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PubMedDate not supplied

Design and study of rifampicin oral controlled release formulations.

Oral controlled release formulations of rifampicin have been developed by using hydroxypropyl methylcellulose polymer at different ratios. From in vitro release data, we found that the release was extended with an increase of polymer proportion from 20% to 40%. However, increase in polymer beyond 40% resulted in no significant change in the release rate. There was a distinct difference in the release rate and release character due to variation in the compression force. The release kinetics were analyzed using Ritger and Peppas exponential equation. Stability studies at ambient storage conditions for 1 year showed that formulations were stable.

Algorithms↗
PubMed1998

Anatomic region-based dynamic range compression for chest radiographs using warping transformation of correlated distribution.

The purpose of this paper is to investigate the effectiveness of our novel dynamic range compression (DRC) for chest radiographs. The purpose of DRC is to compress the gray scale range of the image when using narrow dynamic range viewing systems such as monitors. First, an automated segmentation method was used to detect the lung region. The combined region of mediastinum, heart, and subdiaphragm was defined based on the lung region. The correlated distributions, between a pixel value and its neighboring averaged pixel value, for the lung region and the combined region were calculated. According to the appearance of overlapping of two distributions, the warping function was decided. After pixel values were warped, the pixel value range of the lung region was compressed while preserving the detail information, because the warping function compressed the range of the averaged pixel values while preserving the pixel value range for the pixels which had had the same averaged pixel value. The performance was evaluated with our criterion function which was the contrast divided by the moment, where the contrast and the moment represent the sum of the differences between the pixel values and the averaged values of eight pixels surrounding that pixel, and the sum of the differences between the pixel values and the averaged value of all pixels in the region-of-interest, respectively. For 71 screening chest images from Johns Hopkins University Hospital (Baltimore, MD), this method improved our criterion function at 11.7% on average. The warping transformation algorithm based on the correlated distribution was effective in compressing the dynamic range while simultaneously preserving the detail information.

Humans↗
PubMed2000

Synthesis and modification of the whistles of the bottlenose dolphin, Tursiops truncatus.

A signal-processing algorithm was developed to analyze harmonic frequency-modulated sounds, to modify the parameters of the analyzed signal, and to synthesize a new analytically specified signal that resembles the original signal in specified features. This algorithm was used with dolphin whistles, a frequency-modulated harmonic signal that has typically been described in terms of its contour, or pattern of modulation of the fundamental frequency. In order to test whether other features may also be salient to dolphins, the whistle analysis calculates the energies at the harmonics as well as the fundamental frequency of the whistle. The modification part of the algorithm can set all of these energies to a constant, can shift the whistle frequency, and can expand or compress the time base or the frequency of the whistle. The synthesis part of the algorithm then synthesizes a waveform based upon the energies and frequencies of the fundamental and first two harmonics. These synthetic whistles will be useful for evaluating what acoustic features dolphins use in discriminating different whistles.

Algorithms↗
PubMed2004

A wavelet-based region of interest encoder for the compression of angiogram video sequences.

A new method for the compression of angiogram video sequences is presented. The method is based on the philosophy that diagnostically significant areas of the image should be allocated the greatest proportion of the total allocated bit budget. The approach uses a three-dimensional wavelet-coder based on the popular set partitioning in hierarchical trees algorithm. Incorporated into this framework are a region-of-interest (ROI) detection stage and a texture-modeling stage. The combined result is an approach that models the high-frequency wavelet coefficients for some diagnostically unimportant regions of the image in an extremely efficient manner. This allows additional bits to be used within the ROI to improve the quality of the diagnostically significant areas. Results are compared for a number of real data sets and evaluated by trained cardiologists.

Algorithms↗
PubMed2006

JPEG compression history estimation for color images.

We routinely encounter digital color images that were previously compressed using the Joint Photographic Experts Group (JPEG) standard. En route to the image's current representation, the previous JPEG compression's various settings-termed its JPEG compression history (CH)-are often discarded after the JPEG decompression step. Given a JPEG-decompressed color image, this paper aims to estimate its lost JPEG CH. We observe that the previous JPEG compression's quantization step introduces a lattice structure in the discrete cosine transform (DCT) domain. This paper proposes two approaches that exploit this structure to solve the JPEG Compression History Estimation (CHEst) problem. First, we design a statistical dictionary-based CHEst algorithm that tests the various CHs in a dictionary and selects the maximum a posteriori estimate. Second, for cases where the DCT coefficients closely conform to a 3-D parallelepiped lattice, we design a blind lattice-based CHEst algorithm. The blind algorithm exploits the fact that the JPEG CH is encoded in the nearly orthogonal bases for the 3-D lattice and employs novel lattice algorithms and recent results on nearly orthogonal lattice bases to estimate the CH. Both algorithms provide robust JPEG CHEst performance in practice. Simulations demonstrate that JPEG CHEst can be useful in JPEG recompression; the estimated CH allows us to recompress a JPEG-decompressed image with minimal distortion (large signal-to-noise-ratio) and simultaneously achieve a small file-size.

