Original Article
MRI quantitative T2* mapping on thrombus to predict recanalization after endovascular treatment for acute anterior ischemic stroke

https://doi.org/10.1016/j.neurad.2017.03.006Get rights and content

Abstract

Background

In anterior acute ischemic stroke (AAIS) treated with endovascular treatment (EVT), the susceptibility vessel sign (SVS+ or SVS−) is related to recanalization results (TICI 2b/3) and clinical outcome. However, a binary qualitative assessment of thrombus using SVS does not reflect its complex composition. Our aim was to assess whether a quantitative MRI marker, Thrombus-T2* relaxation time, may be assessable in clinical routine and may to predict early successful recanalization after EVT, defined as a TICI 2b/3 recanalization obtained in 2 attempts or less.

Material and methods

Thrombus-T2* relaxation time was prospectively obtained from consecutive AAIS patients treated by EVT (concomitant aspiration and stent retriever). Quantitative values were compared between early recanalization and late or unsuccessful recanalization.

Results

Thirty patients with AAIS were included and Thrombus-T2* relaxation time was obtained in all patients. Earlier TICI 2b/3 recanalization were obtained in 22 patients (73%) and was significantly associated with SVS+ (1/8 vs. 16/22, P = 0.01) and a shorter Thombus-T2* relaxation time (mean SD, range: 257, 18–50 ms vs. 45 9, 35–60 ms, P < 0.001).

Conclusion

A new quantitative MRI biomarker, the Thrombus-T2* relaxation time is assessable in clinical routine. In a preliminary study of 30 patients, a shorter Thombus-T2* relaxation time is related to earlier recanalization after EVT using combination of stent retriever and aspiration.

Introduction

Large randomized control trials have shown benefits of endovascular thrombectomy (EVT) associated with IV tPa compared to IV tPa alone in acute anterior ischemic stroke (AAIS) [1]. Nevertheless, EVT fails to reopen the occluded artery in almost 30% of cases [1]. Thrombus composition may be a key factor to address in order to decrease the recanalization failure rate [2], [3], [4], [5].

The susceptibility vessel sign (SVS) on MRI GRE sequence is related to the thrombus composition and appears in red blood cell predominant thrombi [6], [7]. Retrospective and monocentric studies have shown that the qualitative evaluation of the SVS could help predict recanalization and functional outcome after EVT [8], [9], [10], [11], [12]. However, this binary assessment of thrombus composition (either SVS+ or SVS−) may not reflect the more complex nature of thrombi [2], [13], [14]. Moreover, SVS+ defined as the presence of a hypo-intense signal exceeding the diameter of the artery in GRE sequence can be difficult to determine in clinical practice, since some thrombi may show a hypo-intense signal with a diameter equal or slightly above the contralateral artery contours [6].

T2* maps are commonly used to assess the cardiac and liver iron load in thalassemic patients [15], [16]. Measuring Thrombus-T2* value might provide more quantitative insight into thrombus composition than simple qualitative evaluation using SVS. In AAIS, it has been shown that after two EVT attempts using stent retrievers, the likelihood of successful recanalization [17], [18] and favorable outcome [18], [19], [20] significantly decreases.

Our aim was to assess whether measurement of Thrombus-T2* RT within the thrombus may help predict early (in 2 or less attempts) TICI 2b/3 recanalization.

Section snippets

Materials and methods

A single-center, retrospective, analysis of consecutive patients was performed according to the protocol of stroke treatment at our center. In accordance with the French legislation, Institutional or Ethics Committee approval was not required for this study because it only utilized anonymized data collected as part of routine clinical care.

Baseline characteristics

Thirty-five consecutive patients were admitted between June 2015 and June 2016 for AAIS that underwent an MRI with Thrombus-T2* RT measurement before EVT. Five patients were excluded because of failure to reach optimal positioning in the intracranial vasculature with the intermediate aspiration catheter (or into the cervical carotid artery with the guiding catheter). Excluded patients did not differ from the study population according to baseline demographic criteria (data not shown).

Thirty

Discussion

Our work shows that in AAIS patients with MRI as the initial imaging workup, a quantitative biomarker of thrombus composition (Thrombus-T2* RT) is accessible in clinical routine. In addition, Thrombus-T2* RT measurements help to identify patients with early recanalization from those with late or unsuccessful recanalization after EVT.

Since the thrombus is the primary target of current stroke treatments, understanding its composition is essential in determining the most effective strategy [2],

Conclusion

Our study demonstrates that the Thrombus-T2* RT is a simple, quantitative biomarker that is related to the number of attempts to reach successful recanalization after EVT. Larger studies are required to confirm these results in order to use this biomarker as a tool to adapt EVT strategy to the thrombus composition in AAIS.

Author's contributions

BR has imagined the study, interpreted the pictures, analysed the data and written the manuscript.

BN has interpreted the pictures, analysed the data and written the manuscript.

CV has analysed the data and made a critical review of the manuscript.

DDB has analysed the data and made a critical review of the manuscript.

GDB has performed the statistical analysis and made a critical review of the manuscript.

DH has interpreted the pictures and made a critical review of the manuscript.

NO has analysed

Disclosure of interest

The authors declare that they have no competing interest.

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    1

    Olivier Naggara and Jean Michel Serfaty have equally contributed to this work.

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