The CT (Computed Tomography) scan or the CAT (Computer-Aided Tomography) scan is a diagnostic procedure that takes a detailed cross-sectional x-ray picture of a "slice" of the body.
To get a CT scan, the patient lies very still on a table, which is slowly moved horizontally while the x-ray machine rotates around the patient and takes pictures from many angles. A computer then combines the pictures into a very detailed cross-sectional image. The length of the procedure depends on the areas to be x-rayed. For the chest area, the procedure takes about 20 seconds.
CT scans can show the shape, size and the exact location of organs and tissues in any "slice" of the body more clearly than other diagnostic tools. This technique can help find enlarged lymph nodes, which might contain cancer that has spread from the lung. CT scans are more sensitive than routine chest x-rays in finding early lung cancers. CT scans are also used in detecting masses in the liver, adrenal glands, brain and other internal organs that may be affected by the spread of lung cancer.