Mitigating respiratory motion in radiotherapy: rapid, shallow, non-invasive mechanical ventilation for internal thoracic targets

Research output: Contribution to journalArticlepeer-review

Authors

  • Nicholas S. West
  • Christopher Snowden
  • James Prentis
  • Jill Mckenna
  • Muhammad Shahid Iqbal
  • Christopher Walker

Colleges, School and Institutes

Abstract

Purpose Reducing respiratory motion during the delivery of radiotherapy reduces the volume of healthy tissues irradiated and may decrease radiation induced toxicity. The purpose of this study was to assess the potential for rapid shallow non-invasive mechanical ventilation to reduce internal anatomy motion for radiotherapy purposes. Material and methods Ten healthy volunteers (age 22-54years; mean 38years; 6 female and 4 male) were scanned on an MR scanner during normal breathing and at 2 ventilator induced frequencies; 20 and 25 breaths per minute for 3 minutes. Sagittal and coronal cinematic datasets, centred over the right diaphragm were used to measure internal motions across the lung–diaphragm interface; repeat scans assessed reproducibility. Physiological parameters and participant experiences were recorded to quantify tolerability and comfort. Results Physiological observations and experience questionnaires demonstrated rapid shallow non-invasive ventilation technique was tolerable and comfortable. Motion analysis of the lung-diaphragm interface demonstrated respiratory amplitudes and variations reduced in all subjects using rapid shallow non-invasive ventilation compared to spontaneous breathing; mean amplitude reductions of 56% and 62%, for 20 and 25 breaths per minute respectively. The largest mean amplitude reductions were found in the posterior of the right lung; 40.0mm during normal breathing to 15.5mm (p<0.005) and 15.2mm (p<0.005) when ventilated with 20 and 25 breaths per minute respectively. Motion variations also reduced with ventilation; standard deviations in the posterior lung reduced from 14.8mm during normal respiration to 4.6mm and 3.5mm at 20 and 25 breaths per minute respectively. Conclusion To our knowledge, this is the first study to measure internal anatomical motion using rapid shallow mechanical ventilation to regularise and minimise respiratory motion, over a period long enough to image and deliver radiotherapy. Rapid frequency, shallow, non-invasive ventilation generates large reductions in internal thoracic and abdominal motions, the clinical application of which could be profound; enabling dose escalation (increasing treatment efficacy) or high dose ablative radiotherapy.

Details

Original languageEnglish
JournalInternational Journal of Radiation: Oncology - Biology - Physics
Early online date26 Nov 2018
Publication statusE-pub ahead of print - 26 Nov 2018