Biomechanical Effects of Plastic Heel Cup on Plantar Fasciitis Patients Evaluated by Ultrasound Shear Wave Elastography.

The plastic heel cup has been adopted to treat plantar heel problems for years. However, its mechanisms and biomechanical effects are yet to be fully understood. The purpose of this study was to investigate the effects of the plastic heel cup on the microchamber and macrochamber layers of the heel pad by comparing the stiffness (in terms of the shear wave speed) and thickness of these two layers with and without a plastic heel cup during static standing. Fifteen patients with unilateral plantar fasciitis were recruited. The shear wave speed and thickness of the microchamber and microchamber layers of each symptomatic heel pad during standing measured by ultrasound shear wave elastography were compared between conditions with and without a plastic heel cup. It was found that a plastic heel cup reduced the shear wave speed of the microchamber layer to 55.5% and increased its thickness to 137.5% compared with the condition without a plastic heel cup. For the microchamber layer, the shear wave speed was reduced to 89.7%, and thickness was increased to 113.6% compared with the condition without a plastic heel cup. The findings demonstrate that a plastic heel cup can help to reduce the stiffness and increase the thickness for both layers of the heel pad during standing, suggesting that the mechanism of a plastic heel cup, and its resulting biomechanical effect, is to reduce the internal stress of the heel pad by increasing its thickness through confinement.

Noise Induced Hearing Loss and Tinnitus-New Research Developments and Remaining Gaps in Disease Assessment, Treatment, and Prevention.

Long-term noise exposure often results in noise induced hearing loss (NIHL). Tinnitus, the generation of phantom sounds, can also result from noise exposure, although understanding of its underlying mechanisms are limited. Recent studies, however, are shedding light on the neural processes involved in NIHL and tinnitus, leading to potential new and innovative treatments. This review focuses on the assessment of NIHL, available treatments, and development of new pharmacologic and non-pharmacologic treatments based on recent studies of central auditory plasticity and adaptive changes in hearing. We discuss the mechanisms and maladaptive plasticity of NIHL, neuronal aspects of tinnitus triggers, and mechanisms such as tinnitus-associated neural changes at the cochlear nucleus underlying the generation of tinnitus after noise-induced deafferentation. We include observations from recent studies, including our own studies on associated risks and emerging treatments for tinnitus. Increasing knowledge of neural plasticity and adaptive changes in the central auditory system suggest that NIHL is preventable and transient abnormalities may be reversable, although ongoing research in assessment and early detection of hearing difficulties is still urgently needed. Since no treatment can yet reverse noise-related damage completely, preventative strategies and increased awareness of hearing health are essential.

Asymmetric Thickness of Oblique Capitis Inferior and Cervical Kinesthesia in Patients With Unilateral Cervicogenic Headache.

OBJECTIVE: The purpose of this study was to compare the thickness of the oblique cervical inferior (OCI) and the error of the head reposition test between the painful and nonpainful sides of patients with cervicogenic headache (CeH) and between the patients and the asymptomatic group. METHODS: Thirteen patients (24.5 ± 4.8 years) and 14 asymptomatic participants (23.9 ± 2.7 years) were included. The head reposition test was recorded by a 3-dimensional motion analysis system. The thickness of the OCI was recorded by ultrasonography. The measured outcomes were compared between the painful and nonpainful sides and with the asymptomatic participants. RESULTS: The thickness of the OCI in the rest condition on the painful side (9.92 ± 2.31 mm) was smaller than that of the nonpainful side (10.56 ± 2.24 mm). The constant error of the head-to-target test toward the nonpainful side was smaller in the patients with CeH (-1.6 ± 4.3°) than in the asymptomatic group (3.3 ± 3.7°, P = 0.005). CONCLUSION: Asymmetric OCI and cervical proprioception were demonstrated in patients with CeH.

Spatial-dependent mechanical properties of the heel pad by shear wave elastography.

