Tissue Vibration Research Articles

A Comparison of Sung and Spoken Phonation Onset Gestures Using High-Speed Digital Imaging

Phonation onset is important in the maintenance of healthy vocal production for speech and singing. The purpose of this preliminary study was to examine differences in vocal fold vibratory behavior between sung and spoken phonation onset gestures. Given the greater degree of precision required for the abrupt onset sung gestures, we hypothesize that differences exist in the timing and coordination of the vocal fold adductory gesture with the onset of vocal fold vibration. Staccato and German (a modified glottal plosive, so named for its occurrence in German classical singing) onset gestures were compared with breathy, normal, and hard onset gestures, using high-speed digital imaging. Samples were obtained from two subjects with no history of voice disorders (a female trained singer and a male nonsinger). Simultaneous capture of acoustical data confirmed the distinction among gestures. Image data were compared for glottal area configurations, degree of adductory positioning, number of small-amplitude prephonatory oscillations (PPOs), and timing of onset gesture events, the latter marked by maximum vocal fold abduction, maximum adduction, beginning of PPOs, and beginning of steady-state oscillation. Results reveal closer adductory positioning of the vocal folds for the staccato and German gestures. The data also suggest a direct relationship between the degree of adductory positioning and the number of PPOs. Results for the timing of onset gesture events suggest a relationship between discrete adductory positioning and more evenly spaced PPOs. By contrast, the overlapping of prephonatory adductory positioning with vibration onset revealed more unevenly spaced PPOs. This may support an existing hypothesis that less well-defined boundaries interfere with normal modes of vibration of the vocal fold tissue.

Tissue vibration in prolonged running

The impact force in heel–toe running initiates vibrations of soft-tissue compartments of the leg that are heavily dampened by muscle activity. This study investigated if the damping and frequency of these soft-tissue vibrations are affected by fatigue, which was categorized by the time into an exhaustive exercise. The hypotheses were tested that (H1) the vibration intensity of the triceps surae increases with increasing fatigue and (H2) the vibration frequency of the triceps surae decreases with increasing fatigue. Tissue vibrations of the triceps surae were measured with tri-axial accelerometers in 10 subjects during a run towards exhaustion. The frequency content was quantified with power spectra and wavelet analysis. Maxima of local vibration intensities were compared between the non-fatigued and fatigued states of all subjects. In axial (i.e. parallel to the tibia) and medio-lateral direction, most local maxima increased with fatigue (supporting the first hypothesis). In anterior–posterior direction no systematic changes were found. Vibration frequency was minimally affected by fatigue and frequency changes did not occur systematically, which requires the rejection of the second hypothesis. Relative to heel-strike, the maximum vibration intensity occurred significantly later in the fatigued condition in all three directions. With fatigue, the soft tissue of the triceps surae oscillated for an extended duration at increased vibration magnitudes, possibly due to the effects of fatigue on type II muscle fibers. Thus, the protective mechanism of muscle tuning seems to be reduced in a fatigued muscle and the risk of potential harm to the tissue may increase.

Quantification of Soft-Tissue Vibrations in Running: Accelerometry versus High-Speed Motion Capture

Soft-tissue vibrations can be used to quantify selected properties of human tissue and their response to impact. Vibrations are typically quantified using high-speed motion capture or accelerometry. The aim of this study was to compare the amplitude and frequency of soft-tissue vibrations during running when quantified by highspeed motion capture and accelerometry simultaneously. This study showed: (a) The estimated measurement errors for amplitude and frequency were of the same order of magnitude for both techniques. (b) There were no significant differences in the mean peak frequencies and peak amplitudes measured by the two methods. (c) The video method showed an inability to capture high frequency information. This study has shown that a tradeoff has to be made between the accuracy in amplitude and frequency when these methods are employed to quantify soft tissue vibrations in running.

