Automatic detection of anatomical landmarks on the knee joint using MRI data.

PURPOSE: To propose a new automated learning-based scheme for locating anatomical landmarks on the knee joint using three-dimensional (3D) MR image data. MATERIALS AND METHODS: This method makes use of interest points as candidates for landmarks. All candidates are evaluated by a "coarse to fine" 3D feature descriptor computed from manually placed landmarks in training datasets. The results are refined using a multi-classifier boosting system. We demonstrate our method by the detection of 24 landmarks on the knee joint of 35 subjects. To verify the robustness, the test datasets differ in contrast, resolution, patient positioning, and health condition of the knee joint. The proposed method is evaluated by measuring the distance between manually placed landmarks and automatically detected landmarks and the computational cost for detecting one landmark in a 3D dataset. RESULTS: The results reveal that the method is capable of localizing landmarks with a reasonable accuracy (1.64 ± 1.03 mm [mean ± standard deviation]), sensitivity (97%) and run time efficiency (4.82 s). CONCLUSION: This study suggests that the proposed method is an accurate and robust approach for the automated landmark detection in various MR datasets. The proposed method can be used as the initialization or constraint in higher level medical image processing workflows such as in kinematic description, segmentation and registration.

Automatic model-based semantic registration of multimodal MRI knee data.

PURPOSE: To propose a robust and automated model-based semantic registration for the multimodal alignment of the knee bone and cartilage from three-dimensional (3D) MR image data. MATERIALS AND METHODS: The movement of the knee joint can be semantically interpreted as a combination of movements of each bone. A semantic registration of the knee joint was implemented by separately reconstructing the rigid movements of the three bones. The proposed method was validated by registering 3D morphological MR datasets of 25 subjects into the corresponding T2 map datasets, and was compared with rigid and elastic methods using two criteria: the spatial overlap of the manually segmented cartilage and the distance between the same landmarks in the reference and target datasets. RESULTS: The mean Dice Similarity Coefficient (DSC) of the overlapped cartilage segmentation was increased to 0.68 ± 0.1 (mean ± SD) and the landmark distance was reduced to 1.3 ± 0.3 mm after the proposed registration method. Both metrics were statistically superior to using rigid (DSC: 0.59 ± 0.12; landmark distance: 2.1 ± 0.4 mm) and elastic (DSC: 0.64 ± 0.11; landmark distance: 1.5 ± 0.5 mm) registrations. CONCLUSION: The proposed method is an efficient and robust approach for the automated registration between morphological knee datasets and T2 MRI relaxation maps.

Correlation between psychometric tests and mismatch negativity in preschool children.

The objective was to determine whether mismatch negativity (MMN) is suitable to supplement subjective psychometric subtests of central hearing. We assessed 13 healthy children and 32 children with central auditory processing disorder (CAPD). Three different types of sound deviants were presented in a multi-deviant MMN design. At group level, the incidence of MMN was always higher in clinically diagnosed controls. Children with better results in the subtest Auditory Memory Span had a higher incidence of MMN. The controls also had peak latencies that occurred significantly earlier in frontal, central and temporal electrode sites. The area under the curve (AUC) displayed an asymmetric distribution in CAPD children, who tended to have a left-hemispheric dominance. AUC, peak latency, and the incidence of MMN reflected the discriminative ability of CAPD children. Hence, these characteristics could be used for investigating children with deficits in central hearing and can supplement psychometric tests.

Preliminary study on the quantitative analysis of vocal loading effects on vocal fold dynamics using phonovibrograms.

OBJECTIVES: The purpose of the present study was to determine whether high-speed digital imaging with phonovibrogram (PVG) analysis would identify changes in vocal fold vibratory characteristics following prolonged reading (vocal fatigue) in subjects with normal voice to evaluate the voice effects of vocal loading. METHODS: Three healthy subjects' larynges were examined with an endoscopic high-speed imaging system at 4 different levels of vocal load. Vocal fold dynamics were segmented and processed by PVGs. The PVG images were quantitatively described by a parameter set enabling an individual characterization of vocal fold dynamics. To reveal differences between the subjects, we performed a linear discrimination analysis. Within each subject, the identification of vocal loading effects was performed by statistical analysis (1-way analysis of variance), and 2-tailed paired t-tests were used as a consistency check between left and right vocal fold sides. RESULTS: For each subject, the PVG analysis enabled a precise quantification of the entire range of vocal fold dynamics. Independently of the high-speed videos (vocal loads), each subject could be identified by his or her PVG parameters on linear discrimination analysis. In all subjects, the effect of vocal loading was reflected by alterations of PVG parameters representing the posterior opening and closing dynamics. Evaluation within subjects revealed slight asymmetric vibratory behavior between the left and right vocal folds, confirming earlier assumptions. CONCLUSIONS: Within the investigated subjects, vocal loading does affect the vibratory characteristics of the vocal folds. Left-right vocal fold vibratory asymmetries do occur in healthy voices and can be identified by PVGs. High-speed digital imaging in combination with PVG analysis seems to be a promising tool for investigation of vocal fold fatigue and disorders resulting even from small dynamic changes.

