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PubMed2000

Positron emission tomographic imaging of acoustic neuromas.

Positron emission tomography (PET) examination with both [11C]methyl-l-methionine (Met) and [18F]fluoro-2-deoxyglucose (FDG) was performed in the same patients with acoustic neuroma wherever possible in order to compare the usefulness of the two methods. The study included six patients who visited the Osaka City University Hospitals, between April 1994 and October 1998, for complaints associated with acoustic neuroma. All patients were examined by magnetic resonance imaging (MRI) and Met-PET. Four patients were examined by FDG-PET. The tumor's region of highest accumulation was selected as the region of interest; the tumor/normal ratio (T/N ratio) was defined as the ratio of radioisotope counts for tumor and normal gray matter. All tumors in this series were detected by MRI. In the Met-PET images, four tumors were easily identified, with a high T/N ratio. However, two tumors could not be identified using Met-PET. On FDG-PET, no cases could be identified. The T/N ratio for the four patients with positive Met-PET findings averaged 1.694 +/- 0.266. PET, especially Met-PET, is a powerful means of examination providing functional information on tumors in acoustic neuroma. Met-PET may therefore be useful for acoustic neuroma, which is known to proliferate slowly, as for malignant tumors, in evaluating the proliferating potential of a tumor, in determining patients in whom to perform radiological treatment and in monitoring post-treatment progress.

Adult↗
PubMed2000

Acoustic neuroma: deterioration of speech discrimination related to thresholds in pure-tone audiometry.

Pure-tone and speech audiometry were performed in 231 patients with a unilateral acoustic neuroma. Tumor sizes were obtained through imaging. Audiometric parameters, such as the mean pure-tone thresholds, the maximum discrimination, the slope of the speech audiogram, the roll-over index and the difference between the speech reception threshold and the Fletcher index, were studied and compared with data in the literature. Results showed that patients with an acoustic neuroma have worse speech discrimination than can be expected from the pure-tone audiogram. However, the results presented here indicate that hearing impairments nowadays are not as severe as those described in earlier studies. More patients with a unilateral acoustic neuroma are detected, including even those with a minor hearing impairment. The roll-over index is not characteristic for patients with an acoustic neuroma.

Adult↗
PubMed1999

Evaluation of rhinostereometry compared with acoustic rhinometry.

Measurement of the nasal mucosa is a challenging task. There are many different methods; each with advantages and disadvantages. In the last decade two new methods have been used extensively: acoustic rhinometry and rhinostereometry. Many studies with rhinostereometry have shown interesting results. However, there have been doubts about this method, since only a few investigators have used it, and it has never been compared with other methods. On the other hand, the acoustic rhinometer has been compared with many other methods. In this study, we compare the results of measurements with acoustic rhinometry and rhinostereometry. Thirty patients with vasomotor rhinitis participated in the study. They were challenged with three histamine concentrations on two occasions. resulting in 180 observations with each method. The results were compared with each other using the linear correlation test, and showed a poor but significant correlation (p < 0.01. r = 0.25). We conclude that acoustic rhinometry and rhinostereometry are sensitive methods for studying nasal mucosal swelling, but that there is poor correlation between the two methods.

Acoustics↗
PubMed1996

Evaluation of acoustic rhinometry and posterior rhinomanometry as tools for inhalation challenge studies.

