Abstract
We propose a new markerless tracking technique of lung tumor motion by using an X-ray fluoroscopic image sequence for real-time image-guided radiation therapy (IGRT). A core innovation of the new technique is to extract a moving tumor intensity component from the fluoroscopic image intensity. The fluoroscopic intensity is the superimposition of intensity components of all the structures passed through by the X-ray. The tumor can then be extracted by decomposing the fluoroscopic intensity into the tumor intensity component and the others. The decomposition problem for more than two structures is ill posed, but it can be transformed into a well-posed one by temporally accumulating constraints that must be satisfied by the decomposed moving tumor component and the rest of the intensity components. The extracted tumor image can then be used to achieve accurate tumor motion tracking without implanted markers that are widely used in the current tracking techniques. The performance evaluation showed that the extraction error was sufficiently small and the extracted tumor tracking achieved a high and sufficient accuracy less than 1 mm for clinical datasets. These results clearly demonstrate the usefulness of the proposed method for markerless tumor motion tracking.
Highlights
In radiation therapy, to irradiate sufficient dose to tumors and avoid unnecessary dose to the surrounding healthy tissues are crucial to achieve significant treatment effects and reduce adverse effects
The observed fluoroscopic intensity I(x, y) is the result of superimposition of a tumor intensity component Ia(x, y) and the background intensity that is the sum of all the other components Ib(x, y) of the rest of the structures passed through the X-rays
We have developed the dynamic decomposition method to extract the moving lung tumor image component from kV Xray fluoroscopic images and applied it to the tumor tracking
Summary
To irradiate sufficient dose to tumors and avoid unnecessary dose to the surrounding healthy tissues are crucial to achieve significant treatment effects and reduce adverse effects. The larger margins cover the wider regions of surrounding healthy tissues. In this sense, motion management is necessary for effective treatment, especially for abdominal and thoracic tumors [2,3,4]. The extraction can be represented by subtracting the background intensity Ib from the observed fluoroscopic one I. Note that the extraction of the tumor component Ia from the fluoroscopic image I is generally ill posed. It is often very difficult for one to recognize a tumor in an X-
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