Veli Kolehmainen

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Model reduction is often required in optical diffusion tomography (ODT), typically due to limited available computation time or computer memory. In practice, this often means that we are bound to use sparse meshes in the model for the forward problem. Conversely, if we are given more and more accurate measurements, we have to employ increasingly accurate(More)
PURPOSE The present study characterized pole and ski forces in classical technique cross-country skiing. Eight elite junior cross-country skiers performed diagonal skiing at 65%, 75%, 90%, and 100% of maximum speed on a stable 100-m-low uphill (2.5 degrees ). METHOD : The ski and the pole forces (vertical (Fz) and horizontal (Fy) directions) on the right(More)
We propose a method which utilizes the radiative transfer equation in optical tomography. In this approach, the radiative transfer equation is used as light propagation model in those regions in which the assumptions of the diffusion theory are not valid and the diffusion approximation is used elsewhere. Both the radiative transfer equation and the(More)
In this study we consider the recovery of smooth region boundaries of piecewise constant coefficients of an elliptic PDE −∇ · a∇Φ + bΦ = f from data on the exterior boundary ∂Ω. The assumption is that the values of the coefficients (a, b) are known a priori but the information about the geometry of the smooth region boundaries where a and b are discontinous(More)
We consider the recovery of smooth 3D region boundaries with piecewise constant coefficients in Optical Tomography (OT). The method is based on a parametrisation of the closed boundaries of the regions by spherical harmonic coefficients, and a Newton type optimisation process. A boundary integral formulation is used for the forward modelling. An advantage(More)
| The reconstruction of impedance distribution in electrical impedance tomography (EIT) is a nonlinear ill-posed inverse problem. In order to obtain stable solution the problem has to be regularized. One of the most common methods for this is the generalized Tikhonov reg-ularization. The regularization matrices that are usually used with the Tikhonov method(More)
| We propose a method for the regularization of biomedical inverse problems and discuss its application to the electrical impedance tomography (EIT). The approach is deterministic but it has a clear statistical interpretation. The method is based on available anatomical information on the investigated object, that can be only of approxima-tive nature. The(More)
In this paper a source model for optical diffusion tomography is proposed. The light propagation is modelled with the radiative transfer equation (RTE) in the vicinity of the laser sources and the diffusion approximation (DA) is used elsewhere. The solution of the RTE is used to construct a Dirichlet boundary condition for the DA on a fictitious boundary(More)
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