Objective measures of upper respiratory function are needed to understand the effects of inhaled toxicants on the nasal passages. Acoustic rhinometry (AR) is a simple new technique that determines nasal volume by measuring the cross-sectional area of the upper airway as a function of the distance along the nasal passage. This study compares acoustic rhinometry with the more traditional posterior rhinomanometry (NAR) and correlates these objective measures with the symptom of nasal congestion. Healthy young adults (n = 29) were studied on 4 days, each separated by at least 1 wk, in a climate-controlled environmental chamber for 6 h, with exposure to clean air or sidestream tobacco smoke (SS) (2 h, 1, 5, and 15 ppm CO). The coefficient of variation for single measurements was 8-15% (AR) and 4% (NAR); for across-day measurements it was 15-25% (AR) and 13-15% (NAR); and for between days it was 19-27% AR and 17-21% (NAR). These coefficients were similar in subjects with a history of environmental tobacco smoke sensitivity (ETS-S) and those with no history of ETS sensitivity (ETS-NS). At baseline, the perception of unilateral nasal congestion was significantly correlated with unilateral nasal dimensions or nasal resistance; the symptom of baseline bilateral nasal congestion (estimated for both nasal passages simultaneously) correlated less well with objective measures of nasal patency. Under challenge conditions (SS at 1-15 ppm CO), there were typically significant correlations between changes in unilateral congestion and both unilateral rhinomanometry and acoustic rhinometry, but correlations of bilateral congestion and measurable dimensions were much lower. ETS-S and ETS-NS subjects differed in correlations between bilateral subjective and objective measures: ETS-S subjects showed significant correlation between baseline congestion and NAR; in contrast, ETS-NS subjects showed significant correlation between baseline congestion and acoustic rhinometry. These results indicate that NAR and AR are complementary tests for use in inhalation challenge studies and have different correlations with nasal congestion under baseline and challenge conditions.

Acoustics↗
PubMed2004

Acoustic stimulation promotes the expression of inducible nitric oxide synthase in the vestibule of guinea pigs.

Loud acoustic stimulation is known to cause inner ear disturbance. We examined immunohistochemically the vestibule of 12 guinea pigs after acoustic stimulation. The animals were divided into two equal groups: a control group and an acoustic stimulation group. The temporal bones were fixed by means of a cardiac infusion of fixative and immunohistochemically stained for inducible nitric oxide synthase (iNOS). The temporal bones in the control group did not show any iNOS. In the acoustic stimulation group, immunoreactivity for iNOS was detected in the supporting cells and sensory cells of the sensory epithelium, in the dark cell areas and in the vestibular ganglion cells. These findings suggest that free radicals are involved in the pathogenesis of noise-induced inner ear damage. Furthermore, free radicals may cause vestibular damage, as is seen in noise-induced inner ear damage.

Acoustic Stimulation↗
PubMed2000

Some acoustic characteristics in the voices of 6- to 10-year-old children and adults: a comparative sex and developmental perspective.

This study is a follow-up investigation of some of the acoustic characteristics reported for a group of twenty 6-, 8- and 10-year-old children's voices (Whiteside SP, Hodgson C. Log Phon Vocol 1999; 24: 6-13) and compares the data of these children with data from a group of nine adults. The acoustic characteristics for both the children and the adults were examined as a function of age and sex. Fundamental frequency (F0) and the standard deviation (SD) of F0 were investigated for the entire duration of a phrase-final vowel. In addition, the first three formant frequencies of the midpoints for the phrase-final vowel were also investigated, with reference to phonetic context. All acoustic parameters were investigated by examining the age, sex and context-determined differences. Results indicated significant age differences for all acoustic parameters investigated, which were characterized by a general decrease in the frequency values of parameters with increasing age. In addition, significant sex differences were found for all parameters, with the females generally having higher formant frequency values than their male peers across all ages. Significant phonetic context differences were only found for the second formant frequency, with formant values being highest for the context "jar" and lowest for the context "bar". No significant interactions were found for age-by-context, sex-by-context or age-by-sex-context comparisons. Relative formant frequency differences were also examined using Fant's Kn factor, by considering sex-, age- and context-linked patterns. The data also provided some evidence for parallel developmental patterns in the different phonetic contexts of a phrase-final vowel. Furthermore, the results showed that there was some evidence of all three types of the aforementioned patterns in addition to phonetic context-determined changes in K2 factor values. The results reported here, therefore, provide further evidence for age- and sex-linked differences in the patterns of development and maturation of the vocal apparatus.

Adult↗
PubMed2005

Does the acoustic waveform mirror the voice?

