An informational handout regarding CT-related radiation dose and risk was prepared for parents and guardians of pediatric outpatients (18 years old and younger) referred to the imaging department of a tertiary-care children's hospital for nonemergent CT. Over a 2-month period, parents were asked if they would be willing to fill out a survey while waiting in the reception area for the child's CT scan. An initial survey was completed by each participant before reading the handout, and a final survey was completed after reading the handout. The handout and final survey were not given to the parent until the initial survey was submitted.

Parents of children undergoing major trauma, children with emergent conditions requiring immediate care, and suspected victims of nonaccidental trauma were excluded from the study. To minimize attention bias, referring clinicians were not alerted to the existence of the study. Before the initiation of the study, the institutional review board (IRB) reviewed the study protocol, including the handout and surveys, and granted the study exempt status from further direct IRB supervision. The study met the guidelines established by the Health Insurance Portability and Accountability Act.

The English-language informational handout was titled “Radiation exposure from CT: A guide for parents” (Fig. 1). After the handout briefly described CT and its associated radiation, it provided a table comparing radiation exposure from several activities with that of background radiation, based on effective whole-body dose. The comparison table included the following sources of radiation and was based on the following dose estimations: daily background radiation with dose estimated at 0.01 mSv [23]; a 3-hour airline flight, at 0.015 mSv [24]; a chest radiograph, at 0.02 mSv [25]; head CT, at 1.11 mSv; and abdominopelvic CT, at 5.57 mSv. The effective doses for head and abdominal CT were calculated from the dose-length product data obtained from the most common scanning protocols at our institution and converted to a whole-body effective dose using body region-specific normalized effective dose conversion factors (0.0021 for head CT and 0.014 for abdominal CT) [26].

The handout emphasized that although the longterm effects of CT are controversial and incompletely understood, the low levels of radiation exposure from CT are assumed to slightly increase the risk of cancer [2, 6, 9]. We estimated the lifetime risk of fatal cancer attributable to radiation from a single abdominal CT examination in infancy to be about one in 3,000 (0.03%). Brenner et al. [2] estimated the attributable risk to be approximately 0.23%, using unadjusted adult settings. Our estimation reflected an adjustment based on the typical 50 mAs used at our institution, versus the 404 mAs used by Brenner et al., and assuming a linear correlation between mAs and fatal cancer risk. The concept of risk was further illustrated in the handout by showing that the lifetime risk of fatal cancer for a North American child younger than 15 years would increase from a baseline of approximately 700 in 3,000 (23%) [2] to about 701 in 3,000 after undergoing an abdominal CT examination as an infant.

Alternatives to CT were listed in the handout, including observation in some circumstances. Specific alternatives were not offered to parents on an individual basis. Parents were advised that if they had any questions or concerns regarding the information in the handout, a staff radiologist would be available for discussion before their child underwent CT.

The handout was 757 words long and scored at an eighth-grade readability level according to the Flesch-Kincaid method, using Microsoft Word word-processing software. Assuming an average eighth-grade reading speed of 150 words per minute [27], most parents would be able to read the handout in fewer than 5 minutes.

Initial and final surveys were provided to each study participant to be completed before and after reading the informational handout, respectively (Appendix 1). The first four questions of the initial survey were identical to the first four questions of the final survey. These questions assessed parental knowledge regarding the use of radiation and the increased risk of cancer, their willingness to have their child undergo CT recommended by the child's doctor, and their willingness to have their child undergo CT in a hypothetic scenario in which their child's doctor thought that observation would be just as valuable. Parents were also asked the age of their child in the initial survey and their perceived change in level of concern and understanding after reading the handout in the final survey.

Surveys and handouts were administered by the secretarial staff during business hours. Physicians were involved only in that a radiologist needed to be available to answer questions that parents might have. Both surveys were completed before the child underwent CT. Only one parent or guardian was asked to complete the initial and final survey for each child undergoing CT.

Responses to questions of whether radiation uses cancer and increases the risk of radiation (before and after reading the handout) were paired and tested for statistical significance using the two-sided McNemar chi-square test. Ordered categoric responses to questions assessing willingness to allow the child to undergo CT were also paired and tested for statistical significance using the Stuart-Maxwell test, which tests marginal homogeneity for all categories simultaneously. If one of these questions was not answered, the pair was excluded from the calculation of statistical significance. No significance test was performed on responses to questions included only in the final survey. All calculations were performed using Excel 2002 (Microsoft). A change was considered to be statistically significant at p < 0.01.

Sample size was determined with special attention given to the proportion of parents who might become unwilling to allow the child to undergo CT after reading the handout. With a sample size of 100 parents, if no parents refused the study, the test had 80% power to exclude a proportion of less than 1.6%. After the study was completed, a 95% exact binomial confidence interval was applied to the observed proportion.

One hundred two parents were surveyed. Two parents did not return the final surveys so the initial surveys were also discarded. A total of 100 initial and 100 final surveys were included in the results. Two respondents left one question unanswered; thus, the number of responses does not total 100 for every question. The average patient age was 7.4 years old (SD, 5.3 years), ranging from less than 1 year to 17 years.

Before reading the handout, 66 (66%) of 100 parents believed CT uses radiation, versus 99 (99%) of 100 after reading it (p < 0.01). Before reading the handout, 13 (13%) of 98 believed CT increases the lifetime risk of cancer, versus 86 (86%) of 100 after reading it (p < 0.01). Although only yes or no responses were elicited for this question, 10 participants answered yes to the question but then also indicated in the margin their understanding that the increase in cancer risk was slight. Parents indicated their perceived change in understanding of risks as listed in Table 1. Fifty-nine percent of the respondents reported that this information either was new to them or clarified their understanding. Of note, of the 41 parents who claimed they already knew the information, or that their doctor had explained all of it to them, 71% answered that CT does not cause an increased risk of cancer on the initial survey.

When asked both before and after reading the handout how willing they were to have their child undergo CT recommended by their doctor, parents responded as listed in Table 2. Willingness to have their child undergo CT did not change after reading the handout in 80 (81%) of 99 respondents. The level of concern increased for 14 (14%) of 99 and decreased for five (5%) of 99 respondents. This change was not statistically significant (p = 0.10). No parent reported unwillingness to do the study. One parent asked to speak to a radiologist for further clarification, but no parent (95% CI = 0-3.6%) refused or requested to defer the child's CT after reading the handout.

When asked how their concern about the risks associated with CT changed after reviewing the handout, parents responded as listed in Table 3. The reported change in level of concern was similar to the change in willingness to have the child undergo CT as described in the preceding paragraph, with most parents reporting no change in level of concern.

When asked how willing they would be to have their child undergo CT if their doctor thought that observation would be just as valuable as CT, parents responded as listed in Table 4. Willingness to have their child undergo CT in this situation did not change after reading the handout in 73 (74%) of 99 respondents. The preference changed toward more willing to observe in 23 (23%) of 99 and toward more willing to use CT in three (3%) of 99 respondents. Overall, the average change toward more willing to observe was statistically significant (p < 0.01).