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PubMed2006

A fast and effective model for wavelet subband histograms and its application in texture image retrieval.

This paper presents a novel, effective, and efficient characterization of wavelet subbands by bit-plane extractions. Each bit plane is associated with a probability that represents the frequency of 1-bit occurrence, and the concatenation of all the bit-plane probabilities forms our new image signature. Such a signature can be extracted directly from the code-block code-stream, rather than from the de-quantized wavelet coefficients, making our method particularly adaptable for image retrieval in the compression domain such as JPEG2000 format images. Our signatures have smaller storage requirement and lower computational complexity, and yet, experimental results on texture image retrieval show that our proposed signatures are much more cost effective to current state-of-the-art methods including the generalized Gaussian density signatures and histogram signatures.

Algorithms↗
PubMed2006

Comments on 'The effect of logarithmic compression on the estimation of the Nakagami parameter for ultrasonic tissue characterization'.

In a recently published paper (Tsui et al 2005 Phys. Med. Biol. 50 3235-44), the authors demonstrated estimation of the Nakagami parameter of the logcompressed envelopes and the application of such an approach in ultrasonic tissue characterization. The comments in this letter suggest that the authors ignored some important statistical properties of logcompressed data leading to serious errors in their studies and results.

Algorithms↗
PubMed1986

Quantitative analysis of intervertebral disc structure.

A reduction in signal intensity from the nucleus can be a feature of intervertebral disc disease. It has been established that T1 and T2 relaxation times of the nucleus decrease with age and that evidence of disc degeneration can be determined before classical clinical features are apparent. A robust multiple point algorithm has been developed which now enables proton density and T1 and T2 values to be computed for each pixel, providing images which are effectively spatial maps of these parameters. Such high resolution maps have provided quantitative data from volunteers, patients and cadavers. These studies have been carried out with specially constructed coils and the cadaveric information compared with cut sections. The spatial maps revealed detailed anatomic structures including the laminae of the annulus and relative levels of hydration. These levels, which are known to be related to the ability of the disc to withstand compressive loads, can now be measured in vivo. Analysis of the proton density and relaxation times in vivo has demonstrated that both water content and the chemical environment in the nucleus change during aging. The results are consistent with changes in the glycosaminoglycan content and fixed charged density measured by other chemical and physical techniques. Such detailed methods can be used to investigate the effects of aging and disease on disc structure and have enabled observations to be made of the effects of stress on the normal disc.

Adolescent↗
PubMed2006

A safe and cost-effective short hospital stay protocol to identify patients at low risk for the development of significant hypocalcemia after total thyroidectomy.

OBJECTIVE: The objective of this retrospective chart review was to determine if serial postoperative serum calcium levels early after total thyroidectomy can be used to develop an algorithm that identifies patients who are unlikely to develop significant hypocalcemia and can be safely discharged within 24 hours after surgery. METHODS: Records of 135 consecutive patients who underwent total/completion thyroidectomy and were operated on by the senior author from 2001 to 2005 have been reviewed. For the entire study group, reports of the early postoperative serum calcium levels (6 hours and 12 hours postoperatively), final thyroid pathology, preoperative examination, inpatient course, and postoperative follow up were reviewed. An endocrine medicine consultation was obtained for all patients while in the hospital after surgery. For patients who developed significant hypocalcemia, reports of their management and the need for readmission or permanent medications for hypoparathyroidism were reviewed. According to the change in serum calcium levels between 6 hours and 12 hours postoperatively, patients were divided into two groups: 1) positive slope (increasing) and 2) nonpositive (nonchanging/decreasing). RESULTS: All patients with a positive slope (50/50) did not develop significant hypocalcemia in contrast to only 59 of 85 patients (69.4%) with a nonpositive slope (P < .001, positive predictive value of positive slope in predicting freedom from significant hypocalcemia = 100%, 95% confidence interval = 92.9-100). In the nonpositive slope group, 61 patients had a serum calcium level > or =8 mg/dL at 12 hours postoperatively (< or =0.5 mg/dL below the low end of normal), and 53 (87%) of these patients remained free of significant hypocalcemia in contrast to only 6 (25%) of 24 patients with serum calcium level <8 mg/dL at 12 hours postoperatively (sensitivity = 90%, positive predictive value = 87%). In addition, of the eight patients who developed significant hypocalcemia in the nonpositive slope group with a serum calcium level > or =8 mg/dL at 12 hours postoperatively, 7 (88%) patients developed the signs and symptoms during the first 24 hours after total thyroidectomy. Readmission and permanent need for calcium supplementation happened in two patients, respectively, all with serum calcium levels <8 mg/dL at 12 hours after total thyroidectomy. The compressive and/or symptomatic large multinodular goiter as an indication for thyroidectomy was associated with developing significant hypocalcemia (P < .05). There was no statistically significant correlation between the development of significant hypocalcemia and gender, age, thyroid pathology other than goiter, or neck dissection. CONCLUSION: Patients with a positive serum calcium slope (t = 6 and 12 hours) after total thyroidectomy are safe to discharge within 24 hours after surgery with patient education with or without calcium supplementation. In addition, patients with a nonpositive slope and a serum calcium level > or =8 mg/dL at 12 hours postoperatively (< or =0.5 mg/dL below the low end of normal) are unlikely to develop significant hypocalcemia, especially beyond 24 hours postoperatively, and therefore can be safely discharged within 24 hours after total thyroidectomy with patient education and oral calcium supplementation. Our management algorithm identifies those patients at low risk of developing significant hypocalcemia early in the postoperative course after total thyroidectomy to allow for a short hospital stay and safe discharge.

