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Results for “Measuring algorithm”

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PubMed1996

Automatic fetal head measurements from sonographic images.

RATIONALE AND OBJECTIVES: We designed an image processing technique to automatically measure the biparietal diameter (BPD) and head circumference (HC) from prenatal sonograms. We evaluated the performance of the algorithm by comparing the resulting measurements with those made by experienced sonographers. METHODS: Thirty-five digitized sonograms of the fetal head were obtained during routine imaging. The BPD and HC were automatically computed by detecting the inner and outer boundaries of the fetal skull using the computer vision technique known as the "active contour model." Six experienced sonographers also measured the BPD and HC on these images. RESULTS: The algorithm failed to locate the boundaries in two of the 35 cases. For the remaining cases, the mean absolute difference between the automated measurements and the average of the six observers was 1.4% for BPD and 2.9% for HC. The correlations were .999 for the BPD and .994 for the HC. The computer's measurements were no different from the six observers' measurements than the observers' measurements were from one another. CONCLUSION: The tested algorithm effectively and accurately measures BPD and HC automatically. We are currently in the process of integrating this algorithm into an ultrasound machine.

Algorithms↗

PubMed1992

Results obtained by using a computerized image analysis system designed as an aid to diagnosis of cutaneous melanoma.

Results obtained using a computerized image analysis system as an aid to clinical diagnosis of melanoma are reported. The system comprises a colour television camera connected through a digitizing board to a 386 personal computer. By means of original algorithms able to measure the shape, the colours and texture of a pigmented lesion of the skin, the system provides eight on/off indicators that are matched with the histological diagnosis to identify benign and malignant pigmented lesions. The chances that a given lesion is malignant increase with the increasing number of positive indicators. The training field of the system was constituted of images and data of 169 cutaneous lesions in 165 patients. Taking two positive indicators as the threshold between pigmented benign and malignant lesions, the efficiency of the system is 0.98, the positive predictive value is 0.45 and the negative predictive value is 0.95. These values were confirmed in a series of 44 pigmented lesions, 10 of which were melanoma, that constitute the present test series. The authors conclude that this computerized image analysis system should be regarded as a useful aid to diagnosis for a non-expert clinician. The system limit is transformation within a naevus.

Adult↗

PubMed1996

Growth characteristics of the human nasal septum.

Using a specially designed algorithm for the measurement of the surface area of shapes with highly irregular contours, growth curves were developed for post-natal septal growth in humans using post-mortem specimens of a study population of 30 cases, distributed over the age range from birth to 62 years. From the results a rapid growth phase for the total septum is evident immediately after birth, lasting until the second year of life. Then, a gradual deceleration of growth is recognized with a plateau eventually being reached at the age of 36 years. Mathematical analysis of the growth curve shows that the curve for the total septum is the sum of two separate mathematical equations, representing the cartilaginous and bony contribution, respectively. It is demonstrated that the cartilaginous septum reaches adult dimensions (lateral surface area) at the age of two years. Subsequent growth of the septum is due to expansion of the perpendicular plate, i.e. the bony parts of the septum.

Adolescent↗

PubMed1996

Both oral and transdermal estrogen increase growth hormone release in postmenopausal women--a clinical research center study.

To determine if the mode of 17 beta-estradiol (E2) administration affects growth hormone (GH) concentrations, eight postmenopausal women were studied under the following conditions: (1) control (no E2), (2) oral E2 (Estrace, 1 mg every 12 h for 2 weeks) and (3) transdermal E2 (Estraderm patch, 0.1 mg, two patches changed daily for 2 weeks). Blood was collected every 5 min for 24 h and assayed for serum GH concentrations using a sensitive chemiluminescence assay. Serum E2 levels were comparable during both E2 treatment regimens when measured with a specific chemiluminescence assay. The 24-h integrated GH concentrations (IGHC, min . micrograms/L) increased in all eight subjects from (mean +/- SE) 494 +/- 102 during control to 860 +/- 111 (P < 0.05) and 832 +/- 149 (P < 0.05) during oral and transdermal E2, respectively. Both E2 treatments significantly increased GH pulse height, individual pulse area, incremental pulse amplitude, interpeak valley concentration, and interpeak valley nadir (as measured by Cluster algorithm) when compared with control. No significant differences were observed in the number of GH pulses per 24 h. Insulin-like growth factor-I (IGF-I, micrograms/L) concentrations decreased from 165 +/- 19 (control) to 109 +/- 11 (oral E2, P < 0.05) and 122 +/- 15 (transdermal E2, P < 0.05). No statistically significant differences in attributes of pulsatile GH release or IGF-I concentrations were observed between the oral and transdermal E2 treatments. We conclude that both oral and transdermal E2 treatment increase serum GH concentrations in postmenopausal women. This increase is manifested by larger GH pulses and higher basal (interpulse) GH levels, not by changes in pulse frequency. Both routes of E2 administration decrease serum IGF-I concentrations, which may attenuate IGF-I negative feedback on pituitary somatotrophs and hypothalamic somatostatin secretion, resulting in enhanced pulsatile GH release.