Analysis of the Auditory Feedback and Phonation in Normal Voices.

PURPOSE: The aim of this study was to investigate the auditory feedback mechanisms and voice quality during phonation in response to a spontaneous pitch change in the auditory feedback. Does the pitch shift reflex (PSR) change voice pitch and voice quality? Quantitative and qualitative voice characteristics were analyzed during the PSR. METHOD: Twenty-eight healthy subjects underwent transnasal high-speed video endoscopy (HSV) at 8000 fps during sustained phonation [a]. While phonating, the subjects heard their sound pitched up for 700 cents (interval of a fifth), lasting 300 milliseconds in their auditory feedback. The electroencephalography (EEG), acoustic voice signal, electroglottography (EGG), and high-speed-videoendoscopy (HSV) were analyzed to compare feedback mechanisms for the pitched and unpitched condition of the phonation paradigm statistically. Furthermore, quantitative and qualitative voice characteristics were analyzed. RESULTS: The PSR was successfully detected within all signals of the experimental tools (EEG, EGG, acoustic voice signal, HSV). A significant increase of the perturbation measures and an increase of the values of the acoustic parameters during the PSR were observed, especially for the audio signal. CONCLUSIONS: The auditory feedback mechanism seems not only to control for voice pitch but also for voice quality aspects.

Visualization and quantification of the medial surface dynamics of an excised human vocal fold during phonation.

SUMMARY: The purpose of this investigation was to investigate physical mechanisms of vocal fold vibration during normal phonation through quantification of the medial surface dynamics of the fold. An excised hemilarynx setup was used. The dynamics of 30 microsutures mounted on the medial surface of a human vocal fold were analyzed across 18 phonatory conditions. The vibrations were recorded with a digital high-speed camera at a frequency of 4,000 Hz. The positions of the sutures were extracted and converted to three-dimensional coordinates using a linear approximation technique. The data were reduced to principal eigenfuctions, which captured over 90% of the variance of the data, and suggested mechanisms of sustained vocal fold oscillation. The vibrations were imaged as the following phonatory conditions were manipulated: glottal airflow, an adductory force applied to the muscular process, and an elongation force applied to the thyroid cartilage. Over the range of variables studied, only the variation in glottal airflow yielded significant changes in subglottal pressure and fundamental frequency. All recordings showed high correlation for the distribution of the dynamics across the medial surface of the vocal fold. The distribution of the different displacement directions and velocities showed the highest variations around the superior region of the medial surface. Although the computed vibration patterns of the two largest empirical eigenfunctions were consistent with previous experimental observations, the relative prominence of the two eigenfunctions changed as a function of glottal airflow, impacting theories of vocal efficiency and vocal economy.

A quantitative study of the medial surface dynamics of an in vivo canine vocal fold during phonation.

OBJECTIVES/HYPOTHESIS: The purpose of this study was to measure the medial surface dynamics of a canine vocal fold during phonation. In particular, displacements, velocities, accelerations, and relative phase velocities of vocal fold fleshpoints were reported across the entire medial surface. Although the medial surface dynamics have a profound influence on voice production, such data are rare because of the inaccessibility of the vocal folds. STUDY DESIGN: Medial surface dynamics were investigated during both normal and fry-like phonation as a function of innervation to the recurrent laryngeal nerve for conditions of constant glottal airflow. METHODS: An in vivo canine model was used. The larynx was dissected similar to methods described in previous excised hemilarynx experiments. Phonation was induced with artificial airflow and innervation to the recurrent laryngeal nerve. The recordings were obtained using a high-speed digital imaging system. Three dimensional coordinates were computed for fleshpoints along the entire medial surface. The trajectories of the fleshpoints were preprocessed using the method of Empirical Eigenfunctions. RESULTS: Although considerable variability existed within the data, in general, the medial-lateral displacements and vertical displacements of the vocal fold fleshpoints were large compared with anterior-posterior displacements. For both normal and fry-like phonation, the largest displacements and velocities were concentrated in the upper medial portion. During normal phonation, the mucosal wave propagated primarily in a vertical direction. Above a certain threshold of subglottal pressure (or stimulation to the recurrent laryngeal nerve), an abrupt transition from chest-like to fry-like phonation was observed. CONCLUSIONS: The study reports unique, quantitative data regarding the medial surface dynamics of an in vivo canine vocal fold during phonation, capturing both chest-like and fry-like vibration patterns. These data quantify a complex set of dynamics. The mathematical modeling of such complexity is still in its infancy and requires quantitative data of this nature for development, validation, and testing.

