High-Pitch Computed Tomography Coronary Angiography – A New Dose Saving Algorithm: Estimation of Radiation Exposure

Purpose:

To estimate effective dose and organ equivalent doses of prospective ECG-triggered high pitch CTCA.

Materials and Methods:

For dose measurements, an Alderson-Rando-phantom equipped with thermoluminescent dosimeters was used. The effective dose was calculated according to ICRP 103. Exposure was performed on a second-generation dual-source scanner (SOMATOM Definition Flash, Siemens Medical Solutions, Germany). Following scan parameters were used: 320mAs per rotation, 100 and 120kV, pitch 3.4 for prospectively ECG-triggered high pitch CTCA, scan range of 13.5cm, collimation 64×2 x 0.6mm with z-flying focal spot, gantry rotation time 280ms, simulated heart rate of 60 beats per minute.

Results:

Depending on the applied tube potential, the effective whole-body dose of the cardiac scan ranged from 1.1 mSv to 1.6 mSv and from 1.2 to 1.8 mSv for males and females, respectively. The radiosensitive breast tissue in the range of the primary beam caused an increased female-specific effective dose of 8.6%±0.3% compared to males. Decreasing the tube potential, a significant reduction of the effective dose of 35.8% and 36.0% can be achieved for males and females, respectively (p<0.001).

Conclusion:

The radiologist and the CT technician should aware of this new dose saving strategy to keep the radiation exposure as low as reasonable achievable.