Administration, Cutaneous↗

PubMed1995

Radiotherapy treatment planning with dynamic wedges--an algorithm for generating wedge factors and beam data.

If the jaws of a linear accelerator are moved under computer control during irradiation, dose distributions similar to those with wedge filters can be produced. Varian linear accelerators utilize this effect to give a 'dynamic wedge', using segmented treatment tables (STTs). An algorithm is described to generate the dose per monitor unit at any point in a beam, using the STT values. Dynamically wedged beams are modelled as the superposition of static asymmetric beams, using an algorithm based on beam data measured for symmetric beams. Predictions of wedge factors, depth doses and profiles generated using the algorithm are compared with measurements. Good agreement is found between predictions and measurements. The calculation time is typically 5 ms/dose point on a PC with a 486DX processor.

Algorithms↗

PubMed2006

Attenuation-corrected 99mTc-MIBI SPECT in overweight patients with chronic ischaemic dysfunction: a comparison to NH3 PET and implications for the diagnosis of myocardial viability.

OBJECTIVE: We determined the value of attenuation correction (AC) of myocardial perfusion estimation with (99m)Tc-MIBI SPECT in overweight patients by comparison of uncorrected (filtered back-projection (FBP) and corrected (an iterative algorithm with a measured attenuation coefficients map (FL-AC)) (99m)Tc-MIBI relative uptake to perfusion data obtained in the same patients with NH3 PET. In addition, the impact of attenuation correction for the assessment of myocardial viability with (99m)Tc-MIBI SPECT was determined using FDG PET as the reference method. METHODS: Thirty consecutive overweight patients (BMI=28+/-4) with left ventricular dysfunction underwent a resting (99m)Tc-MIBI SPECT and a PET study (NH3 and FDG). (99m)Tc-MIBI SPECT scans were reconstructed without attenuation correction (FBP) and with attenuation correction (FL-AC). The left ventricle was divided into 16 segments, in which the relative uptake was quantified using circumferential profiles. A relative uptake > or = 60% was considered consistent with viable myocardium for FDG and MIBI. RESULTS: The absolute difference between (99m)Tc-MIBI SPECT and NH3 PET uptakes was less pronounced in the inferior (12+/-10% vs. 17+/-12%, P<0.001), anteroseptal (12+/-11% vs. 16+/-12%, P=0.009) and septal (15+/-12% vs. 18+/-14%, P=0.003) regions (FL-AC vs. FBP, respectively). The sensitivity of MIBI for diagnosing myocardial viability increased from 83 to 100% (P=0.034), without loss in specificity. CONCLUSION: Attenuation correction improves myocardial perfusion estimation by (99m)Tc-MIBI SPECT in the inferior, anteroseptal and septal regions and increases its sensitivity for the diagnosis of myocardial viability.

Algorithms↗

PubMed1999

Assessment of 3-dimensional computer-generated cephalometric measurements.

The purpose of this study was to assess the reliability of 3-dimensional computer-generated linear and angular measurements produced by different computer algorithms and various combinations of cephalogram projections compared with direct and CT measurements. A computer program was written to provide 4 computer algorithms and 4 combinations of cephalogram projections generating 22 linear and 10 angular 3-dimensional measurements from 20 landmarks. A new technique to produce biplanar cephalograms from a single x-ray source using a special facebow was developed, and its reliability was assessed. Sets of lateral, frontal, and basilar cephalograms of a human dried skull were taken both with 20 radiopaque landmark markers and without markers. Paired t tests based on marker position demonstrated reliability of the facebow; there were no statistically significant differences in repositioning the skull over time using the facebow at P <.05. In the ideal situation, with minimal head rotation and landmark identification error (with the facebow and radiopaque markers), the average error of linear measurements was 1. 5 mm and 3.5(o) for the angular measurements. Subsequent trials evaluated the errors in head position (within 5(o) of head rotation) and in landmark identification (by removing all markers); two-way ANOVA with Scheffé groupings concluded that the vector intercept with manual adjustment algorithm using the lateral-frontal biplanar projection provides not only greater accuracy but also clinical practicality for both linear (mean of 2.2 mm error) and angular (mean of 4.0(o) error) measurements compared with direct or CT measurements (P <.05). The effect of landmark identification error was found to be slightly greater than the head rotation error in the accuracy of 3-dimensional linear and angular measurements (mean, 2.85 mm error for linear and 4.4(o) error for angular measurements). Lastly, this study concluded that linear measurements in the transverse direction were found to have a slightly larger error than vertical measurements. Anteroposterior measurements have the least error.

