1 / 11

1D and 3D Models of Auto-Regulated Cerebrovascular Flow

1D and 3D Models of Auto-Regulated Cerebrovascular Flow. THE 26th ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY K T Moorhead, S M Moore, J G Chase , T David, J Fink Department of Mechanical Engineering University of Canterbury

yin
Download Presentation

1D and 3D Models of Auto-Regulated Cerebrovascular Flow

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. 1D and 3D Models of Auto-Regulated Cerebrovascular Flow THE 26th ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY K T Moorhead, S M Moore, J G Chase, T David, J Fink Department of Mechanical Engineering University of Canterbury Christchurch, New Zealand

  2. Structure of the CoW • Responsible for distributing blood to the major regions of the brain • Blood can be re-routed through the circle to maintain homeostasis • Previous Models • No auto-regulation • No transient dynamics

  3. 1 D and 3 D Geometry 1 D Model 3 D Model Efferent arteries resistances time-variable Circulus and afferent artery resistances constant CAD reconstruction of MRA scan Porous block represents capillary bed effects

  4. Standard PI feedback control law Resistance dynamics of contraction/dilation Amount of change is limited Dynamic Auto-Regulation • Resistance limits • Deadband • Memory • Peripheral resistance ratio based on Hillen (1986) 6:3:4:75:75 • Total influx = 12.5 cm3s-1 Control gains match the time dependent velocity profile of the MCA from thigh cuff experiments of Newell et al. (1994) - 20 sec response time for a 20% pressure drop

  5. Error in flowrate NO YES q = qref? Change in control input Calculate new flowrate Change in resistance R P2 P1 q 1 D Fluid Model Poiseuille Flow Constant resistance between nodes captured by simple circuit analogy: System is highly nonlinear: A(x(t))*x(t) = b(t) Solve system iteratively between resistance and flow rates

  6. 3 D Model Geometry

  7. Results – Ideal Configuration Ipsilateral Efferent flowrates • All circulus vessels present • 20 mmHg pressure drop in the RICA • Very good agreement in efferent flux profiles between models

  8. Results – Ideal Configuration Circulus Flowrates • 1 D model ACoA experiences greater pressure losses because this artery is least well approximated by Poiseuille Flow • Increase resistance of the ACoA 9-fold in the 1 D model to produce same effective resistance as 3 D model Significant improvement

  9. Results – Absent Ipsilateral ACA1 ACA2 Ipsilateral Efferent flowrates • 1 D model has the ACoA resistance increased 9-fold as previously • Ipsilateral ACA2 can not reach its reference flowrate even before a pressure drop is imposed • Good agreement between models – models get same “wrong” answer

  10. Conclusions • 1 D and 3 D CoW models created • Models include non-linear dynamics of auto-regulation using PI controller • Model verified against limited clinical data and prior research • Excellent agreement between models for efferent flux profiles • 1 D ACoA not well approximated by Poiseuille flow increase ACoA resistance 9-fold to obtain good agreement in circulus flowrates between models Future work includes more physiologically accurate auto-regulation and geometry modelling, more clinical verification using existing data, and modelling of greater variety of potential structures and pathological conditions

  11. Punishment of the Innocent Questions ???

More Related