Anatomy of the celiac axis and superior mesenteric artery and its significance in radiation therapy.

PURPOSE

In the radiation therapy of upper gastrointestinal malignancies, treatment of lymph nodes in the region of the celiac axis and superior mesenteric axis is often mandated. This study was undertaken to determine the relationship of the celiac axis and superior mesenteric arteries to the vertebral bodies--the radiographically visualized reference structures during simulation.

METHODS AND MATERIALS

Twenty-three celiac angiograms and 24 superior mesenteric angiograms performed preoperatively in 24 patients treated at the University of Pennsylvania from 1984 to 1989 for pancreatic carcinoma were examined. The location of the origin of the celiac and superior mesenteric arteries was determined in each case.

RESULTS

In 48% of the celiac angiograms, the celiac axis arose from the aorta high at the pedicle of the T-12 vertebral body, contrary to the common belief that the celiac axis arises near the T12-L1 interspace. The superior mesenteric artery arose at the level of L-1 in 83% of the 24 angiograms and below the pedicle of L-1 in 5 (21%). However, none arose below the L1-2 interspace.

CONCLUSION

The variability demonstrated in the levels from which these vessels arise strongly suggests individualized treatment planning, including angiographic, CT or MRI data should be performed if tight margins are used. These studies would additionally optimize treatment of the tumor bed. Consideration for dose at field edges (i.e., "buildup") and day to day variation in set-up is required in determining the field borders. Treatment volumes tightly encompassing T12 and L1 could risk undertreating regional lymph nodes associated with these vessels.