By Lori Kiefert
Radiologic Technologist

Computed tomography, more commonly known as a CAT scan, is a non-invasive, medical imaging method typically used for diagnostic and treatment procedures. Acquiring detailed graphical images of the internal organs and parts of the body, computed tomography is so detailed that it can show, and distinguish between, bone, soft tissue, internal organs, muscles and tumors, empowering physicians with a unique tool to diagnose medical conditions and aid their treatment.  
The speed of CT scanning has made it a valuable tool of emergency medicine; “Pan-scans” of the head, neck, chest, abdomen, and pelvis have replaced multiple x-rays for trauma victims, helping to assess areas of trauma and identify any structural damage. A CT scan can quickly reveal whether a stroke patient has bleeding in the brain. With intravenous contrast agents, CT scans can detect pulmonary embolisms, potentially fatal blood clots that lodge in the arteries in the lungs.
Computed tomography has a wide range of uses in medicine.  It can show cancers in different parts of the body, helping a doctor measure its spread and apply targeted treatments.  Using a computer and a rotating x-ray device, two- or three-dimensional pictures are created of the area being scanned. As the beam passes through the body, different tissues absorb different amounts of radiation.  
Each x-ray leaves the patients’ body as an x-ray “snapshot,” showing one position (angle).  Up to 1,000 different “snapshots” are collected during one complete rotation. The data is then sent to a special computer, which uses the “snapshots” to form three-dimensional cross-sectional images of the scanned areas. These cross-sections are called tomograms, hence the term “Computed Tomography”.  
The image depends on the body structure’s absorption of the x-rays; bone turns up white, air turns up black, and tissues and mucus turn up in shades of gray. Radiologists, physicians who are trained to “read” x-rays, use what is called HU or Hounsfield Units to determine the density or structure of material within the body.
There are pros and cons to using computed tomography in medical procedures. CT requires more radiation than traditional x-rays, and the more detailed and complex the CT scan is, the more radiation exposure there is to the patient.  However, for most patients, the risk of allowing a problem like cancer to continue unchecked is worse that the risk from radiation exposure.  Also, the quality of computed tomography is much higher than a traditional x-ray.  Fast identification of things like internal bleeding, which a traditional x-ray would not be able to detect, is another reason why a physician may order at CT scan over a conventional x-ray exam.  
Your Health is coordinated by Mercy Hospital.