The primary objective of this study is to determine if quantitative Dynamic contrast-enhanced magnetic resonance (DCE MR) perfusion imaging accurately quantifies right and left pulmonary artery blood flow as compared with phase contrast flow velocity mapping (PC), the current gold standard of flow volume measurements.

Many conditions of the heart or the lungs lead to differences in how the blood is pumped to the lungs. Specifically, some areas of the lung may receive less blood supply than others. We would like to do a research study in children and adolescents who have a heart condition or a chronic or stable lung condition. We are doing this study to see if measuring the circulation of blood in the lungs in children is possible using magnetic resonance imaging (MRI) with a special dye (contrast medium) injection called Magnevist®.

Inclusion Criteria:

Cardiac Patients:

1. Patients > 6 years of age
2. Patients with suspected or confirmed congenital or acquired heart disease
3. Who undergo a clinically indicated MRI scan, including gadolinium (MRI contrast medium)
4. And receive gadolinium (= MRI contrast medium) as part of their clinical investigation

Pulmonary Patients:

1. Patients > 6 years of age
2. Patients with a chronic and stable lung condition, such as cystic fibrosis, severe asthma.

Exclusion Criteria:

1. Children under the age of 6 will be excluded as they are routinely scanned under general anesthesia
2. Patients in whom MRI is contraindicated (e.g. pacemaker, ocular metal, claustrophobia, tattoos)
3. Patients with a known allergy to gadolinium.
4. Patients with a history of allergic disposition or have anaphylactic reactions
5. Moderate-to-severe renal impairment (defined as having a GFR/ eGFR < 60 mL/min)
6. Have Sickle Cell anemia
7. Known pregnancy, or breast feeding
8. Patient is uncooperative during a MRI without sedation or anesthesia