Many unaware of radiation risk from CT scans reports new study

Robin Wulffson MD's picture
CT scan, SPECT scan, radiation, cancer risk, medical necessity

A computerized tomography (CT) scan is a common medical procedure useful for the diagnosis of a multitude of medical disorder. Although most individuals are aware that the procedure involves exposure to ionizing radiation, most are unaware of the degree of health risk the procedure involves. Researchers from the University of Washington (Seattle, Washington) conducted a study to quantify that risk as well as determine the average patient’s understanding of the procedure and its medical necessity. They published their findings online on December 31, 2012 in the journal JAMA Internal Medicine.

CT scans are high-powered X-rays that provide clearer images; however, they expose patients to between ten and 100 times more radiation than a normal head or chest X-ray. The researchers noted that medical radiation exposure is a controversial topic among both the lay public and medical professionals. They explained that data regarding what patients know about radiation from commonly performed imaging studies such as CT scans and single photon emission computed tomography (SPECT) scans are limited. Therefore, they conducted a survey addressing patient knowledge and understanding of radiation from CT and SPECT scans.

From February through December 2011, the investigators randomly surveyed patients who underwent a CT or SPECT scan at their medical center. The 16-question survey comprised two sections. Section 1 measured knowledge and perception regarding the health risk and benefits of the procedures. The last question of this section asked the patients if the scan that they were about to undergo exposed them to radiation. Only patients who answered in the affirmative were instructed to continue to section 2. Section 2 contained five additional questions that assessed knowledge and perception of radiation. The researchers then reviewed the medical records of the respondents. They then estimated each patient’s radiation exposure.

During the study period, 324 patients were asked to complete the survey; of those, 78 either declined or were ineligible. Furthermore, 11 surveys were incomplete; thus, ineligible for inclusion. The data was derived from the remaining 235 patients (72%). Among those patients, 50 underwent a cardiac (heart) SPECT and 185 underwent a CT scan. The majority of the patients (63%) were men, with an average age of 55 years (range: 18-89 years). More than half the patients (58%) had at least a college education and 17% reported current or past healthcare field employment. The estimated patient radiation dose was 12.7 ± 4.6 mSv for CT and 14.6 ± 9.4 mSv for cardiac SPECT.


For survey section 1, 69% reported that their healthcare provider was the primary source of health information. About half (51%) believed that the procedure was definitely necessary and that the results would make them feel better (51%) or live longer (45%). Only 3% responded that they thought about radiation exposure before undergoing the scan. Almost all (90%) responded that it was important to be informed of imaging risks, 84% reported that the ordering healthcare provider explained the indications (reasons) for the scan; however, 81 (34%) of the patients were unaware that the procedure exposed them to radiation.

A total of 154 patients responded that they were aware that the scan exposed them to radiation and completed survey section 2. Among those, 45% reported that the ordering healthcare provider informed them of the radiation. The survey 2 patients were asked to compare their scan with one year of background radiation (the amount of radiation present in the environment). Most (85%) underestimated the amount of radiation and 88% reported that they were not worried about the radiation exposure from the scan. Only 5% of the respondents believed that scan radiation would increase their lifetime risk of cancer. Almost all (95%) of the patients reported that it was more important to determine their medical problem than to worry about radiation exposure.

The researchers noted that a well-informed patient has an understanding of radiation dose and potential health risks of radiation prior to undergoing a radiology procedure. They stressed that it was important for patients to be made aware of the benefits and risks of the procedure so that they could share in the decision-making process regarding whether it should be done.

Take home message:
This study underscores the need for healthcare professionals to explain the benefits and risks of a procedure before a patient submits to it. Unfortunately, due to time constraints, or other factors, this is often not done. With the population increase and increased patient enrollment due to the Affordable Care Act, coupled with the projected increase in physician shortage, this problem is likely to worsen. Thus, a patient needs to serve as his or own advocate, if possible, and ask the healthcare provider about risks vs. benefits. Often, a friend, relative, or caregiver can perform this role if the patient is unable to perform this role.

A single CT or SPECT scan does not entail a significant risk increase for cancer; however, some patients undergo a number of repeat procedures for a chronic condition. Often, the number of CT or SPECT procedures can be reduced by performing some of the follow-up with procedures involving less or no radiation. For example, patients who suffer from recurrent kidney stones may be able to skip a scan altogether, undergo a standard X-ray, or have an ultrasound exam, which has no radiation exposure.

Reference: JAMA Internal Medicine