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PubMed1979

Differential diagnosis of hypoechoic and anechoic masses with gray scale sonography: new observations.

With the technological advances in gray scale sonography that have permitted the use of higher-frequency transducers and expansion of the acoustic dynamic range, increasing problems in differentiating solid masses and fluid-filled masses have become apparent. These difficulties can be overcome by strict adherence to proper scanning techniques, which involve transducer selection, tissue attenuation compensation, and alterations in patient position. The availability of variable-dynamic-range signal processing and the use of real-time scanning can further increase one's confidence in the correct interpretation of these masses. The primary criteria for determining that a mass is fluid-filled have been expanded to include the presence of reverberation echoes, the "lateral shades" sign, and the presence of septations. In the past, hypoechoic masses with low-level internal echoes were termed "complex". Both fluid-filled masses and solid masses may fall into this category. By use of the sonographic criteria, an attempt should be made to determine whether a mass is primarily fluid-filled or solid. Specific anatomic locations and pathologic conditions in which differential diagnosis may be difficult are illustrated; these include abdominal masses, hepatic and renal masses, and pelvic masses.

Abdominal Neoplasms↗

PubMed1993

The effects of sound overexposure on the spectral response patterns of nucleus magnocellularis in the neonatal chick.

Spectral response plots from single cells in the chick nucleus magnocellularis were obtained following a 48 h exposure to a 0.9 kHz pure tone at 120 dB sound pressure level and after a recovery period of 12 days. Immediately after removal from the exposure, a variety of changes in the spectral response patterns of nucleus magnocellularis cells were noted. In particular, at recovery day 0, there was a significant decrease in spontaneous rate; a substantial loss of threshold sensitivity and frequency selectivity; and alterations in both the slope and dynamic range of the rate-intensity function. Interestingly, the maximum discharge rate appeared unaffected by the intense sound. Twelve days after removal from overstimulation, auditory function appeared to be operating at normal levels of efficacy as spontaneous rate, threshold sensitivity, frequency selectivity, and the dynamic range of the rate-intensity function were statistically identical to similar measures in nonexposed control birds. The loss and restoration of auditory function is correlated to structural damage and repair of the avian basilar papilla.

Acoustic Stimulation↗

PubMed1987

Laser-stimulated luminescence used to measure x-ray diffraction of a contracting striated muscle.

An integrating x-ray area detector that operates on the basis of laser-stimulated luminescence was used in a diffraction study of muscle contraction. The area detector has a dynamic range of 1 to 10(5), a sensitivity about 60 times greater with approximately 1/300 as much fog background as x-ray film. It is erasable and reusable but, like film, can integrate at a practically unlimited counting rate. The high sensitivity and wide dynamic range of the detector resulted in a sufficient reduction in the exposure time to make possible the recording of a clear x-ray diffraction pattern, with up to 2.0-nanometer axial spacing, from a contracting frog skeletal muscle in as little as 10 seconds with synchrotron radiation. During the isometric contraction of the muscle, most of the actin diffraction lines increased in intensity without noticeable changes in their peak positions. Changes also occurred in diffraction intensities from the myosin heads. The results indicate that during contraction the structure of the actin filaments differs from that in the rigor state, suggesting a possible structural change in the actin subunits themselves; the myosin heads during contraction retain the axial periodicity of the myosin filament and become aligned in a more perpendicular manner to the actin filaments.

Actin Cytoskeleton↗

PubMed1989

Solid-phase electrochemical enzyme immunoassay with attomole detection limit by flow injection analysis.

A sandwich electrochemical enzyme immunoassay with flow injection analysis for the model antigen mouse IgG has been developed with alkaline phosphatase as the enzyme label. The enzyme substrate, 4-aminophenyl phosphate and its enzymatic reaction product, 4-aminophenol have been studied by cyclic and hydrodynamic voltammetry. The determination of 4-aminophenol by flow injection analysis with electrochemical detection (FIAEC) has a linear range of 5.0 x 10(-8) to 1.0 x 10(-5) M, a detection limit of 2.4 x 10(-8) M, and a sample throughput of 72 samples/h. The detection limit is set by a background capacitance response, which depends on the ionic strength difference between the sample and the mobile phase. The sandwich immunoassay has been characterized with respect to substrate concentration for the enzymatic reaction, detection limit, dynamic range and sources of error. Mouse IgG can be determined with a detection limit of 0.81 pg ml-1 by a 30-min substrate incubation time and a six orders of magnitude linear dynamic range.

