Lucerne milestone approach for benchmarking and education: Towards ultra-low dose endovascular aortic repair

The aim of this single-center case series is to demonstrate that an ultra-low dose (ULD) can be routinely achieved in the hybrid operating room in standard endovascular aortic repair (EVAR) for infrarenal abdominal aortic aneurysm by adjusting the manufacturer's predefined imaging parameters, hardware configurations and user protocols (including benchmarking).

The hybrid operating room manufacturer predefined EVAR software setup of the dose exposure control software (OPTIQ, Siemens Healthineers, Forchheim, Germany) at our university medical center was screened for possible improvements regarding radiation dose application. Tests on a water-equivalent as well as polymethyl methacrylate phantom model to assess the impact of technical settings were performed, including comparison of settings for exposure control software, different magnification, collimation configurations and detector distance. All results were transferred into modified setups for the exposure control software and a new ULD procedure protocol for EVAR. Additionally, to standardize the clinical pathway, the Lucerne EVAR Milestone Approach (LEMA) was introduced including preoperative, perioperative, and postoperative milestones for technical procedure content and dose benchmarking during EVAR. A validation of the new settings including revised software setup, procedure protocol, and applicability of LEMA on a consecutive EVAR case series was conducted. Ten consecutive patients undergoing EVAR for low and medium complexity infrarenal abdominal aortic aneurysm were included. The primary outcome parameter was intraoperative dose area product (DAP, measured in Gy·cm²). Secondary outcomes were median fluoroscopy time (in minutes:seconds), cumulative air kerma (in mGy), clinical success, and occurrence of endoleaks.

New ULD settings compared with previous manufacturers standard settings of dose exposure control software reduced DAP for both fluoroscopy (0.0382 Gy·cm²/min vs 0.3 Gy·cm²/min) and angiography (2.36 Gy·cm²/min vs 2.48 Gy·cm²/min). Digital magnification and collimation decreased DAP. Application of the new ULD standard EVAR protocol resulted in a median DAP of 5.6 Gy·cm² (range, 3.54-12.1 Gy·cm²). Median fluoroscopy time was 16 minutes and 32 seconds. Type I endoleaks occurred in no patients (0%), type II in five patients (50%), and type III in no patients (0%). No patient had to undergo reintervention owing to endoleak or absence of diameter shrinkage during the first postoperative year.

Revision of the manufacturer-predefined EVAR setup by testing and ensuring optimal imaging parameters and hardware configurations in combination with LEMA enabled performance of ULD standard EVAR procedures routinely without compromising imaging quality.