A 68-year-old man presents with pleuritic chest pain and dyspnoea. He underwent hip replacement surgery 10 days ago. Vitals: HR 110/min, BP 124/78 mm Hg, RR 24/min, SpO₂ 92% on room air. There is no leg swelling. Wells score indicates intermediate probability of pulmonary embolism (PE). According to standard diagnostic strategies used in Canada, which is the most appropriate next step?