Dose lowering strategies in coronary angiography MDCT (CAMDCT):influence on imaging quality

Purpose: The use of coronary angiography MDCT (CA-MDCT) is rapidly increasing since the overall good accuracy of the technique and the wide range informations given. The need to perform coronary CA-MDCT with thin collimations and low pitch has however lead to a significant increase in patient exposure to ionizing radiation. The exposure to the patient and the absorbed dose are directly dependent to the mA and the voltage of the Tube. However the change of these parameters can also influence image quality. The aim of our study is to determine the diagnostic accuracy of CA-MDCT with different dose saving protocols. Methods and Materials: 509 patients (319 Males, 64±11,43 YO mean age, mean HR 59.1 bpm) studied between April 2008 and August 2010 who underwent CA-MDCT for suspected CAD were selected. Acquisition protocol: 210 (41%) without any radiation dose saving protocol (Group A), 228 (45%) with retrospective gating and Dose modulation (Group B) and 71 (14%) with prospective gating and 80KV (Group C). 2 Observers scored each coronary segment according to the AHA 17 segment model. Coronary Angiography was considered as the standard of reference. Dose absorbed was recorded as mSv. Results: A total of 6617 segments were scored. Diagnostic images were obtained for each coronary artery in all Patients with overall accuracy of 98 %. Group A showed a mean dose of 16.05 mSv, Group B 8.2 mSv and Group C 1.2 mSv. Conclusion: Step and Shoot protocol with low KV can guarantee a high diagnostic image quality with a significant dose reduction