Inclusion Criteria:

- Histological diagnosis of small cell or non-small cell lung cancer or metastatic
tumor to the lung being scheduled for localized radiation therapy (including
radiosurgery)

- No prior or future planned surgery for the treatment of the lung cancer.

- Age ≥ 18 years

- Karnofsky 60%

- Not pregnant.

- Ability to understand and the willingness to sign a written informed consent document

- Ability and willingness to participate in breathing training and compliance wiht
breathing apparatus so that radiation doses are optimally linked to 4D-CT images

- Ability to tolerate CT contrast

Exclusion Criteria:

- No prior thoracic radiotherapy will be permitted

- Uncontrolled intercurrent illness including, but not limited to, ongoing or active
infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
arrhythmia, or psychiatric illness/social situations that would limit compliance with
study requirements

- Pregnant women

- Severe COPD that requires chronic prednisone or multiple inhalers

- Underlying collagen vascular disease or intrinsic lung disease that could complicate
expected sequelae of radiation (idiopathic pulmonary fibrosis, Wegener's
granulomatosis)

- Oxygen dependence at baseline

- Recent lung surgery or abdominal surgery (within 3 weeks) that would compromise
respiratory pattern.