Cyclic motion encoding for enhanced MR visualization of slip interfaces

To develop and test a magnetic resonance imaging-based method for assessing the mechanical shear connectivity across tissue interfaces with phantom experiments and in vivo feasibility studies. External vibrations were applied to phantoms and tissue and the differential motion on either side of interfaces within the media was mapped onto the phase of the MR images using cyclic motion encoding gradients. The phase variations within the voxels of functional slip interfaces reduced the net magnitude signal in those regions, thus enhancing their visualization. A simple two-compartment model was developed to relate this signal loss to the intravoxel phase variations. In vivo studies of the abdomen and forearm were performed to visualize slip interfaces in healthy volunteers. The phantom experiments demonstrated that the proposed technique can assess the functionality of shear slip interfaces and they provided experimental validation for the theoretical model developed. Studies of the abdomen showed that the slip interface between the small bowel and the peritoneal wall can be visualized. In the forearm, this technique was able to depict the slip interfaces between the functional compartments of the extrinsic forearm muscles. Functional shear slip interfaces can be visualized sensitively using cyclic motion encoding of externally applied tissue vibrations.

Liquid Accumulation in Vibrating Vocal Fold Tissue: A Simplified Model Based on a Fluid-Saturated Porous Solid Theory

The human vocal fold is treated as a continuous, transversally isotropic, porous solid saturated with liquid. A set of mathematical equations, based on the theory of fluid-saturated porous solids, is developed to formulate the vibration of the vocal fold tissue. As the fluid-saturated porous tissue model degenerates to the continuous elastic tissue model when the relative movement of liquid in the porous tissue is ignored, it can be considered a more general description of vocal fold tissue than the continuous, elastic model. Using the fluid-saturated porous tissue model, the vibration of a bunch of one-dimensional fibers in the vocal fold is analytically solved based on the small-amplitude assumption. It is found that the vibration of the tissue will lead to the accumulation of excess liquid in the midmembranous vocal fold. The degree of liquid accumulation is positively proportional to the vibratory amplitude and frequency. The correspondence between the liquid distribution predicted by the porous tissue theory and the location of vocal nodules observed in clinical practice, provides theoretical evidence for the liquid accumulation hypothesis of vocal nodule formation (Jiang, Ph.D., dissertation, 1991, University of Iowa).

Doppler Vibrometry: Assessment of Arterial Stenosis by Using Perivascular Tissue Vibrations without Lumen Visualization

To correlate vibration frequency and duration at Doppler vibrometry with stenosis severity determined at catheter angiography. Sixteen patients (eight women) scheduled to undergo abdominal or pelvic angiography were recruited after providing informed consent. An ultrasonography (US) scanner was customized to acquire raw echo data before conventional Doppler processing. Data were acquired from perivascular tissue regions proximal to stenoses, close to the most narrow lumen, and distal to stenoses in the renal, hepatic, common iliac, and superior mesenteric arteries. The data were processed to quantify vibration frequency and duration. The minimum lumen diameter and the pre- and poststenotic lumen diameters were quantified from angiograms. One patient with a hepatic artery stenosis did not yield measurable vibrometry data due to significant bowel gas. Stenoses (diameter reduction, 43%-91%) were angiographically measured in the six renal arteries, four hepatic arteries, three iliac arteries, and one superior mesenteric artery yielding vibrometry data. Three iliac arteries were normal (<30% diameter reduction at angiography). For these 17 arteries, the vibration frequency was higher with a greater percentage of stenosis [Pearson r = .75; P < .001) and a smaller minimum lumen diameter (r = .72; P < .001). The vibration duration increased with a greater percentage of stenosis (r = .7; P < .001). Preliminary results indicate that the vibration frequency and duration can be used to quantitatively estimate stenosis severity. Doppler vibrometry is complementary to duplex US and does not require lumen visualization.

Capillary Supply of the Soft Palate Muscles Is Reduced in Long-Term Habitual Snorers