Sentence repetition and digit span: potential markers of bilingual children with suspected SLI?

PURPOSE: Digit span and sentence repetition are identified as potential markers for specific language impairment (SLI). We investigated if language learning of bilingual children with suspected language impairment (biSLI) was also influenced and led by memory constraints. METHOD: In a retrospective study, 19 children with SLI and 25 controls (ages 4;9-5;9), as well as 15 biSLI children and 14 controls (ages 5;1-8;9) were compared with regard to their performance on a digit span and sentence repetition task. RESULTS: Both groups with language impairment (SLI/biSLI) showed reduced performance on both tasks. Sentence repetition predicted language comprehension, and the digit span task predicted grammar abilities of the SLI, biSLI, and their controls. CONCLUSION: Sentence repetition and short-term memory provide information on language comprehension and grammar abilities in language-impaired mono- and bilingual children and confirm their function as SLI markers.

A method for characterizing stapes prostheses by their mechanical transfer function.

In this contribution, we present and evaluate a method for characterizing stapes prostheses by their mechanical transfer function. The measurements were carried out after a stapedotomy surgery was performed in three human temporal bones conserved in 4% formaldehyde. The inner ear was drained of fluid. Successively, one of three different stapes prostheses was inserted. After such preparation, the prosthesis piston movement compared to the incus movement is measured with laser vibrometry. The magnitude transfer function considered is defined as the amplitude of the prosthesis piston movement compared to the amplitude of the incus movement. Measurements were made in a frequency range from 500Hz to 4kHz. The measured amplitudes roughly ranged between 10nm and 100nm. A great advantage of the presented method is the fact that only a small portion of the ossicular chain influences the measurement, mainly the joint between the prosthesis and the incus. Furthermore, the usage of cadaver temporal bones allows for an automated measurement setup, long term experiments and the access of measurement positions inapproachable during in vivo measurements. With this method, the different kinds of prostheses could be evaluated on incuses of different diameters.

A wavelet-based approach for a continuous analysis of phonovibrograms.

Recently, endoscopic high-speed laryngoscopy has been established for commercial use and constitutes a state-of-the-art technique to examine vocal fold dynamics. Despite overcoming many limitations of commonly applied stroboscopy it has not gained widespread clinical application, yet. A major drawback is a missing methodology of extracting valuable features to support visual assessment or computer-aided diagnosis. In this paper a compact and descriptive feature set is presented. The feature extraction routines are based on two-dimensional color graphs called phonovibrograms (PVG). These graphs contain the full spatio-temporal pattern of vocal fold dynamics and are therefore suited to derive features that comprehensively describe the vibration pattern of vocal folds. Within our approach, clinically relevant features such as glottal closure type, symmetry and periodicity are quantified in a set of 10 descriptive features. The suitability for classification tasks is shown using a clinical data set comprising 50 healthy and 50 paralytic subjects. A classification accuracy of 93.2% has been achieved.

Effects of consonant-vowel transitions in speech stimuli on cortical auditory evoked potentials in adults.

We examined the neural activation to consonant-vowel transitions by cortical auditory evoked potentials (AEPs). The aim was to show whether cortical response patterns to speech stimuli contain components due to one of the temporal features, the voice-onset time (VOT). In seven normal-hearing adults, the cortical responses to four different monosyllabic words were opposed to the cortical responses to noise stimuli with the same temporal envelope as the speech stimuli. Significant hemispheric asymmetries were found for speech but not in noise evoked potentials. The difference signals between the AEPs to speech and corresponding noise stimuli revealed a significant negative component, which correlated with the VOT. The hemispheric asymmetries can be referred to rapid spectral changes. The correlation with the VOT indicates that the significant component in the difference signal reflects the perception of the acoustic change within the consonant-vowel transition. Thus, at the level of automatic processing, the characteristics of speech evoked potentials appear to be determined primarily by temporal aspects of the eliciting stimuli.

Does direct MR galactography have the potential to become an alternative diagnostic tool in patients with pathological nipple discharge?