The heel pad plays an important role in gait, and its biomechanical behavior and functionality are determined by its specialized architecture and mechanical properties. The purpose of this study was to apply supersonic shear wave elastography, an ultrasound-based noninvasive modality that can quantitatively estimate the shear stiffness of the tissue, to investigate the spatial-dependent mechanical properties of the heel pad. Measurements were conducted in 40 heel pads of 20 normal participants aged between 20 and 30 years by shear wave elastography. The continuous change in local shear stiffness of the heel pad along the depth direction of the heel pad was measured. The result showed that the mechanical properties of the heel pad were highly heterogeneous but followed a simple and specific pattern that local heel pad shear stiffness was highest beneath the plantar skin and decreased continuously with increasing depth. This finding provides a better understanding of the heel pad biomechanics and basis for further investigation of the heterogeneous properties of the heel pad.

Mechanical deformation of posterior thoracolumbar fascia after myofascial release in healthy men: A study of dynamic ultrasound imaging.

BACKGROUND: Myofascial release (MR) on the posterior thoracolumbar fascia (PLF) is one of the manual techniques aim to restore the normal length and tension of restricted fasciae and muscles. OBJECTIVES: The present study aimed to quantify the immediate effects of MR on fascial properties of the PLF in healthy men. DESIGN: Cross-sectional study. METHOD: Participants (N = 10, aged 22.8 ± 2.0 years) performed a press-down to maximal voluntary contraction (MVC) in the prone position. Deformation of the PLF was measured using an ultrasonographic apparatus. Force output was simultaneously measured. The stiffness index and hysteresis index were then represented by the slope of the loading curve, and the percentage of the area within the loading-unloading curve. One-way ANCOVA was used to compare differences in the stiffness index or hysteresis index of the PLF before and after MR. Two-way repeated ANOVA was used to compare deformation of the PLF or force output after MR. RESULTS: The primary findings included a decrease (before: 24.1 ± 8.3 vs. after: 18.9 ± 5.3 N/mm; mean difference, -5.2 ± 4.9 N/mm, p = 0.002 < 0.05) in the stiffness index of the PLF and a greater difference in deformation of the PLF between 50% and 100% MVC (before: Def50% = 6.5 ± 1.8 mm and Def100% = 9.8 ± 1.9 mm vs. after: Def50% = 6.4 ± 2.5 mm and Def100% = 10.2 ± 2.4 mm; p = 0.037 < 0.05, power = 58.5%). CONCLUSION: After MR, stiffness of the PLF decreased in healthy men.

An Artifact in Supersonic Shear Wave Elastography.

Supersonic shear wave elastography is a novel ultrasound technology that allows objective evaluation of soft tissue stiffness. The purpose of this study is to report an artifact in supersonic shear wave elastography that may strongly affect the accuracy and quality of the measurement of soft tissue stiffness, and to step-by-step describe how the artifact was found and how it was verified by a series of experiments under different conditions. There were a total of three longitudinal band-like artifacts, 1.3 cm apart from each other on the entire image along the length of the SuperLinear SL15-4 transducer surface, with the middle one at the center of the image. When using supersonic shear wave elastography, users should be keenly aware of the possible occurrence of the artifact and avoid it by choosing the quantification measurement regions of interest (ROIs) away from the artifact regions.

Increased sliding of transverse abdominis during contraction after myofascial release in patients with chronic low back pain.