Aminophenols↗

PubMed1996

Parasympathetic control of heart period during early postnatal development in the rat.

Basal autonomic control of the heart period (HP) changes considerably during the early postnatal period in the rat. Although studies in the developing animal have examined the ability of the sympathetic branch to decrease HP during physiological challenge, few studies have examined the emerging capabilities of the parasympathetic branch to alter HP during early development. To determine the extent of parasympathetic control of HP in the young rat, we used a modified dive reflex procedure and electrical stimulation of the vagal nerve to examine the range of parasympathetic effects on HP in postnatal day 3-24 rats. Modified dive reflex manipulations produced maximal parasympathetically-mediated HPs that were longer just after birth and at weaning than at intervening ages. Direct vagal nerve stimulation studies revealed significant decreases with age in the HP at maximal vagal activation and in the intrinsic HP. The dynamic range, or difference between minimal and maximal parasympathetic effects on HP was similar across ages when assessed from the results of vagal stimulation. Nerve stimulations also revealed age-independent and relatively linear transfer functions relating parasympathetic stimulation frequency and HP during early life. Therefore, several parameters characterizing parasympathetic control of HP, including the dynamic range and transfer function, remain reasonably stable throughout the early postnatal period in the rat. These data provide a framework delineating the autonomic limits within which cardiac responses operate in the young rat. Knowledge of changes in these limits across time affords a firmer physiological basis for cross-age comparisons of autonomically-mediated cardiac changes.

Animals↗

PubMed2006

Oscillating neurons in the cochlear nucleus: II. Simulation results.

A computer model of sustained chopper neurons in the ventral cochlear nucleus is presented and investigated. In the companion paper, the underlying neurophysiological and neuroanatomical data are demonstrated. To explain the preference of chopper neurons for oscillations with periods which are multiples of a 0.4 ms synaptic delay, we suggest a model of circularly connected chopper neurons. In order to simulate chopper neurons within a physiological dynamic range for periodicity encoding, it is necessary to assume that they receive an input from onset neurons. Our computer analysis of the resulting simple neuronal network shows that it can produce stable oscillations. The chopping can be triggered by an amplitude-modulated signal (AM). The dynamic range and the synchronous response of the simulated chopper neurons to AM are enhanced significantly by an additional input from onset neurons. Physiological properties of chopper neurons in the cat, such as mean, standard deviation, and coefficient of variation of the interspike interval are matched precisely by our simulations.

Acoustic Stimulation↗

PubMed2005

Robust estimation of protein expression ratios with lysate microarray technology.

MOTIVATION: The protein lysate microarray is a developing proteomic technology for measuring protein expression levels in a large number of biological samples simultaneously. A challenge for accurate quantification is the relatively narrow dynamic range associated with the commonly used chromogenic signal detection system. To facilitate accurate measurement of the relative expression levels, each sample is serially diluted and each diluted version is spotted on a nitrocellulose-coated slide in triplicate. Thus, each sample yields multiple measurements in different dynamic ranges of the detection system. This study aims to develop suitable algorithms that yield accurate representations of the relative expression levels in different samples from multiple data points. RESULTS: We evaluated two algorithms for estimating relative protein expression in different samples on the lysate microarray by means of a cross-validation procedure. For this purpose as well as for quality control we designed a 1440-spot lysate microarray containing 80 identical samples of purified bovine serum albumin, printed in triplicate with six 2-fold dilutions. Our analysis showed that the algorithm based on a robust least squares estimator provided the most accurate quantification of the protein lysate microarray data. We also demonstrated our methods by estimating relative expression levels of p53 and p21 in either p53(+/+) or p53(-/-) HCT116 colon cancer cells after two drug treatments and their combinations on another lysate microarray. AVAILABILITY: http://www.cs.tut.fi/~mirceanc/lysate_array_bioinformatics.htm

Algorithms↗

PubMed1995

The perception of amplified speech by listeners with hearing loss: acoustic correlates.

