ESTRO 2024 - Abstract Book

S3281

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

1703

Poster Discussion

dynamic anthropomorphic thorax phantom for quality assurance of motion management in radiotherapy

Sara Abdollahi 1,2 , Ali Asghar Mowlavi 3 , Mohammad Hadi Hadizadeh Yazdi 1 , Sofie Ceberg 4 , Marianne Camille Aznar 5 , Fatemeh Varshoee Tabrizi 6 , Roham Salek 7 , Matthias Guckenberger 2 , Stephanie Tanadini-Lang 2 1 Ferdowsi University of Mashhad, Physics, Mashhad, Iran, Islamic Republic of. 2 University Hospital of Zurich, Radiation Oncology, Zurich, Switzerland. 3 Hakim Sabzevari University, Physics, Sabzevar, Iran, Islamic Republic of. 4 Lund University, Medical Radiation Physics, Lund, Sweden. 5 University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom. 6 Reza Radiotherapy and Oncology Center, Radiation Oncology, Mashhad, Iran, Islamic Republic of. 7 Mashhad University of Medical Science, Radiation Oncology, Mashhad, Iran, Islamic Republic of

Purpose/Objective:

Radiotherapy for moving targets presents a significant challenge, necessitating the implementation of various motion management techniques. These techniques must be rigorously validated using a realistic patient-imitating geometry. The primary objective of this study was to develop a dynamic anthropomorphic phantom that accurately emulates a patient's size, anatomy, and tissue density while also incorporating key characteristics of thoracic breathing patterns.

Material/Methods:

A breast cancer patient's computed tomography (CT) scan served as a basis for generating casting molds using additive manufacturing (3D Printing) for lungs, heart, ribs, and vertebral column. A cavity was incorporated into the left lung diaphragm to allow the placement of a tumor. Three tumor structures were custom-designed to integrate radiochromic films, a PTW microDiamond detector, and a PTW PinPoint 3D ion chamber. In the right lung, a water filled sphere was introduced to replicate the desired HU value of water as a reference. Various materials underwent testing to accurately mimic the physical density and electron density characteristics of the lung, bone and soft tissue of a real patient within the context of CT imaging. To simulate respiratory dynamics, a custom-made pump system and dedicated software were developed to cyclically inflate and deflate the lungs. The extent of respiratory motion was quantified using a 4DCT scan capturing ten different respiratory phases. The reproducibility of dynamic performance was also evaluated through five 4DCT and five gated Cone Beam CT (CBCT) scans. Following the registration of bony anatomy images, the chest wall, diaphragm and tumor positions were compared. For comprehensive evaluation, end-to-end tests were performed for motion-encompassing and respiratory gating techniques in the scope of lung stereotactic body radiation therapy (SBRT) for two different tumor sizes. The dose measurements were performed using Gafchromic EBT3 films and PTW microDiamond detector.

Results:

The movement observed between the end of exhalation and the end of inhalation in the chest wall was between 0.4cm to 1.3cm in the anterior direction and 0.2cm to 0.7cm in the lateral direction. The diaphragm exhibited movement in a superior-inferior direction within a range of 0.5cm to 1.6cm for the left lung and 1cm to 3.6cm for the