Errors in power-law estimations of inflow rates for intracranial aneurysm CFD |
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| Institution: | 1. Biomedical Simulation Laboratory, Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, Ontario, Canada;2. Division of Neuroradiology, Geneva University Hospitals, Geneva, Switzerland;3. Joint Division of Medical Imaging, Department of Medical Imaging, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada;4. Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Ontario, Canada;5. Division of Radiology, Geneva University Hospitals, University of Geneva, Geneva, Switzerland;1. Mechanical Engineering, University of Missouri, Columbia, MO, USA;2. Orthopaedic Surgery, University of Missouri, Columbia, MO, USA;3. Bioengineering, Orthopaedic Surgery, University of Missouri, Columbia, MO, USA;4. Bioengineering, University of Missouri, Columbia, MO, USA;1. Department of Mechanical Engineering, Myongji University, San 38-2, Nam-dong, Cheoin-gu, Yongin, Gyeonggi-do, South Korea;2. Department of Radiology, Seoul National University College of Medicine, Seoul, South Korea;1. Department of Radiology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, 325000, China;2. Department of Neurosurgery, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China;1. Centre Universitaire d׳Informatique, Université de Genève, 7, route de Drize, CH-1227 Switzerland;2. Laboratoire de Médecine Expérimentale (ULB 222 Unit), Université Libre de Bruxelles, CHU de Charleroi, Belgium;3. CREATIS INSA-Lyon, France;4. Center for Excellence in Vascular Biology, Department of Pathology, Brigham and Women׳s Hospital and Harvard Medical School, Boston, MA 02115, United States;5. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Boston MA 02139, United States;6. Unit of Biochemistry and Cellular Biology (URBC), Namur Research Institute for LIfe Sciences (NARILIS), University of Namur (UNamur), 61 Rue de Bruxelles, B-5000 Namur, Belgium;1. Department of Computational Physiology, Simula Research Laboratory, Lysaker, Norway;2. Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada;3. Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino, Italy;4. Department of Radiology and Imaging Sciences, Emory University, GA, USA;1. Department of Neurosurgery, Mie University Graduate School of Medicine, Tsu, Mie, Japan;2. Department of Neurosurgery, Mie Chuo Medical Center, National Hospital Organization, Tsu, Mie, Japan;3. Department of Neurosurgery, Ise Red Cross Hospital, Ise, Mie, Japan |
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| Abstract: | Patient-specific inflow rates are rarely available for computational fluid dynamics (CFD) studies of intracranial aneurysms. Instead, inflow rates are often estimated from parent artery diameters via power laws, i.e. Q ∝ Dn, reflecting adaptation of conduit arteries to demanded flow. The present study aimed to validate the accuracy of these power laws. Internal carotid artery (ICA) flow rates were measured from 25 ICA aneurysm patients via 2D phase contrast MRI. ICA diameters, derived from 3D segmentation of rotational angiograms, were used to estimate inflow rates via power laws from the aneurysm CFD literature assuming the same inlet wall shear stress (WSS) (n = 3), velocity (n = 2) or flow rate (n = 0) for all cases. To illustrate the potential impact of errors in flow rate estimates, pulsatile CFD was carried out for four cases having large errors for at least one power law. Flow rates estimated by n = 3 and n = 0 power laws had significant (p < 0.01) mean biases of −22% to +32%, respectively, but with individual errors ranging from −78% to +120%. The n = 2 power law had no significant bias, but had non-negligible individual errors of −58% to +71%. CFD showed similarly large errors for time-averaged sac WSS; however, these were reduced after normalizing by parent artery WSS. High frequency WSS fluctuations, evident in 2/4 aneurysms, were also sensitive to inflow rate errors. Care should therefore be exercised in the interpretation of aneurysm CFD studies that rely on power law estimates of inflow rates, especially if absolute (vs. normalized) WSS, or WSS instabilities, are of interest. |
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| Keywords: | Aneurysm Computational fluid dynamics Wall shear stress Flow rates Magnetic resonance imaging |
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