A 37-year-old man has a 2-year history of increasing right wrist pain that is worse at night and aggravated by activity. He denies systemic symptoms, history of trauma, or recent weight loss. On physical exam he has tenderness over the dorsal radiocarpal joint. Radiographs of the right wrist are shown in Figure A. Which of the following imaging studies would be most sensitive for determining the stage of this patient's underlying condition?