<prompt> Best investigation when there is clinical suspicion of pulmonary embolism in a patient is-D-Dimmer AssayMultidetector CT angiographyDoppler ultrasoundCatheter angiography  <response>: Answer is B Multidetector CT Angiography: For patients with strong clinical suspicionshigh likehood of DVT. Imaging tests are obligatory. CT scan with intravenous contrast Multidetector CT Angiography is the test of choice for the diagnosis of PE. Invasive catheter based pulmonary Angiography is highly specific but reserved for patients with unsatisfactory chest CT or those who require an interventional procedure like catheter directed thrombolysis or embolectomy. 