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
In Renal cell carcinoma investigation of choice to evaluate inferior venacava & renal vein for thrombus – 
Select and explain. 
A. IVP, B. Coloured doppler, C. USG, D. CT scan
B: Coloured doppler
Answer: B: Coloured doppler 
Explanation: MRI is the investigation of choice to detect renal vein or IVC involvement in RCC. Doppler USG is indicated when MRI is unavailable or contraindicated