ESTRO meets Asia 2024 - Abstract Book

S334

Physics – Motion management and adaptive radiotherapy

ESTRO meets Asia 2024

changes in practice, e.g., patient training for reproducible breathing or changes in fiducial use. This study provides a demonstration of how data can be collected, analysed and used for research and clinical decision making.

Keywords: Synchrony, target tracking, data analysis

References:

[1] Tudor GSJ. et al. (2020) Geometric Uncertainties in Daily Online IGRT: Refining the CTV-PTV Margin for Contemporary Photon Radiotherapy. British Institute of Radiology, London, UK. https://doi.org/10.1259/geo-unc igrt

326

Proffered Paper

Need of ITV margin for mediastinal tumours in patients treated with DIBH technique

Karthick Raja M 1 , Arun S Oinam 1 , Budhi Singh Yadav 1 , Divya Khosla 1 , Harkant Singh 2

1 Department of Radiotherapy and oncology, PGIMER, Chandigarh, India. 2 Department of Cardiovascular and Thoracic Surgery, PGIMER, Chandigarh, India

Purpose/Objective:

While treating thoracic tumours with radiation, respiratory-induced motion is the biggest challenge. Despite many three-dimensional (3D) technologies developed for the treatment of cancer, respiratory-induced motion is a major drawback. Deep Inspiration Breath Hold (DIBH) one of the techniques tries to nullify the respiratory induced motion and thereby reduce the radiation to the nearby normal structure by reducing clinical target volume (CTV) to planning treatment volume (PTV) margin. This study aimed to analyze the inter-fraction variations of the center of mass of the gross tumour volume (GTV) in mediastinal lymphoma patients with DIBH Planning computed tomography (CT) and DIBH 3D kilovoltage (KV) cone beam CT (CBCT).

Material/Methods:

Ten patients with pathologically proven lymphoma (both Hodgkin and non-Hodgkin) who had residual disease in the mediastinum were included in this pilot study. Patients who fulfilled the inclusion criteria were simulated by the DIBH technique with the help of the C-RAD system. The gross tumour volume (GTV) was contoured and the CTV margin (1cm) was given, which included the prechemotherapy volume and further trimmed according to the anatomical barriers and OARs. A PTV margin of 5mm was given for all the patients. During treatment, the inter fraction variations were monitored with daily DIBH KV CBCT. The CBCTs were imported to the contouring station where the GTV of all CBCTs were contoured, which was compared with planning CT. The inter-fraction variation of the GTV and extent of the GTV motion in the left-right (LR), superior-inferior (SI) and anterior-posterior (AP) directions, as well as Dice Similarity Coefficient (DSC), was calculated from the DIBH planning and DIBH 3D KV CBCT.

Results: