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
Investigation of choice in parathyroid pathology is – 
Select and explain. 
A. CT Scan, B. Gallium scan, C. Thallium scan, D. Tc – Thallium substraction scan
D: Tc – Thallium substraction scan
Answer: D: Tc – Thallium substraction scan 
Explanation: Presently, Tc - 99m sestamibi is the best available agent for parathyroid scanning. Therefore, Technetium - sestamibi (Tc - 99m MIBI) is the investigation of choice in the localization of parathyroid tumor.
Tc - 99m thallium subtraction scan is the second choice.