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CT scans – more harm than good?

September 16, 2015

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This blog post was written for Zesty by Sarrina Tursunova, a University Student at The Imperial College School of Medicine currently studying Biomedical Sciences.

Computed Tomography (CT) scans have become a routine procedure in medicine. They function by processing images taken from various angles by X-rays and combining them into 3D cross-sectional images of the body. X-rays are a type of ionizing radiation with multiple medical applications. Although they allow quick and easy visualization of complex body structures, they are classified carcinogens – substances that have been linked to causing cancer by damaging the cell’s DNA.

A new study published online (22 July 2015) in the Journal of the American College of Cardiology by the Stanford University School of Medicine has revealed that even the lowest doses of radiation are sufficient in causing DNA damage.

The amount of radiation a person is exposed to during a CT scan is comparable to the total amount of background radiation a person is subject to within a whole year. Nevertheless, the amount of radiation exposure differs depending on the type of scan performed, the duration of the procedure and the number of scans required.

In the study, the Stanford research team evaluated blood samples from 67 patients that required CT angiograms by labeling their blood with biomarkers than can detect DNA damage before and after a CT scan. Even after a single scan some damage was visible. Although most of the cells repaired themselves, a small proportion of the cells died. A potential problem can arise when the exposed cells are incapable of repairing the DNA damage, which may cause the cells to become cancerous.

These findings raise the possibility that radiation exposure from cardiac CT angiography may cause DNA damage that can lead to mutations if damaged cells are not repaired or eliminated properly.

Patricia Nguyen, MD (Stanford Medicine)

So, do the risks of CT scanning outweigh the benefits and should you be refusing the procedure?

CT scans are an incredibly useful tool and the study does not advocate patients to decline having a scan done. Although more research is required to determine whether the damage caused by a single scan is a causal factor for cancer development that has long-term negative consequences, it is advised that doctors always use the lowest doses of radiation possible, even if that means not using the highest quality CT scans.

It is important to note that we did not detect any DNA damage in patients receiving the lowest doses of radiation and who were of average weight and had regular heart rates.

Patricia Nguyen, MD (Stanford Medicine)

As a patient, always ask your doctor what dose of radiation is being used, so they know that you are well informed and wish to be included in the decisions of your medical treatment.

 

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