Audibility-based approaches to hearing-aid selection generally have focused on the long-term average speech spectrum (LTASS). Advances in amplification technology (e.g., multiband signal processing, level-dependent frequency shaping, full dynamic range compression, adaptive compression) make it difficult to predict the audibility of short-term components of speech from the amplified LTASS. This study was designed to quantify the audibility of a specific phonemes as processed by two different hearing-aid circuits (linear and full dynamic range compression), and to investigate the relation between audibility and performance on a nonsense syllable recognition task. Data were obtained from three subjects with moderate sensorineural hearing loss. Nine unvoiced consonants were presented in two vowel contexts (/i/ and /a/) in both the pre- and post-vocalic position at three intensities. While the performance on selected conditions appeared to vary by hearing-aid type, only one subject showed a statistically significant difference between the two hearing-aid systems. Acoustic analyses revealed a variety of spectral and temporal changes to the speech signal following processing. Estimates of audibility were based upon each subject's thresholds and an acoustic analysis of the amplified signal that varied across phonemes and consonant position. A signal detection approach was used to predict performance from a simple measure of audibility.

Amplifiers, Electronic↗

PubMed2002

Optimization of photoconducting receivers for THz spectroscopy.

We have studied the sensitivity and noise of optically gated dipole receivers made from ion implanted Si and GaAs in an optimized time domain THz spectrometer. The spectrometer uses a room temperature, dc biased, semi-insulating GaAs stripline source capable of generating up to 30 microW average power. The 10% amplitude system bandwidth for 10 microm (50 microm) dipole receivers is 3 THz (1.5 THz). A dynamic range of 4 x 10(5) Hz(-1/2) is achieved using a 10 microm dipole GaAs receiver and 2 x 10(6) Hz(-1/2) using a 50 microm dipole for a total laser power of 110 mW and THz beam power of 20 microW. The dynamic range achieved with comparable silicon receivers is a factor of 2 smaller.

Electric Conductivity↗

PubMedDate not supplied

Chest radiographic image quality: comparison of asymmetric screen-film, digital storage phosphor, and digital selenium drum systems--preliminary study.

Conventional screen-film radiography does not display all regions of the thorax satisfactorily. Three chest radiographic techniques display both the lung and the mediastinum with good contrast. These techniques are asymmetric screen-film (ASF), digital storage phosphor (DSP), and digital selenium drum (DSD) imaging. ASF systems use two asymmetric screen-film combinations to produce a wide-latitude image of the thorax with good contrast in the lungs. In DSP systems, image data are acquired digitally with a wide dynamic range by using the optical output of a photostimulable phosphor plate; in DSD systems, the wide-range digital image data are acquired by using the electronic charge generated on a drum coated with a thin layer of amorphous selenium. The appearance of a DSP or DSD radiograph is then determined by user-selected image processing operations: tone scaling, spatial frequency processing, and dynamic range compensation. Digital chest radiographs processed with strong regional equalization provide both excellent contrast in the lungs and effective display of the mediastinum and chest wall. At visual comparison, the high lung contrast and good mediastinal, retrocardiac, and subdiaphragmatic detail provided by the DSD method distinguish it from the other two methods.

Humans↗

PubMed1997

Electrical stimulation of the auditory nerve. I. Correlation of physiological responses with cochlear status.

