Interstitial lung disease classically produces "lines and/or dots" instead of the patchy "cloud-like" opacities seen with alveolar-filling disease.

Linear Interstitial disease (LIFElines) may be:
L - lymphangitic metastases
I - inflammation including infection
F - fibrosis
E - edema

In the DDX of CHF (congestive heart failure) look for clinical signs outside the chest:
Elevated JVP (jugular venous pulse)
Peripheral Edema
and, inside the chest:
Pulmonary Edema (perihilar patchy alveolar filling)