Cracking, in petroleum refining, the process by which heavy hydrocarbon molecules are broken up into lighter molecules by means of heat and usually pressure and sometimes catalysts. Cracking is the most important process for the commercial production of gasoline and diesel fuel. 1  Cracking of petroleum yields light oils (corresponding to gasoline), middle-range oils used in diesel fuel, residual heavy oils, a solid carbonaceous product known as coke, and such gases as methane, ethane, ethylene, propane, propylene, and butylene.
Cholangiography is the imaging of the bile duct (also known as the biliary tree) by x-rays. percutaneous transhepatic cholangiography (PTC): Examination of liver and bile ducts by x-rays. This is accomplished by the insertion of a thin needle into the liver carrying a contrast medium to help to see blockage in liver and bile ducts.
Magnetic resonance cholangiopancreatography (MRCP) is the technique that through use of magnetic resonance imaging. visualises the intra-and extrahepatic bile ducts and the pancreatic duct. First described in 1986, the technique has improved over the years.Today, MRCP is almost comparable to endoscopic retrograde cholangiopancreatography (ERCP) which is the other, invasive, imaging modality for the biliary tree.ne limitation of the MRCP technique in the detection of gall stones is that the slices are thicker than 5 mm, which requires partial volume averaging. This can lead to false-negative results when a stone is smaller than 5 mm in diameter.