title: Dynamic estimation of the myocardial oxygen extraction ratio during dipyridamole stress by MRI: a preliminary study in canines.
abstract: The myocardial oxygen extraction fraction (OEF) reflects the balance between myocardial oxygen supply and demand. The feasibility of quantifying myocardial OEF was demonstrated with MRI during pharmacologic vasodilation in dogs. Dipyridamole was infused intravenously to increase blood flow and change in myocardial oxygen content. Arterial and coronary sinus blood sampling was performed during dipyridamole-induced vasodilation to measure the myocardial blood oxygen content. Myocardial T(2) was measured dynamically during the vasodilation, and quantified with a simplified diffusion model as a function of myocardial OEF and blood volume. The results showed a strong correlation (R(2) = 0.89) between myocardial OEF values measured by MRI and those measured by blood sampling. Regional differences in the OEF were demonstrated by direct infusion of dipyridamole into coronary arteries in dogs. Combined with vasodilator stress, dynamic assessments of the OEF may provide a putative measurement of myocardial flow reserve and allow consecutive monitoring of myocardial dose and response.
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri 63110, USA. zhengj@mir.wustl.edu
authors.forename: Jie
authors.initials: J
authors.lastname: Zheng
authors.forename: Jinghua
authors.initials: J
authors.lastname: Wang
authors.forename: Mark
authors.initials: M
authors.lastname: Nolte
authors.forename: Debiao
authors.initials: D
authors.lastname: Li
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gropler
authors.forename: Pamela K
authors.initials: PK
authors.lastname: Woodard
mesh_terms: D000818:Animals; D001810:Blood Volume / Q000502:physiology; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels; D004176:Dipyridamole; D004285:Dogs; D005240:Feasibility Studies; D007089:Image Enhancement / Q000379:methods; D007262:Infusions, Intravenous; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology*; D014665:Vasodilator Agents
chemical_list: D014665:Vasodilator Agents; D004176:Dipyridamole; D010100:Oxygen