Introduction 1 6 7 11 12 13 14 16 Materials and methods Population n n n n n n CT scan and reconstruction parameters All examinations were performed with a 64-slice CT scanner (Sensation 64, Siemens, Forcheim, Germany) with the following parameters: slices/collimation 32/0.6 mm, rotation time 330 ms, effective temporal resolution (with 180° algorithm) 165 ms, 120 kv, 900 mAs, table feed/s 11.63 mm, effective slice thickness 0.6 mm, reconstruction increment 0.3 mm, field of view (FOV) 140–180 mm, isotropic voxel resolution of 0.4 × 0.4 × 0.4 mm. Patients with heart rate >70 bpm received 100 mg of metoprolol per os 1 h prior the examination. A bolus of 100 ml of high iodinated contrast material (400 mg/ml iomeprol, Iomeron 400, Bracco, Milan, Italy) was injected into an antecubital vein of the right arm with a flow rate of 5 ml/s, followed by a 40-ml saline chaser. A bolus-tracking technique was used for the synchronization between arterial passage of contrast material and MSCT-CA. Data were reconstructed by retrospective gating in end-diastolic phase (from -300 to -450 ms before the peak of the subsequent R wave) or end-sistolic phase to better image the right coronary artery (RCA). Image and data analysis 17 All data were analysed with post-processing tools such as multiplanar reconstructions (MPR), curved MPR (cMPR), maximum intensity projections (MIP), and volume rendering (VR) to three-dimensionally image the complex anatomy of the coronary artery tree. Disagreement was solved by a consensus reading. Segments were classified according to the American Heart Association (AHA) scheme. Variants considered were: the coronary dominance (right, left, balanced), the variable origin of the conus branch and sinus node artery, the left main (LM) length, the presence of the intermediate branch, the number of diagonal and marginal branches. Anomalies of origin and course, intrinsic coronary anomalies (myocardial bridging, aneurisms >1.5 mm) and termination anomalies (fistulas) were checked. Prevalence data of single coronary artery variants and anomalies were collected. Results 1 Table 1 Our population resulted heterogeneous because of the multiethnic Dutch population Ethnic group n The Netherlands 88.95 (483) Middle East Asia 3.31 (18) South-East Asia 2.94 (16) East Europe 1.84 (10) South Europe 1.10 (6) South America 0.92 (5) Africa 0.92 (5) 2 3 n n n 18 n n n 1 n n 2 n 2 Table 2 Segments visualized according to the American Heart Association classification Segments n 1 99.8 (542) 2 99.3 (539) 3 97.8 (531) 4 92.4 (502) 5 95.9 (521) 6 100 (543) 7 100 (543) 8 97.8 (531) 9 98.7 (536) 10 73.7 (400) 11 100 (543) 12 99.4 (540) 13 97.2 (528) 14 64.3 (349) 15 72.4 (393) a 21.9 (119) a Table 3 RCA LAD LCX LM ND Variants   n Conus branch From proximal RCA 64.1 (348)  From ostial RCA 22.3 (121)  From aorta 11.6 (63)  ND 2 (11) Sinus node artery From RCA 65.4 (355)  From LCX 16.6 (90)  From RCA and LCX 9.2 (50)  From LCX and pulmonary artery 0.2 (1)  From aorta 0.2 (1)  ND 8.4 (46) LM length <1 cm 41.6 (226)  1–2 cm 47.3 (257)  >2 cm 7 (38) Intermediate branch  21.9 (119) Diagonal branches from LAD ND 1.3 (7)  1 25 (136)  2 49.7 (270)  >2 24 (130) Septal branches from LAD  93 (505) Marginal branches from LCX ND 0.6 (3)  1 35.2 (191)  2 46.2 (251)  >2 18 (98) Fig. 1 a b c e  Fig. 2 a c d f g i  2 3 Fig. 3 arrow a b c arrowhead d e f  n 4 Table 4 LM PDA Coronary anomalies n Myocardial bridging 10.9 (59) Absent LM 3.3 (18) Rotation of the aortic root with normal coronary origin from the sinuses of Valsalva 2.6 (14) Coronary aneurysms 1.6 (9) Anomalies of origin and course 1.5 (8) Fistulas 0.5 (3) Early take-off of PDA 0.5 (3) 4 5 Fig. 4 arrowhead a b c d e  Fig. 5 arrowhead a b c d e f g h i  6 7 Fig. 6 a b c d e f  Fig. 7 a b c d e f  Discussion 19 20 21 18 normal normal variant anomaly 18 22 18 23 24 25 1 4 5 26 6 6 1 27 12 2 7 11 28 29 14 16 30 31 33 n n n 18 34 Furthermore, the septal branches of the left anterior descending artery (LAD) were detected in the 93% (505/543). The opportunity of reporting septal branches of LAD must be taken into account because of the hemodinamic relevance of these vessels. 35 18 12 13 12 13 Compared with 16-slice CT-CA, 64-slice CT-CA provides improved temporal resolution and isotropic spatial resolution which allow optimal three-dimensional visualization of the variable and complex anatomy of coronary arteries. Sixty-four-slice CT-CA may non-invasively define normal anatomical variants from potentially dangerous anomalies and support the clinical management of referring cardiologists and cardiac surgeons.