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Biomedical subjects

Tien-Chen Liu

Publications and source records attributed to Tien-Chen Liu.

At least 19 recordsLinked to original sources
PubMed2006

Biomechanical modeling and design optimization of cartilage myringoplasty using finite element analysis.

The purpose of this study was to determine the acoustic transfer characteristics of cartilage for optimal cartilage myringoplasty. In order to do so, we developed a cartilage plate/tympanic membrane-coupled model using finite element analysis. Cartilage specimens of the tragus were obtained from fresh human cadavers, and the parameters of the tragus were determined by curve fitting and cross-calibration. A cartilage plate was used to repair an eardrum perforation, and the new coupled tympanic membrane-cartilage complex was loaded into our 3-dimensional biomechanical model of the middle ear for analysis. Our results show that first the beta-damping value of the cartilage plate depends on frequency. The value of beta damping was close to 3 x 10(-4) s at lower frequencies and 5 x 10(-6) s at higher frequencies. Secondly, reducing cartilage thickness leads to an improvement of its acoustic transfer qualities. From an acoustics point of view, the 0.1- to 0.2-mm cartilage plate seems to be most preferable with regard to tympanic membrane vibration. Furthermore, thicknesses of 0.2 mm at lower frequencies and 0.1 mm at higher frequencies were regarded as good compromises between sufficient mechanical stability and low acoustic transfer loss.

Biomechanical Phenomena↗
PubMed2006

The effects of masking on the activation of auditory-associated cortex during speech listening in white noise.

CONCLUSIONS: Noise-induced masking has different effects on the two hemispheres during speech listening. Auditory-associated cortices in the left hemisphere were more affected by masking than the right side. However, activation of primary and secondary auditory cortices was not affected in both sides under the masking with high signal to noise ratio. OBJECTIVES: The purpose of this study was to investigate the effects of masking on the central auditory system during speech listening in white noise. MATERIALS AND METHODS: Twelve healthy young subjects with normal hearing participated in this study. Functional magnetic resonance imaging (fMRI) was performed while subjects were listening to speech sounds alone and speech plus white noise binaurally. RESULTS: In humans, the activation of several regions including the middle parts of the superior and middle temporal gyri, parahippocampal gyrus, cuneus and thalamus of the left hemisphere was significantly reduced under the masking paradigm with +5 dB signal to noise ratio. In addition, reduced activation was also found at the lingual gyrus, anterior and middle parts of the superior temporal gyrus (STG), uncus, fusiform gyrus, and inferior frontal gyrus of the right hemisphere during masking.

Acoustic Stimulation↗
PubMed2006

Changes in activation of the auditory cortex following long-term amplification: an fMRI study.

CONCLUSION: Speech-elicited activation decreased after monaural amplification bilaterally during unaided or aided ear stimulation, but tended to recover later at the contralateral hemisphere during aided ear stimulation. OBJECTIVES: The purpose of this study was to investigate the changes in the activation pattern of auditory cortex following long-term monoaural amplification. PATIENTS AND METHODS: Serial functional magnetic resonance images were obtained while speech sounds were presented to the aided (right) and unaided (left) ears of eight hearing-impaired subjects before, 3 months, and 9 months after beginning the use of a single hearing aid. The results were analyzed by group analysis. RESULTS: Before hearing aid fitting, we found that activation patterns of the auditory cortex were somewhat segmented in the left hemisphere, regardless of whether the speech sounds were delivered to right or left ear. Cross projection was lost in response to right ear stimulation. After hearing aid fitting, on the unaided side stimulation, the activation tended to decrease progressively on both sides 3 months and 9 months after beginning monoaural amplification. On the aided side stimulation, activation also decreased 3 months after amplification bilaterally, but tended to recover at the contralateral hemisphere after 9 months of amplification. Cross projection was restored in response to right ear stimulation.

Acoustic Stimulation↗
PubMed2006

Three-dimensional reconstruction and modeling of middle ear biomechanics by high-resolution computed tomography and finite element analysis.

