Computer measurement of oral movement in swallowing

Semi-automatic tracking, smoothing and segmentation of hyoid bone motion from videofluoroscopic swallowing study

Motion analysis of the hyoid bone via videofluoroscopic study has been used in clinical research, but the classical manual tracking method is generally labor intensive and time consuming. Although some automatic tracking methods have been developed, masked points could not be tracked and smoothing and segmentation, which are necessary for functional motion analysis prior to registration, were not provided by the previous software. We developed software to track the hyoid bone motion semi-automatically. It works even in the situation where the hyoid bone is masked by the mandible and has been validated in dysphagia patients with stroke. In addition, we added the function of semi-automatic smoothing and segmentation. A total of 30 patients’ data were used to develop the software, and data collected from 17 patients were used for validation, of which the trajectories of 8 patients were partly masked. Pearson correlation coefficients between the manual and automatic tracking are high and statistically significant (0.942 to 0.991, P-value<0.0001). Relative errors between automatic tracking and manual tracking in terms of the x-axis, y-axis and 2D range of hyoid bone excursion range from 3.3% to 9.2%. We also developed an automatic method to segment each hyoid bone trajectory into four phases (elevation phase, anterior movement phase, descending phase and returning phase). The semi-automatic hyoid bone tracking from VFSS data by our software is valid compared to the conventional manual tracking method. In addition, the ability of automatic indication to switch the automatic mode to manual mode in extreme cases and calibration without attaching the radiopaque object is convenient and useful for users. Semi-automatic smoothing and segmentation provide further information for functional motion analysis which is beneficial to further statistical analysis such as functional classification and prognostication for dysphagia. Therefore, this software could provide the researchers in the field of dysphagia with a convenient, useful, and all-in-one platform for analyzing the hyoid bone motion. Further development of our method to track the other swallowing related structures or objects such as epiglottis and bolus and to carry out the 2D curve registration may be needed for a more comprehensive functional data analysis for dysphagia with big data.

Computer-assisted assessment of hyoid bone motion from videofluoroscopic swallow studies

Videofluoroscopic examination of swallowing remains the standard for evaluation of patients with swallowing complaints. Although attempts have been made to objectify aspects of the study, findings from the study are largely subjective and reliant on clinician training and judgment leading to considerable inter-rater variability. We describe a computerized image analysis program designed to objectify one component of the swallow study, the movement of the hyoid bone. Hyoid motion has been shown to be different in dysphagic versus non-dysphagic patients. Reduced hyoid elevation is also considered a risk factor for aspiration; however, there has not been much work done on actually quantifying hyoid motion and associating it with other aspects of the swallow study. The clinician is prompted to define the hyoid bone in a calibration frame, and the system then tracks that region of interest throughout the rest of the study. This system shows strong correlations with manual analysis and can account for head position changes during the study. While the hyoid bone was reported on in this study, other regions of interest within the image field could also be tracked using this technique. A more quantitative analysis such as this has the opportunity to improve the inter-rater reliability of the test and therefore lead to more consistent findings from swallow studies.

Internal kinematics of the tongue in relation to muscle activity and jaw movement in the pig

To explore the coordinative characteristics of tongue deformation, muscle activity and jaw movement during feeding, six ultrasonic crystals were implanted into the tongue body of ten 12-week-old Yucatan minipigs 1 week before the recording. These crystals formed a wedge-shaped configuration to allow recording dimensional changes in lengths, anterior and posterior widths and posterior thicknesses of the tongue body during feeding. Wire electromyographic activities (EMG) of superior and inferior longitudinalis, verticalis/transversus, genioglossus, styloglossus, masseter and digastricus and jaw movements were recorded simultaneously. Signals from these three sources were synchronized for real-time analyses. The results indicate: (i) dimensional changes were stereotypical in relation to each cycle of all three feeding behaviours; (ii) during chewing, expansion of tongue widths mainly occurred in the occlusal phase of jaw movement and was less coupled with the activity of tongue muscles, but the expansions of length and thickness were seen in the opening and closing phases and were better coupled with the activity of tongue muscles (P < 0.05); (iii) ingestion was characterized by the two-phased jaw opening, early expansion of anterior width prior to the occlusal phase and strong associations between tongue deformation and muscle activity; (iv) during drinking, the duration of the opening and closing phases was significantly prolonged (P < 0.01), the durations of tongue widening and lengthening were significantly shortened (P < 0.05) and anterior widening was predominant in the opening rather than in the closing or occlusal phases as compared with chewing and ingestion; and (v) the intrinsic tongue muscles did not show more or stronger correlations with the tongue deformation than did the extrinsic tongue muscles. These results suggest that (i) regional widening, lengthening and thickening of the tongue body occurs sequentially in relation to jaw movement phases, but the initiation of tongue dimensional expansions does not correspond with the activation of tongue muscles simultaneously; (ii) there is a better coupling between tongue deformations and tongue muscle activations in the sagittal (lengthening and thickening) than the transverse (widening) planes; and (iii) the patterns and ranges of tongue deformation and their relations to muscle activity and jaw movement are task-specific and the expansion magnitudes of tongue deformation does not have closer correlations with the amount of EMG activity in the intrinsic than the extrinsic tongue or jaw muscles.

Regional volumetric change of the tongue during mastication in pigs

Structure and movement of the tongue have been studied extensively, but little study has been carried on its 3D deformation and ensuing volumetric changes during various functions. The purpose of this study is to investigate the volumetric changes of a regional section of the tongue during feeding. Four 12-week-old Yucatan miniature pigs were used. During natural mastication and water drinking, the width, length, thickness and volumetric changes were measured using six implanted ultrasonic crystals, which circumscribed a wedge-shaped volume in the region of the tongue body. Jaw movements were videotaped and digitized. Signals from these two sources were synchronized to allow real-time analyses. Significant volumetric changes (P < 0.001) were found in chewing, ingestion and drinking, and these changes were stereotypical in relation to rhythmic jaw movements. Volumetric change during chewing was not only more regular, but significantly larger (45.6%, P < 0.001) than that during ingestion (31.4%). The volumetric changes were less regular in drinking and the changing range (30.4%) was close to that during ingestion. Real-time analysis indicated that the volume began increasing at late jaw closing and reached the peak at late power stroke. The increase in duration of volume only took up 33.4% of the total chewing cycle length; significantly shorter than that of volume decrease. Correlation analysis revealed that the change in posterior dorsal and ventral widths had the greatest positive association with volumetric change (r = 0.43) in direction. The covariance calculations further indicated that dimensional changes in length and thickness coupled negatively with volumetric changes in amplitude. These results revealed that regional volumetric change of the tongue occurs during feeding and chewing requires larger volumetric changes than do ingestion and drinking. Volumetric expansion occurs in the phase of power stroke during chewing and is coupled with increases in widths in the direction and with decreases of thickness and length in the amplitude. The results further suggested that the regional volumetric expansion may play the determinant role in functional load production on its surrounding tissues, and may also imply that neuromuscular control of the tongue is region-specific, a notion incompatible with traditional scheme of categorizing muscle function in the tongue.