PURPOSE: Recent evidence suggested the significance of integrity of the tension balance of the muscle-fascia corset system in spinal stability, particularly the posterior musculofascial junction which is adjacent to dorsal located paraspinal muscles joining each other at lateral raphe (LR). The purpose of this study was to compare the contraction of the transversus abdominis (TrA) at both anterior and posterior musculofascial muscle-fascia junctions in patients with low back pain (LBP) and asymptomatic participants before and immediately after a sustained manual pressure to LR. METHODS: The present observational cohort study used a single-instance, test-retest design. The outcome variables included the resting thickness (Tr), the thickness during contraction (Tc), change in thickness (ΔT), sliding of musculofascial junction (ΔX), muscle length at rest (L) and displacement pattern (ΔD) of the TrA using ultrasonography. Vertical tolerable pressure at the LR was applied manual for 1 min. Tr, Tc, ΔT, and ΔX were analyzed by three-way ANOVA (musculofascial junction sites*group* pre-post manual release). ΔL and ΔD were analyzed by two-way ANOVA (group* pre-post manual release). RESULTS: Participants with LBP revealed less Tc, ΔT and ΔX at both sites (p < 0.005). After myofascial release, LBP group demonstrated a positive ΔD of the musculofascial junctions at both end (p < 0.001). Nevertheless, both groups increased the ΔT and ΔX at both sites (p < 0.001 and 0.001, respectively). CONCLUSION: The result indicated immediately effect of sustained manual pressure on musculofascial junction of TrA and supported the concept that the possible imbalanced tension of the myofascia corset of TrA in patients with LBP.

Modeling and Analysis of the Viscoelastic Response of the Ankle Ligament Complex in Inversion Ankle Sprain.

Since inversion ankle sprain (IAS) damages ankle ligaments and induces changes in their viscoelastic properties, evaluating these properties may provide an approach to assess injury. The study purposes were to investigate how the viscoelastic properties of the ankle ligament complex can be used to quantitatively assess IAS, and to investigate the usefulness of the stretched exponential function to analyze the relaxation behavior of the ankle ligament complex. Fifteen participants with unilateral IAS and 15 controls were included. The relaxation behavior of each ankle was measured by an instrumented anterior drawer test, and was then curvefitted by the stretched exponential function. By a modeling approach, both parameters of the function were found to be associated with the viscous response. Statistical analysis was performed to determine differences in these two parameters between sprained and uninjured ankles. It was found that sprained ankles exhibited significantly lower viscous response than uninjured ankles. No significant difference was found among uninjured ankles. In conclusion, by using the viscoelastic properties, sprained ankles were successfully differentiated from uninjured ankles. In clinical application, this method could be a diagnostic tool for quantitative assessment of IAS injury. The stretched exponential function was a useful model to analyze the relaxation behavior.

Relationship between viscosity of the ankle joint complex and functional ankle instability for inversion ankle sprain patients.

OBJECTIVES: Measurement of viscosity of the ankle joint complex is a novel method to assess mechanical ankle instability. In order to further investigate the clinical significance of the method, this study intended to investigate the relationship between ankle viscosity and severity of functional ankle instability. DESIGN: Cross-sectional study. METHODS: 15 participants with unilateral inversion ankle sprain and 15 controls were recruited. Their ankles were further classified into stable and unstable ankles. Ankle viscosity was measured by an instrumental anterior drawer test. Severity of functional ankle instability was measured by the Cumberland Ankle Instability Tool. Unstable ankles were compared with stable ankles. Injured ankles were compared with uninjured ankles of both groups. The spearman's rank correlation coefficient was applied to determine the relationship between ankle viscosity and severity of functional ankle instability in unstable ankles. RESULTS: There was a moderate relationship between ankle viscosity and severity of functional ankle instability (r=-0.64, p<0.0001). Unstable ankles exhibited significantly lower viscosity (p<0.005) and more severe functional ankle instability (p<0.0001) than stable ankles. Injured ankles exhibited significantly lower viscosity and more severe functional ankle instability than uninjured ankles (p<0.0001). CONCLUSIONS: There was a moderate relationship between ankle viscosity and severity of functional ankle instability. This finding suggested that, severity of functional ankle instability may be partially attributed to mechanical insufficiencies such as the degenerative changes in ankle viscosity following the inversion ankle sprain. In clinical application, measurement of ankle viscosity could be a useful tool to evaluate severity of chronic ankle instability.

Quantitative evaluation of the viscoelastic properties of the ankle joint complex in patients suffering from ankle sprain by the anterior drawer test.

PURPOSE: Biological tissues such as ligaments exhibit viscoelastic behaviours. Injury to the ligament may induce changes of these viscoelastic properties, and these changes could serve as biomarkers to detect the injury. In the present study, a novel instrument was developed to non-invasive quantify the viscoelastic properties of the ankle in vivo by the anterior drawer test. The purpose of the study was to investigate the reliability of the instrument and to compare the viscoelastic properties of the ankle between patients suffering from ankle sprain and controls. METHODS: Eight patients and eight controls participated in the present study. The reliability test was performed on three randomly chosen subjects. In patient and control test, both ankles of each subject were tested to evaluate the viscoelastic properties of the ankle. The viscosity index was defined for quantitatively evaluating the viscosity of the ankle. Greater viscosity index was associated with lower viscosity. Injured and uninjured ankles of patient and both ankles of controls were compared. RESULTS: The instrument exhibited excellent test-retest reliability (r > 0.9). Injured ankles exhibited significantly less viscosity than uninjured ankles, since injured ankles of patients had significantly higher viscosity index (8,148 ± 5,266) compared with uninjured ankles of patients (948 ± 617; p = 0.008) and controls (1,326 ± 613; p < 0.001). CONCLUSIONS: The study revealed that the viscoelastic properties of the ankle can serve as sensitive and useful clinical biomarkers to differentiate between injured and uninjured ankles. The method may provide a clinical examination for objectively evaluating lateral ankle ligament injuries.

Quantification of skeletal muscle fibrosis at different healing stages using sonography: a morphologic and histologic study in an animal model.

OBJECTIVES: This study attempted to quantify the degree of muscle fibrosis on sonograms of injured gastrocnemius muscles at different healing stages in a rat model. Correlations between the quantifications and histologic assessments of the injured muscles were also determined. METHODS: Sonograms and histologic findings of gastrocnemius muscle fibrosis were obtained during the second, third, and fourth weeks after surgically induced lesions in the right gastrocnemius muscles of 15 Wistar rats. The echo intensity, reflecting the degree of brightness on a sonogram, was divided into 256 gray levels instead of decibels. The mean echo intensity of each pixel in the region of interest was calculated as a summation of the echo intensities in all pixels divided by the pixel numbers in the region. To control individual variations among the rats, we calculated a K value, defined as the difference in the mean echo intensity between normal and affected muscles. RESULTS: Significant correlations (r > 0.7; P < .05) between mean echo intensity and K values and the fibrous tissue percentage were identified. The mean echo intensity in the injured gastrocnemius muscles was significantly (P = .029) greater than that in the normal muscles 3 weeks after injury. In histologic assessments, muscle fibrosis was most prominent 3 weeks after injury. However, the differences in fibrosis at different healing stages were not significant. CONCLUSIONS: Mean echo intensity and K values can reflect the extent of fibrosis in affected muscles and may be valuable for quantifying muscle fibrosis in clinical practice.

Bilateral upper limb trainer with virtual reality for post-stroke rehabilitation: case series report.

PURPOSE: Stroke is a leading cause of disability with many survivors having upper limb (UL) hemiparesis. UL rehabilitation using bilateral exercise enhances outcomes and the Bilateral Upper Limb Trainer (BUiLT) was developed to provide symmetrical, bilateral arm exercise in a 'forced' and self-assistive manner, incorporating virtual reality (VR) to provide direction and task specificity to users as well as action observation-execution and greater motivation to exercise. METHODS: The BUiLT + VR system was trialled on five post-stroke participants with UL hemiparesis: one sub-acute and four chronic. The intervention was supplied for 45 min, 4 days/week for 6 weeks. The Fugl-Meyer Upper Extremity score (FMA-UE) was used as the primary outcome measure. Secondary outcome measures used were UL isometric strength and the Intrinsic Motivation Inventory (IMI) questionnaire. RESULTS: The BUiLT + VR therapy increased FMA-UE scores from 1 to 5 and overall strength in the shoulder and elbow. Motivation at the end of intervention was positive. CONCLUSIONS: Therapy using the BUiLT + VR system is reliable, can be administered safely and has a positive trend of benefit as measured by the FMA-UE, isometric strength testing and IMI questionnaire.

