Features of Aneurysm Walls and Intraluminal Thrombus on MR Imaging That Are Associated with Sac Shrinkage After Endovascular Aortic Repair

Q: What are the key findings of this study?

Absence of endoleaks on 6-month MRI was associated with greater 12-month aneurysmal sac shrinkage compared with endoleak presence.

Q: What is the clinical evidence from this study?

Study design: Observational. Population: Abdominal aortic aneurysm or common iliac artery aneurysm treated with endovascular aneurysm repair (EVAR) (n=49). Intervention: Absence of endoleak (Non-EL) and favorable MRI sac features (Clear-EL, homogeneous or concentric intra-aneurysmal thrombus, increased wall enhancement/thickness) vs. Presence of endoleak (EL) and unfavorable MRI features (Unclear-EL, heterogeneous or non-concentric intra-aneurysmal thrombus). Primary outcome: Aneurysmal sac volume change ratio (VCR) at approximately 12 months after EVAR (p=<0.001).

Q: What does this research mean for the field?

The absence of endoleaks detected on 6-month post-EVAR MRI is significantly associated with greater 12-month aneurysmal sac shrinkage compared to the presence of endoleaks. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

To investigate the relationships among endoleak morphology, intra-aneurysmal thrombus signal organization, aneurysmal wall enhancement, aneurysmal wall thickness, and aneurysmal sac volume change ratio after endovascular aneurysm repair using MRI.

Teppei Nakagomi; Takahiko Mine; Tetsuro Sekine; Masashi Abe; Daisuke Yasui; Seigoh Happoh; Shimpei Ikeda; So Ueshima; Takahiro Tomoda; Yasuhiro Kawase; Masahiro Fujii; Ryo Fukumoto; Kouta Yamada; Hiromitsu Hayashi; Shin‐ichiro Kumita

doi:10.2463/mrms.mp.2026-0059

January 1, 2026Magnetic Resonance in Medical SciencesOpen Access

Features of Aneurysm Walls and Intraluminal Thrombus on MR Imaging That Are Associated with Sac Shrinkage After Endovascular Aortic Repair

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Key result

Absence of endoleaks on 6-month MRI linked to greater 12-month aneurysm sac shrinkage after EVAR.

P<0.001
n=49

Why the study?

Delayed aneurysmal rupture caused by persistent endoleaks remains a major cause of long-term mortality after EVAR, but the prognostic MRI features of endoleaks, intra-aneurysmal thrombus, and the aneurysmal wall are not fully understood.

Do MRI features of endoleak morphology, intra-aneurysmal thrombus organization, and aneurysmal wall enhancement and thickness predict aneurysmal sac volume change ratio at 1 year in patients undergoing endovascular aortic repair?

Key Points

To investigate the relationships among endoleak morphology, intra-aneurysmal thrombus signal organization, aneurysmal wall enhancement, aneurysmal wall thickness, and aneurysmal sac volume change ratio after endovascular aneurysm repair using MRI.
Enrolled patients who underwent gadolinium-enhanced MRI between April 2019 and January 2026 for pre- and post-EVAR surveys of abdominal aortic aneurysms, common iliac artery aneurysms, or both, with follow-up MRI performed at approximately 6 months post-EVAR.
Used a 3T scanner to evaluate T2-weighted imaging, T1-weighted black-blood imaging, and Gd-enhanced fast time-of-flight spoiled gradient recalled echo sequences, categorizing endoleak morphology (Clear-EL vs. Unclear-EL) and thrombus signal patterns (Concentric-IAT vs. Non-concentric-IAT).
Calculated the aneurysmal sac volume change ratio using CT volumetry on a 3D workstation comparing early post-EVAR images to 1-year follow-up scans, and stratified patients by post-to-pre ratios of wall enhancement and thickness using a 110% cutoff.
Image analysis categorized intra-aneurysmal thrombi into homogeneous (methemoglobin or hemosiderin patterns) and heterogeneous types (subdivided into concentric patterns including onion layer and gradation, versus non-concentric patterns including multi-cracking, random, and mixed).
Patients were classified into wall enhancement (post-to-pre ratio ≥110%) and non-enhancement groups, as well as wall thickness (post-to-pre ratio ≥110%) and non-thickness groups, to analyze their correlations with sac volume change ratio and baseline aneurysm diameter.