Over recent decades, much effort has been invested in the search for acoustic correlates of vocal function and dysfunction. The convenience of non-invasive voice measurements has been a major incentive for this effort. The acoustic signal is a rich but also very diversified source of information. Computer literacy and technical curiosity in the voice care and voice performance communities are now higher than ever, and tools for voice analysis are proliferating. On such a busy scene, a review may be useful of some basic principles for what we can and cannot hope to determine from non-invasive acoustic analysis. One way of doing this is to consider communication by voice as though it were engineered, with layered protocols. This results in a scheme for systematizing the many sources of variation that are present in the acoustic signal, that can complement other strategies for extracting information.

Humans↗
PubMed2005

Acoustic characteristics of crying in infantile laryngomalacia.

The purpose of this study was to add to the extant data base of acoustic cry studies by profiling the condition of laryngomalacia. We hypothesized that the acoustic characteristics of crying produced by an infant with laryngomalacia would differ compared to previously reported cry data for normal infants. An entire episode of crying was audio recorded and acoustically analyzed for the occurrence of expiratory and inspiratory cry segments, as well as the long-time average spectral (LTAS) characteristics. Results obtained for the infant were found to be considerably different from what has been previously reported for normal infants. The overall duration of the infant's crying episode was longer, with proportionately fewer expiratory phonations and more inspiratory phonations compared to normal infants. The LTAS results were reflective of aperiodic components in the glottal source spectrum. Collectively, the infant's unusual crying aspects were not limited solely to those acoustic features resulting from a prolapse of supraglottic soft tissue, and therefore provide new insight into the vocal fold vibratory behavior characterizing infantile laryngomalacia.

Acoustics↗
PubMed2003

Evaluation of non-reassuring fetal heart rate patterns with fetal pulse oximetry combined with vibratory acoustic stimulation.

OBJECTIVE: To determine the value of fetal pulse oximetry and vibratory acoustic stimulation in the presence of non-reassuring fetal heart rate patterns during labor. DESIGN: Prospective study in women monitored by cardiotocography and fetal pulse oximetry during labor. MATERIALS AND METHODS: During a period of 18 months, 907 consecutive parturients in labor were monitored by cardiotocography. Out of these women, 63 were selected on the basis of a non-reassuring fetal heart rate tracing during the first stage of labor. In these cases, fetal pulse oximetry was applied. Vibratory acoustic stimulation was applied in fetuses without spontaneous reactivity in order to evaluate the fetal status. RESULTS: Our cases were classified into three groups, according to the lower fetal oxygen saturation levels, from the time of oximetry application until delivery. Group A consisted of 29 cases where fetal oxygen saturation levels were > or = 41%, group B (20 cases) with fetal oxygen saturation of 31-40% and group C (14 cases) with levels of < 30%. Spontaneous reactivity was observed in 15 fetuses of group A and seven of group B, while no case of reactivity was noted in group C. Vibratory acoustic-induced reactivity was associated with low fetal oxygen saturation levels. The mean umbilical artery pH levels were 7.29 +/- 0.051 in group A, 7.21 +/- 0.057 in group B and 7.04 +/- 0.05 in group C. CONCLUSION: Fetal pulse oximetry should be indicated not only in fetuses without any reactivity but also in those with induced reactivity, after the application of vibratory acoustic stimulation.

Acoustic Stimulation↗
PubMed1993

The spatial distribution of cavitation induced acoustic emission, sonoluminescence and cell lysis in the field of a shock wave lithotripter.

This study examines the spatial distribution of various properties attributed to the cavitation field generated by a shock wave lithotripter. These properties include acoustic emission and sonoluminescence, which result from violent bubble collapse, and the degree of cell lysis in vitro, which appears to be related to cavitation. The acoustic emission detected with a 1 MHz, 12 cm diameter focused hydrophone occurs in two distinct bursts. The immediate signal is emitted from a small region contained within the 4 MPa peak negative pressure contour. A second, delayed, burst is emitted from a region extending further along the beam axis. The delay between these two bursts has also been mapped, and the longest delay occurs at positions close to the regions of maximum peak negative pressure. Sonoluminescence from both single and multiple shocks occurs in a broader region than the acoustic emission but the measurement technique does not allow time resolution of the signal. Cell lysis occurs in a relatively small region that correlates closely with the immediate acoustic emission for a shock propagating in a gelatine solution.

