TECHNICAL NOTES   

International Angiology 2004 September;23(3):276-83

Copyright © 2004 EDIZIONI MINERVA MEDICA

language: English

Non spiral and spiral (helical) flow patterns in stenoses. In vitro observations using spin and gradient echo magnetic resonance imaging (MRI) and computable fluid dynamic modeling

Stonebridge P. A. ¹, Buckley C. ², Thompson A. ³, Dick J. ⁴, Hunter G. ⁵, Chudek J. A. ⁵, Houston J. G. ³, Belch J. J. F. ⁴

¹ Department of Surgery, The Institute of Cardiovascular Research, Ninewells Hospital and Medical School, Dundee, Scotland, UK 2 Magnetic Resonance Research Centre, Department of Chemical Engineering, University of Cambridge, Cambridge, UK 3 Department of Radiology, The Institute of Cardiovascular Research, Ninewells Hospital and Medical School, Dundee, Scotland, UK 4 Department of Vascular Medicine, The Institute of Cardiovascular Research, Ninewells Hospital and Medical School, Dundee, Scotland, UK 5 Department of Chemistry, Dundee University, Dundee, Scotland, UK

Aim. Phys­io­log­i­cal blood flow pat­terns are them­selves poor­ly under­stood ­despite their ­impact on arte­ri­al dis­ease. ­Stable spi­ral (hel­i­cal) lam­i­nar flow (SLF) has been ­observed in nor­mal sub­jects. The pur­pose of the ­present study is to devel­op a meth­od of mag­net­ic res­o­nance (MR) flow pat­tern vis­u­al­iza­tion and to ana­lyze spi­ral and non-spi­ral flow pat­terns with and with­out lumi­nal nar­row­ing in vitro. The flow con­di­tions were then mod­eled using com­pu­ta­tion­al fluid dynam­ics (Star-CD).
Meth­ods. Lam­i­nar integ­rity was exam­ined in a flow-rig using spin and gra­di­ent echo mag­net­ic res­o­nance imag­ing (MRI) in non-ste­nosed and ste­nosed con­duits in the pres­ence of non-spi­ral and spi­ral flow.
­Results. No dif­fer­ence was ­observed in a non-ste­nosed con­duit ­between non-spi­ral and spi­ral flow. In the pres­ence of a sten­o­sis spi­ral flow pre­serves flow veloc­ity coher­ence where­as non-spi­ral flow increas­ing­ly lost coher­ence begin­ning prox­i­mal to the sten­o­sis. Com­pu­ta­tion­al fluid dynam­ic mod­el­ing of the in vitro experi­ment ­showed ­marked dif­fer­enc­es ­between the 2 flow pat­terns. Non-spi­ral flow pro­duced great­er inward­ly direct­ed forc­es just ­beyond the sten­o­sis and great­er out­ward pres­sures at more dis­tal sites. The near wall tur­bu­lent ener­gy was up to 700% less with spi­ral flow over non-spi­ral flow ­beyond the sten­o­sis.
Con­clu­sion. Spi­ral flow ­appears to offer clear flow pro­file sta­bi­liz­ing advan­tag­es over non-spi­ral flow, by sig­nif­i­cant­ly reduc­ing the tur­bu­lence ­caused by a sten­o­sis. Spi­ral flow also pro­duc­es lower forc­es act­ing on the ves­sel wall.