OBJECTIVE: To present a systematic and practical approach that uses high-resolution computed tomography to derive models of the middle ear for finite element analysis. STUDY DESIGN: This prospective study included 31 subjects with normal hearing and no previous otologic disorders. Temporal bone images obtained from 15 right ears and 16 left ears were used for evaluation and reconstruction. METHODS: High-resolution computed tomography of temporal bone was performed using simultaneous acquisition of 16 sections with a collimated slice thickness of 0.625 mm. All images were transferred to an Amira visualization system for three-dimensional reconstruction. The created three-dimensional model was translated into two commercial modeling packages, Patran and ANSYS, for finite element analysis. RESULT: The characteristic dimensions of the model were measured and compared with previously published histologic section data. This result confirms that the geometric model created by the proposed method is accurate except that the tympanic membrane is thicker than when measured by the histologic section method. No obvious difference in the geometrical dimension between right and left ossicles was found (P > .05). The three-dimensional model created by finite element method and predicted umbo and stapes displacements are close to the bounds of the experimental curves of Nishihara's, Huber's, Gan's, and Sun's data across the frequency range of 100 to 8000 Hz. CONCLUSION: The model includes a description of the geometry of the middle ear components and dynamic equations of vibration. The proposed method is quick, practical, low-cost, and, most importantly, noninvasive as compared with histologic section methods.

Adolescent↗
PubMed2005

Hemispheric difference in activation patterns of human auditory-associated cortex: an FMRI study.

The purpose of this study was to demonstrate interhemispheric differences in activation patterns of the auditory-associated cortex elicited by a series of sounds. Functional magnetic resonance imaging was performed while different sounds were presented binaurally to 10 healthy subjects with normal hearing. Characteristic activation patterns were elicited although variability was shown between subjects. The activation number was significantly higher on the right than on the left side for non-speech (but not for speech) stimulations. As stimulation increased in complexity (from a pure tone to white noise to ocean wave sounds to classical music), the activation pattern of the superior temporal lobe became more pronounced in both hemispheres while that of the auditory cortex tended to become more sustained and concentrated on the right rather than on the left side. No hemispheric differences in activation pattern were seen in response to speech.

Acoustic Stimulation↗
PubMed2005

Involvement of nitric oxide generation in noise-induced temporary threshold shift in guinea pigs.

The present study explored the role of endogenous nitric oxide (NO) in the temporary threshold shift caused by acoustic trauma. Guinea pigs were exposed to broadband white noise at a level of 105+/-2dB sound pressure level (SPL) for 10min, causing a temporary threshold shift (TTS). The guinea pigs were divided into six groups (N-1 to N-6) according to survival days after noise exposure (0, 1, 2, 3, 7, 28days). Auditory brainstem responses (ABR) were recorded before noise exposure, immediately after noise exposure and before sacrifice. Immediately after animals were sacrificed, the stria vascularis and the spiral ligament of the lateral wall of each individual cochlea were harvest as a unit and prepared for assay of NO. There was a significant correlation (P<0.001) between the NO concentration and final ABR threshold in the noise exposure groups. But the return of ABR threshold to pre-noise-exposed level is early than that of NO concentration. An average 16.2dB threshold shift was found immediately after noise exposure. The threshold returned to the pre-noise-exposed level on the second post-exposure day. Comparing to unexposed control animals, the NO concentration increased nearly threefold immediately following noise exposure and decreased to twofold when the hearing threshold had returned to the pre-noise-exposed level. On the seventh post-exposure day the NO concentration was not different from that in unexposed control animals. Those findings indicate that endogenous NO is generated in the noise-induced temporal threshold shift and its concentration is correlated with the hearing loss.

Animals↗
PubMed2005

Deep neck infection in diabetic patients: comparison of clinical picture and outcomes with nondiabetic patients.

