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Table 2 Assumed and estimated parameters and their variations for the models using a sphere.

From: Data-guide for brain deformation in surgery: comparison of linear and nonlinear models

Mechanical model

Young modulus

Poisson's ratio

Force

Assumed

0.45

3000

Fx = 1500

     

Fy = 1500

     

Fz = 1500

Estimated

0.45 ± 0.0056

3000 ± 175.6

Fx = 1500 ± 90.8

     

Fy = 1500 ± 87.9

     

Fz = 1500 ± 93.2

Nonlinear model

C100

C010

C200

C020

g 1 +g 2

Force

Assumed

263

263

491

491

0.815

Fx = -300

      

Fy = 300

      

Fz = 300

Estimated

263

±4.0401

263

±7.8404

491

±14.4139

491

±13.4578

0.815

±0.0083

Fx = -300 ± 9.1726

      

Fy = 300 ± 10.0278

      

Fz = 300 ± 8.7998

  1. We use sphere as a simple model of the brain. Specific parameters are assumed and the resulting deformations of specific points are used in the optimization process. Other points are used for testing of the optimization process. Then, the parameters are changed and the optimization process is repeated to estimate the model parameters again. The results illustrate that the brain deformation can be modeled by the proposed models and the proposed optimization method can accurately estimate the model parameters. For each model, we have done this process and have compared the accuracy of models using the matching errors of the points used in the optimization process and those that are not used. Note that the optimization process estimates the parameters of the nonlinear model more accurately (with less bias and variance) compared with the mechanical model.