by speech scientists.

Algorithms↗

PubMedDate not supplied

Spatiotemporal visualization of the tongue surface using ultrasound and Kriging (SURFACES).

Analyzing the motion of the human tongue surface provides valuable information about speech and swallowing. One method to analyse this motion is to acquire two-dimensional ultrasound images and extract the tongue surface contours from them. Quantitative and statistical analysis of these extracted contours is made difficult because of the absence of physical fleshpoint markers on them. In this research, this problem is overcome by pre-processing the contours using Kriging. Pre-processing includes extrapolating and resampling the contours on a regular spatial grid. The preprocessed contours can then be visualized as spatiotemporal surfaces. A dedicated user interface called SURFACES is designed to aid in the generation, visualization and quantitative comparisons of these spatiotemporal surfaces.

Algorithms↗

PubMedDate not supplied

Tongue motion averaging from contour sequences.

In this paper, a method to get the best representation of a speech motion from several repetitions is presented. Each repetition is a representation of the same speech captured at different times by sequence of ultrasound images and is composed of a set of 2D spatio-temporal contours. These 2D contours in different repetitions are time aligned first by a shape based Dynamic Programming (DP) method. The best representation of the speech motion is then obtained by averaging the time aligned contours from different repetitions. Procrustes analysis is used to measure the contour similarity in the time alignment process and to get the averaged best representation. To get the point correspondence for Procrustes analysis, a nonrigid point correspondence recovery method based on a local stretching model and a global constraint is developed. Synthetic validations and experiments on real tongue motion are also presented in this paper.

Algorithms↗

PubMedDate not supplied

Principal components representation of the two-dimensional coronal tongue surface.

This paper uses principal components (PC) analysis to represent coronal tongue contours for the 11 vowels of English in two consonant contexts (/s/, /l/), based upon five replicated measurements in three sessions for each of 6 subjects. Curves from multiple sessions and speakers were overlaid before analysis onto a common (x, y) coordinate system by extensive preprocessing of the curves including: extension (padding) or truncation within session, translation, and truncation to a common x range. Four PCs plus a mean level allow accurate representation of coronal tongue curves, but PC shapes depend strongly on the degree of padding or truncation. The PCs successfully reduced the dimensionality of the curves and reflected vowel height, consonant context, and physiological features.

Adult↗