<prompt> What is the definitive method of diagnosing pulmonary embolism?Ventilation perfusion imagingPositron Emission TomographyHigh Resolution CTPulmonary angiography  <response>: CT pulmonary angiography is the first line diagnostic test for pulmonary embolism.It has the advantages of visualising the distribution and extent of the embolism,or highlighting an alternative diagnosis,such as consolidation,pneumothorax or aoic dissection. Reference:Davidsons medicine-22nd edition,page no:722. 