Algorithms↗

PubMed2005

MSAID: multiple sequence alignment based on a measure of information discrepancy.

We propose an algorithm of global multiple sequence alignment that is based on a measure of what we call information discrepancy. The algorithm follows a progressive alignment iteration strategy that makes use of what we call a function of degree of disagreement (FDOD). MSAID begins with distance calculation of pairwise sequences, based on FDOD as a numerical scoring measure. In the next step, the resulting distance matrix is used to construct a guide tree via the neighbor-joining method. The tree is then used to produce a multiple alignment. Current alignment is next used to produce a new matrix and a new tree (with FDOD scoring measure again). This iterative process continues until convergence criteria (or a stopping rule) are satisfied. MSAID was tested and compared with other prior methods by using reference alignments from BAliBASE 2.01. For the alignments with no large N/C-terminal extensions or internal insertions MSAID received the top overall average in the tests. Moreover, the results of testing indicate that MSAID performs as well as other alignment methods with an occasional tendency to perform better than these prior techniques. We, therefore, believe that MSAID is a solid and reliable method of choice, which is often (if not always) superior to other global alignment techniques.

Algorithms↗

PubMed2004

Association of specific haplotypes of D2 dopamine receptor gene with vulnerability to heroin dependence in 2 distinct populations.

CONTEXT: Dopamine receptor-mediated pathways play critical roles in the mechanism of addiction. However, associations of the D(2) dopamine receptor gene (DRD2) with substance abuse are controversial. OBJECTIVE: To determine whether susceptibility sites resided at DRD2. DESIGN: Haplotype-based case-control analysis of 2 distinct populations using 10 single nucleotide polymorphisms (SNPs) with heroin dependence. SETTING: Universities of Mainz and Bonn, Germany, and 3 local hospitals in southwestern China. Patients Cases and control subjects recruited from China (486 cases, 313 controls) and Germany (471 cases, 192 controls). INTERVENTIONS: Genotyping for 10 SNPs by 5'-exonuclease fluorescence assays. The D' value of linkage disequilibrium and haplotypes were generated by the expectation-maximization algorithm. MAIN OUTCOME MEASURES: Genotype, allele, and haplotype frequencies were compared between cases and controls by chi(2) tests constructed for each population. An additional 32 SNPs randomly distributed in the genome were genotyped for detecting population admixture in the 2 populations. RESULTS: A haplotype block of 25.8 kilobases (kb) was defined by 8 SNPs extending from SNP3 (TaqIB) at the 5' end to SNP10 site (TaqIA) located 10 kb distal to the 3' end of the gene. Within this block, specific haplotype cluster A (carrying TaqIB1 allele) was associated with a high risk of heroin dependence in Chinese patients (P = 1.425 x 10(-22); odds ratio, 52.80; 95% confidence interval, 7.290-382.5 for 8-SNP analysis). A putative recombination "hot spot" was found near SNP6 (intron 6 ins/del G), creating 2 new daughter haplotypes that were associated with a lower risk of heroin dependence in Germans (P = 1.94 x 10(-11) for 8-SNP analysis). There was no evidence of population stratification in either population. CONCLUSIONS: These results strongly support a role of DRD2 as a susceptibility gene with heroin dependence in Chinese patients and was associated with low risk of heroin dependence in Germans.

Adult↗

PubMed2000

Calculation of volumes and systolic indices of heart ventricle from Halobatrachus didactylus: echocardiographic noninvasive method.

The purpose of this work is to calculate end-systolic and end-diastolic volumes of Halobatrachus didactylus ventricles, from two-dimensional (2D) echocardiographic images, comparing four different linear methods, and to derive systolic indices of ventricular function-fractional shortening, ejection fraction, stroke volume, and cardiac output independent of the Fick principle. Echocardiography provided high resolution images of cardiac structures and allowed accurate linear measurements. The Simpson algorithm proved to be the best method of calculating ventricle volumes. As a corollary, ventricular mass can be derived from echocardiographic volume data. This noninvasive method promises wide utilization in experimental comparative cardiovascular biology.

