ESTRO 2021 Abstract Book

S1495

ESTRO 2021

the FoV was adjusted due to the off-isocentric treatment. The reference SI was acquired in conjunction with the patient positioning. Recording of the motion during the whole treatment session, including the FLASH delivery was executed for one patient. The motion was analyzed by retrieving data from the SS system log files. Results The individual camera exposure settings for all canine cancer patients and SI for two of them are presented (Table 1, Figure 1b, 1d). For the patient where surface guided motion management during beam-delivery was used, motion up to 3 cm between patient setup and treatment start was recorded (Figure 1e) and treatment was postponed until full anesthesia was reached. The total vector offset from the reference SI was 0.1 mm at the time of radiation delivery indicated by the SS system (Figure 1e). The same offset was also observed 1.72 s before beam-on and 1.63 s afterwards. For patients with very dark fur, it was challenging to obtain an acceptable SI due to hardware limitations. When encountering the maximum exposure time, the signal could not be further amplified which resulted in either a decreased speed of the SS system or decreased reconstructed surface regions (Dalmatian vs Labrador, Figure 1b and 1d).

Conclusion We have demonstrated that motion management during FLASH-RT is important and feasible using SGRT. It was shown that the surface scanning system can cover the required FoV and capture images during the off-