Pediatric 64-MDCT Coronary Angiography With ECG-Modulated Tube Current: Radiation Dose and Cancer Risk

OBJECTIVE. The purpose of our study was to measure the radiation dose from ECG-gated CT coronary angiography in children and to estimate the cancer risk associated with the radiation dose. MATERIALS AND METHODS. Organ doses were measured with a 5-year-old pediatric phantom and thermoluminescent dosimeters on a 64-MDCT scanner. Four retrospectively ECG-gated CT coronary angiography protocols with four simulated heart rates and the corresponding pitches were studied. The lifetime attributable risk of cancer incidence was estimated for children in the United States and Hong Kong according to the National Academies Biologic Effects of Ionizing Radiation VII report. RESULTS. The effective doses were 16.45, 12.17, 11.97, and 11.81 mSv for the four protocols, respectively. The corresponding lifetime attributable risks estimated for 5-year-old U. S. boys and girls were 0.14%similar to 0.20% and 0.43%similar to 0.60%, respectively, and for 5-year-old Hong Kong boys and girls were 0.22%similar to 0.33% and 0.61%similar to 0.85%. In relation to the total cancer incidence (baseline cancer incidence plus lifetime attributable risk), lifetime attributable risk from radiation exposure contributed up to 0.99% and 3.51% for Hong Kong boys and girls and up to 0.46% and 1.57% for U. S. boys and girls. CONCLUSION. Our results suggest that radiation dose and cancer risk of CT coronary angiography to pediatric patients are not negligible, more so in Hong Kong children than in U. S. children. Therefore, these examinations should be well justified clinically.