Background: Snoring and obstructive sleep apnea (OSA) cause vibration and stretch of the upper airway tissues that may result in neuromuscular damage and changes in the microcirculation. Objectives: The aim of this investigation was to test whether long-term snoring affects capillary supply in soft palate muscles. Methods: Samples from the palatopharyngeus (PP) and uvula (UV) muscles were collected from 8 patients undergoing uvulo-palatopharyngoplasty because of habitual snoring and OSA. Control samples were obtained at autopsy. The muscles were analyzed using immunohistochemistry and morphometry. Results: The patients’ palate muscles had a lower capillary density (PP 443 vs. 711 capillaries/mm², p < 0.001, and UV 452 vs. 624 capillaries/mm², p = 0.009), a lower number of capillaries related to an individual muscle fiber (PP 1.3 vs. 2.7, p = 0.003, and UV 1.0 vs. 1.9, p = 0.03) and a lower number of capillaries related to the fiber size (PP 0.9 vs. 2.1, p = 0.001, and UV 0.6 vs. 1.9, p = 0.002). Conclusions: Our results indicate that reduced capillary supply of palate muscles plays a pathophysiological role in long-term snorers and OSA. The cause of the low capillary supply is unclear, but neuromuscular injury due to repeated vibratory and stretch trauma of the soft palate during snoring is a plausible mechanism.

Real‐time sonoelastography of hepatic thermal lesions in a swine model

Sonoelastography has been developed as an ultrasound-based elasticity imaging technique. In this technique, external vibration is induced into the target tissue. In general, tissue stiffness is inversely proportional to the amplitude of tissue vibration. Imaging tissue vibration will provide the elasticity distribution in the target region. This study investigated the feasibility of using real-time sonoelastography to detect and estimate the volume of thermal lesions in porcine livers in vivo. A total of 32 thermal lesions with volumes ranging from 0.2 to 5.3 cm3 were created using radiofrequency ablation (RFA) or high-intensity focused ultrasound (HIFU) technique. Lesions were imaged using sonoelastography and coregistered B-mode ultrasound. Volumes were reconstructed from a sequence of two-dimensional scans. The comparison of sonoelastographic measurements and pathology findings showed good correlation with respect to the area of the lesions (r2 = 0.8823 for RFA lesions, r2 = 0.9543 for HIFU lesions). In addition, good correspondence was found between three-dimensional sonoelastography and gross pathology (3.6% underestimate), demonstrating the feasibility of sonoelastography for volume estimation of thermal lesions. These results support that sonoelastography outperforms conventional B-mode ultrasound and could potentially be used for assessment of thermal therapies.

S300 – Comparison of Endoscopy Diagrams for Obstructive Sleep Apnea

Objectives Most methods of waking and sedated sleep endoscopy evaluating the upper airway in obstructive sleep apnea inconsistently predict surgical results. Goals of exam have been to identify levels of obstruction or levels of tissue vibration. Examinations provide little information on airway structure. A novel method of describing airway collapse using airway structures has been developed. The objectives of this study are to compare sleep and wake examination: 1) during inspiration, and 2) expiration. Methods A retrospective review evaluated waking and sedated clinical endoscopic endoscopy. Clinical endoscopic examination was performed supine at end expiration. Sedated endoscopy used propofol anesthesia evaluated the airway during both inspiration, expiration, and with elimination of airway mechanoreceptors. Defined structural butressess included salpingo/palatopharyngeus, levator, and uvular muscle groups for the epi-pharynx and the epiglottis, lateral hypopharynx, vallecular and proximal tongue base for the hypopharynx. Structures were scored on 3 and 4 point scales with agreement indicating exact matching. Results Severity of obstruction scored higher on sedated exam than clinical exam. Structural agreement in epipharynx was 52%, 29%, and 24%, and in hypopharynx, 48%,24%, and 38%. False negative and positive assessment occurred in epipharynx (levator 30% and uvula 40%) but not in hypopharynx. Conclusions Consistent with a greater loss of muscle tone during sleep, exact agreement between wake and sleep exams was low, however, supine end expiratory exam predicted patterns of airway collapse in hypopharynx. Pattern of collapse in epipharynx is confounded by ventilation during wake.

Modulated ultrasound and multifrequency radiation force

Modulating ultrasound can create dynamic ultrasound radiation force to induce local tissue vibration. Using different types of modulating signals produces radiation force with weighted multifrequency components. Modulation signals with frequency fr produce force with components at multiples of fr. Both amplitude modulation (AM) and double sideband suppressed carrier (DSB-SC) amplitude modulation were explored. Different waveforms were investigated such as sine, square, triangle, and sawtooth for modulating continuous wave ultrasound. A 3.0 MHz transducer produced ultrasound which was measured with a needle hydrophone and used to derive and analyze the spectrum of the radiation force function. The modulated ultrasound was used to vibrate a steel sphere in a gelatin phantom, and the motion was measured using a laser vibrometer. The measured spectra were used to find the frequency response of the sphere. Different modulating signals were used to produce multifrequency radiation force. The sphere frequency response was recovered using different modulating signals. Weighted multifrequency radiation force was produced by modulating ultrasound with different signals. Application of multifrequency radiation force can be used to measure the frequency response of objects or tissue. [This work was supported in part by grants EB002167, EB002640, and CA091956 from NIH.]

