Jouko Tervo

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The paper considers the intensity modulated radiation therapy (inverse) treatment planning. An approach to determine the trajectories of the leaves of the multileaf collimator (MLC) in order to produce the prescribed intensity distribution is developed. The paper concentrates on the multiple static delivery technique. A mathematical model for calculating(More)
A method for the stabilization of stationary and timevarying autoregressive models is presented. The method is based on the hyperstability constrained LSproblem with nonlinear constraints. The problems are solved iteratively with Gauss-Newton type algorithm that sequentially linearizes the constraints. The proposed method is applied to simulated data in the(More)
Stability of time-varying autoregressive (TVAR) models is an important issue in many applications such as time-varying spectral estimation, simulation and analysis of EEG and time-varying linear prediction coding (TVLPC). For stationary AR-models there are methods that guarantee stability, but the for non-adaptive time-varying approaches there are no such(More)
The stability of autoregressive (AR) models is an important issue in many applications such as spectral estimation, simulation and decoding of linear prediction coded (LPC) signals. There are methods for AR parameter estimation that guarantee the stability of the model, that is, all roots of the characteristic polynomial of the model have moduli less than(More)
The paper deals with a distributed parameter system related to the socalled fixed-bed bioreactor. The original nonlinear partial differential system is linearized around the steady state. We find that the linearized system is not exactly controllable but it is approximatively controllable when certain algebraic equations hold. We apply frequency-domain(More)
A methodology, called by the name parametrization, is presented here for calculating open-loop controls for linear distributed-parameter systems. It is based on the theory of certain type of pseudo-differential operators (ΨDO). These operators have features which are useful from practical and computational viewpoints. The operators form an algebra, and(More)
The paper considers pseudo-differential boundary value control systems. The underlying operators form an algebra D with the help of which we are able to formulate typical boundary value control problems. The symbolic calculus gives tools to form e.g. compositions, formal adjoints, generalized right or left inverses and compatibility conditions. By a(More)
A new approach for the inverse treatment planning in radiation therapy with the multileaf colli-mator (MLC) technique is presented. The application of the MLC-techniques requires an algorithm for the computation of the positions or velocities of leaves as a function of time such that the prescribed dose in the patient space is obtained. First the intensity(More)