This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thromboembolism and Fat Embolism Syndrome, Subject name: Medicine
Which investigation is most diagnostic of pulmonary emboli? 
Select and explain. 
A. CTPA, B. V/P scan, C. HRCT, D. D- Dimer Assay
A: CTPA
Answer: A: CTPA 
Explanation: Computed Tomography Pulmonary Angiography (CTPA) is the initial imaging modality of choice for stable patients with a suspected pulmonary embolism. Pulmonary angiography shows emboli directly but it is an invasive procedure CT is noninvasive, cheaper and widely available. so, it's the most diagnostic investigation of choice. - D-Dimer is the screening investigationin PE pt's