S2015
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
temperature-dependent parameters α (T) and β (T) [4]. To simulate potential MR thermometry artefacts, systematic and random temperature errors were introduced using Gaussian distributions. The impact of these uncertainties was evaluated through standard deviations and dose–volume histograms (DVHs) of temperature and EQD2. Results: Mean temperatures and changes in EQD2 and TCP derived from vaginal probe and MR thermometry, are summarised in Table 1. Vaginal probe temperatures ranged from 39.1–39.7 °C, resulting in EQD2 and TCP increases of 2.4–4.3 Gy and 9–59 %, respectively. MR- based temperatures within the CTV (39.4–40.3 °C) yielded higher EQD2 (3.4–7.1 Gy) and TCP (10–75 %) values. The corresponding DVHs for temperature and EQD2 are shown in Figure 1. Systematic errors produced changes of up to 2 Gy in EQD2 and 10 % in TCP. However, since MR thermometry artefacts generally occur randomly rather than systematically, random errors led to only small deviations (0.2 Gy in EQD2). Clinically, within the therapeutic range (39- 44ºC), EQD2 and TCP errors remained within 0.7 Gy and 1.1 %, respectively.
Garrè ML, Garibotto F, Milanaccio C, Piccolo G, Crocco M, Ramaglia A, Di Profio S, Barra S, Belgioia L. High dose craniospinal irradiation as independent risk factor of permanent alopecia in childhood medulloblastoma survivors: cohort study and literature review. J Neurooncol. 2022 Dec;160(3):659- 668. doi: 10.1007/s11060-022-04186-2. Epub 2022 Nov
12. PMID: 36369416; PMCID: PMC9758075. Keywords: paediatric radiotherapy, alopecia, optimization
Mini-Oral 4854
Magnetic resonance thermometry-based estimation of equivalent radiation dose and tumour control probability in combined radiotherapy and hyperthermia Carolina Carrapiço-Seabra 1 , Sergio Mingo Barba 2 , Jeremy Godart 1 , Patrick V Granton 1 , Henrike Westerveld 1 , Martine Franckena 1 , Gerard C van Rhoon 1 , Sergio Curto 1 1 Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, Netherlands. 2 School of Engineering, Zürich University of Applied Sciences (ZHaW), Winterthur, Switzerland Purpose/Objective: Hyperthermia, the elevation of target temperature up to 44 ºC, is clinically applied as concomitant cancer treatment to enhance radiotherapy effectiveness. In locally advanced cervical cancer (LACC), multiple studies have shown that combining deep hyperthermia with radiotherapy significantly improves treatment outcomes compared to radiotherapy alone [1-3]. This study aimed to (i) quantify the additional biologic effect given by hyperthermia in terms of equivalent radiation dose in 2 Gy fractions (EQD2) and tumour control probability (TCP) using probe-based and magnetic resonance (MR)-based temperature measurements, and (ii) assess the impact of MR thermometry uncertainties on these metrics in combined radiotherapy and hyperthermia. Material/Methods: Three patients with LACC were included. Patients were treated with external beam radiotherapy (EBRT) delivered in 23 daily fractions of 2.0 Gy, combined with at least four weekly MR-guided hyperthermia (MRgHT) sessions. Following EBRT and MRgHT, patients received a brachytherapy boost. Temperature data acquired during MRgHT – intraluminal thermometry probes at surrogate locations and MR thermometry - were integrated with radiotherapy dose distributions to quantify the radiosensitising effect of hyperthermia within the clinical target volume (CTV), in terms of EQD2 and TCP. Calculations were based on an extended linear–quadratic model incorporating
Conclusion: Compared with probe-based temperatures, MR-based temperatures provided higher EQD2 and TCP
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