Registration of Portal Images using Self-organizing Maps

G. Matsopoulos, P. Asvestas, K. Delibasis, N. Mouravliansky, and N. Uzunoglu (Greece)


Medical imaging, image registration, self-organizingmaps


Portal imaging refers to a procedure for monitoring the setup geometry in radiation therapy using X-ray images acquired in very high energy (approximately 10 MeV). Portal imaging has become significant in recent years, since it provides a means for the detection of setup errors, including the exclusion of part of the target volume from the beam or unwanted inclusion of normal tissue. In this paper, a new method, for the registration of portal images is presented. The method employs Self Organizing Maps (SOMs), which operate on the original raw data, in order to estimate the displacement and the angle of rotation of a treatment image with respect to a reference one. The proposed registration method was tested on phantom and real data and an average error below 1mm was achieved. The obtained results strongly indicate that the proposed system is suitable for detecting and quantifying patient setup errors.

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