Gilles P. Soulez MD, Presenter: Speaker, Bracco Group Speaker, Siemens AG Research Grant, Siemens AG Research Grant, Bracco Group Research Grant, Cook Group Incorporated Research Grant, Object Research Systems Inc

1) Know the risk factors of abdominal aortic aneurysm (AAA) rupture and the role of maximal diameter (D-max) measurement in therapeutic algorithm. 2) Discuss the variability of D-max measurement and the importance of standardized measurement to improve reproducibility. 3) Understand the challenge of AAA segmentation on CT scanner examination before and after endovascular repair (EVAR) and on unenhanced studies. 4) Understand the utility of AAA modeling for automated D-max and AAA volume measurements. 5) Understand the future developments in AAA modeling to predict AAA rupture, improve endovascular repair (EVAR) planning, EVAR rehearsal, and patient follow-up after EVAR. This session is part of Canada Presents at RSNA 2014.

Aneurysm size is the most important predictive factor for AAA rupture . Accordingly, rupture risk increases with size, with a 3-15% risk per year for those with a 5-6 cm aneurysm, 10-20% for 6-7 cm aneurysms, 20-40% for 7-8 cm aneurysms, and 30-50% for those with a diameter greater than 8 cm. AAA growth rate is correlated to its diameter and to the risk of rupture . The main indications for a procedure are Dmax ;5.5 cm in men, ;5.0 to 5.4 cm in women, or symptomatic AAA.; Computer modeling have raised the possibility of patient specific risk prediction based on AAA geometry. After computer modeling , AAA with a higher bulge location (P<.020) and lower mean averaged area (P<.005) are associated with AAA rupture however the addition of these indices in a predictive model based on current treatment criteria modestly improved the accuracy to detect aneurysm rupture. AAA segmentation is the first step before AAA modeling. CT-scanner is the modality of choice for AAA evaluation before and after endovascular repair (EVAR). AAA lumen segmentation can be easily performed after contrast injection but thrombus segmentation is far more challenging. Considering the high incidence of renal failure in this population, patient follow-up after EVAR with unenhanced CT-scanner is needed. Semi- automated segmentation of AAA on unenhanced CT-scanner can also be achieved with a high reproducibility. This open the door to patient follow-up with low-dose unenhanced CT-scanner. In this setting, Dmax or AAA volume measurement can be calculated while minimizing exposure to iodine contrast and ionizing radiation to exclude EVAR failure. AAA modeling is a necessary step for EVAR planning and stent selection. AAA can be used to enable a 2D/3D image registration between preoperative CT scanner and fluoroscopy to improve guidance during EVAR procedure and mimize fluoroscopy time and contrast injection. Finally, modeling of AAA can be combined with finite element analysis to enable EVAR reharsal.

Soulez, G, Modeling of Abdominal Aortic Aneurysm before, during and after Endovascular Repair: Potential Impact on Patient Management.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14002198.html