In this observational study, the investigators evaluate the sensitivity of T1-MRI to identify lung perfusion changes in pediatric patients with CF (age = 6-11) before and after initiating FDA-approved Trikafta therapy. The investigators compare these Lung T1 MRI assessments (% Normal lung perfusion) to currently best-available assessments of lung function in CF patients (i.e., MBW (LCI( and Spirometry (FEV1 % Predicted).

This is a prospective study with 3 study visits to evaluate the utility of Magnetic Resonance Imaging (MRI) and clinical lung function assessments to detect changes in Cystic Fibrosis (CF) patients before and after administration of the FDA-approved Trikafta therapy. The 3 study visits include:

Visit 1: Before starting Trikafta Visit 2: 3 months from start of Trikafta Visit 3: 6 months from start of Trikafta

Along with the clinical assessments (MBW and Spirometry), all participants will undergo an MRI scan of the lungs to generate quantitative lung T1 maps. The investigators will compare the lung T1 MRI (% Normal Lung Perfusion) to Multiple Breath Washout (LCI) and spirometry (FEV1 % Predicted) as methods to assess lung changes with administration of Trikafta. The investigators will obtain additional clinical assessments from participant's medical records.

This is a multi-site study involving 3 sites.

Inclusion Criteria:

• Male or female individuals with a diagnosis of cystic fibrosis and have at least one copy of the F508del mutation.

Exclusion Criteria:

• Subject who cannot hold their breath for up to 15 seconds.
• Subjects who are pregnant.
• Subjects with MRI contraindication (e.g., heart pacemaker, heart defibrillator, metal in within the body.

Patients with cystic fibrosis (CF) who are planning to start Trikafta therapy once approved

Unsure if individual data will need to be presented.