In this video, Dr. P K Julka, Senior Director, Oncology Daycare Center, Lajpat Nagar, New Delhi, will discuss the role of PET CT in diagnosis. PET-CT plays an important role in the diagnosis because in most of the cancers, it is not known where the cancer has spread. Through PET scan, the area can be known and treated accordingly. PET scan cannot trace brain lesions so MRI of brain is necessary.