S2247
Physics - Intra-fraction motion management and real-time adaptive radiotherapy
ESTRO 2026
Non-invasive mechanical ventilation (NIMV) has shown to minimize respiratory motion for radiotherapy without requiring active patient cooperation1,2. Conscious unmedicated subjects are trained to be ventilated through a facemask covering mouth and nose (Figure 1) at 60 breaths per minute (brpm) with 15cmH2O positive end expiratory pressure (PEEP). Previously, NIMV used 60% oxygen (60%O2)3. Here NIMV was tested with ambient air (21%O2) in case oxygen is unavailable, and to overcome any clinical issues with administering 60%O2. Material/Methods: Ten healthy volunteers underwent NIMV at 60brpm with both 21%O ₂ and 60%O ₂ . Volunteers were blinded to the oxygen concentration that they received in the two NIMV sessions each lasting 10 minutes. Vital signs oxygen saturation (SpO ₂ (%)), transcutaneous carbon dioxide (PtcCO ₂ (mmHg)), and heart rate (HR (bpm)) were monitored continuously to verify their values remained within predefined safety limits (i.e., SpO ₂ ≥ 94%; PtcCO ₂ ≥ 20 and ≤ 50 mmHg; HR ≥ 50 and ≤ 120 bpm). The Wilcoxon signed-rank test was used to test for statistically significant differences between 21%O ₂ and 60%O ₂ . Subjects’ comfort during NIMV was measured using a short questionnaire using a 5-point Likert scale (1, very uncomfortable; 5, very comfortable). Results:
Management for Radiotherapy. Intell. Oncol. 2025 Jul; 10.1016/j.intonc.2025.06.006[2] Zhang X et. al. Modeling of artificial intelligence-based respiratory motion prediction in MRI-guided radiotherapy: a review. Radiat. Oncol. 2024; 10.1186/s13014-024- 02532-4[3] Zakeri A et al. Comput Methods Programs Biomed. 2024 Jun; 10.1016/j.cmpb.2024.108158 [4] Woo S et. al. CBAM: Convolutional Block Attention Module arXiv:1807.06521 [cs.CV] 10.48550/arXiv.1807.06521[5] Zijp L et.al. 2004 Extraction of the respiratory signal from sequential thorax cone-beam X-ray images. In: International Conference on the Use of Computers in Radiation Therapy, pp 507-9 Keywords: motion prediction, kV planar, intrafraction Digital Poster Highlight 3149 Non-invasive mechanical ventilation with ambient air for respiratory-motion management in radiotherapy is feasible and comfortable. Irma W.E.M. van Dijk 1,2 , Myrthe Bosse 1,2 , Michael J. Parkes 1,2 , Markus F. Stevens 3 , Joost G. van den Aardweg 4 , Thomas Weststrate 1,2 , Tabitha F. Cox 5 , Nicholas S. West 5 , Brian V. Balgobind 1,2 , Arjan Bel 1,2 1 Department of Radiation Oncology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands. 2 -- , Cancer Center Amsterdam, Treatment and Quality of Life, Amsterdam, Netherlands. 3 Department of Anaesthesiology, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands. 4 Department of Respiratory Medicine, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands. 5 Northern Centre for Cancer Care, The Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, United Kingdom
Purpose/Objective:
During NIMV with 21%O ₂ and 60%O ₂ , vital signs remained within predefined safety limits (Figure 2). SpO ₂ was higher during ventilation with 60%O ₂ compared to ventilation with 21%O ₂ (median, 100% vs 99%; p<0.05). PtcCO ₂ and HR were not significantly different in 21%O ₂ vs 60%O ₂ (medians, 36 vs 37 mmHg; p>0.05, and 66 bpm vs 71 bpm; p>0.05). Subjects rated NIMV equally comfortable (scores 3.6 and 3.5) in 21%O ₂ and 60%O ₂ . Conclusion: NIMV at 60 brpm with added PEEP is as feasible with 21%O ₂ as 60%O ₂ . Therefore, 60%O ₂ may be omitted during NIMV at 60 brpm with PEEP. Using ambient air
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