A 35-year-old man is brought to the trauma center with acute severe head injury following a motor vehicle collision. He is drowsy and has a blown right pupil. Non-contrast CT head shows a lens-shaped hyperdensity in the right frontoparietal region that does not cross the midline but does not respect the suture lines. The neurosurgeon needs rapid confirmation of the diagnosis and exact location for emergency burr hole placement. Which investigation is most appropriate?