Journal of Cardiovascular Computed Tomography Volume 3, Issue 6, (November-December 2009)
Ryo Nakazato, MDa, Damini Dey, PhD, Ariel Gutstein, MDC, Ludovic Le Meunier, PhD, Victor Y. Cheng, MD, Raymond Pimentel, BSc, William Paz, BSca, Sean W. Hayes, MD, Louise E. J. Thomson, MBChB, John D. Friedman, MD, FACC, Daniel S. Berman, MD, FACC
BACKGROUND: Technical advances to minimize radiation exposure because of imaging are in ac¬cord with the "as low as reasonably achievable" principle.
OBJECTIVE: We aimed to determine whether coronary calcium scoring (CCS) by multidetector CT at a tube voltage of 100 kVp yields comparable results to the standard 120-kVp protocol while reducing radiation dose.
METHODS: Sixty consecutive outpatients were scanned with a dual-source CT scanner with both thel20- and 100-kVp protocols. The calcium threshold was 130 Hounsfield units (HUs) for 120 kVp and 147 HU for 100 kVp, as determined from phantom data. All 100-kVp scans were scored by an expe¬rienced reader blinded to 120-kVp data.
RESULTS: Image quality was comparable for 100- and 120- kVp scans. Mean Agatston scores for 100 and 120 kVp were 189 ± 484 and 189 ± 498 (P = 0.92), with perfect correlation (r = 1.0; P < 0.0001; 95% limits of agreement, -36 to 37; bias, 0.6). Mean coronary calcium volume scores for 100 and 120 kVp were 143 ± 370 mm3 and 149 ± 392 mm3 (P = 0.26), with perfect correlation (r = 1.0; P < 0.0001; 95% limits of agreement, -35 to 32 mm3; bias, -1.4 mm3). The mean absolute difference for Agatston scores between the protocols was 16.9, with excellent agreement (K = 0.95; P < 0.0001). Mean effective radi¬ation dose for the 100-kVp protocol was significantly lower (1.17 mSv versus 1.70 mSv; P < 0.0001).
CONCLUSION: A reduced tube current protocol using 100 kVp gives equivalent CCS results at re¬duced radiation exposure compared with a standard protocol at 120 kVp