Computed tomography (CT) is a medical diagnostic tool that allows the visualization of internal structures within the human body. This aids physicians in diagnosing disease, viewing internal abnormalities and assessing the extent of trauma damage.

During a typical CT procedure, the patient lies on a table. The tabletop then moves the patient through a gantry which houses an x-ray tube and detector array. The x-ray tube rotates around the patient and x-rays pass through the patient to the detector array and thousands of x-ray measurements are acquired. The computer then processes this information and displays the corresponding images on a computer screen. This imaging technique avoids any superimposition of organs or tissues upon one another that might occur during other types of x-ray tomographic studies.

The CT exam creates images analogous to a single slice of bread from a whole loaf. (See figure 1) Hence, the world "slice" is often used to describe a view of patient anatomy.

The quality of an image depends on the nature of the x-ray source and detectors, the number and speed of the measurements made, the details of the reconstruction technique (algorithm), the machine characteristics and the methods of data display and interpretation. The computer allows healthcare professionals to shade, rotate, correlate and measure anatomy in the image. These data can be manipulated to derive even more precise clinical information. While conventional x-ray can discern tissue density difference of 5%, CT scan distinguish density difference of 1% or less.