The first CT scanner that proved to be commercially viable was conceived and created by Sir Godfrey Hounsfield in UK using X-rays at the EMI Central Research Laboratory. It was introduced to the public in 1972 as an "EMI Scanner".

  

During a CT scan, an X-ray system produces the X-ray slices as it rotates around the object being scanned.  In this system,  the X-ray sensors are placed on the opposite side of the object across the X-ray source.  A large number of X-ray data scans are taken, which are then combined by the computer into the final CT scan image by a process known as tomographic reconstruction.

     

Old CT scanners produce simple 2-D cross-sectional images only, but thanks to faster computers and better software, modern CT scanners today can display even continuously changing high-resolution 3-D cross-sections that can be viewed from various perspectives in real time on monitors.

    

Figure 1.  A photo of a CT scanner (left) and a 3-D CT scan image (right).

     

CT scanning is primarily a medical diagnostic tool that can be used for 'visualizing' a variety of medical problems, some of which are shown in Table 1.

 

Table 1. Examples of Medical Problems that CT can 'Visualize'

Part of the Body	Medical Problem
Head	brain and skull injuries, ruptured aneurysm, brain bleeding/blood clots, stroke, brain tumors, skull malformations, inflammation of the paranasal sinuses, facial bone and tissue damage due to trauma, temporal bone diseases, brain cancer (for radiation therapy planning), etc.
Chest	changes in the lung parenchyma, pneumonia, emphysema, fibrosis, cancer, pulmonary embolism, etc.
Heart	coronary artery disease,
Abdomen / Pelvis	cancer, renal stones, appendicitis, pancreatitis, diverticulitis, abdominal aortic aneurysm, bowel obstructions, tumors, fractures, osteoporosis,
Extremities	bone fractures and dislocations, injuries to ligaments, etc.