Youkyung Bae

Faster dynamic imaging of speech with field inhomogeneity corrected spiral fast low angle shot (FLASH) at 3 T

To evaluate the impact of magnetic field inhomogeneity correction on achievable imaging speeds for magnetic resonance imaging (MRI) of articulating oropharyngeal structures during speech and to determine if sufficient acquisition speed is available for visualizing speech structures with real‐time MRI.

Real-time magnetic resonance imaging of velopharyngeal activities with simultaneous speech recordings.

Objective To examine the relationships between acoustic and physiologic aspects of the velopharyngeal mechanism during acoustically nasalized segments of speech in normal individuals by combining fast magnetic resonance imaging (MRI) with simultaneous speech recordings and subsequent acoustic analyses. Design Ten normal Caucasian adult individuals participated in the study. M id sagittal dynamic magnetic resonance imaging (MRI) and simultaneous speech recordings were performed while participants were producing repetitions of two rate-controlled nonsense syllables including /zanaza/ and /zunuzu/. Acoustic features of nasalization represented as the peak amplitude and the bandwidth of the first resonant frequency (F1) were derived from speech at the rate of 30 sets per second. Physiologic information was based on velar and tongue positional changes measured from the dynamic MRI data, which were acquired at a rate of 21.4 images per second and resampled with a corresponding rate of 30 images per second. Each acoustic feature of nasalization was regressed on gender, vowel context, and velar and tongue positional variables. Results Acoustic features of nasalization represented by F1 peak amplitude and bandwidth changes were significantly influenced by the vowel context surrounding the nasal consonant, velar elevated position, and tongue height at the tip. Conclusions Fast MRI combined with acoustic analysis was successfully applied to the investigation of acoustic-physiologic relationships of the velopharyngeal mechanism with the type of speech samples employed in the present study. Future applications are feasible to examine how anatomic and physiologic deviations of the velopharyngeal mechanism would be acoustically manifested in individuals with velopharyngeal incompetence.

Validity of the nasometer measuring the temporal characteristics of nasalization.

Objective: To examine the validity of the Nasometer (KayPENTAX, Lincoln Park, NJ) in measuring the temporal characteristics of nasalization by comparing the Nasometer measures to the measures from an external criterion procedure. Design: Speech samples consisted of three rate-controlled nonsense syllables, which varied in their vowel compositions: /izinizi/, /azanaza/, and /uzunuzu/. Acoustic data were recorded simultaneously through the Nasometer and an external criterion procedure (a specialized microphone set that collected acoustic signals separately for the nasal and oral channels). Speech segment durations measured from the two instrumental conditions were compared on the Nasometer display and the Computerized Speech Lab (KayPENTAX, Lincoln Park, NJ) display. Five durational variables were measured: total utterance duration, nasal onset interval, nasal consonant duration, nasal offset interval, and total nasalization duration. Participants: Fourteen normal adults who speak American English as their first language participated in the study. Results: No significant differences were found between the measures from the Nasometer and those from an external criterion procedure in all the durational variables pertinent to nasalization. Different vowels, however, yielded significantly different patterns in these durational variables, in which the low vowel /a/ context revealed significantly longer total nasalization duration than did the high vowel /i/ and /u/ contexts. Conclusions: The results suggest that the Nasometer can be used as a valid tool to measure the temporal characteristics underlying nasalization and confirm significant vowel effects on the temporal patterns of nasalization.

Dynamic imaging of speech and swallowing with MRI

Dynamic imaging with MRI holds great promise for visualizing soft tissue structures in the oropharyngeal region during speech and swallowing studies. However, MRI suffers from historically slow acquisition speed and sensitivity to significant magnetic susceptibility differences in this region. In this work, we describe our efforts in creating high temporal resolution, serial acquisitions of the muscles of the oropharyngeal region. We describe our imaging approach that leads to acquisition rates of up to 21 frames per second. Additionally, we compare the serial acquisition scheme to gated acquisitions that suffer from temporal blur due to limited repeatability of the dynamic action.

Magnetic resonance imaging of velar muscle tissue distribution in healthy adults

Objectives To examine muscle tissue distribution along the length of the velum in living individuals using magnetic resonance imaging (MRI). Design Using the three-dimensional MRI data acquired from 10 normal white adults, two area measures including the muscular area and the total velar area were obtained from 10 oblique slices running perpendicular to velar length. A polynomial regression analysis was performed where the proportion of the muscular to the total velar area was regressed on the slice numbers running along the length of the velum. Results The proportion of the muscular to total velar area increased from the anterior section of the velum, reaching a maximum (33.24%) in the midsection, and decreasing in the posterior section of the velum. A third-order (cubic) polynomial function that best illustrated the proportional data (R2 = .47) was derived. Conclusions The present study demonstrated that MRI is a viable tool to examine the muscle tissue distribution of the velum in living individuals. Although the overall pattern in the muscle tissue distribution of the healthy velum was similar to that reported in previous literature based on cadaver specimens, the participants in the present study appeared to have greater muscular proportion of the velum. The muscular proportion measure derived from the healthy living individuals can be used as an additional parameter accounting for sufficient intravelar muscle mass for future studies.

