ESTRO 2024 - Abstract Book

S5953

RTT - Treatment planning, OAR and target definitions

ESTRO 2024

To check that the bolus dimension was appropriate, radiochromic filmstrips were placed both in front of and behind the bolus, and they were read two hours after the treatment.

Results:

SBRT treatment was delivered to a sternum metastasis with a total dose of 3000 cGy in 3 consecutive days on Elekta Unity.

After performing dosimetry using a planner (Monaco v5.51.11), the radiophysics service observed that the area between the chin and the neck reached an absorbed dose between 100 cGy and 150 cGy per session. During the treatment, the 1 cm thick bolus was placed, measuring 10 cm in longitudinal axis and 30cm from leftto right. The different coloration of the radiochromic films were read every day after the treatment, to check whether the bolus covered the area where the dose increases.

The maximum dose regions measured in the films were Dmax 155.8 cGy/fx in front of the bolus and Dmax 30.5 cGy/fx behind the bolus, an 80% reduction.

The median time of the whole radiation treatment was 31 minutes. The treatment was well tolerated with no incidences, and the patient did not report any acute toxicity in the skin.

Conclusion:

Placement of a 1cm bolus in the patient’s neck during a thoracic RT performed on 1.5 Tesla MR- Linac allowed to protect this area from the ESE.

To guarantee adequate protection, the 1 cm bolus should not overlap with the treatment area or cause discomfort the patient, since they must maintain the fixed position for around 30 minutes per session. This tool was well tolerated and allowed to reduce the absorbed dose by 80%.

Keywords: MR-LINAC, ELECTRON STREAMING EFFECT, BOLUS

910

Digital Poster

Comparison of Eclipse and RayStation in Multi-Criteria Optimization in Prostate Cancer Radiotherapy

Yuk Kwong Wong 1,2 , Wan Shun Leung 2 , Curtise K.C. Ng 3 , Hing Ming Hung 1

1 Pamela Youde Nethersole Eastern Hospital, Clinical Oncology, Hong Kong, Hong Kong. 2 The Hong Kong Polytechnic University, Department of Health Technology and Informatics, Hong Kong, Hong Kong. 3 Curtin Medical School, Discipline of Medical Radiation Science, Perth, Australia