35 Impact forces, soft tissue vibrations and muscle tuning

35 Impact forces, soft tissue vibrations and muscle tuning

Anatomical Vibrations That Implantable Microphones Must Overcome

The goal of this study was to measure the tissue vibration amplitude that would be associated with an implantable microphone. Totally implantable hearing devices have been desired by the hard-of-hearing community for some time. However, an implanted microphone must pick up desired acoustic signals in the presence of undesired signals, including vibration. To design an effective microphone, the level of tissue vibrations originating from anatomical sources and the implanted transducer must be understood. Using a laser Doppler vibrometer and an accelerometer, tissue vibrations were measured under the following conditions: (1) Normal control subjects during vocalization (n=4); (2) Vocalization and biological sounds measured on cranium and in soft tissue on normal subjects (n=6); (3) Transducer vibration measured on Otologics semi-implantable hearing device wearer (n=1) and human cadavers (n=4 ears). Anatomical noise vibrations are 20 to 25 dB greater in soft tissue for frequencies less than 1,000 Hz than on the cranium, whereas vibrations due to implanted transducers are 20 to 25 dB greater on the cranium than in soft tissue inferior to the mastoid. Chewing vibrations are 10 to 15 dB greater than vocalization on the mastoid. Mastoid vibration levels measured in patients are equivalent to those in cadavers. Vibration levels do not vary significantly with respect to location on the cranium next to the pinna. The greatest anatomical vibrations that an implanted microphone must overcome are because of vocalization in the soft tissue inferior to the mastoid and chewing vibrations on the mastoid. A human cadaver is an appropriate model for transducer cranial vibration studies. If the implantable microphone is placed on the cranium near the pinna, it makes little difference with regard to actual location.

Acquired Arteriovenous Fistula at an Unusual Site

Case Report A 72-year-old woman presented with right inguinal swelling 2 days after coronary angiography via a femoral artery. A thrill and bruit were felt and heard at the inguinal area. Sonography, performed with a multifrequency 5–12 MHz linear array transducer (HDI 5000, Philips Medical Systems), revealed normal common and superficial femoral vessels on grayscale, color Doppler, and duplex examinations. However, when the transducer was placed above the site of maximum bruit, an artery with a high-resistance waveform was seen (Fig. 1A) that was followed by a low-resistance waveform, leading to a turbulent high-velocity flow on spectral display and a mosaic pattern on color Doppler imaging (Fig. 1B). By tracing the vessel to its origin at the common iliac artery, it was proven to be the inferior epigastric artery. Moving forward from the origin of the inferior epigastric artery, a classical arterialized flow was seen in the draining vein (Fig. 1C). These findings suggested an AVF. In addition, perivascular soft-tissue speckling color artifact was seen surrounding the fistula. This artifact is caused by perivascular tissue vibration due to turbulent continuous blood flow between the feeding artery and the draining vein (Fig. 1D). These findings were consistent with an AVF of the inferior epigastric vessels. The patient was discharged, and the fistula closed spontaneously.

Harmonic motion detection in a vibrating scattering medium

Dynamic ultrasound radiation force can induce local tissue vibration. To understand the tissue response, we developed a method to ultrasonically measure the induced motion. We present a model for motion detection in a vibrating scattering medium. We developed a harmonic pulsed excitation method using tonebursts repeated at frequency fr. This excitation method creates a multifrequency force with components at harmonics of fr. We use pulse‐echo ultrasound and narrowband Kalman filtering to perform multifrequency motion detection. In an experiment, a 3.0 MHz air‐backed transducer was used to create the radiation force, and with the same transducer performed pulse‐echo motion detection at 9.0 MHz. Bovine muscle was used for radiation force excitation and motion detection. We present simulation results for a parameterized model of motion detection in a scattering medium. We show experimental measurements of vibration displacement and phase for motion with amplitude of 0.1–10 μm. Our simulation model provides a platform to optimize detection of small harmonic motion in a scattering medium. Multifrequency harmonic pulsed excitation and detection methods are presented that induce and measure very small amplitude harmonic motion.