Acoustics↗
PubMed2006

Evaluation of mineral oil as an acoustic coupling medium in clinical MRgFUS.

We empirically evaluate mineral oil as an alternative to the mixture of de-gassed water and ultrasound gel, which is currently used as an acoustic coupling medium in clinical magnetic resonance guided focused ultrasound (MRgFUS) treatments. The tests were performed on an ExAblate 2000 MRgFUS system (InSightec Inc., Haifa, Israel) using a clinical patient set-up. Acoustic reflections, treatment temperatures, sonication spot dimensions and position with respect to target location were measured, using both coupling media, in repeated sonications in a tissue mimicking gel phantom. In comparison with the water-gel mix, strengths of acoustic reflections from coupling layers prepared with mineral oil were on average 39% lower and the difference was found to be statistically significant (p = 3.3 x 10(-8)). The treatment temperatures were found to be statistically equivalent for both coupling media, although temperatures corresponding to mineral oil tended to be somewhat higher (on average 1.9 degrees C) and their standard deviations were reduced by about 1 degrees C. Measurements of sonication spot dimensions and positions with respect to target location did not reveal systematic differences. We conclude that mineral oil may be used as an effective non-evaporating acoustic coupling medium for clinical MRgFUS treatments.

Acoustics↗
PubMed1987

A comparison of oto-acoustic emissions and brain stem electric response audiometry in the normal newborn and babies admitted to a special care baby unit.

Brainstem auditory evoked potentials and oto-acoustic emissions have been recorded in 30 normal newborns and in 112 infants admitted to a special care baby unit as part of a study to determine whether these tests can be used to detect the hearing impaired infant. All the ears tested in the normal newborns, where the infant was quiet enough to complete the test, produced a brain stem electric response at a stimulus level less than or equal to 53 dB nHL (dB relative to normal hearing) and 96% produced an oto-acoustic emission at the highest level tested of 41 dB nHL. The mean threshold of the oto-acoustic emission in the normal newborns was 17.7 dB lower than the mean brain stem electric response threshold. The range of thresholds were similar. In the special care infants 84% of ears produced a brain stem electric response at a screening level of 43 dB nHL and 81% of ears produced an oto-acoustic emission at a screening level of 31 dB nHL.

Acoustic Stimulation↗
PubMed2004

Cellular telephone use and risk of acoustic neuroma.

Despite limited evidence, cellular telephones have been claimed to cause cancer, especially in the brain. In this Danish study, the authors examined the possible association between use of cellular telephones and development of acoustic neuroma. Between 2000 and 2002, they ascertained 106 incident cases and matched these persons with 212 randomly sampled, population-based controls on age and sex. The data obtained included information on use of cellular telephones from personal interviews, data from medical records, and the results of radiologic examinations. The authors obtained information on socioeconomic factors from Statistics Denmark. The overall estimated relative risk of acoustic neuroma was 0.90 (95% confidence interval: 0.51, 1.57). Use of a cell phone for 10 years or more did not increase acoustic neuroma risk over that of short-term users. Furthermore, tumors did not occur more frequently on the side of the head on which the telephone was typically used, and the size of the tumor did not correlate with the pattern of cell phone use. The results of this prospective, population-based, nationwide study, which included a large number of long-term users of cellular telephones, do not support an association between cell phone use and risk of acoustic neuroma.

Adult↗
PubMed1996

Effect of aging on the click-rate induced facilitation of acoustic reflex thresholds.

Acoustic reflex thresholds are known to improve with an increase in the click-repetition rates from 50/sec to 300/sec. In the current study this improvement was used to evaluate auditory processing in older subjects. Acoustic reflex thresholds were obtained from 16 human adult ears within each of the following four groups: young male, young female (18-28 years), older male and older female (50-65 years). The probe tone frequency was 226 Hz and the intensity of the probe tone was 85 dB SPL (sound pressure level). Clicks were delivered ipsilaterally to each ear at repetition rates of 50, 100, 150, 200, and 300/sec. The mixed MANOVA revealed a significant effect for the repetition rate and a significant age and rate interaction. Rate integration in dB was computed by subtracting the highest acoustic reflex threshold from the lowest threshold of each ear. Statistical analyses revealed reduced rate integration in the older subjects, suggesting less efficient processing of faster stimuli within the acoustic reflex pathway.

