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The Magic of CT Scans

April 15, 2011

The Magic of CT Scans

David Douglas, Lead Technician for Special Procedures (from left); Imelda Torres, R.N., Cardiac Care Unit; Arleen Ramirez, N.A., Cardiac Care Unit; and Kurur Babu, Diagnostic Radiologist ready a patient for a CT scan. Computed Tomography is a medical imaging method employing X-rays and a high speed computer to process available data and generate images of the organs within the human body

HOUSTON - The invention of Computed Tomography has undoubtedly been one of the greatest advances for the diagnosis and treatment of disease ranging from strokes to cancers.

Computed Tomography, or more commonly known as “CT,” is a medical imaging method employing special X-ray equipment and sophisticated computers to generate images or pictures of the organs within the human body.

CT produces images of various body structures based on their ability to block the X-ray beam. These images can then be viewed on a computer monitor, printed on film, or transferred to a CD.

Bone is very dense and tends to block almost all X-rays. Structures such as the liver only block some of the X-rays hitting it. Therefore, you can generate a picture of the body based on differences of the density of the organs visualized. CT scans of internal organs, bones, soft tissue, and blood vessels provide greater clarity and reveal more detail than regular X-ray exams.

CT scans are invaluable for the diagnosis and treatment of disease in our current age. However, like most tests they are not perfect.

Usage of CT has increased dramatically over the last two decades. An estimated 72 million scans were performed in the United States in 2007. Because CT uses ionizing radiation, it is estimated that approximately 0.4 percent of current cancers in the United States may be a result of CTs.

While this percentage is low, it is important to keep this in mind when undergoing a CT scan. It is important to weigh the value of the diagnostic information provided by the CT against the very small, but real risks of the radiation exposure. Putting this into perspective, a routine CT scan of the chest carries 53 times more radiation exposure than a routine chest X-ray.

While this is a definite increase in radiation, a chest CT can find serious and potentially life-threatening disease processes such as blood clots in the lungs, and ruptures or dissections of the blood vessel connected to the heart which cannot be seen by a routine chest X-ray.

Life itself is not without risk. Annually, a person is exposed to the equivalent of half a chest CT from background radiation originating from space. You are irradiated from your environment, even while walking in the park. This dose depends very much on where you live. In some areas, even the rocks (particularly granite) can increase your yearly exposure to four times the dose you would receive from just one chest CT.

For every positive, there is a negative. In the end, insightful and educated choices help us achieve a good balance between risk and benefit.

By William M. Gregory, M.D.

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Awarded re-designation for Magnet Recognition for Excellence in Nursing Services in 2008, the Michael E. DeBakey VA Medical Center serves as the primary health care provider for more than 120,000 veterans in southeast Texas. Veterans from around the country are referred to the MEDVAMC for specialized diagnostic care, radiation therapy, surgery, and medical treatment including cardiovascular surgery, gastrointestinal endoscopy, nuclear medicine, ophthalmology, and treatment of spinal cord injury and diseases. The MEDVAMC is home to a Post Traumatic Stress Disorder Clinic; Network Polytrauma Center; an award-winning Cardiac and General Surgery Program; Liver Transplant Center; VA Epilepsy and Cancer Centers of Excellence; VA Substance Abuse Disorder Quality Enhancement Research Initiative; Health Services Research & Development Center of Excellence; VA Rehabilitation Research of Excellence focusing on mild to moderate traumatic brain injury; Mental Illness Research, Education and Clinical Center; and one of the VA’s six Parkinson’s Disease Research, Education, and Clinical Centers. Including the outpatient clinics in Beaumont, Conroe, Galveston, Houston, Lufkin, and Richmond, MEDVAMC outpatient clinics logged more than one million outpatient visits in fiscal year 2010. For the latest news releases and information about the MEDVAMC, visit