Algorithms↗
PubMedDate not supplied

Brain-stem auditory evoked responses as indicators of early brain insult.

The relationship between cranial ultrasonograms (SONOs) and brain-stem auditory evoked responses (BAERs) was evaluated in 2 independent samples of newborn infants at risk for brain injury (n = 113 and 203). Features of the BAER wave forms subjected to stepwise linear discriminant analysis formed the basis of an algorithm used to detect and follow early brain injury. Using this algorithm, information derived from BAERs reliably predicted SONO abnormalities at least 82.3% of the time in the initial study which was replicated with the second sample (77.3%). The wave I component latency (CL) and the wave III-V inter-peak latency interval (IPL) were independent of each other, and both contributed to a prediction of SONO abnormality. Possible mechanisms for these BAER results include compromise to the cochlear membrane or to the auditory nerve itself as well as prolongation of transmission in the brain-stem due to brain-stem hemorrhage, edema, or compression. Normative BAER values and non-linear regression functions for the wave I, III and V CLs, and the I-III, III-V, and I-V IPLs were calculated across age using data from 109 infants who demonstrated normal BAER patterns and had no history of SONO abnormalities. Our analyses indicate BAER techniques, where a single higher intensity is used to produce the BAER wave form, are both valid and efficient for use in the evaluation of early brain injury.

Brain Injuries↗
PubMed1997

Numerical conversion of transient to harmonic response functions for linear viscoelastic materials.

Viscoelastic material behavior is often characterized using one of the three measurements: creep, stress-relaxation or dynamic sinusoidal tests. A two-stage numerical method was developed to allow representation of data from creep and stress-relaxation tests on the Fourier axis in the Laplace domain. The method assumes linear behavior and is theoretically applicable to any transient test which attains an equilibrium state. The first stage numerically resolves the Laplace integral to convert temporal stress and strain data, from creep or stress-relaxation, to the stiffness function, G(s), evaluated on the positive real axis in the Laplace domain. This numerical integration alone allows the direct comparison of data from transient experiments which attain a final equilibrium state, such as creep and stress relaxation, and allows such data to be fitted to models expressed in the Laplace domain. The second stage of this numerical procedure maps the stiffness function, G(s), from the positive real axis to the positive imaginary axis to reveal the harmonic response function, or dynamic stiffness, G(j omega). The mapping for each angular frequency, s, is accomplished by fitting a polynomial to a subset of G(s) centered around a particular value of s, substituting js for s and thereby evaluating G(j omega). This two-stage transformation circumvents previous numerical difficulties associated with obtaining Fourier transforms of the stress and strain time domain signals. The accuracy of these transforms is verified using model functions from poroelasticity, corresponding to uniaxial confined compression of an isotropic material and uniaxial unconfined compression of a transversely isotropic material. The addition of noise to the model data does not significantly deteriorate the transformed results and data points need not be equally spaced in time. To exemplify its potential utility, this two-stage transform is applied to experimental stress relaxation data to obtain the dynamic stiffness which is then compared to direct measurements of dynamic stiffness using steady-state sinusoidal tests of the same cartilage disk in confined compression. In addition to allowing calculation of the dynamic stiffness from transient tests and the direct comparison of experimental data from different tests, these numerical methods should aid in the experimental analysis of linear and nonlinear material behavior, and increase the speed of curve-fitting routines by fitting creep or stress relaxation data to models expressed in the Laplace domain.

Algorithms↗
PubMed2001

The effects of formulation factors on the moist granulation technique for controlled-release tablets.