PURPOSE: To compare direct magnetic resonance galactography (dMRG) and conventional galactography (CGal). MATERIALS AND METHODS: Thirty women underwent CGal and dMRG. Duct localization and the depth of the assumed underlying pathology in CGal and dMRG were analyzed. RESULTS: Comparing CGal and dMRG, there was no significant difference regarding sector localization, but for depth of pathology (P=.023). CONCLUSION: Duct localization with dMRG was possible with the same reliability as with CGal. Thus, dMRG may have the potential to become an alternative method to CGal.

Assessment of the variability of vocal fold dynamics within and between recordings with high-speed imaging and by phonovibrogram.

OBJECTIVES/HYPOTHESIS: The goal of the study was to assess the variability of healthy vocal fold dynamics. Quantitative parameters describing mean regularity and vibration characteristics of vocal fold dynamics along the entire glottal axis were analyzed. STUDY DESIGN: Prospective study with 14 young healthy females with no history of voice problems. High-speed videoendoscopy was used to capture vocal fold vibratory characteristics while subjects were producing vowel /i/ with comfortable pitch and loudness over three different recording sessions. METHODS: The analysis of the data was achieved by using the objective image analysis technique, phonovibrography. RESULTS: The objective analysis of the high-speed video data showed no statistically significant changes in endoscopic voice parameters for normal young female voices. CONCLUSIONS: Analysis suggests that endoscopic parameters obtained from phonovibrograms are consistent from day to day in normal voices. Further studies are needed to objectively rate the presence and degree of these parameters in disordered voices.

Variability of normal vocal fold dynamics for different vocal loading in one healthy subject investigated by phonovibrograms.

We investigate the potential of high-speed digital imaging technique (HSI) and the phonovibrogram (PVG) analysis in normal vocal fold dynamics by studying the effects of continuous voice use (vocal loading) during the workday. One healthy subject was recorded at sustained phonation 13 times within 2 consecutive days in the morning before and in the afternoon after vocal loading, respectively. Vocal fold dynamics were extracted and visualized by PVGs. The characteristic PVG patterns were extracted representing vocal fold vibration types. The parameter values were then analyzed by statistics regarding vocal load, left-right PVG asymmetries, anterior-posterior PVG asymmetries, and opening-closing differences. For the first time, the direct impact of vocal load could be determined by analyzing vocal fold dynamics. For same vocal loading conditions, equal dynamical behavior of the vocal folds were confirmed. Comparison of recordings performed in the morning with the recordings after work revealed significant changes in vibration behavior, indicating impact of occurring vocal load. Left-right asymmetries in vocal fold dynamics were found confirming earlier assumptions. Different dynamics between opening and closing procedure as well as for anterior and posterior parts were found. Constant voice usage stresses the vocal folds even in healthy subjects and can be detected by applying the PVG technique. Furthermore, left-right PVG asymmetries do occur in healthy voice to a certain extent. HSI in combination with PVG analysis seems to be a promising tool for investigation of vocal fold fatigue and pathologies resulting in small forms of dynamical changes.

The pitch rise paradigm: a new task for real-time endoscopy of non-stationary phonation.

As standard stroboscopy is restricted to the recording of periodic vocal fold vibrations, observations of non-stationary laryngeal mechanisms demand real-time recording systems, the most advanced being the high-speed video technique. It allows the registration of laryngeal parameters during a variation of the fundamental frequency. The aim of this study was to compare amplitude and frequency parameters of vocal fold vibration during stationary and non-stationary phonation, i.e. a monotonous pitch rise. Twenty-nine young female adults with no incidence of voice disorders were examined while performing two different phonation tasks: sustained phonation with a constant frequency and a monotonous pitch rise. Endoscopic recordings and the acoustic signals were acquired simultaneously. Both acoustic and laryngeal parameters were derived for short time intervals of 17.8 ms for the constant pitch and pitch rise conditions. Instantaneous frequency, sound pressure level, vibratory amplitudes of the vocal folds and the type of glottal closure were compared. At the beginning of the pitch rise, the acoustic and laryngeal parameters were similar to the parameters that occurred within the sustained phonation conditions. In contrast, the laryngeal parameters at the middle and at the end of the pitch rise differed substantially from those during sustained phonation. For the first time, quantitative measures of the growing glottal chink and the vibration amplitude decrease during pitch increase could be taken. In general, the image evaluation of the pitch rise paradigm can be subdivided into the starting, the raising and the final phase. As each phase can be considered as quasi-stationary, existing software modules are capable of analysing the process by treating each phase separately. Hence, the pitch rise condition may be suitable for clinical examination to detect information of voice disturbances that cannot be visualized during sustained phonation.