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Research Papers

Approach to Validate Simulation-Based Distribution Predictions Combining the Gamma-Method and Uncertainty Assessment: Application to Focused Ultrasound

[+] Author and Article Information
Esra Neufeld

Foundation for Research on Information
Technologies in Society (IT'IS),
Zeughausstrasse 43,
Zürich 8004, Switzerland
e-mail: neufeld@itis.ethz.ch

Adamos Kyriacou

Foundation for Research on Information
Technologies in Society (IT'IS),
Zeughausstrasse 43,
Zürich 8004, Switzerland
e-mail: adamos@itis.ethz.ch

Wolfgang Kainz

Division of Physics,
Center for Devices and Radiological Health,
U.S. Food and Drug Administration,
Silver Spring, MD 20993
e-mail: wolfgang.kainz@fda.hhs.gov

Niels Kuster

Foundation for Research on Information
Technologies in Society (IT'IS),
Zeughausstrasse 43,
Zürich 8004, Switzerland;
Swiss Federal Institute of Technology
(ETH) Zürich,
Zürich 8092, Switzerland
e-mail: kuster@itis.ethz.ch

1Corresponding author.

Manuscript received February 9, 2016; final manuscript received July 18, 2016; published online August 9, 2016. Assoc. Editor: Tina Morrison.This work is in part a work of the U.S. Government. ASME disclaims all interest in the U.S. Government's contributions.

J. Verif. Valid. Uncert 1(3), 031006 (Aug 09, 2016) (8 pages) Paper No: VVUQ-16-1002; doi: 10.1115/1.4034323 History: Received February 09, 2016; Revised July 18, 2016

This paper presents a novel approach for simulation validation by combining systematic, National Institute of Standards and Technology-guideline-based uncertainty assessment with the gamma dose distribution comparison method, and applies the approach to simulated and measured complicated pressure distributions in the field of focused ultrasound. Simulations require verification and validation to demonstrate that they correctly implement the underlying model and sufficiently capture the real-world behavior of the system of interest within the context-of-use. Uncertainty assessment is necessary to determine the quality (strength, success, and range) of the validation. The combined approach of systematic uncertainty evaluation and the gamma-method presented herein permits thorough validation with meaningful and reasonable tolerances (expanded uncertainty: 1.04 dB = 12.7%, 1.88 wavelengths), whereas point-wise comparison would have resulted in an unacceptably large uncertainty (>10 dB) due to the impact of distortion. The approach presented also provides a scalar agreement metric and a natural means of visualizing areas of disagreement. Verification is achieved by identifying the critical physical and numerical phenomena and ascertaining correct handling by means of analytical and numerical benchmarks. The generality of the verification and validation approach presented makes it applicable to a wide range of computational models, beyond the highlighted acoustic simulations.

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References

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Figures

Grahic Jump Location
Fig. 1

Photos of the setup for in vitro ultrasonic measurements. The side-walls of the water-tank were lined with an acoustic absorber to minimize reflections (a). The entire exposure setup featuring the transducer (b) is shown in (c), and (d) shows the setup next to the robotic measurement arm with the extension on which the hydrophone is mounted.

Grahic Jump Location
Fig. 2

Cross section of the absolute pressure amplitude through the location of the peak for the reference simulation (a). The local maxima named SS, SW, SE, NW, and NE, extracted to ascertain the local distortion effects of the focal region, are marked as white points (b), while the center of the focal region is marked as a black point.

Grahic Jump Location
Fig. 3

Gamma-method for comparison of results with tolerances calculated by uncertainty analysis (see Table 9). The normalized pressure resulting from the measurements (a) and the simulation (b) are plotted on a plane through the maximum, while (c) shows the corresponding γ index distribution. Perfect agreement can be seen for these tolerances as all γ indices lie below a value of 1.0.

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