Joy Ku

Publications (6) View all

• Source

  Available from: Michael A Sherman

  Article: Simbios: an NIH national center for physics-based simulation of biological structures.

  Scott L Delp, Joy P Ku, Vijay S Pande, Michael A Sherman, Russ B Altman
  [show abstract] [hide abstract]
  ABSTRACT: Physics-based simulation provides a powerful framework for understanding biological form and function. Simulations can be used by biologists to study macromolecular assemblies and by clinicians to design treatments for diseases. Simulations help biomedical researchers understand the physical constraints on biological systems as they engineer novel drugs, synthetic tissues, medical devices, and surgical interventions. Although individual biomedical investigators make outstanding contributions to physics-based simulation, the field has been fragmented. Applications are typically limited to a single physical scale, and individual investigators usually must create their own software. These conditions created a major barrier to advancing simulation capabilities. In 2004, we established a National Center for Physics-Based Simulation of Biological Structures (Simbios) to help integrate the field and accelerate biomedical research. In 6 years, Simbios has become a vibrant national center, with collaborators in 16 states and eight countries. Simbios focuses on problems at both the molecular scale and the organismal level, with a long-term goal of uniting these in accurate multiscale simulations.
  Journal of the American Medical Informatics Association 11/2011; 19(2):186-9. · 3.61 Impact Factor
• Source

  Available from: biofluids.net

  Article: Comparison of CFD and MRI flow and velocities in an in vitro large artery bypass graft model.

  Joy P Ku, Christopher J Elkins, Charles A Taylor
  [show abstract] [hide abstract]
  ABSTRACT: Bypass graft failures have been attributed to various hemodynamic factors, including flow stasis and low shear stress. Ideally, surgeries would minimize the occurrence of these detrimental flow conditions, but surgeons cannot currently assess this. Numerical simulation techniques have been proposed as one method for predicting changes in flow distributions and patterns from surgical bypass procedures, but comparisons against experimental results are needed to assess their usefulness. Previous in vitro studies compared simulated results against experimentally obtained measurements, but they focused on peripheral arteries, which have lower Reynolds numbers than those found in the larger arteries. In this study, we compared simulation results against measurements obtained using magnetic resonance imaging (MRI) techniques for a phantom model of a stenotic vessel with a bypass graft under conditions suitable for surgical planning purposes and with inlet Reynolds numbers closer to those found inthe larger arteries. Comparisons of flow rate and velocity profiles were performed at maximum and minimum flows at four locations and used simulation results that were temporally and spatially averaged, key postprocessing when comparing against phase contrast MRI measurements. The maximum error in the computed volumetric flow rates was 6% of the measured values, and excellent qualitative agreement was obtained for the through-plane velocity profiles in both magnitude and shape. The in-plane velocities also agreed reasonably well at most locations.
  Annals of Biomedical Engineering 04/2005; 33(3):257-69. · 2.37 Impact Factor
• Article: In vivo validation of a one-dimensional finite-element method for predicting blood flow in cardiovascular bypass grafts.

  Brooke N Steele, Jing Wan, Joy P Ku, Thomas J R Hughes, Charles A Taylor
  [show abstract] [hide abstract]
  ABSTRACT: Current practice in vascular surgery utilizes only diagnostic and empirical data to plan treatments and does not enable quantitative a priori prediction of the outcomes of interventions. We have previously described a new approach to vascular surgery planning based on solving the governing equations of blood flow in patient-specific models. A one-dimensional finite-element method was used to simulate blood flow in eight porcine thoraco-thoraco aortic bypass models. The predicted flow rate was compared to in vivo data obtained using cine phase-contrast magnet resonance imaging. The mean absolute difference between computed and measured flow distribution in the stenosed aorta was found to be 4.2% with the maximum difference of 10.6% anda minimum difference of 0.4%. Furthermore, the sensitivity of the flow rate and distribution with respect to stenosis and branch losses were quantified.
  IEEE Transactions on Biomedical Engineering 07/2003; 50(6):649-56. · 2.28 Impact Factor
• Article: Internet-based system for simulation-based medical planning for cardiovascular disease.

  Brooke N Steele, Mary T Draney, Joy P Ku, Charles A Taylor
  [show abstract] [hide abstract]
  ABSTRACT: Current practice in vascular surgery utilizes only diagnostic and empirical data to plan treatments, which does not enable quantitative a priori prediction of the outcomes of interventions. We have previously described simulation-based medical planning methods to model blood flow in arteries and plan medical treatments based on physiologic models. An important consideration for the design of these patient-specific modeling systems is the accessibility to physicians with modest computational resources. We describe a simulation-based medical planning environment developed for the World Wide Web (WWW) using the Virtual Reality Modeling Language (VRML) and the Java programming language.
  IEEE Transactions on Information Technology in Biomedicine 07/2003; 7(2):123-9. · 1.68 Impact Factor
• Source

  Available from: stanford.edu

  Article: In vivo validation of numerical prediction of blood flow in arterial bypass grafts.

  Joy P Ku, Mary T Draney, Frank R Arko, W Anthony Lee, Frandics P Chan, Norbert J Pelc, Christopher K Zarins, Charles A Taylor
  [show abstract] [hide abstract]
  ABSTRACT: In planning operations for patients with cardiovascular disease, vascular surgeons rely on their training, past experiences with patients with similar conditions, and diagnostic imaging data. However, variability in patient anatomy and physiology makes it difficult to quantitatively predict the surgical outcome for a specific patient a priori. We have developed a simulation-based medical planning system that utilizes three-dimensional finite-element analysis methods and patient-specific anatomic and physiologic information to predict changes in blood flow resulting from surgical bypass procedures. In order to apply these computational methods, they must be validated against direct experimental measurements. In this study, we compared in vivo flow measurements obtained using magnetic resonance imaging techniques to calculated flow values predicted using our analysis methods in thoraco-thoraco aortic bypass procedures in eight pigs. Predicted average flow rates and flow rate waveforms were compared for two locations. The predicted and measured waveforms had similar shapes and amplitudes, while flow distribution predictions were within 10.6% of the experimental data. The average absolute difference in the bypass-to-inlet blood flow ratio was 5.4 +/- 2.8%. For the aorta-to-inlet blood flow ratio, the average absolute difference was 6.0 +/- 3.3%.
  Annals of Biomedical Engineering 07/2002; 30(6):743-52. · 2.37 Impact Factor