OBJECTIVE: To compare the difference in the clinical picture and outcomes between diabetic and nondiabetic patients with deep neck infections. STUDY DESIGN AND SETTING: We retrospectively reviewed the records of patients who were diagnosed with deep neck infections and who received treatment at the Department of Otolaryngology of National Taiwan University Hospital between 1997 and 2002. One hundred eighty-five patients were included in our study. Fifty-six patients with diabetes mellitus were enrolled for further analysis (diabetic group) and compared with the other 129 patients without diabetes mellitus (nondiabetic group) in demography, etiology, bacteriology, treatment, duration of hospital stay, complications, and outcome. RESULTS: The parapharyngeal space was the space most commonly involved in both the diabetic (33.9%) and nondiabetic groups (40.3%). Odontogenic infections and upper airway infections were the 2 leading causes of deep neck infection in diabetic and nondiabetic groups. Streptococcus viridans is the most commonly isolated organism in the nondiabetic group (43.7%). However, the most common organism in the diabetic group was Klebsiella pneumoniae (56.1%). There were 89.3% of diabetic patients, versus 71.3% of nondiabetic patients, with abscess formation ( P = 0.0136). Surgical drainage was performed more frequently in the diabetic group than in the nondiabetic group (86.0% versus 65.2%, P = 0.0142). In comparison with the nondiabetic group, the diabetic group tended to have older mean age (57.2 y versus 46.2 y, P = 0.0007), longer duration of hospital stay (19.7 days versus 10.2 days, P < 0.0001), more frequent complications (33.9% versus 8.5%, P < 0.0001), and more frequent tracheostomy or intubation (19.6% versus 6.2%, P = 0.0123). CONCLUSIONS: Patients with diabetes mellitus are susceptible to deep neck infection. We should pay more attention when dealing with deep neck infections in patients with diabetes mellitus because those patients tend to have complications more frequently and a longer duration of hospital stay. Empirical antibiotics should cover K. pneumoniae in patients with deep neck infection who have diabetes mellitus.

Abscess↗
PubMed2004

Deep neck infection: analysis of 185 cases.

PURPOSE: This study reviews our experience with deep neck infections and tries to identify the predisposing factors of life-threatening complications. METHODS: A retrospective review was conducted of patients who were diagnosed as having deep neck infections in the Department of Otolaryngology at National Taiwan University Hospital from 1997 to 2002. Their demographics etiology, associated systemic diseases, bacteriology, radiology, treatment, duration of hospitalization, complications, and outcomes were reviewed. The attributing factors to deep neck infections, such as the age and systemic diseases of patients, were also analyzed. RESULTS: One hundred eighty-five charts were recorded; 109 (58.9%) were men, and 76 (41.1%) were women, with a mean age of 49.5 +/- 20.5 years. Ninety-seven (52.4%) of the patients were older than 50 years old. There were 63 patients (34.1%) who had associated systemic diseases, with 88.9% (56/63) of those having diabetes mellitus (DM). The parapharyngeal space (38.4%) was the most commonly involved space. Odontogenic infections and upper airway infections were the two most common causes of deep neck infections (53.2% and 30.5% of the known causes). Streptococcus viridans and Klebsiella pneumoniae were the most common organisms (33.9%, 33.9%) identified through pus cultures. K. pneumoniae was also the most common infective organism (56.1%) in patients with DM. Of the abscess group (142 patients), 103 patients (72.5%) underwent surgical drainages. Thirty patients (16.2%) had major complications during admission, and among them, 18 patients received tracheostomies. Those patients with underlying systemic diseases or complications or who received tracheostomy tended to have a longer hospital stay and were older. There were three deaths (mortality rate, 1.6%). All had an underlying systemic disease and were older than 72 years of age. CONCLUSIONS: When dealing with deep neck infections in a high-risk group (older patients with DM or other underlying systemic diseases) in the clinic, more attention should be paid to the prevention of complications and even the possibility of death. Early surgical drainage remains the main method of treating deep neck abscesses. Therapeutic needle aspiration and conservative medical treatment are effective in selective cases such as those with minimal abscess formation.

Abscess↗
PubMed2004

Effects of limiting the number of active electrodes on Mandarin tone perception in young children using cochlear implants.

OBJECTIVE: To evaluate the short-term effects of varying the number and location of programmed electrodes on Mandarin tone perception in young children using Nucleus CI 24 implants. MATERIAL AND METHODS: Six children using CI 24 implants participated in the study. The Mandarin tone recognition of each subject was assessed using a self-designed word list containing 80 words under 5 different map conditions. The map conditions were: (i) the subject's current map with all functional electrodes; (ii) removing (i.e. not programming) the even-numbered active electrodes; (iii) removing the five most apical electrodes; (iv) removing the six most basal electrodes; and (v) removing all electrodes except the six most apical. RESULTS: Reducing the number of active electrodes caused a small but significant decrease in performance of Mandarin tone perception. However, a relatively high tone perception score (58.1%) could be maintained even when subjects used only six apical electrodes. The location of the electrodes, i.e. apical or basal, did not appear to be important in tone perception. For each individual tone, the scores for tones 1 and 4 were significantly higher than those for tones 2 and 3 for all map conditions. Comparing tone perception with word recognition, reducing the number of active electrodes had a much more negative effect on word recognition. CONCLUSIONS: A small but significant decrease in Mandarin tone perception was observed when the number of active electrodes was reduced in children using CI 24 implants. The location of the electrode is not important in tone recognition. Moreover, tone recognition is far more resistant than word recognition to the negative effects of reducing the number of active programmable electrodes, possibly because it relies mostly on temporal envelopes while word recognition requires more spectral details.

