Angiographic Anatomy and Relevance of 3 and 9 O'clock Arteries During Radioembolization

Purpose: 3 and 9 o'clock arteries (3&9As) which supply the common hepatic duct connect hepatic with duodenal/pancreatic territories. The study purpose is to describe the angiographic anatomy of 3&9As and discuss their relevance when performing radioembolization (RE) of liver malignancies.

Materials and methods: The anatomy of the 3&9As was systematically investigated by a retrospective analysis of angiograms, technetium Tc-99 m-macroaggregated albumin (MAA) scintigrams, yttrium-90 (Y90) Bremsstrahlung-SPECT/CT datasets, and clinical data of 153 patients who underwent RE between 2010 and 2013.

Results: Analysis of preprocedural angiograms identified 3&9As in 36 (24%) of the 153 patients. Following embolization of the gastroduodenal artery, 3&9As were seen in 53 cases (35%). The three most common origins of the 3&9As were the right hepatic artery (n = 14), the cystic artery (n = 11), and S5 and S6 segmental arteries (n = 5 each). Extrahepatic Tc-99 m-MAA deposition in the territory of the 3&9As was significantly more frequent when 3&9As were detectable on preprocedural angiograms (28%_visible vs. 11%_{not visible}; p = 0.001) and especially when the 3&9As were not embolized or bridged prior to RE (50%_{not occluded/bridged} vs. 19%_{occupied/bridged}; p = 0.043). The presence of extrahepatic Y90 Bremsstrahlung after RE (n = 17) was attributable to microsphere diversion via the 3&9A territory in four patients and possible diversion via this territory in nine patients. Five of these 13 patients presented with epigastric pain, nausea, or vomiting (CTCAE severity grade ≤ 3) (p = 0.014).

Conclusion: 3&9As are commonly detectable during evaluation angiography prior to RE, have a variable angioanatomic origin, and should be prophylactically occluded to prevent complications.