PET images will be acquired using a Gemini Time-of-Flight (TF) 64 scanner (Philips Healthcare, Best, The Netherlands). Quantitative myocardial perfusion at rest and during hyperemia in ml -1. min -1. g -1 of myocardial tissue will be measured using oxygen-15-labelled water (H215O). Pharmacological stress is induced by infusion of adenosine intravenously at a rate of 140 µg/kg/min. Two minutes after the start of adenosine vasodilation reaches a steady state and H215O will be given intravenously as a bolus followed with the start of a 6-minutes emission scan. Directly after the PET sequence, a low dose CT attenuation scan (CTAC) is acquired after which the infusion of adenosine is terminated. Technetium-99m sestamibi is injected intravenously after the second CTAC scan. A stress SPECT-scan is performed 45 minutes after the stress PET scan.