Controlled-release tablets were prepared by the moist granulation technique (MGT), a granulating method that uses very limited amounts of liquid and requires microcrystalline cellulose (MCC) to absorb moisture. Acetaminophen (APAP) was the model drug, and the polymer hydroxypropylcellulose (HPC) served as the controlled-release agent. The effects of varying drug, binder (polyvinylpyrrolidone, PVP), polymer, and MCC levels on granule properties and tablet dissolution were studied. Dissolution testing was carried out in distilled water using the USP paddle method. In all cases, the granules flowed and compressed well. The granule properties were evaluated by calculating the mean particle size for all batches from sieve analysis data. The results indicate that MGT can be applied to control drug release, and at a polymer content of 44.6% or more, the process is robust enough to allow slight variations in formulation factors without affecting drug release.

Acetaminophen↗
PubMed2005

Osteoporosis due to glucocorticoid use in children with chronic illness.

Osteoporosis is increasingly recognized as a complication of chronic childhood illnesses, particularly when glucocorticoids (GCs) are necessary for treatment. Elucidation of the mechanisms leading to bone fragility in these settings requires disentanglement of the relative contributions of myriad risk factors, including disease activity, muscle weakness, immobilization, delayed growth and puberty, compromised nutrition, and osteotoxic medications. Over the years, bone mass and density evaluations by dual energy X-ray absorptiometry (DXA) have become popular for assessing bone health in children; however, such measurements are difficult to interpret because of the confounding effect of bone size and the lack of DXA-based densitometric criteria for defining osteoporosis in childhood. Recently, a new diagnostic approach for evaluation of densitometric data in children has been suggested, driven by Frost's mechanostat theory. A diagnostic algorithm based on the mechanostat theory of bone-muscle development is proposed for the characterization of bone disease in children with chronic illness. In addition to DXA-based assessments, techniques such as peripheral quantitative computerized tomography and ilial histomorphometry, for which there are pediatric reference data, are gaining ground in the characterization of skeletal changes due to chronic illness. Although these diagnostic techniques expand our understanding of osteoporosis in children, they do not replace clinical assessment. Concrete clinical evidence for GC-induced bone fragility can be seen in spinal changes due to vertebral compression, with spinal morphometry emerging as an essential, but frequently overlooked, tool in the evaluation of children's bone health. Presently, osteoporosis treatment in the chronic illness setting remains experimental and should be restricted to clinical studies. Following an understanding of the natural history of GC-induced osteoporosis in children, randomized, placebo-controlled prevention and intervention trials will be the next step toward the development of clinical practice guidelines.

Adolescent↗
PubMed1997

Diagnostic utility of ultrasonography of leg veins in patients suspected of having pulmonary embolism.

BACKGROUND: The standard diagnostic approach in patients suspected of having pulmonary embolism starts with perfusion-ventilation lung scanning. If the resulting scan is not diagnostic, pulmonary angiography should be done. The use of tests for deep venous thrombosis has been advocated as an adjunct to establishing the diagnosis of pulmonary embolism, but no prospective studies have provided adequate information about the value of these tests. OBJECTIVE: To determine the accuracy and potential clinical utility of compression ultrasonography in the diagnosis of pulmonary embolism. DESIGN: Prospective cohort study with blinded assessment of ultrasonographic results. SETTING: Teaching hospital. PATIENTS: 397 consecutive inpatients and outpatients in whom pulmonary embolism was clinically suspected. MEASUREMENTS: Sensitivity and specificity of compression ultrasonography. Perfusion-ventilation scanning and angiography were the conjoint gold standard for determining the presence or absence of pulmonary embolism. Also calculated were the number of angiograms and lung scans avoided and the number of patients unnecessarily treated when compression ultrasonography was included in the diagnostic strategy. RESULTS: The overall sensitivity of compression ultrasonography for deep venous thrombosis in patients with pulmonary embolism was 29% (95% CI 22% to 37%); the specificity was 97% (CI, 94% to 99%). Adding ultrasonography to the diagnostic approach before lung scanning would avoid approximately 14% of lung scans and 9% of angiograms but would lead to unnecessary treatment of 13% of patients who have an abnormal ultrasonographic result (2% to 4% of all those receiving anticoagulation). When compression ultrasonography is done only in patients with a nondiagnostic lung scan, 9% of angiographies are prevented at the cost of unnecessarily treating 26% of patients who have an abnormal ultrasonographic result (2% of all patients receiving anticoagulation). CONCLUSION: The diagnostic value of compression ultrasonography for the detection of deep venous thrombosis in patients suspected of having pulmonary embolism is limited; the gain in diagnostic efficiency obtained through the use of ultrasonography may be offset by a loss in diagnostic accuracy.

