Attempts to Bronchial Tumor Motion Tracking in Portal Images during Conformal Radiotherapy Treatment
This is a feasibility study of tumor motion tracking in images generated by radiotherapy treatment beam. The objective is to control the beam during free breathing so as to reduce the irradiated zone and thus preserve healthy tissues. Two algorithms were tested on portal images sequences. Optical flow estimation (standard Horn and Schunck’s algorithm), applied to images from a patient, gave poor results because of low contrast and absence of texture in these images. Target tracking algorithm (block-matching), tested on images of a phantom with a radio-opaque marker, gave satisfactory results: mean absolute error was less than 1 mm. Hence, tumor tracking in portal images is possible, provided that a marker can be implanted in tumor’s vicinity. For images without markers, further work is necessary to assess if the small amount of motion information contained in such images can be reliably exploited.
Keywordsmedical imaging motion tracking portal image
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