ESTRO 2025 - Abstract Book

S2699

Physics - Dose calculation algorithms

ESTRO 2025

3387

Proffered Paper A novel patient-specific method combined with a stochastic hemodynamic model to quantify the dose in circulating blood during radiotherapy treatments Marina García-Cardosa 1 , Chris Beekman 2 , Carlos Huesa-Berral 1,2 , Rosa Meiriño 3 , Elena Antolin 4 , Pablo Borja Aguilar 4 , Marta Vidorreta 5 , Roberto Cuevas 6 , Benigno Barbés 6 , Juan Diego Azcona 4,7 , Felipe Ángel Calvo 3 , Javier Burguete 1,7 , Harald Paganetti 2 1 Physics and Applied Mathematics, University of Navarra, Pamplona, Spain. 2 Radiation Oncology, Massachusetts General Hospital, Boston, USA. 3 Radiation Oncology, Clínica Universidad de Navarra, Madrid, Spain. 4 Medical Physics and Radiation Protection, Clínica Universidad de Navarra, Madrid, Spain. 5 Siemens Healthineers, Siemens, Madrid, Spain. 6 Medical Physics and Radiation Protection, Clínica Universidad de Navarra, Pamplona, Spain. 7 IdiSNA, Navarra Institute for Health Research, Pamplona, Spain Purpose/Objective: Accurately quantifying the circulating blood dose from a specific patient during proton or photon radiotherapy is a challenge in blood dosimetry. To address this, we propose FLIP-HEDOS, an innovative model combining the novel FLIP (FLow and Irradiation Personalized) method with the computational tool HEDOS (HEmatological DOSe). By treating blood as a dynamic organ at risk, FLIP-HEDOS offers a patient-specific approach, particularly suited for radiotherapy in the most common cancer locations. Material/Methods: FLIP method [1] quantifies dose to circulating blood along patient-specific vasculature using patient-specific large vessels delineated on MRI and the corresponding blood velocity field from phase-contrast MRI [2]. In contrast, HEDOS [3] is a general stochastic compartmental model that simulates the spatiotemporal distribution of blood particles (BPs) in organs throughout the body. Thus, FLIP is integrated as a patient-specific arterial and venous modules that considers patient-specific tumor location, vasculature flow and volume to maintain the system in equilibrium. Assuming a total blood volume of 5.3 L, a discretization into BPs of 1 mm³ is performed. Simulated BPs travel in FLIP modules with a Lagrangian approach along flowlines defined by the velocity field, but move stochastically through the HEDOS compartments based on predetermined transit time distributions. Simulating the spatiotemporal distribution of BPs allowed us to accumulate blood dose, making use of dynamical 3D dose distributions and beam active times measurements. The cohort of patients analyzed have tumors in thorax abdomen and head-neck areas. Results: FLIP-HEDOS quantifies the dose received by each BP (see Figure), and verifying the number of times that a BP has (re)visited the patient-specific vasculature (Table 1). Findings indicate, regardless of the radiotherapy modality, that if the tumor is close to large vessels (pancreas and liver tumor in Figure), a larger volume of blood will receive dose above a 0.1 Gy threshold which may cause damage to lymphocytes. Furthermore, it was observed that the number of times that a BP visits FLIP module increases with a higher total treatment time value and larger tumor volume.