Introduction 1 2 3 4 5 6 8 9 10 11 12 13 14 15 16 8 13 17 18 19 21 The purpose of this study was to investigate the feasibility and image quality of ECG-gated DSCTA of the chest as a tool to evaluate cardiac and non-cardiac causes of acute chest pain in patients presenting to the emergency department. Materials and methods Patient population Sixty consecutive patients (32 females, 28 males, mean age 58.1±16.3 years, age range 26–84 years) were prospectively included in this study. Intake was performed on weekdays from 7 am to 7 pm from August to October 2006. All patients suffered from acute chest pain and were referred to our department to diagnose or to rule out pulmonary embolism (n=56) or aortic dissection (n=4). Inclusion criteria were acute chest pain >5 min within the previous 24 h and/or elevated serum D-dimer levels. Dyspnea and hemodynamic instability were not considered exclusion criteria. Similarly, all patients irrespective of their mean or regularity of heart rate and irrespective of their ability to perform breath-hold were included. Exclusion criteria included pregnancy, previous adverse reaction to iodinated contrast agent, nephropathy (serum creatinine >1.3 mg/dl), elevated troponine-I or creatine kinase-MB level in the initial blood sample, initial diagnostic ECG changes indicating an acute coronary syndrome (i.e., ST elevation or depression >1 mm, T-wave inversion >4 mm in >2 anatomically contagious leads), and interference with standard clinical care of patients. The study was approved by the local ethics committee; informed consent was obtained. Scan protocol and data reconstruction 1 22 Fig. 1 Scan topogram illustrating planning of the chest pain protocol. The scan range covered the entire chest (red box). Premonitoring for bolus tracking was performed at the level of the aortic root (white line). The border for full tube current for the heart and half tube current for the upper lung is set approximately 2 cm below the tracheal bifurcation. It is delimited by a virtual horizontal line connecting the upper ends of the blue boxes on both sides  Retrospective ECG-gating for phase synchronization was used. For the heart, CT data sets were reconstructed at 70% of the R-R interval with a slice thickness of 0.75 mm (increment 0.5 mm) by using a medium soft-tissue convolution kernel (B26f) (mean field of view, FoV: 151±17 mm, image matrix 512×512). If considered necessary, additional images were reconstructed in 5% steps using the same parameters within the time window of full tube current. Images of the mediastinum (mean FoV: 293±43 mm) including the aorta and pulmonary arteries were reconstructed with a slice thickness of 1 mm (increment 0.8 mm) by using a medium soft-tissue convolution kernel (B30f), and images of the lung were reconstructed with a slice thickness of 2 mm (increment 1.5 mm) by using a sharp convolution kernel (B60f, same FoV as for the mediastinum). All images were transferred to a second Wizard (Siemens) equipped with cardiac post-processing software (Syngo Circulation, Siemens). Data analysis All data were qualitatively evaluated regarding image quality and artifacts of different thoracic structures by two independent readers who are both experienced in cardiovascular radiology. This evaluation was performed on transverse source images, multi-planar reformations (MPR), curved MPR, and thin-slab maximum intensity projections. Image quality and artifacts-lung parenchyma 23 1 Image quality and artifacts-vascular structures 23 Image noise and attenuation-vascular structures 24 Imaging findings Imaging findings indicating the possible underlying cause of acute chest pain were documented in each patient by both readers in consensus. Statistical analysis t P Results All CT scans were well tolerated and were successfully performed in all 60 patients without complications. All patients had a sinus rhythm, and the average heart rate during data acquisition was 74.9±19.0 beats per minute (bpm) (range 45-130 bpm). No beta receptor antagonists or benzodiazepines were administered prior to CT; 13 patients (22%) took oral beta blockers as part of their