Adolescent↗
PubMed1994

A microstructural model for the elastic response of articular cartilage.

A model of articular cartilage is developed in which the continuum stiffness tensor is related to the tissue's microstructure. The model consists of bilinear elastic fibers embedded in an elastic matrix. Homogenization techniques are used to relate this level of organization to the macroscopic response of the tissue. The model includes the effects of spatial orientation of fibers, pre-stress in the fibers and matrix resulting from matrix swelling, slipping at the interface between the fibers and the matrix, fiber buckling in compression, and deformation-induced fiber reorientation. The model predicts increased axial stiffness with increasing stretch due to fiber reorientation, reduced axial and shear stiffness with slipping between fiber and matrix and a sensitivity of the tissue response to the swelling pressure in the matrix, the matrix modulus and the bonding of the fiber matrix interface.

Algorithms↗
PubMed2004

Simultaneous storage of patient information with medical images in the frequency domain.

Digital watermarking is a technique of hiding specific identification data for copyright authentication. Most of the medical images are compressed by joint photographic experts group (JPEG) standard for storage. The watermarking is adapted here for interleaving patient information with medical images during JPEG compression, to reduce storage and transmission overheads. The text data is encrypted before interleaving with images in the frequency domain to ensure greater security. The graphical signals are also interleaved with the image. The result of this work is tabulated for a specific example and also compared with the spatial domain interleaving.

Algorithms↗
PubMed2006

Ambulatory methods for recording cough.

Recording cough sounds to objectively quantify coughing was first performed using large reel-to-reel tape recorders more than 40 years ago. Coughs were counted manually, which is an extremely laborious and time-consuming process. Current technologies including digital recording techniques, data compression and improvements in digital storage capacity should make the process of recording and counting coughs suitable for automation; however, to date no accurate, objective cough monitoring device is available. Cough sounds are easily distinguishable from other vocalizations by the human ear and hence it is reasonable to assume that coughs sounds should have characteristic, identifying acoustic properties. However, the acoustic features of spontaneously occurring cough sounds are extremely variable. Furthermore, in even the worst cases of cough, the time spent speaking is an order of magnitude greater than the time spent coughing. It follows that even an algorithm that mistakes only a very small proportion of speech as cough will still have an unacceptable false positive rate. There is a clear need for an objective measure of cough for use in clinical practice, clinical research and trials of novel treatments. In the near future automated ambulatory systems with sufficient accuracy to be of clinical use should be available.

Acoustics↗
PubMed2004

Exploring lung function with hyperpolarized (129)Xe nuclear magnetic resonance.

With the use of polarization-transfer pulse sequences and hyperpolarized (129)Xe NMR, gas exchange in the lung can be measured quantitatively. However, harnessing the inherently high sensitivity of this technique as a tool for exploring lung function requires a fundamental understanding of the xenon gas-exchange and diffusion processes in the lung, and how these may differ between healthy and pathological conditions. Toward this goal, we employed NMR spectroscopy and imaging techniques in animal models to investigate the dependence of the relative xenon gas exchange rate on the inflation level of the lung and the tissue density. The spectroscopic results indicate that gas exchange occurs on a time scale of milliseconds, with an average effective diffusion constant of about 3.3 x 10(-6)cm(2)/s in the lung parenchyma. Polarization-transfer imaging pulse sequences, which were optimized based on the spectroscopic results, detected regionally increased gas-exchange rates in the lung, indicative of increased tissue density secondary to gravitational compression. By exploiting the gas-exchange process in the lung to encode physiologic parameters, these methods may be extended to noninvasive regional assessments of lung-tissue density and the alveolar surface-to-volume ratio, and allow lung pathology to be detected at an earlier stage than is currently possible.

Algorithms↗
PubMed2006

[Differential diagnosis of hip and groin pain. Symptoms and technique for physical examination].

The differential diagnosis of hip and groin pain with respect to the high frequency of referred pain from the lumbar spine, lower abdomen, and pelvis is demanding. A systematic approach to the hip and groin area is important to identify the origin of pain. Both the history and quality of symptoms and the physical exam are the basics of the diagnostic algorithm. Roentgenograms and possibly an injection with a local anesthetic to the suspected origin of pain often complete the diagnostic work-up.The following report summarizes the typical symptoms of hip and groin disorders. A detailed description of the physical exam including functional tests for impingement, apprehension, adductor-, psoas-, and inguinal-related pain is included.

