Biomedical subjects

Yen-Yu Chen

Publications and source records attributed to Yen-Yu Chen.

10 recordsLinked to original sources

PubMed2006

Medical image compression using DCT-based subband decomposition and modified SPIHT data organization.

OBJECTIVE: The work proposed a novel bit-rate-reduced approach for reducing the memory required to store a remote diagnosis and rapidly transmission it. METHOD: In the work, an 8x8 Discrete Cosine Transform (DCT) approach is adopted to perform subband decomposition. Modified set partitioning in hierarchical trees (SPIHT) is then employed to organize data and entropy coding. The translation function can store the detailed characteristics of an image. A simple transformation to obtain DCT spectrum data in a single frequency domain decomposes the original signal into various frequency domains that can further compressed by wavelet-based algorithm. In this scheme, insignificant DCT coefficients that correspond to a particular spatial location in the high-frequency subbands can be employed to reduce redundancy by applying a proposed combined function in association with the modified SPIHT. RESULTS AND CONCLUSIONS: Simulation results showed that the embedded DCT-CSPIHT image compression reduced the computational complexity to only a quarter of the wavelet-based subband decomposition, and improved the quality of the reconstructed medical image as given by both the peak signal-to-noise ratio (PSNR) and the perceptual results over JPEG2000 and the original SPIHT at the same bit rate. Additionally, since 8x8 fast DCT hardware implementation being commercially available, the proposed DCT-CSPIHT can perform well in high speed image coding and transmission.

Algorithms↗

PubMed2006

Effects of atenolol and losartan on baroreflex sensitivity and heart rate variability in uncomplicated essential hypertension.

Baroreflex sensitivity (BRS) and heart rate variability (HRV) are potential therapeutic targets. The present study was conducted to assess changes in BRS and HRV after monotherapy with losartan versus that of atenolol in uncomplicated essential hypertension. Thirty subjects with uncomplicated essential hypertension were randomized to receive atenolol 50 mg to 100 mg (n = 15) or losartan 50 mg to 100 mg (N = 15) daily for 6 months. Instantaneous systolic blood pressure (SBP) and heart rate were assessed using servo-controlled infrared finger plethysmography before treatment and at the end of 3 months and 6 months after treatment. The fluctuation in SBP and interpulse interval (IPI) was divided into three specific frequency ranges by fast Fourier transform as high frequency (HF; 0.15 Hz-0.4 Hz), low frequency (LF; 0.04 Hz-0.15 Hz), and very low frequency (VLF; 0.004 Hz-0.04 Hz). The BRS was expressed as (1) SBP-IPI transfer function with its magnitude in the HF and LF ranges and (2) BRS index alpha. The HRV was expressed as total power and power in the LF and HF ranges of interpulse interval. Blood pressure was reduced to a similar extent in both groups. Compared with the baseline, BRS did not improve in both groups at month 3. However, BRS was significantly improved in the losartan group (P < 0.05) but not in the atenolol group at month 6. In addition, BRS was significantly higher in the losartan group than the atenolol group at month 3 and month 6 (P < 0.05). Moreover, heart rate variability was significantly reduced in the atenolol group at month 6 (P < 0.05), but not in the losartan group. The HRV in the losartan group was significantly higher than that in the atenolol group at month 6 (P < 0.05). These findings suggest superior effects of losartan on BRS and HRV than atenolol in uncomplicated essential hypertension, which may be beyond blood pressure reduction/resetting.

Adult↗

PubMed2005

Distribution of carotid arterial lesions in Chinese patients with transient monocular blindness.

BACKGROUND AND PURPOSE: Asian patients with cerebrovascular diseases have more intracranial atherosclerosis and less extracranial carotid artery stenosis compared with white patients. We systemically evaluated the distribution of carotid arterial lesions in Chinese patients with transient monocular blindness (TMB), which was rarely reported. METHODS: We prospectively evaluated 105 consecutive patients with TMB. All of the patients received ocular and physical examinations, blood tests for coagulation function and autoimmune diseases, and ultrasonography of cervical and intracranial arteries. All of the carotid lesions were confirmed by magnetic resonance angiography or cerebral angiography. RESULTS: Of the 36 (34.3%) patients with significant carotid stenosis (> or =50%), 16 (15.2%) had extracranial carotid stenosis; 17 (16.2%) had carotid siphon stenosis; and 3 (2.9%) had both. The duration, onset, and patterns of visual loss were not different between patients with and without carotid arterial lesion. CONCLUSIONS: This study signified the importance of carotid siphon stenosis as a probable underlying etiology for TMB in Chinese patients.