Child↗
PubMed2004

Effects of alcohol and noise on temporary threshold shift in Guinea pigs.

The purpose of this study was to investigate the effects of concomitant exposure to noise and alcohol on the auditory thresholds. Twenty-four guinea pigs were equally divided into three groups: the acute intoxication group, the chronic intoxication group and the control group. Animals in the acute group received single intraperitoneal injections of ethanol (2 g/kg). In the chronic group, alcohol was administered via drinking water (10%, v/v) over a 60-day period. All animals were exposed to a white noise at the intensity of 105 dB A for 30 min. Auditory brainstem response (ABR) thresholds and distortion product otoacoustic emission (DPOAE) levels were measured before, immediately after noise exposure and also 1, 2, and 7 days following exposure. The results showed: first, acute alcohol injection caused a significant, temporary elevation of ABR threshold (4.8 dB in average), while chronic alcohol treatment did not change auditory threshold significantly. Second, noise exposure induced a mean threshold shift of 15.4- 19.7 dB. ABR threshold returned to normal 2 days after exposure. Both acute and chronic alcohol treatment did not alter the magnitude and time course of recovery of the temporary threshold shift (TTS). Third, the mean DPOAE amplitudes decreased at most frequencies following acute injection of alcohol. However, the differences did not reach statistical significance. Fourth, the mean DPOAE levels dropped 3.4-9.6 dB in all groups after noise exposure and returned to normal 1 day to 2 days after noise. There were no significant differences in the amount of DPOAE suppression after noise between the three groups. In summary, we have found that acute and chronic treatment of alcohol in combination with noise did not significantly exacerbate TTS or decrease DPOAE amplitudes relative to noise exposure alone.

Alcoholic Intoxication↗
PubMed2004

Mandarin speech perception in nucleus CI 24 implantees using MAPs based on neural response telemetry.

The purpose of this study is to compare speech perception performance in Mandarin-speaking Nucleus CI24 implantee using standard behavior MAPs and NRT-based MAPs. Eight Nucleus CI24 users (5 years and older) participated in the study. They all fulfilled the following criteria: (1) behavioral MAP and NRT thresholds can be reliably obtained; (2) had more than 18 functioning electrodes; (3) had at least 6 months experience using CI. All subjects received speech evaluation under three different MAPs: a traditional behavioral MAP, a MAP predicted from the NRT thresholds of the E22 (electrode 22), E19, E15, E11, E8, E5, E1 and a combined MAP based on the information of NRT thresholds and behavioral threshold/comfortable levels of the E11. The speech evaluation package included word recognition test in quiet, in noise, and a Mandarin sentence test in quiet. Results showed that three MAPs are similar in some subjects, but different in other subjects. Compared to the NRT MAPs, the combined MAPs are more similar to the behavioral MAPs. There was no significant difference in the mean score of the word recognition test in quiet, in noise and sentence test under these three MAP conditions. In conclusion, although the behavioral MAPs and the NRT-based MAPs are not identical, the speech performance of Mandarin-speaking CI24 implantee using MAPs predicted from NRT thresholds appeared to be no worse than the traditional behavioral MAPs. Therefore, in certain cases that behavioral MAPs are difficult to obtain (such as in very young or multiple handicapped children), NRT-based MAPs may serve reliably as an initial estimation.

Action Potentials↗
PubMed2003

Acute effects of alcohol on auditory thresholds and distortion product otoacoustic emissions in humans.

OBJECTIVE: To investigate the acute effects of alcohol consumption on pure-tone thresholds (PTs) and distortion product otoacoustic emissions (DPOAEs) in humans MATERIAL AND METHODS: Eight healthy adults were asked to drink alcohol to the clinical intoxication level. PTs and DPOAEs were determined serially before and after alcohol ingestion. RESULTS: Alcohol had no effect on PTs DPOAE amplitudes above 5500 Hz dropped 30 min and 1 h after alcohol ingestion, returning to the pre-test level 2 h after ingestion. CONCLUSION: In humans, acute alcohol consumption to the intoxication level may cause a temporary reduction in DPOAE amplitudes at high frequencies without affecting auditory thresholds.

