P.1.19 FLASH RADIATION THERAPY: A REVIEW ON THE ULTRA-HIGH DOSE RATE PARADIGM OF RADIOTHERAPY

Abstracts / Physica Medica 127S1 (2024) S1–S82 S47 Material and Methods: Having thoroughly read the related bibliography, the necessary information was collected and summarized into the sections to be discussed. Results: The physics behind Heavy Ion interaction with matter has been studied by numerous scientists and is not as simple as the interaction of single particles, but as it will be shown in this paper, the benefits and applications are overwhelming. However, its implementation, due to cost and technical challenges, presents an obstacle. Conclusion: The applications and benefits are many and promising, unfortunately until new compact and cost-effective designs come to light their applications in the medical field will be suppressed. Physica Medica 127S1 (2024) 104640 https://doi.org/10.1016/j.ejmp.2024.104640 P.1.19 FLASH RADIATION THERAPY: A REVIEW ON THE ULTRA-HIGH DOSE RATE PARADIGM OF RADIOTHERAPY A. Koutsostathis1, V. Rangos1, A. Adamopoulou1, C. Koumenis2, A. G. Georgakilas1 1Department of Physics, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Zografou, Greece, 2Department of Radiation Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States of America Background: FLASH radiotherapy (FLASH-RT) is a new paradigm of radiation therapy, featuring Ultra-High Dose Rate (UHDR) irradiation of tumours, with dose rates of the order of 40 Gy s-1 and higher. While maintaining its anti-tumour effect, FLASH-RT is characterised by a transient hypoxic state, and therefore extended sparing, in healthy tissue, when compared to conventional radiation therapy [1]. Material and Methods: In this review, procedures and findings from numerous preclinical studies have been collected and assessed, in order for the various radiobiological and technical aspects of FLASHRT to be thoroughly presented. Results: While, the underlying mechanisms of the FLASH effect remain under debate, the presently dominant theories focus on the reduction in blood volume irradiation, the rapid depletion of O2 and the detained formation of Reactive Oxygen Species [1]. Recent preclinical trials have employed modified pre-existing therapy settings, such as electron and proton accelerators, and X-Ray synchrotron sources, which allow for UHDR beams [2]. Further technical advances lie on the development of rapid dosimetry and technology for large-field and multiple-fraction irradiation [3]. Conclusions: FLASH-RT has led to a paradigm shift in the field of radiation biology. It shows promising potential to promote new methods of widely applicable antitumour treatments with minimal healthy tissue impact and higher post-irradiation quality of life. References [1] Limoli CL and Vozenin MC. Reinventing Radiobiology in the Light of FLASH Radiotherapy. Annu Rev Cancer Biol. 2023;7:1–21. [2] Wu Y, No HJ, Breitkreutz DY, Mascia AE, Moeckli R, Bourhis J, Schüler E, Maxim PG, Loo BW Jr. Technological Basis for Clinical Trials in FLASH Radiation Therapy: A Review. Appl Rad Oncol. 2021;2:6-14. [3] Maity A and Koumenis C. Shining a FLASHlight on ultrahigh dose rate radiation and possible late toxicity. Clin Cancer Res. 2022;28(17):3636-3638. Physica Medica 127S1 (2024) 104641 https://doi.org/10.1016/j.ejmp.2024.104641 Diagnostic and Interventional Radiology (RAD) P.2.1 COMPARATIVE PERFORMANCE EVALUATION OF DR AND CR ACQUISITIONS AT MOBILE CHEST IMAGING OF NEONATES IN INCUBATORS M. E. Zachou1, I. Antonakos1, A. Stefanoyiannis2, E. Efstathopoulos1 12nd Department of Radiology, National and Kapodistrian University of Athens, Athens, Greece, 22nd Department of Radiology, Nuclear Medicine Division, University General Hospital of Athens “Attikon”, Athens, Greece Background: This study aims to compare computed radiography (CR) and direct digital radiography (DDR) portable imaging systems used to acquire chest x-rays for neonates within incubators in terms of entrance surface dose (ESD), dose area product (DAP ) and image quality (IQ). Materials and Methods: To determine ESD, a digital dosimeter and polymethylmethacrylate (PMMA) plates were used. For the evaluation of IQ, the Leeds TOR 18FG was used, and ImageJ software to calculate the Contrast-to-noise ratio (CNR) and Signal-to-noise ratio (SNR). A figure of merit (FOM) was defined by dividing the CNR with the ESD for each image acquisition. Results: The images with the highest CNR were those acquired using DDR direct exposures and the images with the lowest CNR were those acquired using CR with the image receptor placed within the incubator tray. This is also supported by the FOM scores which demonstrated DDR directly produced the optimal combination concerning CNR and radiation dose. The CNR had a mean increase of 40.3% when comparing DDR direct with CR direct respectively. This was also evident when comparing DDR and CR for in-tray acquisitions, with CNR increasing by a mean of 43.5%. A mean increase of 20.4% was seen in CNR when comparing DDR tray exposures to CR direct. Conclusion: DDR directly produced images of the highest CNR, with the incubator tray reducing CNR for both CR and DDR. However, the DDR tray still had better image quality compared to CR direct. Where possible, DDR should be the imaging system of choice for portable examinations on neonates owing to its superior image quality at lower radiation doses. Physica Medica 127S1 (2024) 104642 https://doi.org/10.1016/j.ejmp.2024.104642 P.2.2 EXPLORING MULTI-SCALE DIAGNOSTICS IN MEDICAL OPHTHALMOLOGY BY ADVANCED PROPER ORTHOGONAL DECOMPOSITION OF OPTICAL COHERENCE TOMOGRAPHY (OCT) IMAGES I. Georgiou1,2 1National Technical University of Athens, Athens, Greece, 2Purdue University, West Lafayette, Indiana, United States Reported works in the literature of health sciences recognize the crucial importance of OCT images as highly reliable means for diagnostics in ophthalmic therapeutics. Due to the complicated interaction physics of the fast traveling light and soft microstructured matter the eye organ is formed it is expected that the typical OCR image is woven as a composition of characteristic patterns over slowly varying micro and fast varying nano scales. Extraction of these slow-fast patterns potentially forms a ground for