Common causes of constrictive pericarditis include injury, infection, and radiotherapy. Radiotherapy is most likely cause in this patient given her history of left-sided breast cancer that was treated with radiotherapy.
CT and MRI can aid in the diagnosis of constrictive pericarditis, as clinically constrictive pericarditis and restrictive cardiomyopathy are similar and may be indistinguishable. In constrictive pericarditis, CT classically shows thickening (>4 mm) of the pericardium, most commonly anteriorly, and pericardial calcifications.
However, radiographical evidence of constrictive pericarditis should also be accompanied by evidence of heart failure. Imaging signs that suggest heart failure (especially right-sided dysfunction) include: a dilated right atrium, dilated hepatic veins, dilated inferior vena cava to more than twice aortic diameter, periportal edema, enlarged superior vena cava to more than the adjacent aorta, reflux of contrast into the inferior vena cava and distal hepatic veins (proximal reflux can be seen with high flow rates).