Algorithms↗
PubMed2005

Lossless generalized-lSB data embedding.

We present a novel lossless (reversible) data-embedding technique, which enables the exact recovery of the original host signal upon extraction of the embedded information. A generalization of the well-known least significant bit (LSB) modification is proposed as the data-embedding method, which introduces additional operating points on the capacity-distortion curve. Lossless recovery of the original is achieved by compressing portions of the signal that are susceptible to embedding distortion and transmitting these compressed descriptions as a part of the embedded payload. A prediction-based conditional entropy coder which utilizes unaltered portions of the host signal as side-information improves the compression efficiency and, thus, the lossless data-embedding capacity.

Algorithms↗
PubMed2003

Optimization of wavelet decomposition for image compression and feature preservation.

A neural-network-based framework has been developed to search for an optimal wavelet kernel that can be used for a specific image processing task. In this paper, a linear convolution neural network was employed to seek a wavelet that minimizes errors and maximizes compression efficiency for an image or a defined image pattern such as microcalcifications in mammograms and bone in computed tomography (CT) head images. We have used this method to evaluate the performance of tap-4 wavelets on mammograms, CTs, magnetic resonance images, and Lena images. We found that the Daubechies wavelet or those wavelets with similar filtering characteristics can produce the highest compression efficiency with the smallest mean-square-error for many image patterns including general image textures as well as microcalcifications in digital mammograms. However, the Haar wavelet produces the best results on sharp edges and low-noise smooth areas. We also found that a special wavelet whose low-pass filter coefficients are 0.32252136, 0.85258927, 1.38458542, and -0.14548269) produces the best preservation outcomes in all tested microcalcification features including the peak signal-to-noise ratio, the contrast and the figure of merit in the wavelet lossy compression scheme. Having analyzed the spectrum of the wavelet filters, we can find the compression outcomes and feature preservation characteristics as a function of wavelets. This newly developed optimization approach can be generalized to other image analysis applications where a wavelet decomposition is employed.

Algorithms↗
PubMed2004

Geometric invariance in image watermarking.

Surviving geometric attacks in image watermarking is considered to be of great importance. In this paper, the watermark is used in an authentication context. Two solutions are being proposed for such a problem. Both geometric and invariant moments are used in the proposed techniques. An invariant watermark is designed and tested against attacks performed by StirMark using the invariant moments. On the other hand, an image normalization technique is also proposed which creates a normalized environment for watermark embedding and detection. The proposed algorithms have the advantage of being robust, computationally efficient, and no overhead needs to be transmitted to the decoder side. The proposed techniques have proven to be highly robust to all geometric manipulations, filtering, compression and slight cropping which are performed as part of StirMark attacks as well as noise addition, both Gaussian and salt & pepper.

Algorithms↗
PubMed2004

Video compression for lossy packet networks with mode switching and a dual-frame buffer.

Video codecs that use motion compensation benefit greatly from the development of algorithms for near-optimal intra/inter mode switching within a rate-distortion framework. A separate development has involved the use of multiple-frame prediction, in which more than one past reference frame is available for motion estimation. In this paper, we show that using a dual-frame buffer (one short-term frame and one long-term frame available for prediction) together with intra/inter mode switching improves the compression performance of the coder. We improve the mode-switching algorithm with the use of half-pel motion vectors. In addition, we investigate the effect of feedback in making more informed and effective mode-switching decisions. Feedback information is used to limit drift errors due to packet losses by synchronizing the long-term frame buffers of both the encoder and the decoder.

Algorithms↗
PubMed1997

A digital filterbank hearing aid: three digital signal processing algorithms--user preference and performance.

