A Comparison of Accuracy of Image- versus Hardware-based Tracking Technologies in 3D Fusion in Aortic Endografting

OBJECTIVES: Fusion of three-dimensional (3D) computed tomography and intraoperative two-dimensional imaging in endovascular surgery relies on manual rigid co-registration of bony landmarks and tracking of hardware to provide a 3D overlay (hardware-based tracking, HWT). An alternative technique (image-based tracking, IMT) uses image recognition to register and place the fusion mask. We present preliminary experience with an agnostic fusion technology that uses IMT, with the aim of comparing the accuracy of overlay for this technology with HWT. METHOD: Data were collected prospectively for 12 patients. All devices were deployed using both IMT and HWT fusion assistance concurrently. Postoperative analysis of both systems was performed by three blinded expert observers, from selected time-points during the procedures, using the displacement of fusion rings, the overlay of vascular markings and the true ostia of renal arteries. The Mean overlay error and the deviation from mean error was derived using image analysis software. Comparison of the mean overlay error was made between IMT and HWT. The validity of the point-picking technique was assessed. RESULTS: IMT was successful in all of the first 12 cases, whereas technical learning curve challenges thwarted HWT in four cases. When independent operators assessed the degree of accuracy of the overlay, the median error for IMT was 3.9 mm (IQR 2.89-6.24, max 9.5) versus 8.64 mm (IQR 6.1-16.8, max 24.5) for HWT (p = .001). Variance per observer was 0.69 mm(2) and 95% limit of agreement ±1.63. CONCLUSION: In this preliminary study, the error of magnitude of displacement from the "true anatomy" during image overlay in IMT was less than for HWT. This confirms that ongoing manual re-registration, as recommended by the manufacturer, should be performed for HWT systems to maintain accuracy. The error in position of the fusion markers for IMT was consistent, thus may be considered predictable

Introduction of a Team Based Approach to Radiation Dose Reduction in the Enhancement of the Overall Radiation Safety Profile of FEVAR

OBJECTIVES: Fenestrated endovascular aneurysm repair (FEVAR) exposes operators and patients to considerable amounts of radiation. Introduction of fusion of three-dimensional (3D) computed tomography (CT) with intraoperative fluoroscopy puts new focus on advanced imaging techniques in the operating environment and has been found to reduce radiation and facilitate faster repair. The aim of this study is to evaluate the radiation dose effect of introducing a team-based approach to complex aortic repair. METHODS: Procedural details for a cohort of 21 patients undergoing FEVAR after fusion-guided (Modern Group) imaging was introduced are compared with 21 patients treated in the immediate 12 months prior to implementation (Historic Group) at a centre with expertise in FEVAR. Non-parametric tests were used to compare procedure time (PT), air kerma, dose-area product (DAP), fluoroscopy time (FT), estimated blood loss (EBL) and pre- and post-operative estimated glomerular filtration rate (eGFR) between the groups. RESULTS: Change in operative approach resulted in a significant reduction in PT for the Modern group (median 285 mins; interquartile range 268–322) compared with the Historic group (450 mins; IQR 360–540 p = <0.001). There were reductions in skin dose for the Modern group (1.6 Gy; IQR 1.09–2.1) compared with the Historic group (4.4 Gy; 3.2–7.05 p = <0.001), and DAP (Modern 159 Gy.cm2; IQR 123–226 vs 264.93 Gy.cm2; 173.3–366.8 for Historic (p = 0.006). There were no significant differences in FT, and pre- and post-operative eGFR between the two groups. Weight and height were distributed equally across both groups. Structured dose reports including the changes in frame rate were not available for analysis. CONCLUSIONS: Implementation of a team-based approach to radiation reduction significantly reduces radiation dose. These findings suggest that the radiation safety awareness that accompanies the introduction of fusion imaging may improve the overall radiation safety profile of FEVAR for patients and providers

Women undergoing endovascular thoracoabdominal aortic aneurysm repair differ significantly from their male counterparts preoperatively and postoperatively