Videofluoroscopic Investigation of Body Position on Articulatory Positioning.

PURPOSE To quantitatively examine the effects of body position on the positioning of the epiglottis, tongue, and velum at rest and during speech. METHOD Videofluoroscopic data were obtained from 12 healthy adults in the supine and upright positions at rest and during speech while the participants produced 12 VCV sequences. The effects of body position, target sounds, and adjacent sounds on structural positioning and vowel formant structure were investigated. RESULTS Velar retropositioning in the supine position was the most consistent pattern observed at rest. During speech, all structures, with varying degrees of adjustment, appeared to work against the gravitational pull, resulting in no significant narrowing in the oro- and nasopharyngeal regions while in the supine position. Minimal differences in the formant data between the body positions were also observed. Overall, structural positioning was significantly dependent on the target and adjacent sounds regardless of body position. CONCLUSIONS The present study demonstrated that structural positioning in response to gravity varied across individuals based on the type of activities being performed. With varying degrees of positional adjustment across different structures, fairly consistent articulatory positioning in the anterior-posterior dimension was maintained in different body positions during speech.

Nasalization Amplitude-Timing Characteristics of Speakers With and Without Cleft Palate:

Objectives: To examine the amplitude-temporal relationships of acoustic nasalization in speakers with a range of nasality and to determine the extent to which each domain independently predicts the speaker’s perceived oral-nasal balance. Design: Rate-controlled speech samples, consisting of /izinizi/, /azanaza/, and /uzunuzu/, were recorded from 18 participants (14 with repaired cleft palate and 4 without cleft palate) using the Nasometer. The mean nasalance of the entire mid-vowel–nasal consonant–vowel (mid-VNV) sequence (amplitude-domain) and the duration of the nasalized segment of the mid-VNV sequence (temporal-domain) were obtained based on nasalance contours. Results: Strong linear and vowel-dependent relationships were observed between the 2 domains of nasalization (adjusted R2 = 71.5%). Both the amplitude- and temporal-domain measures were found to reliably predict the speaker’s perceived oral-nasal balance, with better overall model fit and higher classification accuracy rates observed in /izinizi/ and /uzunuzu/ than in /azanaza/. Despite poor specificity, the temporal-domain measure of /azanaza/ was found to have a strong correlation with the participants’ Zoo passage nasalance scores (r s = .897, p < .01), suggesting its potential utility as a severity indicator of perceived nasality. Conclusions: With the use of relatively simple speech tasks and measurements representing the amplitude and temporal domains of nasalization, the present study provided practical guidelines for using the Nasometer in assessing patients with oral-nasal resonance imbalance. Findings suggest that both domain measures of nasalization should be examined across different vowel contexts, given that each domain may provide clinically relevant, yet different, information.

Structural Changes Following Velopharyngeal Resistance Training (Continuous Positive Airway Pressure Therapy): A Preliminary Report

Objective: To evaluate the feasibility/effectiveness of using magnetic resonance imaging (MRI) to document velopharyngeal (VP) structural changes induced by continuous positive airway pressure (CPAP) therapy. Outcome Measures: Changes in velar length and thickness, levator veli palatini (LVP) length and thickness, velar volume, and intravelar muscular proportion along the course of CPAP therapy participation (Pre-CPAP, Post-CPAP, and withdrawal). Results: Velar and LVP lengths remained nearly the same, with the median changes (Δ) less than 0.6%, across repeated conditions. Although varying in magnitudes of change, median velar volume (Δ4%), velar thickness (Δ20%), LVP thickness (Δ17%), and intravelar muscular proportion (Δ10%) illustrated a consistent pattern of increases following the 8-week CPAP therapy. These VP structural measurements slightly decreased but remained above the pretraining condition after 8-week detraining. Conclusions: This report successfully demonstrated that MRI is a viable tool to document CPAP therapy–induced VP structural changes while providing preliminary empirical data.

Validity of the Nasometer measuring the temporal characteristics of nasalization

Patients with oral‐nasal resonance imbalance may present different characteristics not only in the amplitude but also in the temporal aspects of nasalization. Although nasalance has been the most commonly derived measure from the Nasometer (KayPENTAX), the Nasometer also might be useful in providing another important measure, time. Such measurements, however, should be validated in relation to a separate external criterion procedure. This study examined the validity of the Nasometer measuring the temporal characteristics of nasalization. Fourteen adult American English speakers produced three rate‐controlled nonsense speech samples: /izinizi/, /azanaza/, and /uzunuzu/. Acoustic data recorded through the Nasometer were compared to those recorded through a standard audio recording setup which served as an external criterion procedure. Four timing variables pertinent to nasalization were measured from the digitized acoustic signals: nasal onset, nasal consonant, nasal offset, and total nasalization. No significant differences were found between the two instrumental conditions in any of four timing variables measured, which suggests the Nasometer can be used as a valid tool to measure the temporal features of nasalization. This study also provided a valid way of segmenting speech tasks using the Nasometer and confirmed the significant effect of different vowel contexts on the temporal characteristics of nasalization.