OBJECTIVE: Three digital signal processing algorithms named RangeEar, DynEar, and LinEar were compared with regard to user preference and performance when a wearable digital filterbank hearing aid was used. All three algorithms provided individual frequency shaping via a seven-band filterbank. Compression was used in a low-frequency (LF) and a high-frequency (HF) channel. RangeEar and DynEar used wide dynamic range syllabic compression in the LF channel, whereas LinEar used compression limiting. In the HF channel, RangeEar used a slow acting automatic volume control, whereas DynEar and LinEar used compression limiting. The subjects had access to a manual volume control when using the LinEar or DynEar options. DESIGN: The study included 13 hearing aid users with symmetrical sensorineural losses. In a 1 mo long blind field test, the RangeEar algorithm was compared with the preferred algorithm from an earlier study, DynEar or LinEar. A data logger function was included for objective recording of the total time each algorithm was used and how the volume controls were used. The preference was based on the time used for each algorithm and from subjective statements. Threshold signal-to-noise ratio (S/N-threshold) for speech was tested, and sound quality ratings were obtained through a questionnaire. RESULTS: Of the 13 subjects, six preferred the RangeEar fitting and another four preferred the DynEar fitting. Two subjects preferred the LinEar fitting and one had equal preference for RangeEar and LinEar. The results from the questionnaire showed that the preferred fittings were rated higher concerning overall impression of sound quality and clearness, whereas the S/N for the speech test did not show any differences. Preferences, where stated, could be predicted from auditory dynamic range measurements in the LF and HF frequency ranges. The mean dynamic range was broader for low and narrower for high frequencies for those who preferred the RangeEar or DynEar fitting as compared with those who preferred the LinEar fitting. The preference between RangeEar and DynEar was predicted by differences in the HF range, with the narrower dynamic range for the DynEar preference subjects. CONCLUSION: Most subjects preferred the option of having a wide dynamic range syllabic compressor in the LF channel and having the overall gain in the HF channel adjustable, either manually (DynEar) or automatically (RangeEar).

Adult↗
PubMed2006

Assessment of pretest probability of pulmonary embolism in the emergency department by physicians in training using the Wells model.

INTRODUCTION: Assessment of pretest probability should be the initial step in investigation of patients with suspected pulmonary embolism (PE). In teaching hospitals physicians in training are often the first physicians to evaluate patients. OBJECTIVE: To evaluate the accuracy of pretest probability assessment of PE by physicians in training using the Wells clinical model and to assess the safety of a diagnostic strategy including pretest probability assessment. PATIENTS AND METHODS: 291 consecutive outpatients with clinical suspicion of PE were categorized as having a low, moderate or high pretest probability of PE by physicians in training who could take supervising physicians' advice when they deemed necessary. Then, patients were managed according to a sequential diagnostic algorithm including D-dimer testing, lung scan, leg compression ultrasonography and helical computed tomography. Patients in whom PE was deemed absent were followed up for 3 months. RESULTS: 34 patients (18%) had PE. Prevalence of PE in the low, moderate and high pretest probability groups categorized by physicians in training alone was 3% (95% confidence interval (CI): 1% to 9%), 31% (95% CI: 22% to 42%) and 100% (95% CI: 61% to 100%) respectively. One of the 152 untreated patients (0.7%, 95% CI: 0.1% to 3.6%) developed a thromboembolic event during the 3-month follow-up period. CONCLUSION: Physicians in training can use the Wells clinical model to determine pretest probability of PE. A diagnostic strategy including the use of this model by physicians in training with access to supervising physicians' advice appears to be safe.

Adolescent↗
PubMed2006

Prediction and monitoring the therapeutic response of chronic dermal wounds.

A significant proportion of chronic wounds fail to heal in response to treatment of underlying pathologies combined with good wound care practice. Current prognostic tests to identify these wounds rely on the use of algorithms based on clinically measurable parameters such as wound dimensions and wound duration. Venous leg ulcers may be stratified into healing/non healing at 24 weeks of compression therapy and diabetic foot ulcer treatment outcome assessed using a 3-parameter algorithm. Accurate and reproducible measurement of wound area is required for these algorithms to have clinical utility. Whilst a number of attempts have been made to develop computerised wound-assessment techniques, wound tracing by clinicians combined with planimetry remains the standard methodology. Once treatment has been initiated, it is important to continuously monitor the wound to assess efficacy of treatment. This can be achieved by measuring wound area change over the first weeks of treatment to identify whether re-assessment of treatment strategy is required. A number of algorithms for assessing rate of wound area change have been evaluated to determine a surrogate endpoint for healing. Retrospective analysis of large patient groups indicates that approximately 75% correct prediction of healing outcome can be achieved.

Bandages↗
PubMed2003

A dynamic nonlinear time domain model for reconstruction and compression of cardiovascular signals with application to telemedicine.

A new nonlinear time domain model is proposed in this paper for signals of cardiovascular origin. An equation of the dynamic nonlinear model has been obtained by considering a masking function, which is modulated by a harmonic series with the baseline drift incorporated into the model. Signal reconstruction using model parameters has established the effectiveness of the model for signal compression. Improvement has been effected by using neural networks for reducing the time for optimizing the initial parameters. An improved adaptive optimization step size algorithm has also been implemented. Results show that the technique is able to provide reasonable compression with low error between the original and reconstructed signals. One of the main advantages of the model is its potential of being used for compression of many different types of biosignals transmitted in parallel. Incorporation of the compression model into a telemedicine system has led to considerable saving in transmission time for patient data.

