Overlay tool on therapeutic planning for anterior communicating artery aneurysms

Background. Anatomical variation in the anterior communicating artery complex is one of the challenging points when choosing between endovascular or surgical approach to treat aneurysms in this region. Besides, this is the most common location for aneurysms. Here we present our diagnostic angiography image protocol using the overlay tool to fully understand the anatomical variation of this region which assists in the best therapeutic planning of lesions in this location. Method. The authors performed a review of available data regarding overlay reconstruction tool. Search was conducted via Pubmed and Scielo databases with “overlay tool AND cerebral angiography” as keywords. Articles considered relevant were included in this review, especially those which focused on essential aspects of this specific vascular malformation. Conclusion. The overlay tool from the Allura Xper FD20 (Philips, Best, Netherlands) is an incredible way to better understand the anatomical variation of this region with the fusion of both A1 segments in the same image. Unitermos. Intracranial aneurysms; Subarachnoid hemorrhage; microsurgery Resumo Introdução. A variação anatômica do complexo da artéria comunicante anterior é um dos pontos desafiadores na avaliação do tratamento dos aneurismas com abordagem endovascular ou cirúrgica nesta região. Além disso, este é o local mais comum para aneurismas. Apresentamos aqui nosso protocolo de imagem de angiografia diagnóstica utilizando a ferramenta de sobreposição para entender completamente a variação anatômica desta região que auxilia no melhor planejamento terapêutico das lesões nesta região. Método. Os autores realizaram uma revisão dos dados disponíveis sobre a ferramenta de reconstrução de sobreposição. A pesquisa foi realizada nas bases de dados Pubmed e Scielo com “overlay tool AND cerebral angiography” como palavras-chave. Os artigos considerados relevantes foram incluídos nesta revisão, especialmente aqueles que enfocavam aspectos essenciais dessa malformação vascular específica. Conclusão. A ferramenta de sobreposição do Allura Xper FD20 (Philips, Best, Netherlands) é uma maneira incrível de entender melhor a variação anatômica desta região com a fusão dos dois segmentos A1 na mesma imagem.


METHOD
The authors performed a review of available data regarding overlay reconstruction tool. Search was conducted via Pubmed and Scielo databases with "overlay tool AND cerebral angiography" as keywords. Articles considered relevant were included in this review, especially those which focused on essential aspects of this specific vascular malformation. We also screened article references for further relevant data. A statistical approach could not be conducted due to paucity of data, and therefore, a descriptive summary was performed.
This article was illustrated with cases from the author's service. Our institutional review board has approved this retrospective study. Individual patient consent was not required as data were collected in an anonymous manner and there was no risk to patients.

Technique for Image Acquisition
The diagnostic subtraction angiography (DSA) was done under local anesthesia via a transfemoral approach; using a  (Figures 1 and 2), and not just a unilateral view of the carotid system. This is essential, for example, for planning hemorrhagic control in cases of inadvertent trans operative rupture.  In addition to the asymmetry observed in the anterior communicating complex in more than 80% of cases 6,10,11 , there is also the possibility of fenestrations, duplications of the anterior communicating artery and even the appearance of the azygos pattern 11 .
All these aspects hinder the anatomical understanding of the region and can be better clarified with the use of the overlay tool. To produce the overlay image, we need to do one 3D acquisition for each artery (left and right ICA) with the same FD. After that, the tool "overlay" is chosen in the workstation and the fusion of both 3D is done by the Philips machine.
It seems that the overlay tool could help to better understand this complex region to propose the best treatment option. This has already been described but it is important to assess both carotid, even if the contralateral A1 segment is hypoplastic in non-invasive studies. With this tool, the anatomic configuration might be completely understood so that the best technical approach can be chosen, however, further studies are needed.

CONCLUSION
The overlay tool from the Allura Xper FD20 (Philips, Best, Netherlands) is an incredible way to better understand the anatomical variation of this region with the fusion of both A1 segments in the same image. This is essential for the correct therapeutic planning, whether it might be microsurgical or endovascular. Further studies are needed to better evaluate this tool in this specific aneurysm site.