Nowadays, screening basically requires CT examination, which is more detailed and clearer than X-ray examination, especially in the early stage when the grinding glass changes may not show up clearly or even not show up in the X-ray, but CT can see smaller pieces, multiple, or even lighter grinding glass shadows. In the later stages, especially when the patient is severely ill and cannot be easily moved, X-rays are sometimes done at the bedside to detect an increase or decrease in the exudate shadows in the lungs, as a temporary measure to evaluate the treatment or the evolution of the disease during the clinical course. However, as a diagnostic measure, CT is needed because it can detect earlier lesions and give a chance to save the patient’s life in time. Source: Dr. Yurai