ESTRO 2020 Abstract book

S925 ESTRO 2020

toolkit.

The main component is a sensitive respiratory and motion compensation movement, which was programmed based on the Robot API from KUKA. The desired contact force was set to 5 N. The movement was tested on subjects for different sound positions and breathing patterns. MITK has been extended with filters for the spatial assignment of coordinates and the display of ultrasound images, ea. for creating 3D ultrasound volume by means of scanning movements of a 2D ultrasound head. Results Image acquisition was continuous due to respiratory motion compensation and the transducer could be repositioned and positioned by remote control. The applied and resulting measured force at the transducer was constant. The control concept and image representation are combined in a GUI, whereby the developed filter pipeline allows the simultaneous display of registered ultrasound images and planning data in real time (Fig. 2).

Results When brain motion is applied there was a decrease in total dose delivered (to the specific point of measurement) making the delivered dose not the same as the planned dose. Fig.1a shows the distortion introduced in the relative dose map of the microbeams. Profiles reconstructed using the SSD detector (Fig.1b) show quantitatively the distortion in Gy. Low target scanning speed affect the dose distortion the most with a reduction of the PVDR up to 40% as shown in Fig.2a. This is confirmed by the simulated data as shown in Fig.2b.

Conclusion The SSD was able to reconstruct dose profiles under motion conditions and predict similar effects on FWHM and PVDR variations as per the simulations. Low scanning speed of the target leads to 40% decrease of the PVDR. Higher scan speeds mitigate the dose distortion effects with no effect on the displacement of the microbeams. This has implications for MRT treatment planning when multiple ports are used. The technique developed can be used to assess the effect of motion in MRT for different motion patterns associated to different organs. PO-1607 Development of a Robot Assisted Ultrasound Based Radiation Therapy (USgRT) P.K. Seitz 1 , A. Schwahofer 1 , B. Baumann 2 , R. Bendl 2 1 German Cancer Research Center, Department of Medical Physics in Radiation Oncology, Heidelberg, Germany ; 2 Heilbronn University, Medical Informatics, Heilbronn, Germany Purpose or Objective One of the central problems of radiotherapy is the position monitoring of tumors during irradiation. Therefore, imaging methods are searched in order to detect the tumor position during the irradiation. One approach to this is ultrasound, which requires a constant pressure on the patient surface. The aim of this work is to develop a robot application for respiratory and motion compensation with constant contact pressure. This is to be integrated into a medical image processing program for the registration of ultrasound images with planning data. Material and Methods The lightweight robot (Kuka lbr iwa 7 R800) was integrated into the image processing program Medical Interaction Toolkit (MITK) [1] via a newly developed interface. The detection of the transducer position was observed via an optical tracking system (Spectra, Polaris). Experimental setup is displayed in Fig. 1.

Conclusion A reliable, universal method for motion compensation, under low force constraints, in robot-guided ultrasound imaging has been developed and successfully tested. This is a first step towards a safe, autonomous robot positioning on the patient. In addition, the positional image data could be integrated into a system, providing the basis for image registration for ultrasound-based radiotherapy. [1] Nolden, M., e. al.: The medical imaging interaction toolkit: challenges and advances. International Journal of Computer Assisted Radiology and Surgery 8(4), 607–620 (2013). DOI 10.1007/s11548-013-0840-8 PO-1608 Assessment of shoulder position variation and its impact on VMAT doses using an EPID-based software I . Valverde Pascual 1 , P. Gallego 1 , J. Perez-Alija 1 , N. Jornet 1 , A. Latorre-Musoll 1 , M. Barcelo-Pages 1 , N. Garcia- Apellaniz 1 , P. Carrasco de Fez 1 , M. Lizondo 1 , P. Simon Garcia 1 , P. Delgado-Tapia 1 , M. Adria Mora 1 , A. Ruiz Martinez 1 , M. Ribas 1