Reliability and relationship between 2 measurements of transversus abdominis dimension taken during an abdominal drawing-in maneuver using a novel approach of ultrasound imaging.

STUDY DESIGN: Reliability study of clinical measurement. OBJECTIVES: The primary purpose was to develop a reliable method for measuring muscle length changes of the transversus abdominis (TrA) during contraction. The secondary purpose was to investigate the relationship between changes in thickness and length (as indicated by the lateral sliding of the anterior muscle-fascia junction) of the TrA muscle during an abdominal drawing-in maneuver. We also provide data on between-day reliability of change in thickness (ΔT) of the TrA. BACKGROUND: Ultrasound imaging measurements of TrA thickness at rest (Thr) and during maximal contraction (Thm) have been shown to be reliable. However, limited data exist on quantifying changes in TrA length (as indicated by the lateral sliding of the muscle-fascia junction [Δx]) and ΔT during contraction. METHODS: Eighteen healthy adults (mean ± SD age, 22.6 ± 2.5 years) participated in this study. Brightness mode ultrasound images of the TrA were collected at rest and during an abdominal drawing-in maneuver. Subjects were examined by the same examiner twice within a 48-hour period. ΔT, ΔT/Thr, Thr, Thm, and Δx of the TrA were calculated. Medial-lateral movement of the transducer during measurement was corrected through a custom-written program that used an internal marker created by an echo-absorptive thread attached to the skin. Intraclass correlation coefficients (ICC3,1), within-subject coefficient of variance, and standard error of measurement were calculated. The relationship between ΔT and adjusted Δx of the TrA muscle was investigated. RESULTS: The ICC values for Thr, Thm, and ΔT of the TrA muscle were greater than 0.75, with the exception of the left ΔT (0.62) and left ΔT/Thr (0.49). After adjusting for medial-lateral motion of the transducer, the ICC values of adjusted Δx were above 0.75, and the within-subject coefficient of variance was below 10%. There was no significant correlation between ΔT and adjusted Δx of the TrA. CONCLUSION: Ultrasound imaging measurements of TrA thickness and length change were shown to be reliable using a novel method to control for medial-lateral transducer motion. Measuring different but unrelated dimensional changes in the TrA might provide further insight as to the function of the TrA.

Effects of surgery on the phonation threshold pressure in patients with vocal fold polyps.

BACKGROUND/PURPOSE: There are few objective measurements to assess the results of surgery for vocal fold polyps. This study investigated the effects of surgery on the phonation threshold pressure (PTP) in patients with vocal fold polyps. METHODS: Prospectively, 32 consecutive patients with vocal fold polyps were enrolled. PTP was measured 1 day before and 6 weeks after laryngomicrosurgery, by means of an airflow interruption method. An accelerometer was used to detect the vocal fold vibration instead of using an acoustic signal. RESULTS: In all 32 patients, the average preoperative PTP was 0.51 +/- 0.23 kPa, and 6 weeks after surgery, it was 0.28 +/- 0.17 kPa; this difference was statistically significant (p < 0.001). Individually, PTP decreased in 31 patients after surgery. PTP increased after surgery in only one patient, from 0.74 to 0.75 kPa. Subjectively, all patients could phonate with less effort after surgery. Use of an accelerometer to sense vocal fold vibration was feasible and made it easier to identify the time point of cessation of vocal fold vibration, which is important for PTP measurement. CONCLUSION: Laryngomicrosurgery can lower PTP in patients with vocal fold polyps and improve the ease of phonation. PTP is one of the objective measurements for assessing the effects of surgery in patients with vocal fold polyps. Use of an accelerometer to detect vocal fold vibration improved the measurement of PTP.