Aged↗

PubMed2005

The carboxyl-terminal segment of the adaptor protein ALX directs its nuclear export during T cell activation.

The adaptor protein ALX acts downstream of CD28 to regulate the interleukin-2 (IL-2) promoter during T cell activation. Whereas ALX is predominantly localized to the cytoplasm, ALX partially resides in the nucleus, and the nuclear pool is rapidly depleted in response to T cell receptor (TCR)/CD28 signaling. Here it is shown that this depletion occurs via nuclear export of ALX, which depends on a leucine-rich nuclear export signal (NES) in its carboxyl segment and on the CRM-1 transport protein. Nuclear import of ALX also depends on its carboxyl-terminal segment. Blocking nuclear export of ALX, either pharmacologically, by leptomycin B, or by site-directed mutation of the ALX NES, impairs CD28-mediated phosphorylation of ALX. Additionally, upon overexpression, the ALX NES mutant was found to be impaired in inhibiting TCR/CD28-induced transcriptional up-regulation of the RE/AP composite element from the IL-2 promoter, whereas a truncated form of ALX that is a potent inhibitor of RE/AP activation was found to reside entirely in the cytoplasm. Together, these results show that ALX exerts its effect on IL-2 up-regulation in the cytoplasm and suggest an intricate relationship between the nuclear localization/export, phosphorylation, and activity of ALX in response to TCR and CD28 signaling.

Active Transport, Cell Nucleus↗

PubMed2005

Enhancing ultrasound images by morphology filter and eliminating ringing effect.

Various medical image compression techniques have been proposed for accelerating image propagation in many applications. JPEG2000 is a new generation technique that can encode near lossless ultrasound images at medium bit-rate with diagnostically acceptable quality. Because the coder of JPEG2000 is based on wavelet transform, the reconstructed image will contain some ringing artifacts. Some de-ringing algorithm must be applied to enhance image quality. This study presents quad-tree decomposition and a set of morphological filters for reducing the ringing artifacts of ultrasound images. Specifically, the presented morphological filters use eight predefined morphological operations, including four structuring elements (SE) that include both dilation and erosion. The proposed voting strategy can be used to select the morphological filter for each block to optimize decoded image quality. Image quality can be enhanced by applying the appropriate morphological filter to each block. Experimental results demonstrate that the proposed technique enhances reconstructed ultrasound image quality compared to JPEG2000 at the same bit-rate in terms of both PSNR and the perceptual results.

Algorithms↗

PubMed2004

A wireless PDA-based physiological monitoring system for patient transport.

This paper proposes a mobile patient monitoring system, which integrates current personal digital assistant (PDA) technology and wireless local area network (WLAN) technology. At the patient's location, a wireless PDA-based monitor is used to acquire continuously the patient's vital signs, including heart rate, three-lead electrocardiography, and SpO2. Through the WLAN, the patient's biosignals can be transmitted in real-time to a remote central management unit, and authorized medical staffs can access the data and the case history of the patient, either by the central management unit or the wireless devices. A prototype of this system has been developed and implemented. The system has been evaluated by technical verification, clinical test, and user survey. The evaluation of performance yields a high degree of satisfaction (mean = 4.64, standard deviation--SD = 0.53 in a five-point Likert scale) of users who used the PDA-based system for intrahospital transport. The results also show that the wireless PDA model is superior to the currently used monitors both in mobility and in usability, and is, therefore, better suited to patient transport.

Adult↗

PubMed2004

Primary cough headache is associated with posterior fossa crowdedness: a morphometric MRI study.

The aetiology of primary cough headache (PCH) is obscure. The aim of this study was to investigate the magnetic resonance (MR) morphometric characteristics of the posterior cranial fossa (PCF) in patients with PCH. Eighteen consecutive patients with PCH (14M/4F, mean age 75.1 +/- 6.0 years) and 18 sex- and age-matched control subjects were recruited for study. Based on the midline sagittal MR images, parameters indicating posterior fossa crowdedness were measured. Compared with controls, patients with PCH had a similar size of hindbrain tissue area but a significantly smaller PCF area, resulting in a higher mean hindbrain/PCF ratio (0.78 +/- 0.04 vs. 0.73 +/- 0.06, P = 0.005). In addition, these patients also had a lower position of the cerebellar tonsillar tip, a shorter clivus length and shorter distances from the clivus to the mid-pons and from the basion to the medulla than the control group. Patients with PCH were associated with a more crowded PCF, which might be a contributing factor for the pathogenesis of this headache syndrome.

