S2375
Physics - Quality assurance and auditing
ESTRO 2026
Radiotherapy, Instituut Verbeeten, Tilburg, Netherlands. 5 Pediatric Oncology, Princess Máxima Center, Utrecht, Netherlands. 6 Department of Neurology & Neurosurgery, UMC Utrecht, Utrecht, Netherlands
Purpose/Objective: Hyperthermia, controlled elevation of tumor
temperature up to 43 °C, is clinically combined with radiation therapy to enhance therapeutic outcomes. In the Netherlands, re-irradiation with hyperthermia is one of the standard treatments for locoregional recurrent breast cancer, with harmonized re- irradiation and hyperthermia dose fractionation schedules applied at the Dutch hyperthermia centers [1] [2]. This study focused on delivering prospective calibration and quality assurance (QA) procedures for superficial hyperthermia across Dutch centers as part of the RT-HYPE project (NCT06452485), funded by the Dutch Cancer Society [3]. The goal was to establish standardized procedures to improve the reliability of temperature measurements in all hyperthermia centers in the Netherlands. Material/Methods: Three Dutch institutes providing clinical superficial hyperthermia—Amsterdam UMC, Erasmus MC, and Institute Verbeeten—participated. Their thermometry systems (multi-sensor thermocouples, fiber-optic probes, and single-sensor thermocouples, respectively) were prospectively assessed for accuracy, bias, precision, and stability over a 3-week period. Benchmarking was performed against a universal reference thermometer across all institutes, with measurements taken between 37°C and 43°C in 0.2°C increments. Temperature stability was evaluated weekly by maintaining 40°C for 2 hours assessing short-term (2 hours) and long-term (3 weeks) stability. One center implemented a new calibration procedure during the study to correct deviations found during preliminary testing. To assess (self-)heating behavior, thermometry probes were placed on a human tissue- equivalent phantom and were exposed to the electromagnetic field of a clinical superficial hyperthermia applicator. Probe orientation was varied relative to the main electric field component of the applicator to evaluate angular misalignment effects on temperature readings. Results: Accuracy, bias, precision, and stability results are summarized in Table 1. The updated calibration procedure (b) improved accuracy for one center compared to their original procedure (a). All centers met the existing QA guidelines, confirming compliance with clinical standards for superficial hyperthermia thermometry.
Thermocouples (Figure 1a,b,c) showed measurable self-heating artifacts when misaligned by more than 15° from perpendicular orientation to the main electric field component. As an example of the procedures, thermocouples (Figure 1d) positioned (nearly) perpendicular per clinical protocol, and fiber- optic probes both exhibited negligible artifacts under electromagnetic exposure.
Conclusion: This multi-center initiative demonstrates that the three Dutch centers implemented standardized prospective calibration and QA protocols, and thereby improved the accuracy, bias, precision and stability of temperature measurements in all Dutch superficial hyperthermia centers. The applied quality assurance procedures can prove helpful for newcomers to application of thermo-radiotherapy. References: [1] C. P. Tello Valverde et al., Int J Radiat Oncol Biol Phys, vol. 122, no. 5, pp. 1166-1174, Aug 1 2025.[2] A. Bakker et al., Radiother Oncol, vol. 167, pp. 149-157, Feb 2022.[3] H. J. G. D. van den Bongard, "RT-HYPE - BOOG Study Center," 2025. [Online]. Available: https://www.boogstudycenter.nl/studies/stu
Made with FlippingBook - Share PDF online