Royal Marsden NHS Foundation Trust 1 article published in JoVE Medicine Voluntary Breath-hold Technique for Reducing Heart Dose in Left Breast Radiotherapy Frederick R. Bartlett1, Ruth M. Colgan1, Ellen M. Donovan1, Karen Carr1, Steven Landeg1, Nicola Clements1, Helen A. McNair1, Imogen Locke1, Philip M. Evans2, Joanne S. Haviland3, John R. Yarnold4, Anna M. Kirby1 1Department of Radiotherapy, Royal Marsden NHS Foundation Trust, 2Centre for Vision, Speech and Signal Processing, Faculty of Engineering and Physical Sciences, University of Surrey, 3Clinical Trials and Statistics Unit (ICR-CTSU), Institute of Cancer Research, Sutton, UK, 4Division of Radiotherapy and Imaging, Institute of Cancer Research, Sutton, UK The current priority in breast cancer radiotherapy is to reduce cardiac doses without compromising target tissue coverage. The voluntary breath-hold technique described here is a simple, inexpensive solution to this problem and capable of being instituted widely without the need for specialized equipment.