A 5-year-old girl is admitted to your Paeds ward. The parents give the history that the child has had recurrent, intermittent episodes of fever and respiratory distress over the past 1.5 years, including cough, wheezing, and dyspnea lasting for 3-4 days. With every episode, hemoptysis is present. Now she is diagnosed with Right lower lobe pneumonia which improves upon treatment. On physical examination, the patient is pale, icteric with digital clubbing. Which of the following is the most appropriate next Investigation?