Relationship between plantar pressure and soft tissue strain under metatarsal heads with different heel heights.

BACKGROUND: Metatarsalgia due to increased plantar pressure under the metatarsal head (MTH) is often seen with wearing high-heeled shoes. However, the concomitant soft tissue strain has not been well discussed. The objective of our study was to explore the standing plantar pressure and corresponding soft tissue strain under the metatarsal heads (MTHs) with different heel heights. MATERIALS AND METHODS: Twenty-one healthy subjects (10 male and 11 female) participated. The plantar pressure and soft-tissue thicknesses were measured simultaneously with a load cell and a 10-MHz linear-array ultrasound (US) transducer respectively. The changes in plantar pressure and soft tissue strain under the MTHs were analyzed for different heel heights. RESULTS: As hypothesized, plantar metatarsal pressure significantly increased and shifted to the first and second MTHs with increasing heel height from 2 cm to 4 cm (p < 0.05). However, the change in soft tissue strain under the medial forefoot became insignificant when the heel height was greater than 2 cm (p = 0.473 and 0.517). CONCLUSIONS: Increased heel height resulted in increasing medial forefoot loading pressure; however, the soft tissue exhibited stationary compressibility when the heel height was greater than 2 cm. CLINICAL RELEVANCE: Our finding provides an understanding of the biomechanical changes with wearing high-heeled shoes and suggests possible strategies to reducing discomfort and risk of injury, such as limiting heel height to no greater than 2 cm and using medial padding under MTHs.

Dynamic B-mode ultrasound imaging of vocal fold vibration during phonation.

We used B-mode imaging to study the vibratory phenomena of the vocal folds. The presence of multilayered structures of the vocal folds in the B-mode image was verified by using freshly excised human larynges in vitro. To capture images of vocal fold vibration, a special treatment was used to reconstruct the aliasing B-mode motion pictures of vocal fold vibration. Echo-particle image velocimetry (Echo-PIV) analysis was then applied to trace the tissue particles in the motion pictures. The vibratory behavior of the body (vocal ligament and muscle) of the vocal folds was revealed. Further analysis showed a quasi-longitudinal wave along the body of the vocal folds in the coronal plane. This is, to the best of our knowledge, the first time that vocal fold vibration physiology has been studied using B-mode imaging and Echo-PIV.

Diabetic effects on microchambers and macrochambers tissue properties in human heel pads.

BACKGROUND: The study attempted to highlight the differences of mechanical properties in microchambers and macrochambers between patients with type 2 diabetes mellitus and age-matched healthy volunteers. METHODS: A total of 29 heels in 18 diabetic patients and 28 heels in 16 age-matched healthy participants were examined by a loading device consisting of a 10-MHz compact linear-array ultrasound transducer, a Plexiglas cylinder, and a load cell. Subjects in both groups were on average about 55 years old with a body mass index of approximately 25 kg/m(2). A stepping motor was used to progressively load the transducer on the tested heels at a velocity of 6mm/s from zero to the maximum stress of 78 kPa. Unloaded thickness, strain, and elastic modulus in microchambers, macrochambers and heel pads were measured. FINDINGS: Microchambers strain in diabetic patients was significantly greater than that in healthy subjects (0.291 (SD 0.14) vs. 0.104 (SD 0.057); P<0.001). Macrochambers strain in diabetic patients was significantly less than that in healthy subjects (0.355 (SD 0.098) vs. 0.450 (SD 0.092); P=0.001). Microchambers stiffness in diabetic patients was significantly less than that in healthy persons (393 (SD 371)kPa vs. 1140 (SD 931)kPa; P<0.001). Macrochambers stiffness in diabetic patients was significantly greater than that in healthy persons (239 (SD 77)kPa vs. 181 (SD 42)kPa; P=0.001). INTERPRETATION: Heel pad tissue properties are altered heterogeneously in people with diabetes. Increased macrochambers but decreased microchambers stiffness may cause diminished cushioning capacities in diabetic heels.