Algorithms↗

PubMed2000

Preliminary study of in vivo autofluorescence of nasopharyngeal carcinoma and normal tissue.

BACKGROUND AND OBJECTIVE: In nasopharyngeal cancer, conventional white light endoscopy does not provide adequate information to detect the flat/small lesion and identify the margin of observable tumor. In the present study, we evaluate the potential of light-induced fluorescence spectroscopic imaging for the localization of cancerous nasopharyngeal tissue. STUDY DESIGN/MATERIALS AND METHODS: We built a multiple channel spectrometer specifically for the investigation of fluorescence collected by a conventional endoscopic system. Nasopharyngeal fluorescence were measured in vivo from 27 subjects during the routine endoscopy. The biopsy specimens for histologic analysis were taken from the tissue sites where the fluorescence were measured. RESULTS: Two algorithms to discriminate the nasopharyngeal carcinoma from normal tissue were created based on the good correlation between the tissue autofluorescence and histologic diagnosis. For the two-wavelength algorithm, carcinoma can be differentiated from normal tissue with a sensitivity and specificity of 93% and 92%, respectively. For the three-wavelength algorithm with compensation of variation of blood content in tissue, a sensitivity of 98% and specificity of 95% were achieved. CONCLUSION: Fluorescence endoscopic imaging used with the algorithms developed in this report is an efficient method for detecting the nasopharyngeal carcinoma.

Algorithms↗

PubMed2001

An evolutionary model for the origin of non-randomness, long-range order and fractality in the genome.

We present a model for genome evolution, comprising biologically plausible events such as transpositions inside the genome and insertions of exogenous sequences. This model attempts to formulate a minimal proposition accounting for key statistical properties of genomes, avoiding, as far as possible, unsupportable hypotheses for the remote evolutionary past. The statistical properties that are observed in genomic sequences and are reproduced by the proposed model are: (i) deviations from randomness at different length scales, measured by suitable algorithms, (ii) a special form of size distribution (power law distribution) characterising different levels of genome organisation in the non-coding, and (iii) extensive resemblance in the alternation of coding and non-coding regions at several length scales (self-similarity) in long genomic sequences of higher eukaryotes.

DNA↗

PubMedDate not supplied

Line profile reconstruction from simultaneously recorded secondary and backscattered electron signals.

We propose a reconstruction method of surface morphology using a combination of secondary and back-scattered electron signals from the scanning electron microscope (SEM). Compared with multiple-detector methods, the proposed system requires only conventional secondary and backscattered electron detectors for a line profile reconstruction in one direction. This method is an application of genetic algorithms to the measurement of surface morphology in SEM. We use the chi-square distribution of the reconstruction error as the objective function within a scheme to minimize the number of vertices in the reconstructed surface profile. (The reconstruction error is the relative difference between the calculated and experimental data.) To evaluate the efficacy of our method, a surface profile is successfully reconstructed from a pair of line scans across the center of a latex particle.

Journal Article↗

PubMedDate not supplied

Yield of the screening review of systems: a study on a general medical service.

STUDY OBJECTIVE: To determine the usefulness of screening reviews of the cardiopulmonary and gastrointestinal systems during medical admissions. DESIGN: Case series. SETTING: General internal medicine ward of a university hospital. PATIENTS: 550 consecutive medical patients were initially screened at admission. The authors excluded 265 patients with life-limiting medical conditions, and they studied 98 patients with no known cardiopulmonary disease and 207 patients with no known gastrointestinal disease. INTERVENTIONS: Positive responses to screening systems review questions were evaluated using a standardized testing algorithm. MAIN OUTCOME MEASURES: Numbers of new diagnoses; potential for patient benefit. MAIN RESULTS: The authors made 26 new diagnoses for 25 patients (95% confidence limits, 16 to 37 patients), two of whom may have gained years of life as a result. CONCLUSIONS: The absolute yield of the screening cardiopulmonary and gastrointestinal reviews of systems of 550 patients admitted to an internal medicine service of a university hospital was a new diagnosis in about 5% of patients. An estimate of the cost-effectiveness compares favorably with those of other accepted screening practices.

Adult↗

PubMed1993

Vector quantization distortion of medical ultrasound features.

