All Cohorts  Inclusion Criteria:  Male or female Any age NICU inpatient who is clinically stable and with adequate temperature control to tolerate MRI as determined by the primary clinical team  Cohort 1  Age 0 - 6 months NICU patient on oxygen with a nasal cannula (≤ 2L per minute) (unchanged - supplemental O2 for minimum 24 hours) Maintaining SpO2 > 88% on nasal O2  Cohort 2  Age 0 - 6 months NICU patient who requires a slightly higher level of respiratory support (with High Flow Nasal Cannula > 2L per minute, CPAP, or RAM cannula and O2 unchanged for minimum 24 hours), with FiO2 < 50%. Maintaining SpO2 > 88% on nasal O2  Exclusion Criteria:  General anesthesia within 24 hours prior to MRI or other sedation (e.g. morphine, Versed, fentanyl) within the last 4 hours. Extracorporeal membrane oxygenation (ECMO) support Evidence of any respiratory infection within 1 week of testing (imaging may be rescheduled for a common viral infection such as a cold). Suspected muscular dystrophy or neurologic disorder that may affect lung development. Significant genetic or chromosomal abnormalities that may affect lung development Congenital heart disease Uncontrolled atrial or ventricular arrhythmia Open surgical wounds Need for inotropic support Need for vasodilator agents Need for high level of respiratory support (i.e. FiO2 >50%, and/or higher respiratory support than listed in Cohort 2 Inclusion Criteria, such as invasive ventilation). Standard MRI exclusion criteria as set forth by the CCHMC Department of Radiology (e.g., contraindicated support/implant equipment that is not MR compatible). Infant size not compatible with NICU MRI scanner (~>4.5kg).