CT scans are request by doctors because they are looking for either:

* Broken bones
* Cancers
* Blood clots
* Signs of heart disease
* Internal bleeding

More sepcifically, doctors order chest CT scans because they are looking to:

* Show the size, shape, and position of your lungs and other structures in your chest.
* Follow up on abnormalities that are found on standard chest x rays.
* Find the cause of lung symptoms, such as shortness of breath or chest pain.
* See whether you have a lung problem, such as a tumor, excess fluid around the lungs, a pulmonary embolism, tuberculosis, emphysema, and pneumonia