Algorithms↗
PubMed2004

Optimizing chest compression to rescue ventilation ratios during one-rescuer CPR by professionals and lay persons: children are not just little adults.

OBJECTIVE: To estimate the optimum ratio of chest compressions to ventilations for one-rescuer CPR that maximizes systemic oxygen delivery in children. METHOD: Equations describing oxygen delivery and blood flow during CPR as functions of the number of compressions and the number of ventilations delivered over time were adapted from the former work of Babbs and Kern. These equations were solved explicitly as a function of body weight, using scaling algorithms based upon principles of developmental anatomy and physiology. RESULTS: The optimal compression to ventilation (C/V) ratios for infants and younger children increase sharply as a function of body weight. Optimal C/V ratios are lower for professional rescuers, who take less time to deliver a rescue breath, than for lay rescuers, who interrupt chest compressions for longer to perform ventilations. For professional rescuers the optimal C/V ratio, x*, is approximately 1.6 square root W where the W is the patient's body weight in kg. For lay rescuers the optimum C/V ratio is approximately 2.8 square root W. These values can be approximated for children and teens by the following rules of thumb, based upon the age of the victim: "5 + one half the age in years" for professional rescuers and "5 + age in years" for lay rescuers. CONCLUSIONS: Compression to ventilation ratios in CPR should be smaller for children than for adults and gradually increase as a function of body weight. Optimal CPR in children requires relatively more ventilation than optimal CPR in adults. A universal compression/ventilation ratio of 50:2, targeted to optimize adult resuscitation, would not be appropriate for infants and young children.

Adult↗
PubMed1997

Modelling of free radicals production in a collapsing gas-vapour bubble.

This paper deals with a model linking bubble dynamics under an acoustic pressure field and production of free radicals in the resulting collapses of this bubble. The bubble dynamics model includes interdiffusion of gas and vapour in the bubble as well as evaporation or condensation at the interface, and it assumes uniformity of the internal pressure and perfect gas law for the gas vapour mixture. At the maximum compression of the bubble, all the reactions of dissociation which can occur are assumed at thermodynamic equilibrium. The local composition (especially in free radicals) in the bubble is then calculated by an algorithm based on free energy minimization using the information concerning the maximum compression provided by the bubble dynamics model resolution. Using this model a comparison of free radicals production has been made for two different driving frequencies (20 kHz and 500 kHz), and at given bubble radius and acoustic pressure, an optimum of liquid bulk temperature has been derived for the production of free radicals very similar to the experimental one concerning oxidation reactions in aqueous phase.

Journal Article↗
PubMed2005

Motion-JPEG2000 codec compensated for interlaced scanning videos.

This paper presents an implementation scheme of Motion-JPEG2000 (MJP2) integrated with invertible deinterlacing. In previous work, we developed an invertible deinterlacing technique that suppresses the comb-tooth artifacts which are caused by field interleaving for interlaced scanning videos, and affect the quality of scalable frame-based codecs, such as MJP2. Our technique has two features, where sampling density is preserved and image quality is recovered by an inverse process. When no codec is placed between the deinterlacer and inverse process, the original video is perfectly reconstructed. Otherwise, it is almost completely recovered. We suggest an application scenario of this invertible deinterlacer for enhancing the sophisticated signal-to-noise ratio scalability in the frame-based MJP2 coding. The proposed system suppresses the comb-tooth artifacts at low bitrates, while enabling the quality recovery through its inverse process at high bitrates within the standard bitstream format. The main purpose of this paper is to present a system that yields high quality recovery for an MJP2 codec. We demonstrate that our invertible deinterlacer can be embedded into the discrete.wavelet transform employed in MJP2. As a result, the energy gain factor to control rate-distortion characteristics can be compensated for optimal compression. Simulation results show that the recovery of quality is improved by, for example, more than 2.0 dB in peak signal-to-noise ratio by applying our proposed gain compensation when decoding 8-bit grayscale Football sequence at 2.0 bpp.

Algorithms↗
PubMedDate not supplied

Viscoelastic property detection by elastic displacement NMR measurements.

An attempt was undertaken to analyze the phase changes in the transverse magnetization component, M[perp], determined in NMR response by an elastic wave in the presence of two pulses with opposite magnetic field gradient directions. The obtained theoretical results indicate that such changes are significant in biologic tissues. Their measurement by NMR opens up new possibilities for detecting the displacement and some viscoelastic properties such as the adiabatic compressibility coefficient, amplitude wave damping coefficient, frequency and dispersion strength of elastic relaxation processes, etc. The method may be useful in basic applied research and in medical diagnosis of some diseases resulting in the variation of elastic properties of biological tissues, eg, atherosclerosis.

Algorithms↗