Renal vascular perfusion index in a canine model.

Decreased renal perfusion plays an important role in the progression toward renal failure. In this study, a novel measure was proposed to quantify renal perfusion using canine model. Serial renal vascular images at different vascular areas including the whole vascular tree, interlobar, arcuate and interlobular vessels were captured. Image processing software was designed to analyze the changes of power Doppler intensity of colored pixels within regions-of-interest (ROI). For a given ROI, the power Doppler vascular index (PDVI) was found to fluctuate with the cardiac cycle. It was also noted that the power Doppler signals generated by arterial vessels have different fluctuating waveforms and different phase compared with the signal derived from venous vessels. A power Doppler correlation-map was developed to differentiate the arteries and veins in the ROI. Using the serial power Doppler images and the derived flow direction information, the interlobular perfusion can be strongly quantified. The renal vascular perfusion index (RVPI) defined as the ratio of PDVI(max) versus PDVI(min) was significantly higher in the interlobular vessel areas than three other areas for seven healthy dogs. The RVPI resembles the systolic/diastolic (S/D) ratio that commonly reflects arterial hemodynamics. RVPI and power Doppler correlation-map reveal more "dynamic" sense of vascular perfusion and provide a novel approach for the examination of renal function in clinical practice.

Measurement of cervical multifidus contraction pattern with ultrasound imaging.

Deep muscle training has become the focus of research and exercise for patients with chronic neck pain. The objective of this in vivo study was to establish a non-invasive assessment tool for the activation of deep cervical muscles. The pattern of the change in the thickness of the cervical multifidus is described with a mathematical equation and used to compare the changes among different levels of resistance (0%, 25%, 50%, 75%, and 100%) and at different cervical levels (fourth, fifth, and sixth cervical (C4, C5, and C6) vertebrae). Twenty asymptomatic subjects (five women and 15 men; 24.3+/-4.7 years old) were recruited for this experiment. Ultrasonography (US) with synchronized force recording was used to measure the thickness of the cervical multifidus during progressive isometric extension against resistance. Linear and quadratic models were used to estimate the patterns of change in the thickness of cervical multifidus in relation to force. Two-way analysis of variance with repeated measurement and post hoc analysis were used to investigate the differences in thickness. The change in thickness and force was better fitted by quadratic model (y=ax(2)+bx+c) than by the linear model. The thickness at 50% of maximum contraction was significantly increased compared with that at 25% of maximum contraction. This quantitative non-invasive measurement may provide an assessment tool for further investigation for the physiological function of the deep muscles. Further research is required to investigate whether the change of thickness was predominately determined by the recruitment of muscle fibers or the extensibility of non-contractile tissues.

Laryngeal mechanisms during human 4-kHz vocalization studied with CT, videostroboscopy, and color Doppler imaging.

The objective of this study was to investigate the underlying laryngeal mechanisms during the specific human 4-kHz vocalization. The laryngeal configuration during this vocalization was measured using high-resolution computerized tomographic scan and videostrobolaryngoscopy. The color Doppler imaging (CDI) of medical ultrasound was used to detect the vibrations of glottal and supraglottal mucosa. During the 4-kHz vocalization, the ventricular folds were adducted in the shape of a bimodal chink and the vocal folds were shaped as a "V" with an opening at the posterior glottis. In the coronal view, the laryngeal ventricles had collapsed and a divergent shaped conduit was observed at the posterior portion of the larynx. The surface mucosa vibration detected by CDI was noted over the bilateral ventricular folds and aryepiglottic folds. The vibration displacement was estimated to be on the order of 0.1mm. This vibration amplitude was too small to be detected in videostrobolaryngoscopy. The laryngeal configuration and CDI data suggested a diffuser jet with periodic vorticity bursts in the larynx producing 4 kHz voice.