My Father-in-law Has Colorectal Cancer That Has Metastasized To The

My father-in-law has colorectal cancer that has metastasized to the lung. He is being treated and was told that the mass was diminishing in size. Recently, he developed a bad cough. He was placed on antibiotics. The chest xray shows an area that looks like ice crystals. The doctor says this is inconclusive. It is unknown if he has an infection in the lung. The antibiotic has improved the cough. But what do these crystals mean?