ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

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Elastic deformation of a tapered vascular prosthesis (1991)

How, T. V.

Springer

Journal of materials science 2 (1991), S. 94-100

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ISSN: 1573-4838

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine , Technology

Notes: Abstract An approximate analysis of the elastic properties of tapered microfibrous polyurethane arterial prostheses is presented by considering a tapered conduit to consist of a series of short cylindrical segments. Using this approach, the relatively simple, non-linear finite deformation models developed for cylindrical arterial specimens may be applied to each segment. A constitutive equation based on a polynomial form of strain energy density function is used in this study. The constitutive constants are determined using experimental data obtained from uniform cylindrical grafts and are used to predict the mechanical response of tapered grafts. The variation in local compliance for linear, tapered grafts of uniform and variable wall thickness is determined. Similarly, the variation in longitudinal strain for tapered grafts subjected to various longitudinal tensions is calculated. The primary purpose of this analysis is to provide data for the design of tapered, compliant vascular grafts. It may also be used to characterize the elastic properties of other non-uniform axi-symmetric elastomeric conduits.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00703466

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2

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Effect of compliance mismatch on flow disturbances in a model of an arterial graft replacement (1990)

Miyawaki, F. ; How, T. V. ; Annis, D.

Springer

Medical & biological engineering & computing 28 (1990), S. 457-464

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ISSN: 1741-0444

Keywords: Arteries ; Compliance ; Flow ; Grafts ; Model

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Abstract Flow disturbances in a model of an interposition graft in an arterial segment were measured using an ultrasound Doppler velocimeter. The effect of the degree of compliance mismatch between a stiff ‘graft’ and compliant ‘arterial’ segments was investigated. In steady flow, disturbances were detected when the compliance ratio (stiff to compliant segments) was ≤0·1 and the Reynolds number ≥2200. A recirculation zone just downstream of the distal anastomosis was observed at a Reynolds number ≥2400. Disturbances were also measured under pulsatile flow which consisted of a time-varying component superimposed on a steady flow component. The time-varying flow component was either quasiphysiological or sinusoidal in shape. The Reynolds number was 500 but the frequency parameter varied from 4·2 to 8·5. Significant disturbances were observed for conduits with compliance ratio ≤0·19. The disturbance intensity tended to increase as the compliance ratio decreased and the frequency parameter increased. The magnitude of the disturbance was also greater with the quasiphysiological than the sinusoidal input flow waveform.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02441969

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3

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Development of a Simulator for Endovascular Repair of Abdominal Aortic Aneurysms (1998)

Chong, C. K. ; How, T. V. ; Black, R. A. ; [et al.]

Springer

Annals of biomedical engineering 26 (1998), S. 798-802

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ISSN: 1573-9686

Keywords: Training simulator ; Endoluminal repair ; Stent-grafts ; Simulating fluoroscopic imaging ; Endovascular repair ; Aortic aneurysms

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine , Technology

Notes: Abstract The design and development of a simulator for endovascular repair of abdominal aortic aneurysm (AAA) is described. The simulator consists of an interchangeable model of a human AAA based on computed tomography data and is produced by means of computer-aided design and manufacture (CAD/CAM) techniques. The model has renal, iliac, and femoral arteries, and is perfused with a temperature controlled blood–analog fluid under simulated physiological flow conditions. “Fluoroscopic imaging” is simulated by a computerized imaging system that uses visible light. A movable video camera relays images in the antero–posterior and lateral planes of the AAA to a monitor. The imaging system allows “arteriography” and “road-mapping” to be performed so as to facilitate accurate deployment of endovascular stent-grafts. The system has been used for teaching and demonstrating endovascular techniques to clinicians, as well as the evaluation of new stent-graft devices. Its successful incorporation into endovascular workshops has demonstrated its role in the training of clinicians in endovascular repair of AAA. © 1998 Biomedical Engineering Society. PAC98: 0150-i, 8745Hw, 8759Fm

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1114/1.66

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4

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Viscoelastic behavior of polyurethane vascular prostheses (1987)

How, T. V. ; Annis, D.

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 21 (1987), S. 1093-1108

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: A method of evaluating the in vitro viscoelastic properties of microfibrous Biomer poly(ether-urethane-urea) vascular prostheses is outlined. Quasi-static and dynamic tests were carried out on Biomer grafts of diameter between 3.4 mm and 3.8 mm and wall thickness between 0.25 mm and 0.55 mm. It is shown that the quasi-static compliance of a Biomer graft may be determined from an equation relating transmural pressure, radius, and longitudinal strains in terms of the graft dimensions and material constants. The dynamic compliance spectra were evaluated as a function of the longitudinal and circumferential strains and temperature. Although the ratio of dynamic compliance to quasi-static compliance was linearly related to the logarithm of frequency it was not significantly affected by strains or temperature over the relevant ranges studied. Employing the usual assumptions of linear isotropic incremental elastic theory the dynamic elastic and viscous moduli were calculated as a function of frequency. Biomer grafts were more viscous than canine carotid and femoral arteries, especially at the higher frequencies. The variation in the ratio of dynamic to static incremental modulus with frequency was similar to that observed in the femoral arteries by Bergel (J. Physiol., 156, 458-469 (1961)).

Additional Material: 13 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jbm.820210904

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