Pruned-tree structured vectored quantization (PTSVQ) was applied to the lower five gray scale remapped bits of normal and fatty ultrasound liver images. The upper bits were compressed reversibly. This combination of techniques is termed PTSVQ with splitting. The effect of the compression on the difference in texture between normal and fatty liver images was studied at different compression rates and distortions. The changes in texture were measured by changes in the principal components of the covariance matrix of image vectors. The vectors were the same size as those used in the compression technique. There were clear differences in the components of normal and fatty liver images. These differences were largely removed by the PTSVQ with splitting technique even at average single pixel distortions several times smaller than the image noise. These results suggest that the effect of compression on second order statistics should be measured when evaluating algorithms in addition to the first order average distortion.

Fatty Liver↗

PubMed2003

The effect of surgical stress on insulin sensitivity, glucose effectiveness and acute insulin response to glucose load.

Hyperglycemia after stress is a very common clinical phenomenon. It is generally hypothesized that the underlying cause is a neuroendocrine-mediated deterioration in glucose metabolism. However, the detailed roles of insulin sensitivity, glucose effectiveness and acute insulin response to glucose load in response to stress have not been well established. Hernioplasty was used as a minor stress model for studying stress-induced hyperglycemia. Eleven healthy young men were enrolled voluntarily in this study. Their mean age was 22.0 +/- 0.9 yr and BMI 23.3 +/- 0.6 kg/m2. Frequently sampled i.v. glucose tolerance tests were performed one day before and one day after the surgery. Insulin sensitivity (SI), glucose effectiveness (EG) and area under acute insulin response (AIR) were calculated from "minimal model" algorithms. We also measured fasting concentrations of human GH, ACTH and F on the days of the test. Compared to the pre-operation data, levels of ACTH and F did not change significantly after the surgery. Only GH levels were marginally significant. On the other hand, the SI (0.75 +/- 0.1, 0.52 +/- 0.9 x 10(-5) min(-1)/pmol, p = 0.04), EG (0.023 +/- 0.03, 0.016 +/- 0.003 min(-1), p = 0.01) and AIR (6738.5 +/- 1111.6, 5130.0 +/- 1047.2 pmol, p = 0.005) were all significantly decreased after surgery. The percentages of decrease were 16.3 +/- 15.5, 32.1 +/- 10.3 and 17.8 +/- 10.3%, respectively. Finally, only the changes of EG positively correlate with the changes of ACTH before and after surgery. No significant changes were noted among other stress hormones and the changes of SI, EG and AIR. In conclusion, hernioplasty results in reduced SI, EG and AIR. Among them, although not statistically significant, the EG showed the most distinct decrease after the surgery, which has not been found in previous literature.

Adolescent↗

PubMed2006

Use of a neural mass model for the analysis of effective connectivity among cortical regions based on high resolution EEG recordings.

Assessment of brain connectivity among different brain areas during cognitive or motor tasks is a crucial problem in neuroscience today. Aim of this work is to use a neural mass model to assess the effect of various connectivity patterns in cortical electroencephalogram (EEG) power spectral density, and investigate the possibility to derive connectivity circuits from EEG data. To this end, a model of an individual region of interest (ROI) has been built as the parallel arrangement of three populations, each described as in Wendling et al. (Eur J Neurosci 15:1499-1508, 2002). Connectivity among ROIs includes three parameters, which specify the strength of connection in the different frequency bands. The following main steps have been followed: (1) we analyzed how the power spectral density (PSD) is significantly modified by the kind of coupling hypothesized among the ROIs; (2) with the model, and using an automatic fitting procedure, we looked for a simple connectivity circuit able to reproduce PSD of cortical EEG in three ROIs during a finger-movement task. The estimated parameters represent the strength of connections among the ROIs in the different frequency bands. Cortical EEGs were computed with an inverse propagation algorithm, starting from measurement performed with 96 electrodes on the scalp. The present study suggests that the model can be used as a simulation tool, able to mimic the effect of connectivity on EEG. Moreover, it can be used to look for simple connectivity circuits, able to explain the main features of observed cortical PSD. These results may open new prospectives in the use of neurophysiological models, instead of empirical models, to assess effective connectivity from neuroimaging information.

Brain Mapping↗

PubMed2002

Scratching the sporocyst surface: characterisation of European Aggregata species by atomic force microscopy.

The application of atomic force microscopy to the understanding of surface structure and atomic-scale measurements on the sporocyst of European Aggregata species, intracellular coccidia of the cephalopods Octopus vulgaris and Sepia officinalis, is presented here. Using the roughness mean surface (RMS) as an index, we reveal texture to be a key parameter for characterisation of the sporocyst surface properties, which resolve the historical synonymy within the European Aggregatidae. Roughness measurements from RMS algorithms may also be an important diagnostic taxonomic character for the differentiation of Aggregata species in the future.

Algorithms↗