One of your obstetric patients presents to the office at 25 weeks complaining of severe left calf pain and swelling. The area of concern is slightly edematous, but no erythema is apparent. The patient demonstrates a positive Homan sign, and you are concerned that she may have a deep vein thrombosis. Which of the following diagnostic modalities do you order?
MRI Computed tomographic scanning Venography Real-time ultrasonography