It is estimated that more than 62 million CT scans per year are currently given in the United States, compared to three million 1980. Because CT scans result in a far larger radiation exposure compared with conventional plain-film X-ray, this has resulted in a marked increase in the average personal radiation exposure in the United States, which has about doubled since 1980, largely because of the increased CT usage.

It used to be widely believed that all radiological examinations were essentially harmless, because of the small amounts of radiation involved, but David J. Brenner, Ph.D., and Eric J. Hall, Ph.D., from the Center for Radiological Research at Columbia University show that this is unlikely to be true for CT scans. In particular, Japanese atomic bomb survivors who were about two miles away from the explosions, actually received radiation doses quite similar to those from a CT scan. Sixty years of study of these survivors have provided direct evidence that there will be an increased individual cancer risk, though small, for those who have this same dose of radiation from CT scans. Although the individual risk is small, the large number of CT scans currently being given may result in a future public health problem. In particular, Brenner and Hall suggest that, in a few decades, about two percent of all cancers in the United States may be due to the radiation from CT scans being done now.

The scientists propose to replace CT use, when appropriate, with other options that have no radiation risk, such as ultrasound or magnetic resonance imaging (MRI) and to decrease the total number of CT scans prescribed. Ultimately, the health care system, the doctor, and the patient (who can perhaps best track of the number of CT scans) may have to share the burden of monitoring the appropriate dosage and number of scans.; Source: Columbia University