Do you really need that CT Scan?

In the United States it is estimated that seventy-five million CT scans are performed each year. A CT scan is an excellent test to diagnose a multitude of diseases, both acute and chronic. There is no doubt that these scans save peoples lives everyday. For example, CT scan is the best test to diagnose acute cerebral hemorrhage, internal injuries related to trauma or hard to detect fractures. These are just a few examples of many of how CT has revolutionized medicine. The CT scan has save millions of people from morbidity associated with their individual diseases. But their diagnosis was not without a price. CT scan’s ionization radiation induces fatal cancers in a certain number of patients everyday.

CT scans utilize ionizing radiation or x-rays to create an image.  A CT scan works by exposing the patient to a radiation sources or x-ray source.  The patient is moved through the CT gantry as x-rays pass through their body and are captured in detectors.  There are many types of CT scanners but all work on this basic principle.  Each CT scan gives a patient an average radiation dose of about 10 mSi (mSi or millisivert is a unit used to measure radiation exposure).  This dose is equivalent to three times the background dose the average American receives each year.   

The amount of radiation may not be great but with each exposure your cancer rate increases.  It is estimated that one person, over the course of their lifetime, will develop a deadly cancer for every two thousand CT exams performed.   Seventy-five million CT scan performed each year will induce thirty-seven thousand fatal cancers.  The risk is multiplied for every scan you receive.  If you have ten CT scans then your lifetime risk is one in two hundred (1/2000 times 10) to develop a fatal cancer.      

The best way to prevent these cancers from occurring is to not perform the CT scans.  However, in many cases not having the CT scan would lead to dire consequence or even immediate death.  The condition which the CT scan will diagnose is more deadly than the small risk of inducing a cancer.  If it is decided by your doctor than a CT scan should be performed, the exam should be tailored to the patient and the body part being examined.   

The newest CT scanners deliver greater radiation doses than ever before.  However, the CT operator or CT technologist can tailor an exam in many ways to reduce your radiation exposure.  The thicker the slices (5 millimeter versus 2.5 millimeter) and the smaller the body part exposed decreases radiation exposure.  The technologist also can change the radiation dose or strength of the beam of the radiation delivered.   These dose-reduced images might not be as aesthetically pleasing to the reader but are diagnostic in almost every case.  In many cases, the dose can be reduced in half without much difficulty.   It is even more important in children to limit exposure for they receive greater doses than adult for the same exam partially due to their smaller size.

The purpose of this article is not to persuade a patient to not receive a necessary medical exam.  It is a reminder to patients and doctors alike that there are dangers associated with radiation exposure from CT exams.  The test needs to be used appropriately and should not be overused.  There is a tendency among doctor and lay people today to ‘just get a CT’.   Next time you here that phrase you should think, ‘Is it worth the risk?” The cancers that are induced today won’t manifest themselves until ten or twenty years in the future.   Educated consumers can protect themselves now. 


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