Adult↗
PubMed2002

Community-acquired methicillin-resistant Staphylococcus aureus infections in discharging ears.

OBJECTIVES: Although community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections have recently become an increasing problem in various fields of medicine, they have rarely been studied in the ear. The purpose of this study was to determine the prevalence of community-acquired MRSA infections in discharging ears and to compare the epidemiology of MRSA with that of other pathogens. MATERIAL AND METHODS: Between August 2000 and February 2002, 248 isolates recovered from 221 discharging ears of patients with 3 disease entities (chronic otitis media, acute otitis externa and granular myringitis) were prospectively analyzed using bacteriology. The isolates analyzed using bacteriology were divided into three groups: MRSA, methicillin-susceptible S. aureus (MSSA) and non-SA. RESULTS: S. aureus was found in 108 (43.5%) isolates and MRSA in 27. Therefore, the percentage of MRSA among the S. aureus isolates was 25.0% (27/108). The prevalence of community-acquired MRSA infections in discharging ears was 12.2% (27/221) and the MRSA strains were highly susceptible to vancomycin, teicoplanin, fusidic acid and minocycline. The MRSA-infected patients were older than those infected with other groups of pathogens. Also, MRSA infections appeared to be more common in chronic otitis media than in acute otitis externa or granular myringitis. CONCLUSIONS: Community-acquired MRSA represents an increasing problem. In this study, MRSA strains were highly susceptible to vancomycin, teicoplanin, fusidic acid and minocycline.

Acute Disease↗
PubMed2002

Sinonasal adenocarcinoma: clinical study of nine cases in Taiwan.

OBJECTIVE: Sinonasal adenocarcinoma is an uncommon disease in Taiwan. This paper presents details of the management and outcome of the disease. MATERIAL AND METHODS: The medical records of patients with sinonasal adenocarcinoma who presented to the Department of Otolaryngology, National Taiwan University Hospital between 1983 and 2002 were retrospectively reviewed. Tumors were staged based on the American Joint Committee of Cancer staging criteria. The series included 5 males and 4 females (mean age 51 years; range 28-75 years). RESULTS: No association between sinonasal adenocarcinoma and occupations such as furniture making, wood working or textile working was found. Epistaxis and nasal obstruction were the most common symptoms. Metastasis to bone or liver was found initially at diagnosis in two cases. Treatment was given according to the tumor stage, the clinical condition of the patient and the patient's wishes: two received combined treatment comprising wide surgical resection and radiotherapy, two received radiotherapy only, one received wide surgical resection only and four received no treatment. At a mean follow-up of 30 months (range 2-68 months), 2 patients were free from the disease and 1 was alive with the disease. Six cases died of the disease. Advanced-stage disease was associated with a poor prognosis. Early-stage disease, a well-differentiated histologic type and surgical resection combined with radiotherapy were associated with a favorable result. CONCLUSION: Sinonasal adenocarcinoma has a low incidence in the general population in Taiwan. However, prognosis is poor owing to delayed diagnosis and the consequent advanced stage of the disease.

Adenocarcinoma↗
PubMed2002

Changes in bacteriology of discharging ears.

A bacteriological study on 161 consecutive out-patients presenting with otorrhoea was performed prospectively at a local teaching hospital in Taiwan between August 2000 and June 2001. A total of 177 isolates were recovered. Staphylococcus aureus was found in 77 (43.5 per cent) isolates, and non-Staphylococcus aureus in 100 (56.5 per cent) isolates. Pseudomas sp was found to be the most common pathogen (28.8 per cent) in the non-Staphylococcus aureus group. Staphylococcus aureus had become more common than Pseudomonas aeruginosa in acute otitis externa, granular myringitis, and chronic otitis media in Taiwan. Methicillin-resistant Staphylococcus aureus (MRSA) was also an increasing problem in all three disease entities. The prevalence of community-acquired MRSA infections in discharging ears was found to be 13.7 per cent (22/161). MRSAs were highly susceptible to vancomycin, teicoplanin, fusidic acid, and minocycline. More studies should be done to determine the susceptibility of MRSA to ofloxacin in the future.

Acute Disease↗