Study Design

Type

Observational (n=49)

Multicenter

No

Structured PICO

Do MRI features of endoleak morphology, intra-aneurysmal thrombus organization, and aneurysmal wall enhancement and thickness predict aneurysmal sac volume change ratio at 1 year in patients undergoing endovascular aortic repair?

P

Population

49 older adults (median age 79 years, 18.4% female) undergoing EVAR for abdominal aortic or common iliac artery aneurysms with pre- and 6-month post-EVAR gadolinium-enhanced MRI, followed for approximately 12 months with CT volumetry.

E

Exposure

Gadolinium-enhanced MRI (0.1 mmol/kg body weight injected at 0.1–0.2 mL/s) and non-contrast 3T MRI sequences (T2WI with SSFSE, T1WI with black-blood, and Gd-enhanced Fast TOF SPGR) performed before and at a median of 6.2 (6.0–6.9) months after endovascular aneurysm repair (EVAR) to evaluate endoleak (EL) morphology, intra-aneurysmal thrombus (IAT) signal organization, aneurysmal wall enhancement (AWE), and aneurysmal wall thickness (AWT).

O

Outcome

Aneurysmal sac volume change ratio (VCR) calculated using CT volumetry comparing datasets from the early phase after EVAR and at approximately 12 months (median 12.3 [11.8–14.0] months).surrogate

Main Result

Absolute Event Rate: 89.8% vs 105.9%

p-value: p=<0.001

Limitations

Retrospective, single-center study with a relatively small sample size (n = 49), limiting statistical power and generalizability
Very small sample size in the Clear-EL subgroup (n = 5), where the difference vs Unclear-EL did not reach statistical significance after Bonferroni correction (P = 0.055)
Intra-aneurysmal thrombus characterization was based solely on MRI findings without histopathological confirmation
MRI parameters were obtained from a single post-EVAR examination at ~6 months rather than serial MRI studies
Some aneurysms demonstrated continued sac enlargement despite the absence of non-concentric thrombus patterns, indicating unmeasured confounding factors
Observations should be interpreted as hypothesis-generating

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Implication

Comprehensive post-EVAR MRI assessment of endoleak boundary clarity, intraluminal thrombus signal organization, and aneurysmal wall enhancement and thickness identifies key imaging biomarkers associated with aneurysmal sac shrinkage at 1 year.

Abstract

Purpose: Delayed aneurysmal rupture caused by persistent endoleaks (ELs) remains a major cause of long-term mortality, but the prognostic features of ELs are not fully understood. This study investigated the relationships among EL morphology, intra-aneurysmal thrombus (IAT) signal organization, aneurysmal wall enhancement (AWE), aneurysmal wall thickness (AWT), and aneurysmal sac volume change ratio (VCR) after endovascular aneurysm repair (EVAR) using MRI.

Discussion

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Cite This Study

Nakagomi et al. (2026) conducted an observational in Abdominal aortic aneurysm or common iliac artery aneurysm treated with endovascular aneurysm repair (EVAR) (n=49). Absence of endoleak (Non-EL) and favorable MRI sac features (Clear-EL, homogeneous or concentric intra-aneurysmal thrombus, increased wall enhancement/thickness) vs. Presence of endoleak (EL) and unfavorable MRI features (Unclear-EL, heterogeneous or non-concentric intra-aneurysmal thrombus) was evaluated on Aneurysmal sac volume change ratio (VCR) at approximately 12 months after EVAR (p=<0.001). Absence of endoleaks on 6-month MRI was associated with greater 12-month aneurysmal sac shrinkage compared with endoleak presence.

synapsesocial.com/papers/6af5cd26a40bbe8669e89b94 https://doi.org/10.2463/mrms.mp.2026-0059

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Features of Aneurysm Walls and Intraluminal Thrombus on MR Imaging That Are Associated with Sac Shrinkage After Endovascular Aortic Repair

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

Features of Aneurysm Walls and Intraluminal Thrombus on MR Imaging That Are Associated with Sac Shrinkage After Endovascular Aortic Repair

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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