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  • 2000-2004  (7)
  • 1910-1914
  • 1890-1899
  • Fourier analysis
  • Tomography
  • 1
    Book
    Book
    Boston :Birkhäuser,
    Title: Sampling, wavelets, and tomography /
    Contributer: Benedetto, John , Zayed, Ahmed I.
    Publisher: Boston :Birkhäuser,
    Year of publication: 2003
    Pages: p. cm
    Series Statement: Applied and computational harmonic analysis
    ISBN: 0-8176-4304-4 , 3-7643-4304-4
    Type of Medium: Book
    Language: English
    Keywords: Hamonic analysis ; Wavelets (Mathematics) ; Fourier analysis ; Sampling (Statistics) ; Tomography
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Skeletal radiology 29 (2000), S. 409-412 
    ISSN: 1432-2161
    Keywords: Key words Tarsal bones ; abnormalities ; Tomography ; X-ray computed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To determine the findings of calcaneonavicular coalition on coronal CT. Design. We retrospectively reviewed the CT scans of 14 calcaneonavicular coalitions in eight patients. All coalitions were visible on the axial scans, and the diagnosis was confirmed by surgery in five patients. These CT scans were compared with scans of ten normal feet. Results. We identified two features of calcaneonavicular coalition on coronal CT: lateral bridging (an abnormal bony mass lateral to the head of the talus) and rounding of the talus. All eight patients demonstrated at least one of these two findings. Conclusion. Although calcaneonavicular coalition is best seen on axial CT scans of the feet, there are two abnormalities, lateral bridging and rounding of the head of the talus, which should suggest the diagnosis on coronal CT scans.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of computational analysis and applications 2 (2000), S. 333-371 
    ISSN: 1572-9206
    Keywords: sampling theorem ; Cauchy's integral formula ; Poisson's summation formula ; Fourier analysis ; complex analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract First we show that several fundamental results on functions from theBernstein spaces $$B_\sigma ^p $$ (such as Bernstein's inequality andthe reproducing formula) can be deduced from a weak form of the classicalsampling theorem. In §3 we discuss the mutual equivalence of thesampling theorem, the derivative sampling theorem and a harmonic functionsampling theorem. In §§4–6 we discuss connections between thesampling theorem and various important results in complex analysis andFourier analysis. Our considerations include Cauchy's integral formula,Poisson's summation formula, a Gaussian integral, certain properties ofweighted Hermite polynomials, Plancherel's theorem, the maximum modulusprinciple, and the Phragmén–Lindelöf principle.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Documenta ophthalmologica 101 (2000), S. 233-246 
    ISSN: 1573-2622
    Keywords: binocular vision ; Fourier analysis ; strabismus ; temporal frequency ; visual evoked potential (VEP)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this work was to study the second harmonic in the steady state pattern visual evoked potential (ssVEP) to various stimulus frequencies in subjects with normal and defective binocularity. ssVEPs were elicited by 4 c/deg sinusoidal gratings, with temporal frequencies ranging from 5 to 20 Hz (exp. 1) and 15 to 27.5 Hz (exp. 2). Responses were Fourier analysed and power and phase of the second harmonic to stimulus frequency were measured. For power, binocular enhancement in a bimodal fashion was found both in normals and in subjects with defective binocularity. The power with binocular stimulation was significantly higher in the normal group in the high frequency domain. Latency, estimated from the phase-frequency function, was longer in the group with defective binocularity, but this was statistically significant only for the high frequency domain. The results suggest that a visual system with normal binocular function can follow a stimulus with high temporal frequency more accurately than a system with disturbed binocularity.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 38 (2000), S. 558-561 
    ISSN: 1741-0444
