ESTRO 2022 - Abstract Book

S796

Abstract book

ESTRO 2022

Conclusion The dose distribution calculated using the new CBCT c method showed excellent agreement with the pCT based dose calculation, with superior accuracy compared to the CBCT b method. The main reasons for deviations of the calculated dose distribution were caused by anatomical variations between the pCT and the corrected CBCT. The clinical introduction of the novel CBCT c method will improve the accuracy of the dose estimation in adaptive radiotherapy workflows.

PD-0902 First commissioning tests of the BSD2000-3D Universal Arch MR-compatible hyperthermia device

C. Seabra 1 , I. VilasBoas-Ribeiro 1 , K. Sumser 1 , S. Curto 1 , G.C. van Rhoon 1,2

1 Erasmus MC Cancer Institute, University Medical Center Rotterdam, Department of Radiotherapy, Rotterdam, The Netherlands; 2 Faculty of Applied Sciences, Delft University of Technology, Department of Radiation Science and Technology, Delft, The Netherlands Purpose or Objective Hyperthermia is a potent sensitizer to radiotherapy, and its goal is to increase tumor temperature up to 43°C. Magnetic resonance (MR) guided hyperthermia systems are the latest technology that allows non-invasive temperature monitoring of the target volume and precise energy delivery. Hence, imaging and heating performance are critical components for the success of treatment, making essential the commissioning of such systems. In Erasmus MC, the BSD2000-3D Universal Arch MR-compatible hyperthermia device operates with GE MR450w 1.5T MR scanner (Figure 1a). Comparing to the previous MR compatible systems, the new device includes novel patient positioning and electrical balanced RF-feeds to the 12 dipole- pairs for tumor heating. This study presents the first commissioning experience of the Universal Arch device. We performed tests to, firstly, evaluate the influence of the novel MR-compatible device on MR quality imaging and, secondly, assess the heating quality profile. Materials and Methods All tests were conducted using a cylindrical phantom. The two types of experiments performed are represented in Figure 1b. In experiment A, image quality was evaluated by calculating signal to noise ratio (SNR) in two setups: (i) phantom only and (ii) when phantom is heated with the device, using the clinical MR thermometry (MRT) sequence (Curto et al, 2020). In experiment B, heating performance was evaluated in terms of ability and stability using MRT with the proton resonance frequency shift method. Heating ability was evaluated, in the six experiments, by accessing temperature increase in a region of interest (ROI) of 3cm diameter in the target. For stability, temperature precision was calculated in the same ROI between the same measurements. The Gamma method was applied to compare the reproducibility of the six measurements. Criteria of 5%/5mm was used, given resolution, and required hyperthermia treatment accuracy. Table 1 details these tests.