In Vivo Determination of Hepatic Stiffness Using Steady-State Free Precession Magnetic Resonance Elastography

The objective of this study was to introduce an magnetic resonance elastography (MRE) protocol based on fractional motion encoding and planar wave acquisition for rapid measurements of in vivo human liver stiffness. Vibrations of a remote actuator membrane were fed by a rigid rod to the patient's surface beneath the right costal arch resulting in axial shear deflections of the liver. Data acquisition was performed using a balanced steady-state free precession (bSSFP) sequence incorporating oscillating gradients for motion sensitization. Tissue vibrations of frequency fv = 51 Hz were tuned by twice the sequence repetition time (1/fv = 2TR). Twenty axial images acquired by time-resolved through-plane wave encoding were used for planar elasticity reconstruction. The MRE data acquisition was achieved within 4 breathholds of 17 seconds each. The method was applied to 12 healthy volunteers and 2 patients with diffuse liver disease (fibrosis grade 3). MRE data acquisition was successful in all volunteers and patients. The elastic moduli were measured with values between 1.99 +/- 0.16 and 5.77 +/- 0.88 kPa. Follow-up studies demonstrated the reproducibility of the method and revealed a difference of 0.74 +/- 0.47 kPa (P < 0.05) between the hepatic stiffness of 2 healthy male volunteers. bSSFP combined with fractional MRE enables rapid measurement of liver stiffness in vivo. The used actuation principle supports a 2-dimensional analysis of the strain wave field captured by axial wave images. The measured data indicate individual variations of hepatic stiffness in healthy volunteers.

Volumenreduktion bei Tonsillenhyperplasie im Kindesalter durch ein operatives Ultraschallsystem

We present the results of a prospective study concerning the use of a surgical-ultrasound device (use of ultrasound mechanical vibrations in the tonsil tissue with denaturizing effect on collagen and proteins for tonsil ablation, coablation) for the therapy of non-infectious tonsillar hyperplasia resulting in upper airway obstruction in childhood. 51 patients with a median age of 6.9 years (3.5-12 years) were treated with surgical ultrasound, under general anesthesia. The intervention did not include tissue excision, but the denaturation of hyperplastic tonsil tissue. Intra- and postoperative bleeding, pain (by visual analog scale), tonsil-to-tonsil diameter and swallowing difficulties were under consideration. Also an bacteriological examination of tonsils was performed. The procedure was generally well tolerated. There was no intra- or postoperative bleeding. Swallowing difficulties were described as not very disturbing. Median follow up was 2.1 years. The postoperative "wound healing" lasted 7-9 days. A reduction of tonsil's size was visible since the first post treatment week with the final results occurring after 3-6 months. Intertonsillar distance was 9 mm preoperatively and 22.14 mm after coablation. A higher incidence of bacterial tonsillitis or development of quinsies were not reported. The treatment of tonsilar hyperplasia by means of surgical ultrasound is highly effective and causes relatively mild post surgical complaints without intra- or postoperative bleeding.

Quantification of the input signal for soft tissue vibration during running

Soft tissue compartment vibrations are initiated at heel-strike in heel-toe running. The concept of muscle tuning suggests that the body tries to minimize these vibrations with a muscle adaptation that changes the mechanical properties of the soft tissue compartment. A muscle tuning adaptation can be quantified by determining the biodynamic response, of the soft tissue compartment for different experimental conditions. To determine the biodynamic response a measure of both the input signal and the soft tissue compartment vibrations are required. The input signal for the vibrations is the rapid deceleration of the leg after initial ground contact. The aim of this study was to evaluate three non-invasive methods to quantify the input signal for the triceps surae soft tissue vibrations. Data from a force platform, a shoe mounted accelerometer and a video analysis of a reflective skin marker were used to quantify leg deceleration. Both the shoe mounted accelerometer and skin marker method provided a satisfactory evaluation of the input signal and could be used to determine the biodynamic response of the soft tissue compartment. The impact portion of the ground reaction force is primarily due to the deceleration of the leg at landing. However, due to the influence of the effective body mass on the impact magnitude, the force plate data was not appropriate for quantifying a muscle tuning response.