The purpose of the present study was to evaluate evoked potential and single fibre responses to biphasic current pulses in animals with varying degrees of cochlear pathology, and to correlate any differences in the physiological response with status of the auditory nerve. Six cats, whose cochleae ranged from normal to a severe neural loss (< 5% spiral ganglion survival), were used. Morphology of the electrically evoked auditory brainstem response (EABR) was similar across all animals, although electrophonic responses were only observed from the normal animal. In animals with extensive neural pathology, EABR thresholds were elevated and response amplitudes throughout the dynamic range were moderately reduced. Analysis of single VIIIth nerve fibre responses were based on 207 neurons. Spontaneous discharge rates among fibres depended on hearing status, with the majority of fibres recorded from deafened animals exhibiting little or no spontaneous activity. Electrical stimulation produced a monotonic increase in discharge rate, and a systematic reduction in response latency and temporal jitter as a function of stimulus intensity for all fibres examined. Short-duration current pulses elicited a highly synchronous response (latency < 0.7 ms), with a less well synchronized response sometimes present (0.7-1.1 ms). There were, however, a number of significant differences between responses from normal and deafened cochleae. Electrophonic activity was only present in recordings from the normal animal, while mean threshold, dynamic range and latency of the direct electrical response varied with cochlear pathology. Differences in the ability of fibres to follow high stimulation rates were also observed; while neurons from the normal cochlea were capable of 100% entrainment at high rates (600-800 pulses per second (pps)), fibres recorded from deafened animals were often not capable of such entrainment at rates above 400 pps. Finally, a number of fibres in deafened animals showed evidence of 'bursting', in which responses rapidly alternated between high entrainment and periods of complete inactivity. This bursting pattern was presumably associated with degenerating auditory nerve fibres, since it was not recorded from the normal animal. The present study has shown that the pathological response of the cochlea following a sensorineural hearing loss can lead to a number of significant changes in the patterns of neural activity evoked via electrical stimulation. Knowledge of the extent of these changes have important implications for the clinical application of cochlear implants.

Acoustic Stimulation↗

PubMed2000

Postelectrophoretic staining of proteins separated by two-dimensional gel electrophoresis using SYPRO dyes.

While the classical silver stain has been the method of choice for high sensitivity protein visualization on two-dimensional gel electrophoresis (2-D PAGE), post-electrophoretic fluorescent staining with the SYPRO group of dyes has emerged to challenge silver staining for proteome analysis. The latter offers improved sensitivity, higher dynamic range and easy handling. However, most of the published data were derived from analysis of 1-D gel separations. In this work, we have focused on three commercially available fluorescent dyes, SYPRO Ruby, SYPRO Orange and SYPRO Red (Molecular Probes, Eugene, OR, USA) and studied their sensitivity and dynamic range on 2-D PAGE. The use of a multiwavelength fluorescent scanner to image 2-D protein profiles visualized with fluorescent staining is discussed, and a detailed comparison with analysis by silver staining is also provided. These results demonstrate the advantages of using SYPRO dyes, which are in agreement with the literature based on 1-D gel electrophoresis, and give a more realistic understanding of the performance of these fluorescent dyes with 2-D PAGE.

Dextrans↗

PubMed2000

Rate representation of tones in noise in the inferior colliculus of decerebrate cats.

Neurons in the central nucleus of the inferior colliculus (ICC) of decerebrate cats show three major response patterns when tones of different frequencies and sound-pressure levels (SPLs) are presented to the contralateral ear. The frequency response maps of type I units are uniquely defined by a narrow excitatory area at best frequency (BF: a unit's most sensitive frequency) and surrounding inhibition at higher and lower frequencies. As a result of this receptive field organization, type I units exhibit strong excitatory responses to BF tones but respond only weakly to broadband noise (BBN). These response characteristics predict that type I units are well suited to encode narrowband signals in the presence of background noise. To test this hypothesis, the dynamic range properties of ICC unit types were measured under quiet conditions and in multiple levels of continuous noise. As observed in previous studies of the auditory nerve and cochlear nucleus, type I units showed upward threshold shifts and discharge rate compression in background noise that partially degraded the dynamic range properties of neural representations at high noise levels. Although the other two unit types in the ICC showed similar trends in threshold shift and noise compression, their ability to encode auditory signals was compromised more severely in increasing noise levels. When binaural masking effects were simulated, only type I units showed an enhanced representation of spatially separated signals and maskers that was consistent with human perceptual performance in independent psychoacoustic observations. These results support the interpretation that type I units play an important role in the auditory processing of narrowband signals in background noise and suggest a physiological basis for spatial factors that govern signal detection under free-field listening conditions.