OBJECTIVE: A rational approach to the management of aortic aneurysm disease relies on weighing the risk of aneurysm rupture against the complications and durability of operative repair. In men, seminal studies of infrarenal aortic aneurysm disease and its endovascular management can provide a reasoned argument for the timing and modality of surgery, which is then extrapolated to the management of thoracoabdominal aortic aneurysms (TAAAs). In contrast, there is less appreciation for the natural history of TAAA disease in women and its response to therapy. METHODS: We used a retrospective cohort design of women, all men, and matched men, fit for complex endovascular thoracoabdominal aneurysm repair at two large aortic centers. We controlled for preoperative anatomic and comorbidity differences, and assessed technical success, postoperative renal dysfunction, spinal ischemia, and early mortality. Women and matched men were reassessed at follow-up for long-term durability and survival. RESULTS: Assessing women and all men undergoing complex endovascular aortic reconstruction, we demonstrate that these groups are dissimilar before the intervention with respect to comorbidities, aneurysm extent, and aneurysm size; women have a higher proportion of proximal Crawford extent 1, 2, and 3 aneurysms. Matching men and women for demographic and anatomic differences, we find persistent elevated perioperative mortality in women (16%) undergoing endovascular thoracoabdominal aneurysm repair compared with matched men (6%); however, at the 3-year follow-up, both groups have the same survival. Furthermore, women demonstrate more favorable anatomic responses to aneurysm exclusion, with good durability and greater aneurysm sac regression at follow-up, compared with matched men. CONCLUSIONS: Women and unmatched men with TAAA disease differ preoperatively with respect to aneurysm extent and comorbidities. Controlling for these differences, after complex endovascular aneurysm repair, there is increased early mortality in women compared with matched men. These observations argue for a careful risk stratification of women undergoing endovascular thoracoabdominal aneurysm treatment, balanced with women's good long-term survival and durability of endovascular aneurysm repair

Accuracy of implementing principles of fusion imaging in the follow up and surveillance of complex aneurysm repair

Fusion imaging is standard for the endovascular treatment of complex aortic aneurysms, but its role in follow up has not been explored. A critical issue is renal function deterioration over time. Renal volume has been used as a marker of renal impairment; however, it is not reproducible and remains a complex and resource-intensive procedure. The aim of this study is to determine the accuracy of a fusion-based software to automatically calculate the renal volume changes during follow up. In this study, computerized tomography (CT) scans of 16 patients who underwent complex aortic endovascular repair were analysed. Preoperative, 1-month and 1-year follow-up CT scans have been analysed using a conventional approach of semi-automatic segmentation, and a second approach with automatic segmentation. For each kidney and at each time point the percentage of change in renal volume was calculated using both techniques. After review, volume assessment was feasible for all CT scans. For the left kidney, the intraclass correlation coefficient (ICC) was 0.794 and 0.877 at 1 month and 1 year, respectively. For the right side, the ICC was 0.817 at 1 month and 0.966 at 1 year. The automated technique reliably detected a decrease in renal volume for the eight patients with occluded renal arteries during follow up. This is the first report of a fusion-based algorithm to detect changes in renal volume during postoperative surveillance using an automated process. Using this technique, the standardized assessment of renal volume could be implemented with greater ease and reproducibility and serve as a warning of potential renal impairment

A systematic review of the use of an expertise-based randomised controlled trial design

Acknowledgements JAC held a Medical Research Council UK methodology (G1002292) fellowship, which supported this research. The Health Services Research Unit, Institute of Applied Health Sciences (University of Aberdeen), is core-funded by the Chief Scientist Office of the Scottish Government Health and Social Care Directorates. Views express are those of the authors and do not necessarily reflect the views of the funders.Peer reviewedPublisher PD

Editor's Choice – European Society for Vascular Surgery (ESVS) 2023 Clinical Practice Guidelines on Radiation Safety

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