256-slice CT coronary angiography: in vivo dosimetry and technique optimization.

Purpose: This study was undertaken to compare the different acquisition protocols available in a last-generation multislice computed tomography scanner used for cardiovascular studies, with particular attention to dosimetric aspects.

Materials And Methods: Our study compared prospective and retrospective electrocardiographic-gating techniques for cardiac imaging. For each patient, we performed in vivo dose measurements, using Gafchromic film. We compared the effective dose values estimated from the experimental measurements and the dose data reported on the CT console. Image quality was also assessed.

Results: Prospective acquisition allows for major dose savings compared to retrospective acquisition (mean effective dose, 4.5 mSv with prospective acquisition versus 27.5 mSv with retrospective acquisition). The agreement between the experimental and software-based dose estimates was excellent and showed below 10% of variation of the measured dose.

Conclusion: In patients with regular rhythm and a heart rate lower than 75 bpm, the prospective acquisition technique ensures adequate diagnostic results and allows for significant patient dose savings.