J Cardiovasc Comput Tomogr. 2011 Jul-Aug;5(4):255-63. Epub 2011 May 25.
Tust Techasith, BS, Brian B. Ghoshhajra, MD, MBA, Quynh A. Truong, MD, MPH, Rodrigo Pale, MD, Khurram Nasir, MD, MPH, Michael A. Bolen, MD, Udo Hoffmann, MD, MPH, Ricardo C. Cury, MD, Suhny Abbara, MD, Thomas J. Brady, MD, Ron Blankstein, MD
BACKGROUND: To lower the radiation exposure associated with cardiac CT, it is essential to iden- tify all factors that influence radiation dose.
OBJECTIVES: We explored the effect of heart rhythm during scan acquisition on radiation dose with a 64-slice dual-source cardiac CT. METHODS: Patient and scan data were collected prospectively in 302 consecutive patients referred for a clinical dual-source cardiac CT. Electrocardiograms recorded during acquisition were interpreted by a cardiologist and categorized as (1) normal sinus rhythm (NSR), (2) premature atrial contraction (PAC) or premature ventricular contraction (PVC), or (3) atrial fibrillation or flutter.
RESULTS: Of the 302 patients, 227 (75.2%) were in NSR and had no ectopy, 55 (18.2%) had PAC/PVC, and 20 (6.6%) had atrial fibrillation or flutter during the scan. Patients with irregular rhythm (PAC/PVC and atrial fibrillation or flutter) were older than patients with regular rhythm (61.0 vs 54.8 years; P — 0.006). Patients with NSR had the lowest estimated radiation dose, followed by PAC/PVC and atrial fibrillation/flutter (9.4, 14.5, 20.9 mSv; P < 0.001). The difference remained sig-nificant after adjustments for differences in examination type, tube current and voltage, scan length, pitch, and use of tube current modulation (9.8, 14.1, 17.9 mSv; P < 0.001). No significant association was observed between heart rhythm and subjective image quality although scans with regular rhythm and no ectopy had higher signal-to-noise and contrast-to-noise ratios (P < 0.01).
CONCLUSION: Compared to patients with NSR, patients with atrial fibrillation/flutter had the high¬est radiation exposure, followed by those with PAC/PVC. Even after adjustment for factors associated with radiation exposure, a significant difference in radiation dose persisted. These findings can be used