Ultrasonic interrogation of tissue vibrations in arterial and organ injuries: Preliminary in vivo results

Soft tissues surrounding vascular injuries are known to vibrate at audible and palpable frequencies, producing bruits and thrills. We report the results of a feasibility study where Doppler ultrasound (US) was used to quantitatively estimate the tissue vibrations after induced trauma in an animal model. A software-programmable US system was used to acquire quadrature-demodulated ensembles of received US echoes bypassing clutter filtering and other conventional Doppler processing stages. The waveforms of tissue velocity surrounding the injury site were then estimated from the clutter data using autocorrelation and analyzed to determine vibration characteristics. Six New Zealand white rabbits and two juvenile pigs were used for the study. The femoral artery of the anesthetized animal was punctured with an 18-gauge needle to model a peripheral arterial trauma, and the liver was surgically exposed and incised to model organ trauma. Two types of oscillatory tissue motion were observed: “vibrations” with high frequency (>50 Hz) and low peak-peak amplitude (<1 μm) and “flutter” with low frequency (<50 Hz) and high peak-peak amplitude (>1 μm). Active bleeding in femoral artery punctures produced tissue vibrations at the frequency of 323 ± 214 Hz (mean ± standard deviation, pooled for both rabbits and pigs) and the amplitude of 0.24 ± 0.15 μm. Active bleeding in liver incisions produced vibrations at the frequency of 120 ± 47 Hz and the amplitude of 0.33 ± 0.25 μm. Flutter was observed in punctured arteries at the frequency of 28 ± 13 Hz the amplitude of 2.92 ± 1.75 μm, and in incised livers at the frequency of 26 ± 6 Hz and the amplitude of 1.53 ± 0.76 μm. In a punctured artery, the vibration frequency and phase of tissue surrounding the artery were highly correlated between neighboring locations in tissue (correlation coefficient = 0.98), and with the flow oscillations in the lumen (correlation coefficient = 0.96). This preliminary study indicates that tissue vibrations could provide additional physiologic information for detecting, localizing and monitoring internal bleeding using US. (E-mail: ssikdar@u.washington.edu)

Snoring source identification and snoring noise prediction

This paper investigates the snoring mechanism of humans by applying the concept of structural intensity to a three-dimensional (3D) finite element model of a human head, which includes: the upper part of the head, neck, soft palate, hard palate, tongue, nasal cavity and the surrounding walls of the pharynx. Results show that for 20, 40 and 60 Hz pressure loads, tissue vibration is mainly in the areas of the soft palate, the tongue and the nasal cavity. For predicting the snoring noise level, a 3D boundary element cavity model of the upper airway in the nasal cavity is generated. The snoring noise level is predicted for a prescribed airflow loading, and its range agrees with published measurements. These models may be further developed to study the various snoring mechanisms for different groups of patients.

Application of ultrasound-tagged photons for measurement of amplitude of vibration of tissue caused by ultrasound: theory, simulation, and experiments

We investigate the modulation of an optical field caused by its interaction with an ultrasound beam in a tissue mimicking phantom. This modulation appears as a modulation in the intensity autocorrelation, which is measured by a photon counting correlator. The factors contributing to the modulation are: 1. amplitude of vibration of the particles of the tissue, 2. refractive index modulation, and 3. absorption coefficient in the region of the tissue intercepted by the ultrasound beam and light. We show in this work that a significant part of the contribution to this modulation comes from displacement of the tissue particles, which in turn is governed by the elastic properties of the tissue. We establish, both through simulations and experiments using an optical elastography phantom, the effects of the elasticity and absorption coefficient variations on the modulation of intensity autocorrelation. In the case where there is no absorption coefficient variation, we suggest that the depth of modulation can be calibrated to measure the displacement of tissue particles that, in turn, can be used to measure the tissue elasticity.