Couch-based motion compensation: modelling, simulation and real-time experiments

The paper presents a couch-based active motion compensation strategy evaluated in simulation and validated experimentally using both a research and a clinical Elekta Precise Table™. The control strategy combines a Kalman filter to predict the surrogate motion used as a reference by a linear model pr...

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Bibliographic Details
Published in:Physics in medicine & biology 2012-09, Vol.57 (18), p.5787-5807
Main Authors: Haas, Olivier C L, Skworcow, Piotr, Paluszczyszyn, Daniel, Sahih, Abdelhamid, Ruta, Mariusz, Mills, John A
Format: Article
Language:English
Subjects:
compensation
Humans
model predicitve control
Models, Theoretical
motion
Movement
Patient Positioning
radioptherapy
Radiotherapy, Computer-Assisted - instrumentation
robotic couch
Time Factors
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Summary:The paper presents a couch-based active motion compensation strategy evaluated in simulation and validated experimentally using both a research and a clinical Elekta Precise Table™. The control strategy combines a Kalman filter to predict the surrogate motion used as a reference by a linear model predictive controller with the control action calculation based on estimated position and velocity feedback provided by an observer as well as predicted couch position and velocity using a linearized state space model. An inversion technique is used to compensate for the dead-zone nonlinearity. New generic couch models are presented and applied to model the Elekta Precise Table™ dynamics and nonlinearities including dead zone. Couch deflection was measured for different manufacturers and found to be up to 25 mm. A feed-forward approach is proposed to compensate for such couch deflection. Simultaneous motion compensation for longitudinal, lateral and vertical motions was evaluated using arbitrary trajectories generated from sensors or loaded from files. Tracking errors were between 0.5 and 2 mm RMS. A dosimetric evaluation of the motion compensation was done using a sinusoidal waveform. No notable differences were observed between films obtained for a fixed- or motion-compensated target. Further dosimetric improvement could be made by combining gating, based on tracking error together with beam on off time, and PSS compensation.
ISSN:0031-9155
1361-6560
DOI:10.1088/0031-9155/57/18/5787