us-abem MCQ (SBA): Pulmonary embolism in postpartum patient

A 29-year-old postpartum woman presents 10 days after delivery with pleuritic chest pain and dyspnea. She had an uncomplicated vaginal delivery. Vitals: temperature 99.1 F, blood pressure 118/72 mmHg, heart rate 110 per minute, respiratory rate 24 per minute, oxygen saturation 92 percent on room air. Which diagnostic modality is preferred to evaluate for pulmonary embolism in this patient?