Fast and accurate techniques for optimal design of radiation treatment of tumours and for CT image reconstruction

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This grant application is aimed at two areas of research in Medical Physics: 1) Intensity Modulated Radiation Therapy (IMRT) is the new advanced standard technique for radiotherapy of cancer tumours using multiple high energy radiation beams applied from different angles around the patient, with each beam further divided into narrow beamlets with independent intensities. One of the most sought-after goals in present day radiation therapy research that is unavailable today is adaptive radiation therapy: i.e. the ability to redesign the radiation treatment at the time of each (daily) delivery by obtaining updated CT images of the tumour region and re-planning the treatment to adapt to any displacement or deformation of the tumour(s). One of the most important barriers to the achievement of adaptive radiation therapy is the very long time that present planning systems take to optimize a radiation treatment plan. We have developed a new approach to radiation treatment (Fast Inverse Dose Optimization method - FIDO) that is orders of magnitude faster than present methods and yields excellent radiation treatment plans that satisfy required clinical constraints. In this grant proposal, our radiation treatment research is extended to other modalities (IMAT, iPET, HDR brachytherapy) as well as researching new ideas for calculations of the change in dose deposition to account for day-day motion or deformation of organs in the volume subjected to radiation treatment. 2) The success of Computed Tomography (CT) for diagnostics and treatment planning rests on its ability to produce accurate images that represent the true structure of the region being imaged. Aside from CT intrinsic noise considerations, current image reconstruction algorithms yield unwanted artefacts that vastly degrade the whole image when regions with sharp density changes are present. The proposed research involves new methods (AIR and PAIR) for which we have preliminary results showing the absence of artefacts with the production of accurate image reconstruction. A totally new artefact-free geometrical approach to image reconstruction will be as well investigated.