Animals↗

PubMed2003

Quantitative detection of C-reactive protein using phosphocholine-labelled enzyme or microspheres.

C-reactive protein (CRP) is a positive, acute-phase protein. Plasma levels rise dramatically in response to tissue injury or inflammation and fall rapidly after recovery or treatment. Antibody-based human CRP test systems do not readily detect CRP from other animals due to the species specificity of antibodies directed against human CRP. Thus, generic systems for CRP detection, based solely on the interaction between CRP and phosphocholine (PC), have been developed. PC-bovine serum albumin (PC-BSA) conjugates were produced and either labeled with horseradish peroxidase to facilitate CRP detection in a CRP enzyme-linked sorbent assay (ELSA) or coupled to carboxy-modified microspheres to facilitate the nonenzymatic, turbidimetric detection of CRP. The CRP-ELSA is a competitive assay, where the total assay time is 45 min, the assay sensitivity is 1.06 mg/L CRP, and the dynamic range of the assay is 0-500 mg/L. When PC-BSA conjugate is covalently coupled to carboxylated microspheres, agglutination occurs in the presence of CRP, the extent of which depends on the quantity of CRP present in the sample. Total assay time is 5 min with a dynamic range of 25-500 mg/L. Both assay formats are capable of accurately detecting human CRP and the CRP-ELSA can detect canine CRP as a disease state indicator.

Animals↗

PubMed2000

Real-time quantitative PCR for human herpesvirus 6 DNA.

The diagnosis of human herpesvirus 6 (HHV-6) infection represents a complex issue because the most widely used diagnostic tools, such as immunoglobulin G antibody titer determination and qualitative DNA PCR with blood cells, are unable to distinguish between latent (clinically silent) and active (often clinically relevant) infection. We have developed a new, highly sensitive, quantitative PCR assay for the accurate measurement of HHV-6 DNA in tissue-derived cell suspensions and body fluids. The test uses a 5' nuclease, fluorogenic assay combined with real-time detection of PCR amplification products with the ABI PRISM 7700 sequence detector system. The sensitivity of this method is equal to the sensitivity of a nested PCR protocol (lower detection limit, 1 viral genome equivalent/test) for both the A and the B HHV-6 subgroups and shows a wider dynamic range of detection (from 1 to 10(6) viral genome equivalents/test) and a higher degree of accuracy, repeatability, and reproducibility compared to those of a standard quantitative-competitive PCR assay developed with the same reference DNA molecule. The novel technique is versatile, showing the same sensitivity and dynamic range with viral DNA extracted from different fluids (i.e., culture medium or plasma) or from tissue-derived cell suspensions. Furthermore, by virtue of its high-throughput format, this method is well suited for large epidemiological surveys.

DNA, Viral↗

PubMed2005

Investigation of parametric spectral estimation techniques for elasticity imaging.

Several autoregressive (AR) and autoregressive moving average (ARMA) parametric spectral estimators were evaluated for use in tissue strain estimation. Using both 1-D simulations and in vitro phantom experiments, the performance of these parametric spectral strain estimators were compared against both a nonparametric discrete Fourier transform (DFT) spectral strain estimator and a coherent elastographic technique. Parametric spectral estimator model orders were selected based on a modified strain filter approach. This technique illustrated the trade-offs between different signal-processing parameters and a strain estimator performance measure, namely the area under the strain filter (using applied strain dynamic range of 0.1 to 50%). The Yule-Walker AR spectral strain estimator outperformed all other parametric methods evaluated, but failed to outperform the DFT-based approach. Furthermore, both these spectral strain-estimation techniques exhibit an elastographic signal-to-noise ratio (SNR(e)) and strain estimation dynamic range not achievable using conventional elastography without global stretching.