baseline medication at the time of the scan. Mean scan time was 12.2±2.3 s (range 9.7–17.5 s) and mean scan length was 24.1±2.1 cm (range 19.3–29.7 cm). The reconstruction interval used for image reading was 70% of the R-R interval. In seven patients it was considered necessary to reconstruct additional data sets in 5% intervals within the window of full tube current to obtain images with diagnostic quality. Image quality and artifacts-lung parenchyma Image quality of lung parenchyma was rated as being diagnostic (score 1) by both readers in all 60 patients (100%; excellent inter-observer agreement, kappa =1.0), and pathology both at upper and lower lung parts could be diagnosed or excluded in all 60 patients. Lung parenchyma was rated by both readers as being artifact-free in 42 patients (70%). Breathing artifacts causing stair-step artifacts were encountered in nine patients (15%) by one reader and eight (13%) of these nine patients by the other reader (excellent inter-observer agreement, kappa =0.93). Breathing artifacts were exclusively found at the lung base, i.e., at the end of the breath-hold period. ECG-gating-related artifacts were found in ten patients (17%) by one reader, and in nine (15%) of these ten patients by the other reader (excellent inter-observer agreement, kappa =0.84). The two types of artifacts were not encountered in the same patient, and image quality was diagnostic despite the artifacts. Image quality and artifacts-vascular structures 2 Image noise and attenuation-vascular structures 2 2 2 2 2 2 2 Fig. 2 Mean attenuation values (HU) within different vessels indicating a relatively homogenous contrast distribution between the different thoracic vascular territories. RCA = right coronary artery; LMA = left main coronary artery  P P P P P P P P P P P P 1 Table 1 Pairwise intra-individual comparisons between different thoracic vascular territories   Mean difference Standard deviation 95% confidence interval Lower boundary Upper boundary Aorta Pulmonary trunk -43 11 -75 -11 Aorta RCA 6 5 -10 22 Aorta LCA 5 4 -8 17 Aorta Right ventricle -23 13 -63 18 Aorta Left ventricle 14 5 -3 30 Pulmonary trunk RCA 49 11 16 82 Pulmonary trunk LCA 47 12 12 83 Pulmonary trunk Right ventricle 20 12 -16 57 Pulmonary trunk Left ventricle 57 9 29 84 RCA LCA -1 6 -19 17 RCA Right ventricle -28 13 -69 13 RCA Left ventricle 8 5 -8 24 LCA Right ventricle -27 14 -70 15 LCA Left ventricle 9 6 -10 28 RCA = right coronary artery; LCA = left coronary artery Imaging findings 2 3 4 5 Table 2 Imaging findings in the study population Diagnosis Number of patients (n=60) No pathology 33 Pulmonary embolism 11 Aortic pathology, total 5  Dissection type B 3  Pseudoaneurysm of the aortic arch 1  Plaque rupture 1 Coronary pathology, total 3  Significant stenosis of the LAD 2  Occlusion of the RCA 1 Pulmonary consolidation 3 Pericarditis/pericardial effusion 2 Seropneumothorax 1 Non-small cell lung cancer 1 Synovial cell carcinoma 1 LAD, left anterior descending artery; RCA, right coronary artery Fig. 3 a b c  Fig. 4 a b c  Fig. 5 a b c  Discussion Our study demonstrates that DSCT allows performing an ECG-gated chest examination for visualizing the different thoracic vascular territories at the same time-by employing an adjusted contrast media protocol-within a reasonable breath-hold period, and thus provides a diagnostic image quality in almost all patients. One of the most important findings of this study is that diagnostic data of coronary arteries could be obtained without foregoing heart rate control. Contrast media protocol and scan time 15 25 26 27 28 15 29 30 31 15 Role of CT in the diagnostic pathway of acute chest pain 6 9 32 33 10 11 6 8 7 7 8 Fig. 6 8  Study limitations 34 Conclusion First experience indicates that DSCTA is feasible in patients with acute chest pain and provides diagnostic image quality of the aorta, pulmonary arteries, and coronary artery system as well as of the lung parenchyma and mediastinum in a patient population without foregoing heart rate control. A dedicated contrast media protocol allows for homogenous attenuation of the different thoracic vascular territories.