OPTIMIZED PLANNING AND DELIVERY OF RADIOTHERAPY

University Of Wisconsin Madison, Madison WI

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Abstract

We will develop and test methodologies for optimized planning, conformal beam delivery, and tomographic verifications. The methods will be applicable to contemporary radiotherapy as well as to a fan-beam delivery system we call tomotherapy. Our goal is to suggest strategies which significantly improve dose delivery to the tumor while minimizing dose to critical structures. We will use our unique benchtop system to deliver and tomographically verify the delivery of intensity modulated radiotherapy. The system consists of a GE Orion 4 MV linear accelerator mounted in the horizontal direction, a 64 element xenon-filled ion chamber monitor, a NOMOS MIMiC temporally-modulated multileaf collimator, a computer-controlled phantom translator/rotator, and a GE 736 element xenon-filled CT detector with an associated high-speed data acquisition system. We will improve and test optimization computations, based on either iterative image reconstruction algorithms or a commercial general- purpose optimization package, both of which are capable of predicting the patterns of beam intensity modulation. Both physical and biological objective functions will be used to guide the results of these optimization algorithms. Our benchtop system will be used to deliver the predicted intensity patterns into dosimetry benchmark phantoms. We will improve and test procedures to provide tomographic verification of the treatment delivery. We will use the cross-correlation of tomographic projections to determine translational and/or rotational offsets in patient setup. We will further test the dose reconstruction algorithm which is capable of providing the dose distribution actually delivered based upon a CT representation of the patient and a megavoltage detector system. These methodologies will be validated on our benchtop system.