How Clinical Question Influences Radiation Dose in Paediatric Cardiac CT Scan?

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Number of Cardiac CT examinations in paediatric population is rising. Clinical questions might vary from cardiac anatomy, coronary arteries, cardiac function assessment to chest examination including evaluation of large vessels, eventually combinations of these tasks. Dose reduction in children is especially important. CT scanning mode selection, reduction of kVp and limited extent of scanning in z-axis are the most important parameters for dose reduction. However, dose reduction optimization should not limit the readability of the CCT, and consequently the ability to reply the clinical question. Purpose This study analyses the influence of different clinical questions to radiation dose of paediatric cardiac CT. Methods In total 123 patients (42 females, 81 males) were examined using third generation dual-source CT scanner (SOMATOM Force, Siemens Healthineers, Forchheim, Germany), age mean 10.5 ± SD 5.9 years (min 50 days – max 18.9 years), height 138 ± 39 cm (54 – 200), weight 49 ± 25 kg (3.7 – 103). Three main categories of clinical questions (Q) were set: Q1) Extent of scanning in z-axis: heart only (from carina to diaphragm) or whole chest, Q2) Coronary arteries evaluation: yes/no, Q3) Cardiac function assessment (yes/no). Radiation dose is represented as a dose length product (DLP) in mGy*cm. Effective dose (ED) in mSv and calculated from DLP using converting factor 0.026 mSv/mGy*cm. Multiple regression was used to evaluate influence of clinical question to radiation dose. Results Total DLP was 202 ± 282 mGy*cm (6 – 1751), ED was 5.25 ± 7.33 mSv (0.16 – 45.53). Multiple regression of Total DLP versus Q1-Q3, height, weight and average heart rate showed statistically significant influence of cardiac function assessment (413 ± 263 vs 132 ± 253 mGy*cm, p 0.0001) and weight (p 0.0443). Multiple regression after adjusting to weight showed statistically significant influence of cardiac function assessment only (p <0.0001). Conclusions Only clinical question about cardiac function assessment caused statistically significant higher radiation dose acquired from cardiac CT in paediatric patients. There was no statistically significant influence of coronary artery evaluation and extent of scanning. Abstract Figure.