Algorithms↗

PubMed2004

Use of intraoperative dynamic infrared imaging with detection wavelength of 7-14 microm in the surgical obliteration of spinal arteriovenous fistula: case report and technical considerations.

BACKGROUND AND OBJECTIVE: Although improvements of spatial and temporal resolution in infrared (IR) imaging have enabled intraoperative real-time acquisition of physiological and pathological information on living organs, the imaging qualities of anatomical delineation of blood vessels and functional delineation of blood flow were insufficient to serve as visual monitoring. The main reason was partly due to the lack of an appropriate IR detection IR band (formerly 3 - 5 micro m), and the broad dynamic range in previous modalities. METHODS: To make a good contrast between blood vessels and surrounding tissues, the detection wavelength was shifted to the long-wave (7 - 14 micro m) part of IR spectrum, which includes the peak IR wave from living tissue (9 - 10 micro m), and the dynamic range was confined to +/- 10 degrees C around 35 degrees C. The novel camera system (IRIS IV infrared imaging system) was used for the visual monitoring of blood flow during the obliteration of a spinal perimedullary arteriovenous fistula at Th 7 in 71-year-old male patient. The temperature resolution of camera was 0.15 degrees C, with its intensity resolution of 16 bit (320 x 240 pixels), and data were stored at a rate of 30 frames/second. High-quality delineation of blood vessels and blood flow was obtained all through the procedure without use of cold saline, which was an inevitable procedure to make contrast in the previously used thermography. However, the occasional use of an air blower was helpful to achieve adequate images in the deep and narrow area of the surgical field. The amount of shunt flow reduction was visualized by the intensity in the acquired imaging, which was also confirmed later by digital subtraction angiography. CONCLUSION: From the present experience, it is considered that this type of imaging may be able to substitute intraoperative blood vessel and blood flow monitoring in spinal and other neurosurgical disorders.

Aged↗

PubMed2003

Factors associated with development of speech perception skills in children implanted by age five.

OBJECTIVE: This study investigated factors contributing to speech perception outcomes in children with prelingual deafness after 4 to 7 yr of multichannel cochlear implant use. The analysis controlled for the effects of child, family and implant characteristics so that educational factors most conducive to maximum implant benefit could be identified. DESIGN: One hundred eighty-one 8- and 9-yr-old children from across the US and Canada who received a cochlear implant by age 5 were administered a battery of speech perception tests. Type and amount of educational intervention since implantation constituted the independent variables. Characteristics of the child, the family, and the implant itself constituted intervening variables. A series of multiple regression analyses determined the amount of variance in speech perception ability accounted for by the intervening variables and the amount of additional variance attributable to independent variables. RESULTS: The children achieved an average level of about 50% open-set speech perception through listening alone and almost 80% through lipreading and listening together, but with scores for individual children ranging from 0 to 100% correct. Over half of the variance in speech perception scores was predicted by characteristics of the child, family, implant and educational program. Significant predictors of good speech perception included greater nonverbal intelligence, smaller family size, longer use of the updated SPEAK/CIS processing strategy, a fully active electrode array, greater electrical dynamic range between threshold and maximum comfort level, and greater growth of loudness with increasing stimulus intensity. After the variance due to these variables was controlled, the primary rehabilitative factor associated with good speech perception skill development was educational emphasis on oral-aural communication. CONCLUSIONS: Children with profound hearing loss achieved unprecedented levels of speech perception skill 4 to 7 yr after cochlear implantation. Use of an updated speech processor, such as SPEAK, contributed significantly to improved speech perception skills, even in children who were initially fitted with an earlier strategy, such as M-PEAK. In addition, the audiologist who programs the cochlear implant makes an important contribution to the child's successful outcome with the device. A well-fitted map, as evidenced by a wide dynamic range and optimal growth of loudness characteristics, contributed substantially to the child's ability to hear speech. Finally, the classroom communication mode used in the child's school affects speech perception outcome. Children whose educational program emphasized dependence on speech and audition for communication were better able to use the information provided by the implant to understand speech.

Canada↗