ON THE COVER Cardiovascular magnetic resonance (CMR) image showing the classic "Prussian helmet" sign in a 23-year-old female with congenital aortic stenosis (left) (LV = left ventricle; Ao = aorta). The image resembles the spiked "Pickelhaube" helmet (bottom right) introduced by King Frederick William IV of Prussia in 1842 and worn by the Prussian army and other German military personnel until the first World War. The sign was originally described on aortography during cardiac catheterization, in which the appearance of the spiked helmet is created by the combination of domed aortic valve leaflets in systole (typical in congenital aortic stenosis) and a central high-velocity jet of blood exiting the valve and displacing contrast in the aorta. With CMR, the "spike" is created by high signal from flow in the narrow jet, rather than the "negative" angiographic appearance due to absence of contrast. The fused tips of the aortic valve are shown (top right). Despite the evolution of cardiac imaging techniques, some signs remain reassuringly unchanged. Images provided by Upasana Tayal, MB BS, Saul G. Myerson, MD, FESC, from the University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Department of Cardiovascular Medicine, John Radcliffe Hospital, Oxford, United Kingdom

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