DRR and Portal Image Registration for Automatic Patient Positioning in Radiotherapy Treatment
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Image processing turns out to be essential in the planning and verification of radiotherapy treatments. Before applying a radiotherapy treatment, a dosimetry planning must be performed. Usually, the planning is done by means of an X-ray volumetric analysis using computerized tomography, where the area to be radiated is marked out. During the treatment phase, it is necessary to place the patient under the particle accelerator exactly as considered in the dosimetry stage. Coarse alignment is achieved using fiduciary markers placed over the patient’s skin as external references. Later, fine alignment is provided by comparing a digitally reconstructed radiography (DRR) from the planning stage and a portal image captured by the accelerator in the treatment stage. The preprocessing of DRR and portal images, as well as the minimization of the non-shared information between both kinds of images, is mandatory for the correct operation of the image registration algorithm. With this purpose, mathematical morphology and image processing techniques have been used. The present work describes a fully automatic method to calculate more accurately the necessary displacement of the couch to place the patient exactly at the planned position. The proposed method to achieve the correct positioning of the patient is based on advanced image registration techniques. Preliminary results show a perfect match with the displacement estimated by the physician.
KeywordsRadiotherapy Image registration Image feature enhancement Biomedical image analysis
This work is funded by the Spanish “Ministerio de Educación y Ciencia” under the research project “Automatización de un sistema de planificación de radioterapia mediante técnicas emergentes de registro y fusion de imágenes biomédicas” (ref. TEC2006-13338/TCM). The authors would also like to thank the Radiology Department of the “Hospital Universitario Virgen de la Arrixaca” (Murcia, Spain) for providing all the images used in this paper and for their kind collaboration.
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