ANATOMIC VARIATION OF EXTRAHEPATIC BILIARY TREE-STRUCTURES - IMPORTANCE IN TREATMENT PLANNING FOR RADIATION-THERAPY

PURPOSE: To demonstrate the variable location of biliary tree componen ts and to assess two treatment planning rules of thumb used for locati ng porta hepatic nodes for radiation therapy. MATERIALS AND METHODS: T he distance of the common hepatic duct bifurcation and duodenal papill a from adjacent vertebral bodies was measured on 34 cholangiograms, an d their relationships to particular vertebral body levels were recorde d. Adequacy of treatment volume to encompass porta hepatic lymph nodes was evaluated in 30 of these cholangiograms by constructing radiation portals according to the two rules of thumb. RESULTS: Location of the common hepatic duct bifurcation and duodenal papilla varied widely. T he treatment portal encompassed 13% (four of 30) of cases when the fir st rule of thumb was used and 80% (24 of 30) of cases when the second rule of thumb was used. CONCLUSION: The wide variability of location o f extrahepatic biliary tree structures suggests the need for individua lized treatment planning so that sensitive and dose-limiting healthy t issues can be optimally excluded from radiation treatment portals. Com puted tomography and other imaging modalities enable precise location of biliary tree components for radiation treatment planning.