Inclusion Criteria:

- Must have been treated at University of Health Network with SBRT for an early-stage
NSCLC (T1N0M0; T2N0M0; or T3N0M0 chest wall primary tumours only).

- On follow-up thoracic CT scans, patients must have changes in the previously targeted
lung parenchyma that fit into one of the following three patterns: - Changes that
on CT and clinical grounds are felt to be related to fibrosis

- Changes that on CT and clinical grounds are suspicious for recurrence

- Equivocal changes (uncertain whether the changes represent fibrosis or recurrence)

- Must be greater than 18 years in age

- Must be able to attend regular follow-up including radiologic investigations and
clinical visits

- Written informed consent

Exclusion Criteria:

- Standard contraindications to MRI study (e.g. ferromagnetic prosthesis,
pacemaker/implanted defibrillator, metallic implant in eye, severe claustrophobia,
etc…)

- Contraindications to Gadolinium contrast-agent. May include a history of allergic
reaction to following previous administration of gadolinium or poor renal function
(calculated creatinine clearance < 30 mL/min).

- Patients with surgical resection of the treated portion of lung following their SBRT,
although surgical resection of other parts of the lung is allowed.