Aged↗

PubMed2002

Fat augmentation following microsurgical removal of the vocal nodules.

OBJECTIVES: Autogenous fat augmentation has been used as a treatment for glottic insufficiency. However, no information is available on the effectiveness of fat injection in patients with vocal nodules or recurrent vocal nodules after surgery. STUDY DESIGN: The retrospective study reviews the efficiency of fat injection after surgery in patients with vocal nodules (n = 18) and recurrent vocal nodules (n = 5). METHODS: The perceptual acoustic, phonatory function, and video laryngostroboscopic data were evaluated before and after surgery in 23 patients. RESULTS: Mean follow-up time was 7.5 months. Nineteen patients had excellent results. Two patients had improvement, and no change was observed in two patients. Phonatory function showed significant improvement in shimmer, harmonic-to-noiseratio (P <.05), maximum phonation time, grade, roughness, and breathiness (P <.001). Video laryngostroboscopic rating showed significant improvement in linearity of the vocal fold edge, amplitude of vocal fold vibration, and excursion of the mucosal wave (P <.001). Less improvement was observed in recurrent vocal nodules than in nonrecurrent vocal nodules. CONCLUSIONS: Fat injection is an effective autogenous implant and may be considered as an option in management of patients with vocal nodules after surgery. Recurrence of nodules is a problem, but the procedure may be repeated.

Adipose Tissue↗

PubMedDate not supplied

Results of magnetic resonance imaging assessment, acoustic analysis, phonatory function and perceptual rating of glottic insufficiency before and after fat augmentation: correlated with subjective rating.

Autogenous fat augmentation has been proven effective in the treatment of glottic insufficiency (GI) using both subjective and objective methods of evaluation. However, no information is available in published research regarding the effectiveness and predictability of value parameters with regard to patients' perceptions and concerns. This article retrospectively examines the correlation between subjective and objective examinations and subjective ratings (SRs) in patients with presbylaryngis (n = 14) and sulcus vocalis (n = 2). Acoustic analysis, phonatory function, magnetic resonance imaging (MRI) assessment, and perceptual rating data were evaluated against SRs using pre- and postoperative test results in 16 patients. The mean time over which subjective and objective examinations were performed was 10 months. Twelve patients reported excellent results, while no change was observed in 4 patients. When compared against SR, the kappa value of jitter, shimmer, harmonic to noise ratio, phonation time, grade, roughness, breathiness, and MRI were 0.25, 0, -0.08, -0.11, -0.11, 0.18, 0, and 1, respectively. The agreement between the MRI and SR values was complete, and was the only relationship shown to be significant (p < 0.001). MRI assessment is an effective and reliable examination tool which can be considered for use in assessing the progress of the post-fat injection operation in GI patients during follow-up examinations. Furthermore, due to the excellent agreement between MRI assessment and the patients' subjective feelings, the SR value may serve as a good index of fat survival.

Acoustics↗

PubMedDate not supplied

Fat augmentation for nonparalytic glottic insufficiency.

While autogenous fat augmentation for glottic insufficiency has been used before, relatively little information is currently available on the effectiveness of fat injection in patients with nonparalytic glottic insufficiency resulting from problems such as various defects of vocal atrophy or sulcus vocalis. This paper compares retrospectively the efficiency of fat injection after surgery in patients with vocal atrophy (n = 16) and sulcus vocalis (n = 8). The perceptual acoustic and phonatory functions and videolaryngostroboscopic data were evaluated before and after fat augmentation in 24 patients. The mean follow-up time was 19.5 months. Fifteen patients displayed excellent results; 1 showed some improvement; 6 experienced postprocedure failure, and 2 were not available for follow-up analysis. Perceptual rating showed significant improvement in grade, roughness and breathiness (p < 0.05). The videolaryngostroboscopic rating showed significant improvements in vocal fold edge linearity, vocal fold vibration amplitude and mucosal wave excursion (p < 0.05). More improvement in vocal atrophy was observed compared with sulcus vocalis following fat injection procedures. Our research showed that middle defects improved more compared to those in the anterior and posterior area. Fat injection is an effective autogenous implant and may be considered as an option in the treatment of patients with vocal atrophy or sulcus vocalis. Although fat reabsorption was a problem, repeating the procedure could be considered.

Adipose Tissue↗