Adolescent↗
PubMed2002

Validation study of two-microphone acoustic reflectometry for determination of breathing tube placement in 200 adult patients.

BACKGROUND: Acoustic reflectometry allows the construction of a one-dimensional image of a cavity, such as the airway or the esophagus. The reflectometric area-distance profile consists of a constant cross-sectional area segment (length of endotracheal tube), followed either by a rapid increase in the area beyond the carina (tracheal intubation) or by an immediate decrease in the area (esophageal intubation). METHODS: Two hundred adult patients were induced and intubated, without restrictions on anesthetic agents or airway adjunct devices. A two-microphone acoustic reflectometer was used to determine whether the breathing tube was placed in the trachea or esophagus. A blinded reflectometer operator, seated a distance away from the patient, interpreted the acoustic area-distance profile alone to decide where the tube was placed. Capnography was used as the gold standard. RESULTS: Of 200 tracheal intubations confirmed by capnography, the reflectometer operator correctly identified 198 (99% correct tracheal intubation identification rate). In two patients there were false-negative results, patients with a tracheal intubation were interpreted as having an esophageal intubation. A total of 14 esophageal intubations resulted, all correctly identified by reflectometry, for a 100% esophageal intubation identification rate. CONCLUSIONS: Acoustic reflectometry is a rapid, noninvasive method by which to determine whether breathing tube placement is correct (tracheal) or incorrect (esophageal). Reflectometry determination of tube placement may be useful in airway emergencies, particularly in cases where visualization of the glottic area is not possible and capnography may fail, as in patients with cardiac arrest.

Acoustics↗
PubMed2006

Enriched acoustic environment after noise trauma abolishes neural signs of tinnitus.

Noise-induced hearing loss induces reorganization of the tonotopic map in cat auditory cortex and increases spontaneous firing rate and neural synchrony. We showed previously that keeping cats after noise trauma in an acoustic environment enriched in high frequencies prevents tonotopic map reorganization. Here, we show the effects of low-frequency and high-frequency enriched acoustic environments on spontaneous firing rate and neural synchrony. Exposed cats placed in the quiet environment and in the low-frequency enriched acoustic environment showed increased spontaneous firing rate and synchrony of firing. In contrast, exposed cats placed in the high-frequency enriched acoustic environment did not show significant differences in spontaneous firing rate or synchrony compared with normal hearing controls. This is interpreted as an absence of putative neural signs of tinnitus.

Acoustic Stimulation↗
PubMed1987

The acoustic reflex in diagnostic audiology: from Metz to present.

In 1946, Metz described what was probably the first practical impedance bridge for measurement of the acoustic reflex. Over the next four decades, diagnostic use of the acoustic reflex progressed in parallel with instrumentation refinements. Today, acoustic reflex threshold and decay testing are a routine component of the diagnostic audiology test battery. Recent advances in the measurement of suprathreshold latency and amplitude have further enhanced the diagnostic value of acoustic reflex measurement.

Cochlear Nerve↗
PubMed1993

Loudness balance between acoustic and electric stimulation by a patient with a multichannel cochlear implant.

Estimates of loudness balance were obtained for acoustically and electrically presented 250 Hz sine signals from a patient who uses the Ineraid multichannel cochlear implant. Acoustic and electric loudness matching was possible because the patient evidenced a 25 dB HL threshold at 250 Hz in his nonimplanted ear. The level of the electrical stimulus in microamperes required for a balance of loudness grew linearly with equal increments in decibels for the acoustic stimulus. These data, in concert with the very limited data from previous studies, provide a rationale for using a logarithmic transformation of acoustic to electric intensity in signal processors for cochlear implants.

Acoustic Stimulation↗