Beck L, et al. – Aim of this work was to obtain a range of normal measurements of the adult thoracic aorta and main pulmonary artery applying cardiac MRI, and to assess agreement between measurements made on ECG–gated two–dimensional (2D) breath held steady–state–free precession (SSFP), and three–dimensional (3D) breath held SSFP image acquisitions. Applying 2D and 3D non–contrast MR sequences, they established normal values for transverse diameters of the thoracic aorta and main pulmonary artery in healthy adults. The data indicated that overall both inter–observer agreement, and agreement between 2D and 3D techniques was good. Remarkably, mean diameter differences demonstrated at the aortic annulus, ascending aorta and aortic arch between LC and LSC although significant were less than one millimetre and unlikely to be important in clinical practice.