This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
Delta sign in CT scan is characteristic of 
Select and explain. 
A. Petrositis, B. Otogenic brain abscess, C. Lateral sinus thrombophlebitis, D. Otosclerosis
C: Lateral sinus thrombophlebitis
Answer: C: Lateral sinus thrombophlebitis 
Explanation: Contrast-enhanced CT scan can show sinus thrombosis by typical delta sign. It is a triangular area with rim enhancement and the central low-density area is seen in posterior cranial fossa on axial cuts. MR imaging better delineates thrombus. "Delta sign" may also be seen on contrast-enhanced MRI. MR venography is useful to assess the progression or resolution of thrombus. Ref : Diseases of ENT by Dhingra 6th edition Pgno : 84,85