4D Image Verification
Diploma Thesis from the year 2007 in the subject Computer Science - Applied, grade: 1,0, Friedrich-Alexander University Erlangen-Nuremberg (Lehrstuhl für Mustererkennung), 66 entries in the bibliography, language: English, abstract: Far reaching developments and technical advances took place within the field of radiotherapy in the last years. Radiotherapy within the chest and abdomen area is especially important in the field of radiotherapy. Within this regions, organ and tumor positions are significantly affected by patient respiration. The tumor motion, caused due to respiration is compensated by extending the treated area. This extension covers all possible positions of the tumor and therefore also includes healthy tissue. Several clinical studies provide evidence of a survival advantage for higher dose levels. To spare a maximum of healthy tissue physicians use ’gated radiotherapy’. Common recent approaches for gated radiotherapy are based on the observation of a surrogate. This either can be an implanted fiducial marker or an external signal, which is trying to capture the patients’ respiration. Within this thesis principles and methods of ’gated radiotherapy’ are described. Additionally an overview of recent patents and products related to radiotherapy are presented and advantages and disadvantages of both common approaches are discussed. This discussion leads to a new developed method, which is introduced. The method joins advantages of both known methods but disregards their disadvantages. The developed algorithm is using image guided methods and methods of medical image processing. A mapping between a 4D-CT planning volume and a most recent acquired fluoroscopic sequence of the same patient is calculated before treatment. Using this mapping and an external breathing signal the physician can define gating intervals and treat the patient in certain breathing phases. The developed algorithm is included in an existing prototype developed by Siemens Corporate Research (SCR) in Princeton, NJ, USA. Using this prototype, the application of the method is shown. Furthermore another prototype to acquire respiration synchronized fluoroscopic sequences is developed. Both applications are introduced within this thesis.
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3D volume 4D-CT sequence acquired AcquireIt acquisition algorithm application bad correlations Bellman equation breathing curve including breathing patterns breathing phases column computed path cone beam contours of phases CT scanning datasets dose levels DRR images Dynamic Programming equation exhale external gating external surrogate Figure fluoroscopic sequence frame grabber Furthermore gain field gated radiotherapy gating methods gating window Image Sequence Synchronization including the percentage introduced Level II Phantom LINAC lung cancer markov chain mutual information percentage levels Phantom test sequence phases 6-8 red physicians portal images possible radiation therapy reference breathing cycle reference image reference sequence images respiratory motion RTReg4D showing the computed showing the inverse showing the synthetic shows the contours signal similarity matrix singular value decomposition slow CT scanning SOMATOM Sensation Open standard deviation synthetic generated breathing Target Volume transition matrix treatment planning treatment session tumor contour yellow tumor motion tumor position Varian Medical Systems wild card