**Core Concept**
A T-tube cholangiogram is a radiographic examination used to visualize the biliary tract, particularly after a surgical procedure such as a cholecystectomy or a sphincteroplasty, where a T-tube is inserted into the common bile duct to facilitate drainage and allow for post-operative imaging.

**Why the Correct Answer is Right**
A T-tube cholangiogram involves injecting a contrast agent through the T-tube inserted in the common bile duct, allowing for the opacification of the biliary tree. This examination is typically performed on the 10th post-operative day to assess the patency of the bile ducts and the integrity of the surgical anastomosis. The procedure helps to identify any potential complications, such as bile leaks or strictures, which may require further intervention.

**Why Each Wrong Option is Incorrect**
**Option A:** ERCP (Endoscopic Retrograde Cholangiopancreatography) is a procedure that uses a combination of endoscopy and fluoroscopy to visualize the biliary and pancreatic ducts, but it is not typically performed through a T-tube.
**Option B:** MRCP (Magnetic Resonance Cholangiopancreatography) is a non-invasive imaging modality that uses MRI to visualize the biliary and pancreatic ducts, but it does not involve the insertion of a T-tube or the injection of a contrast agent through it.
**Option D:** PTC (Percutaneous Transhepatic Cholangiography) is a procedure that involves injecting a contrast agent directly into the liver through a needle, allowing for the visualization of the biliary tree, but it is not typically performed through a T-tube.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that a T-tube cholangiogram is a specific type of imaging examination that is typically performed in the post-operative period after a cholecystectomy or a sphincteroplasty, and it should not be confused with other imaging modalities such as ERCP or MRCP.

**✓ Correct Answer: C. T-tube cholangiogram**