This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
Gold standard for diagnosing pulmonary embolism: 
Select and explain. 
A. X-ray chest, B. Ventilation perfusion scan, C. Blood gas analysis, D. Doppler
B: Ventilation perfusion scan
Answer: B: Ventilation perfusion scan 
Explanation: B i.e. V-P Scan Investigation of choice (IOC) for diagnosing pulmonary embolism is pulmonary aeriography followed by ventilation - perfusion scanQ. Advantages & Disadvantages of various tests for DTE Dx Test Advantages Disadvantages 1. Plasm D-dimer ELISA Normal results make PE highly unlikely Level is elevated in various systemic illnesses 2. Lung (V-P) Scanning Standard initial imaging test for PEQ. High probability scans are reliable for detecting PE . normal/near normal scans are reliable for precluding PE Most scans are neither high probability nor normal/near normal; most are equivocal 3. Pulmonary angiography Gold standard for diagnosisQ Invasive, Costly & Uncomfoable ; so not a first line investigation