New radiation dose saving technologies for 256-slice cardiac computed tomography angiography
Purpose This paper aims to evaluate the dose reductions conferred by spiral dynamic z-collimation and axial adaptive z-collimation for retrospectively and prospectively ECG-referenced cardiac CTA, respectively, on a wide coverage, 256-slice CT scanner. Methods Using typical data presented in the literature, a distribution of cardiac CT scan lengths was synthesized. To isolate the effect of z-overscan on effective radiation dose, 1,000 simulated patient scan lengths were then randomly sampled from this distribution and used for subsequent analysis. Results Retrospectively ECG-gated spiral scans with dynamic z-collimation resulted in a mean relative effective dose reduction of 11.7 and 24.3% for MDCT with 40 and 80 mm z-axis detector coverage, respectively. Mean relative dose reduction of prospectively ECG-triggered axial scans with adaptive z-collimation on an 80 mm coverage scanner was 10.0%. Conclusion Dynamic z-collimation for retrospectively ECG-gated spiral scanning and adaptive z-collimation for prospectively ECG-triggered axial scanning are both associated with a significant dose reduction on a wide coverage, 256-slice CT scanner.
Keywords256-Slice MDCT Prospective triggering Retrospective gating Radiation exposure Radiation reduction Coronary CT angiography Step-and-shoot Low dose Dose efficiency
Conflict of interest
Matthew J. Walker and Mark E. Olszewski are employees of Philips Healthcare (Cleveland, OH, USA) and led the data simulation and statistical analysis. All authors reviewed and confirmed the results, and Scott D. Flamm takes scientific responsibility for data integrity.
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