Arthralgia↗
PubMed2005

The comparison of different feed forward neural network architectures for ECG signal diagnosis.

The electrocardiograms (ECGs) record the electrical activity of the heart and are used to diagnose many heart disorders. This paper proposes a two-stage feed forward neural network for ECG signal classification. The research is aimed at the design of an intelligent ECG diagnosis tool that can recognise heart abnormalities while reducing the complexity, cost, and response time of the system. A number of neural network architectures are designed and compared for their ability to classify six different heart conditions. Two network architectures based on one stage and two stage feed forward neural networks are chosen for this investigation. The training and testing ECG signals are obtained from MIT-BIH database. The network inputs are comprised of 12 ECG features and 13 compressed components of each heart beat signal. The performance of the different modules as well as the efficiency of the whole system is presented. Among different architectures, a proposed multi-stage network named NET_BST possesses the highest recognition rate of around 93%. Therefore, this network proves to be a suitable candidate in ECG signal diagnosis systems.

Algorithms↗
PubMed1997

Angiocardiographic digital still images compressed via irreversible methods: concepts and experiments.

We defined, implemented and tested two new methods for irreversible compression of angiocardiographic still images: brightness error limitation (BEL) and pseudo-gradient adaptive brightness and contrast error limitation (PABCEL). The scan path used to compress the digital images is based on the Peano-Hilbert plane-filling curve. The compression methods limit, for each pixel, the brightness errors introduced when approximating the original image (i.e. the difference between the values of corresponding pixels as grey levels). Additional limitations are imposed to the contrast error observed when considering along the scan path consecutive pixels of both the original and the reconstructed image. After previous testing on angiocardiographic images selected as clinically significant from 35 mm films, we enlarged our experiment to a set of 38 coronary angiograms digitally acquired. BEL and PABCEL methods were experimented according to several values of the implied thresholds. Up to a compression ratio of 9:1 for the BEL method and 10:1 for the PABCEL method, no deterioration of the reconstructed images were detected by human observers. After a visual evaluation, we performed a quantitative evaluation. The visualization of pseudo-colour difference images showed the capability of BEL and PABCEL for preserving the most significant clinical details of the original images. For comparison, we applied the JPEG (joint photographic experts group) image-compression standard to the same set of images. In this case, pseudo-colour difference images showed a homogeneous distribution of errors on the image surface. Quantitative compression results obtained by testing the different methods are comparable, but, unlike JPEG, BEL and PABCEL methods allow the user to keep under his direct control the maximum error allowed at each single pixel of the original image. These different behaviors are confirmed by the values obtained for the considered numerical quality quantifiers.

Algorithms↗
PubMedDate not supplied

Robust fuzzy principal component analysis (FPCA). A comparative study concerning interaction of carbon-hydrogen bonds with molybdenum-oxo bonds.

Principal component analysis (PCA) is a favorite tool in chemometrics for data compression and information extraction. PCA finds linear combinations of the original measurement variables that describe the significant variations in the data. However, it is well-known that PCA, as with any other multivariate statistical method, is sensitive to outliers, missing data, and poor linear correlation between variables due to poorly distributed variables. As a result data transformations have a large impact upon PCA. In this regard one of the most powerful approaches to improve PCA appears to be the fuzzification of the matrix data, thus diminishing the influence of outliers. In this paper we discuss a robust fuzzy PCA algorithm (FPCA). The new algorithm is illustrated on a data set concerning interaction of carbon-hydrogen bonds with transition metal-oxo bonds in molybdenum complexes. Considering, for example, a two component model, FPCA accounts for 97.20% of the total variance and PCA accounts only for 69.75%.

Journal Article↗
PubMedDate not supplied

Towards computer assisted evaluation of plagiocephaly.

Plagiocephaly is a common asymmetry of the skull giving the impression that the subject, usually a neonate, has suffered a compressive force acting unilaterally. Normally innocuous, it is a postural deformity that can be suggestive of other significant abnormalities, e.g. joint dysplasia. Although intuitive measurements of plagiocephaly appear in the literature there is little evidence of analytical evaluation. This paper describes a measurement methodology based on black and white photography. A flat-bed scanner and a personal computer facilitated the transformation of the prepared photograph to standard tagged image file format at 256 grey scale. A utility was used to convert the file scan to a monochrome bitmap image which was displayed on the screen and subjected to an algorithm to compute the centroid of the cranial profile. Radials that emerge from the centroid to the cranial circumference at five degree intervals map to a signal display that represents the plagiocephaly.

Cephalometry↗