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Development of An Anthropomorphic Multimodal Abdominal 4D Phantom for MR-Guided Radiotherapy

A Weidner13*, G Echner12, A Runz12, (1) German Cancer Research Center Heidelberg DKFZ, Heidelberg, BW, DE, (2)Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Germany (3)Faculty of Medicine, University of Heidelberg, Heidelberg, Germany


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

The anthropomorphic abdominal 4D phantom will serve to further develop and assure the quality of new irradiation techniques, such as MR-guided Radiotherapy. An anthropomorphic displacement of the abdominal organ induced by the diaphragm can be detected and evaluated with the MRI.

The phantom features a modular design which makes it possible to attach a flexible diaphragm as well as a flexible abdominal wall with different silicones. Actuators on the top can exert pressure on the diaphragm via an exact independent depth adjustment. Furthermore six eyelets are used inside the case to attach the organ model, so the organ model can be attached free-floating via 1mm thin elastic cords. The phantom was filled with agarose to achieve soft tissue conditions and contrast for MRI imaging. All experiments were performed at the MRIdian MR-Linac of the University Hospital Heidelberg.

In total, the same experiment was performed at least twice for each version (4) of the phantom in order to ensure reproducibility of the movement and thus induced change in the position of the organ model. The evaluation of the examination for reproducibility resulted in a deviation of 0.7mm, therefore reproducibility can be assumed. The version two of the Phantom, provides movement ranges closest to the human area, 6.8mm in the cranio-caudal (literature 11.56mm) direction and 6.3mm (literature 3.49mm) in the anterior-posterior direction.

With the developed phantom and organ model, an organ shift induced by the diaphragm could be detected. Furthermore, the displacement of the organ model is within the range of human capabilities. In addition, the displacement in the cranio-caudal direction should be further strengthened, this could be achieved by loosely attaching the organ model in cranio-caudal direction and by integrating a flexible element on the lower side of the phantom to allow a larger longitudinal movement.


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