Surveillance Imaging following Endovascular Aneurysm Repair: State of the Art

Effectiveness of single-energy metal artifact reduction algorithm in CT: application to contrast-enhanced CT with EVAR and coil embolization

This study aimed to evaluate the efficacy of the single-energy metal artifact reduction (SEMAR) algorithm in reducing metal artifacts and enhancing image quality in contrast-enhanced computed tomography (CT) for patients undergoing endovascular aneurysm repair (EVAR) with coil embolization. Thirty-eight patients (mean age 81.0 ± 6 years; 31 men, 7 women) who underwent contrast-enhanced CT following EVAR and internal iliac artery coil embolization between September 2022 and May 2023 were retrospectively analyzed. The Artifact Index (AI) quantified metallic artifacts from internal iliac artery aneurysm coils in CT images, calculated from the standard deviation of the artifact-containing region relative to a reference region. CT values of the external iliac artery at the same slice were also evaluated and compared. Two radiologists independently performed qualitative assessments of SEMAR and non-SEMAR images. SEMAR significantly reduced metal artifacts, decreasing the AI from 171.9 ± 74.5 HU to 35.8 ± 16.9 HU (p < 0.001). The mean CT values of the external iliac artery were similar for SEMAR (259.4 ± 63.7 HU) and non-SEMAR (257.1 ± 63.6 HU, indicating no significant difference. Qualitative assessment scores improved significantly with SEMAR (from 1.0 ± 0.0 to 2.5 ± 0.5; p < 0.001), enhancing visualization of internal iliac artery aneurysms. Interobserver agreement was high (κ = 0.83). The SEMAR algorithm effectively reduces metal artifacts in contrast-enhanced CT, significantly enhancing image quality without altering adjacent artery CT values. These improvements enhance the image quality of post-operative assessments in patients undergoing EVAR with coil embolization.

Utility of 4D CT in endoleak characterization after advanced endovascular aortic repair

OBJECTIVES

To assess the performance of dynamic or 4D CT in characterizing endoleaks in advanced endovascular aortic repair (branched and fenestrated) when other modalities fail to fully characterize the leak, most often conventional CTA.

METHODS

Retrospective review of 13 patients from 2008 to 2021 who underwent 16 4D CTs to characterize endoleaks in branched and fenestrated endovascular aortic repair (FB-EVAR). The 4D CTs were performed covering up to 16 cm of the z-axis, with anywhere between 10 and 40 iterations performed every 2 s. These settings were adjusted depending on graft characteristics and type of endoleak suspected. The scans were assessed for their ability to detect the endoleak (sensitivity), and further to characterize the endoleak by type and subtype (specificity).

RESULTS

Overall sensitivity in 16 scans for endoleak detection was 100%. There was a specificity of 87.5% for determining the type of endoleak (14/16). These results included two studies that were inconclusive and repeated due to technical difficulties. In patients where a specific subtype was not established, the leak was localized to the appropriate target vessel. Average dose for the 4D CT was 4724 mGy*cm (1108-11069), with the outlining higher dose scans secondary to higher iterations in those scans.

CONCLUSIONS

4D CT is a useful adjunctive tool in FB-EVAR surveillance with excellent sensitivity and specificity in characterizing endoleaks. This allows for accurate localization of leaks, which is critical for management planning.

Occult endoleaks revealed during open conversions after endovascular aortic aneurysm repair in a multicenter experience

BACKGROUND

An occult endoleak (OE) may be the underlying cause of aneurysm sac expansion after endovascular aneurysm repair (EVAR). The aim of this study is to describe intraoperative findings of OE during surgical endograft explantations.

METHODS

This is a retrospective, multicenter analysis of all open conversions (OC) after EVAR from 1997 to 2020 in 12 vascular centers. We excluded patients with a preoperative diagnosis of endograft infection, endograft thrombosis, and thoracic-EVAR. An OE was defined as an endoleak revealed during OC not shown on preoperative imaging, which was likely the real cause for sac enlargement. We reported the number of OE, and we described the type of OE in relation to the initial alleged or associated endoleak. A separate analysis of patients with an initial diagnosis of endotension was also performed.

RESULTS

An OE was found in 32/255 patients (12.5%). In the 78.1% of the cases (25/32) a type II endoleak hid a type I or III endoleak. Endotension was the initial diagnosis of 26/255 patients (10.2%). In 4/26 cases (15.4%), a type I or II OE was revealed. In 5/26 cases (19.2%) an endograft infection was found intraoperatively. In 2/26 cases we found an angiosarcoma. Fifteen cases of endotension (57.7%) remained unexplained.

CONCLUSIONS

OE represent a not negligible cause of EVAR failure. A type II endoleak associated with sac enlargement may actually conceal a higher-flow endoleak. In most of the cases, the initial diagnosis of endotension remains unexplained. However, endotension sometimes conceals severe underlying pathologies such as infections.

Contrast-enhanced US Evaluation of Endoleaks after Endovascular Stent Repair of Abdominal Aortic Aneurysm

Ruptured abdominal aortic aneurysm (AAA) carries high morbidity and mortality. Elective repair of AAA with endovascular stent-grafts requires lifetime imaging surveillance for potential complications, most commonly endoleaks. Because endoleaks result in antegrade or retrograde systemic arterialized flow into the excluded aneurysm sac, patients are at risk for recurrent aneurysm sac growth with the potential to rupture. Multiphasic CT has been the main imaging modality for surveillance and symptom evaluation, but contrast-enhanced US (CEUS) offers a useful alternative that avoids radiation and iodinated contrast material. CEUS is at least equivalent to CT for detecting endoleak and may be more sensitive. The authors provide a general protocol and technical considerations needed to perform CEUS of the abdominal aorta after endovascular stent repair. When there are no complications, the stent-graft lumen has homogeneous enhancement, and no contrast material is present in the aneurysm sac outside the stented lumen. In patients with an antegrade endoleak, contrast material is seen simultaneously in the aneurysm sac and stent-graft lumen, while delayed enhancement in the sac is due to retrograde leak. Recognition of artifacts and other potential pitfalls for CEUS studies is important for examination performance and interpretation. Online supplemental material is available for this article. ^©RSNA, 2022.

AAA Revisited: A Comprehensive Review of Risk Factors, Management, and Hallmarks of Pathogenesis

Despite declining incidence and mortality rates in many countries, the abdominal aortic aneurysm (AAA) continues to represent a life-threatening cardiovascular condition with an overall prevalence of about 2-3% in the industrialized world. While the risk of AAA development is considerably higher for men of advanced age with a history of smoking, screening programs serve to detect the often asymptomatic condition and prevent aortic rupture with an associated death rate of up to 80%. This review summarizes the current knowledge on identified risk factors, the multifactorial process of pathogenesis, as well as the latest advances in medical treatment and surgical repair to provide a perspective for AAA management.