ESTRO 2022 - Abstract Book

S1452

Abstract book

ESTRO 2022

Conclusion Custom attenuation correction of radiotherapy hardware setups for combined PET/MRI is necessary for quantitative PET. Good reproducibility of custom corrected PET data has been demonstrated and the presented workflow may serve as a quality assurance (QA) program for multicenter imaging trials.

PO-1654 Back arching during tangential DIBH breast RT detected with live EPID based position monitoring

E. Vasina 1 , N. Kong 2 , J. Ludbrook 2 , G. Govindarajulu 2 , P. Greer 2 , J. Lehmann 2

1 University of Newcastle, NSW, Australia, School of Information and Physical Sciences, Callaghan, Australia; 2 Calvary Mater Newcastle, Radiation Oncology Department, Waratah, Australia Purpose or Objective An electronic portal image device (EPID) based system for real-time monitoring of breath-hold quality during deep inspiration breath-hold (DIBH) breast cancer treatments has been developed [1]. Live EPID-based Inspiration Level Assessment (LEILA) uses internal surrogates, the position of the bony chest wall and the patient’s skin, to assess the alignment of anatomy with the treatment beam. LEILA is currently being tested with patients. Its ability to measure at multiple locations has been utilized to identify instances where the patient arched their back instead of taking a deep breath-hold, which is known cause of lower DIBH quality. [2] Materials and Methods LEILA analyses portal MV images of breast tangents and measures the lung depth (LD) and the distance from the skin to posterior field edge (skin distance, SD) at 3 user-selected locations as shown in Figure 1A. It displays these six parameters in real time and tracks them over time. In this study, breathing and breath-hold of the patients during RT were monitored and directed with the Varian’s RPM or C-RAD’s Catalyst+ systems. In both situations, the breathing window, the allowed motion, was 5 mm. Results The plots of LDs during “Breath-hold 2” in Figure 1B show typical time traces of the 3 LD parameters (superior, midline, and inferior) seen during the DIBH treatments: the time dependences of the superior, midline, and inferior LDs are changing in the same direction. For two patients on the study (Patient A and Patient B) there were instances when the superior LD was decreasing while the midline and inferior LDs were increasing (“Breath-hold 1” in Fig. 1B, and at the start of beam 3 and beam 4 in Fig. 1C). These observations likely indicate arching of the back. For Patient A, the observation was made during 1 beam of 48 beams tested with LEILA. For Patient B, the observation was made for 2 of 36 beams tested. While the amplitude of the changes of the 3 LD parameters during these instances was small, it is clear enough to implement a simple automated trend check during real-time monitoring with LEILA, which alerts the operator of back arching.