Since 1996 proton therapy has been applied very successfully at the Paul Scherrer Institute in Switzerland to irradiate deep-seated, stationary tumors. In order to treat tumors within an organ which moves due to breathing (e.g. lung) motion mitigation strategies need to be implemented to ensure the precise irradiation of the moving target. The aim of this study is to assess the feasibility and compare (via MRI imaging) 2 techniques which "freeze" the movement of the lung by breath hold. One method is suppression of respiratory movement via high-frequency, mechanical ventilation by means of a Jet Ventilator (HFPV). The other technique is deep Inspiration breath-hold (DIBH) with Hyperventilation and simultaneous Inspiration of 100% O2 including daily breath-hold exercise.

Inclusion Criteria:

• ability to give informed consent by signature
• healthy, i.e. normal physical and mental status

Exclusion Criteria:

• contraindications to MRI (non-MRI-suitable electronical & metal implants, claustrophobia)
• women who are pregnant or are breast feeding
• acute or chronic illness
• known or suspected non-compliance, drug or alcohol abuse
• inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant
• presence of any psychological or sociological condition potentially hampering compliance with the study protocol