Eur Radiol (2012) 22:1278–1286 Besides evaluation of the exact cause of PHV dysfunc- tion, MDCT may have complementary clinical value for the surgical planning in patients considered for reoperation after previous PHV implantation. MDCT can be used to evaluate the presence of coronary artery disease (CAD) and the patency of present bypass grafts to serve as an alternative for classical coronary angiography, and the distance be- tween the sternum and the right ventricle can be measured [7]. Patients with a normal functioning PHV may also be candidates for CT assessment of the coronary arteries in newly developed angina. Each PHV type has its own specific imaging character- istics on CT [8, 9]. Most PHVs have limited artefacts but at present little is known about which PHV types and positions induce artefacts to such an extent that they prohibit coronary assessment on MDCT. Knowledge of which PHV types and positions prohibit coronary assessment is clinically impor- tant to determine whether adequate CT assessment of coro- nary segments is to be expected or that the patient should be referred for conventional coronary angiography straight away. The purpose of this study was to determine which PHV types induce artefacts that hamper coronary artery segment assessment on MDCT in a cohort of patients with a PHV in whom an ECG-gated or -triggered PHV had been performed. Materials and methods CT angiogram selection We reviewed all ECG-gated or prospectively triggered PHV CT angiograms (CTAs) performed in the University Medical Center Utrecht and Academic Medical Center Amsterdam between 2003 and September 2011 for the presence of PHVs that were imaged in both systolic and diastolic phase. We excluded CTAs that included only systolic or diastolic imaging, were performed on 16-slice MDCT, non-contrast enhanced imaging as well as CTAs in patients enrolled in an ongoing prospective diagnostic cross-sectional study on CT PHV assessment. Furthermore, patients with multiple CTA examinations were included only once. Patients with a con- comitant mitral or tricuspid annuloplasty ring were included. CTAs were performed on 64 or 256 slice MDCT systems (Brilliance 64 and iCT, Philips Medical Systems, Cleveland, Ohio). Contrast agents [Ultravist (iopromide) - 300 mg I/mL, Bayer Schering Pharma AG, Berlin, Germany or Iomeron (iomeprol) - 400 mg I/mL, Bracco UK Limited, London, United Kingdom] were administered in all patients. Cardiac CTAs were performed with a triphasic or dual phasic contrast injection protocol. The triphasic protocol started with a 100% contrast injection (phase 1) followed by a 30%/70% contrast/ saline mixture (phase 2), and concluded with a saline flush 1279 (phase 3). Contrast volumes were adjusted for the patients body weight with an iodine flow of 1.6 g/s for patients <70 kilogram (kg), 1.8 g/s for patients 70–85 kg and 2.0 g/s for patients >85 kg. The dual phase contrast protocol consisted of a contrast injection of 100 millilitre (mL) followed by a saline flush. For aortic CTAs, a fixed bolus of 100 ml was followed by a saline flush of 50 ml. In general, injection flow was set to 5–6 ml/s. The CTA selection resulted in the inclusion of 82 patients (48 males, 34 females) with 94 PHVs and annulo- plasty rings. The mean age of our study population was 58± 14 years (mean ± SD). All 82 patients underwent CTA exami- nations on 64-slice (n0 27) or 256-slice (n055) MDCT sys- tems. The indications for CTA examinations were: PHV dysfunction (n0 47), aortic aneurysm evaluation (n0 17), aortic dissection (n08), coronary assessment (n03), cardiac other (n0 5) and other (n0 2). In four of 82 patients (5%) beta- blockers were administered to lower the heart rate. Nitroglyc- erin was not routinely administered in our patients. CT data were retrieved from the PACS archive of the Radiology department and sent to a dedicated workstation for image analysis. Heart rate during imaging was obtained from the CT data. DLP values were obtained if dose infor- mation was available. DLP values were converted to radia- tion exposure (mSv) by using 0.017 for cardiac CTAs, and 0.016 (mean of 0.017 for the chest and 0.015 for the abdo- men) for thoraco-abdominal aortic CTAs as conversion fac- tor. Patient and PHV data were obtained from the patient’s medical files. The study was performed under a waiver from the institutional reviewing board. Data on the image quality of the PHV itself in a number of these patients have been previously published [9]. Fig. 1 Coronary artery segments according to the American Heart Association classification [10]. Ao 0 Aorta; RCA 0 Right Coronary Artery; LCA 0 Left Coronary Artery; LM 0 Left Main branch; LAD 0 Left Anterior Descending Coronary Artery; LCX 0 Left Circumflex Coronary Artery