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
Renal GFR is best measured by – 
Select and explain. 
A. Tc 99 DMSA, B. Tc 99 Pyrophosphate scan, C. Tc 99 DTPA, D. Creatinine clearance
C: Tc 99 DTPA
Answer: C: Tc 99 DTPA 
Explanation: Inulin clearance is the gold standard for assessing GFR. It is the preferred measure of GFR when an accurate measure is critical. However, this method is not performed in clinical practice, because of technical complexity and limited availability.
Next to inulin, radiocontrast agents (Tc - DTPA) are most accurate.
However, because of its convenience and low cost, creatinine clearance is most commonly used.