    Keywords: Hydrodynamic simulation ; Pulse duplicator ; Cardiovascular system ; Atrial fibrillation ; Fourier analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Heart valve replacements are often associated with cardiac pathologies, but valvular prostheses are still tested in vitro under the same physiological conditions as for a healthy young man. Therefore a new mock circulatory system of the left heart, the dual activation simulator (DAS), has been built. The DAS allows atrial and ventricular dynamics to be controlled with pumps that activate anatomically shaped silicon models of the cavities. The mitral flow is a two-peak waveform. The E/A ratio can be changed, and the A-wave can be suppressed to simulate, for instance, atrial fibrillation. The cardiac rhythm and the mean flow-rate can be changed at will. The ability of the DAS to reproduce physiological flow is assessed by computation of the aortic input impedance and by harmonic analysis of left ventricular and atrial pressures. It allows the behaviour of valve prostheses to be studied in various conditions of concern to clinicians and can be a useful tool for engineers to improve valve prostheses or validate diagnostic tools such as 3D colour Doppler. The DAS and its capacities are described.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1619-7089
    Keywords: Key words: Behçet’s disease ; Tomography ; emission computed ; Acetazolamide ; Diaschisis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The purpose of this study was to characterise the nature of the baseline perfusion defects found in patients with Behçet’s disease using hexamethylpropylene amine oxime single-photon emission tomography in conjunction with acetazolamide test (Acz SPET). Eleven patients underwent both baseline and Acz SPET. Regions of interest (ROIs) were drawn on the areas with decreased perfusion (D-ROI) and, in the same section, on areas with normal perfusion (N-ROI). The ROIs were then repositioned on the corresponding section on Acz SPET. The mean ROI counts were then transformed into a perfusion index value (PIV) with reference to the global brain counts. In total we found 24 D-ROIs (17 in the cortical and 7 in subcortical grey matter). The influence of Acz infusion was selectively registered in the D-ROIs, where PIVs changed from 1.23±0.17 (baseline SPET) to 1.63±0.23 (Acz SPET) (P〈0.001). No significant difference was seen in the N-ROIs (1.46±0.21 and 1.40±0.17, respectively, on baseline SPET and Acz SPET). Our results demonstrate that Acz infusion increases the regional cerebral blood flow within baseline grey matter perfusion defects. This finding suggests that baseline perfusion abnormalities could reflect a disconnection rather than local vasculitic involvement.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1619-7089
    Keywords: Key words: Arrhythmias ; Imaging ; Tomography ; Infarct size ; Defibrillator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Infarct size as determined by perfusion imaging is an independent predictor of mortality after implantable cardioverter defibrillator (ICD) implantation in patients with coronary artery disease (CAD) and life-threatening ventricular arrhythmias (VA). However, its value as a predictor of VA recurrence and hospitalisation after ICD implantation is unknown. Therefore, the objective of this study was to evaluate whether infarct size as determined by perfusion imaging can help to identify patients who are at high risk for recurrence of VA and hospitalisation after ICD implantation.We studied 56 patients with CAD and life-threatening VA. Before ICD implantation, all patients underwent a uniform study protocol including a thallium-201 stress-redistribution perfusion study. A defect score as a measurement of infarct size was calculated using a 17-segment 5-point scoring system. Study endpoints during follow-up were documented episodes of appropriate anti-tachycardia pacing and/or shocks for VA and cardiac hospitalisation for electrical storm (defined as three or more appropriate ICD interventions within 24 h), heart failure or angina. After a mean follow-up of 470±308 days, 22 patients (39%) had recurrences of VA. In univariate analysis, predictors for recurrence were: (a) ventricular tachycardia (VT) as the initial presenting arrhythmia (86% vs 59% for patients without ICD therapy, P=0.04), (b) treatment with β-blockers (36% vs 68%, P=0.03) and (c) a defect score (DS) ≥20 (64% vs 32%, P=0.03). In multivariate analysis, VT as the presenting arrhythmia (χ2=5.51, P=0.02) and a DS ≥20 (χ2=4.22, P=0.04) remained independent predictors. Cardiac hospitalisation was more frequent in patients with a DS ≥20 (44% vs 13% for patients with DS 〈20, P=0.015) and this was particularly due to more frequent hospitalisations for electrical storm (24% vs 3% for patients with DS〈20, P=0.037). The extent of scarring determined by perfusion imaging can separate patients with CAD into high- and low-risk groups for recurrence of VA and cardiac hospitalisation after ICD implantation.
    Type of Medium: Electronic Resource
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