Estimation of the radiation dose from thoracic CT scans in a cystic fibrosis population.

OBJECTIVE

To determine the radiation exposure associated with CT scans in a population of patients with cystic fibrosis (CF).

METHODS

We reviewed the medical charts of patients with typical CF who received regular medical management in a reference center from birth to March 31, 2004.

RESULTS

Among 80 patients with a total follow-up time of 1,231 person-years, 79 patients received a total of 269 CT scans, including 249 thoracic CT scans. The full parameters of the examination were available for 185 thoracic CT scans, allowing the effective dose (ED) and organ doses to be calculated. The ED was determined by the number of slices and the type of CT scans. The ED per thoracic CT scan was asymmetrically distributed (mean ED, 6.5 mSv; range 1.5 to 29.3 mSv). The mean doses delivered to the four most strongly exposed organs (lungs, breasts, bone marrow, and thyroid gland) were 18.6, 16.9, 5.2, and 3.5 mGy, respectively. The mean lifetime number of CT scans per patient was 3.2 (range, 0 to 13 scans), and the average lifetime ED was 19.5 mSv per patient (range, 2.2 to 75.8 mSv). Age at the first CT scan fell over the years, from 20 years for patients born before 1980 to 1.9 years for patients born after 1997.

CONCLUSION

The mean ED per CT scan in CF patients is about 6.5 mSv. Age at the first CT scan is lower in the most recent generation of patients. The lifetime ED of radiation received by CF patients, especially in the most recent generation, warrants long-term follow-up.