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Relationship between thrombus and aneurysm wall in partially thrombosed intracranial aneurysms visualized with 7T MPRAGE
Bixia Chen1,2, Taku Sato2,3, Oliver Gembruch1,2, Michael Forsting4, Alexander Radbruch4, Jan Rodemerk2, Shiqing He2, Stefan Maderwald1, Harald H. Quick1,5, Mark E. Ladd1,6, Ulrich Sure2, and Karsten H. Wrede1,2
1Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany, 2Department of Neurosurgery, University Hospital Essen, University Duisburg-Essen, Essen, Germany, 3Department of Neurosurgery, Fukushima Medical University, Fukushima, Japan, 4Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University Duisburg-Essen, Essen, Germany, 5High Field and Hybrid MR Imaging, University Hospital Essen, University Duisburg-Essen, Essen, Germany, 6Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

Synopsis

This in-vivo study aimed to investigate the relationship between thrombus characteristics and the aneurysm wall (AW) in partially thrombosed intracranial aneurysms (pTIAs) using MPRAGE at 7T MRI. The AWs with the highest signal intensity ratio of thrombus were significantly thicker. In the histopathological examinations, three cases with hypointensity of the thrombus showed only a few macrophages in the thrombus and a thin AW. Three cases with hyperintensity of the thrombus in the MPRAGE showed abundant macrophages in the thrombus. In 7T MPRAGE, the signal intensity ratio of thrombus in pTIAs correlates with AW thickness and histologic features indicating wall instability.

Introduction

Thrombosed intracranial aneurysms are often associated with increased aneurysm wall instability and present a challenge for treatment1. Recently, contrast enhancement in the aneurysm wall of thrombosed ICAs could be visualized in vivo using high-resolution gadolinium-enhanced 7 Tesla (T) magnetic resonance imaging (MRI)2. However, no studies have evaluated the relationship between the thrombus characteristics and the aneurysm wall. This in-vivo study aimed to investigate the relationship between thrombus characteristics and the aneurysm wall in partially thrombosed intracranial aneurysms using MPRAGE at 7T MRI3, 4.

Methods

Methods The study cohort included fifteen patients (7 males, 8 females) with sixteen partially thrombosed intracranial aneurysms. All subjects were evaluated utilizing a 7T whole-body MR system (MAGNETOM 7T, Siemens Healthcare GmbH, Erlangen, Germany) equipped with a 1/32-channel Tx/Rx head radiofrequency coil (Nova Medical, Wilmington, USA). The gradient system provides 40 mT/m maximum amplitude and a slew rate of 200 mT /m/ms. A modified MPRAGE sequence was obtained with the following sequence parameters: field of view = 270×236 mm2, matrix = 384×336, resolution = 0.7×0.7 mm 2, slice thickness = 0.7mm, repetition time (TR) = 2500 ms, echo time (TE) = 1.54 ms, flip angle = 7 degrees, bandwidth = 570 Hz/pixel, acquisition time = 6 min 13 sec. The signal intensity ratio in the thrombus was defined as the highest signal intensity in the thrombus divided by the signal intensity in the anterior corpus callosum. The signal intensity ratio in the thrombus was compare d to the thickness of the aneurysm wall at 7T MPRAGE. Histopathological findings in six tissue samples were correlated with 7T MRI to identify the microstructures.

Results

The mean signal intensity ratio of thrombus was 0.97 (standard error of the mean 0.14, range 0.27-2.28). The mean thickness of the aneurysm wall was 1.25 mm (standard error of the mean 0.08, range 0.84-1.55 mm). The signal intensity ratio of thrombus significantly correlated with the thickness of the aneurysm wall (p < 0.01) as shown in Figure 2. The aneurysm walls with the highest signal intensity ratio of thrombus were significantly thicker. In the histopathological examinations, three cases with hypointensity of the thrombus in MPRAGE showed only a few macrophages in the thrombus and a thin, degenerated aneurysmal wall (Figure 3). On the other hand, three cases with hyperintensity of the thrombus in the MPRAGE showed abundant macrophages in the thrombus (Figure 4).

Conclusions

In MPRAGE at 7T MRI, the signal intensity ratio of thrombus in partially thrombosed intracranial aneurysms correlates with aneurysm wall thickness and histologic features indicating wall instability.

Acknowledgements

No acknowledgement found.

References

1. Guresir E, Wispel C, Borger V, et al. Treatment of partially thrombosed intracranial aneurysms: Single-center series and systematic review. World Neurosurg . 2018;118:e834-41

2. Sato T, Matsushige T, Chen B, et al. Wall contrast enhancement of thrombosed intracranial aneurysms at 7t mri. AJNR Am J Neuroradiol. 2019;40:1106-11

3. Wrede KH, Johst S, Dammann P, et al. Caudal image contrast inversion in mprage at 7 tesla: Problem and solution. Acad Radiol. 2012;19:172-78

4. Umutlu L, Theysohn N, Maderwald S, et al. 7 tesla mprage imaging of the intracranial arterial vasculature: Nonenhanced versus contrast-enhanced. Acad Radiol. 2013;20:628-34

Figures

Figure 1: Delineation of thrombosed intracranial aneurysms at 7T MRI. Identical structures are marked in all subfigures as follows. White asterisks: intraluminal thrombus; black asterisks: aneurysm lumen; double daggers: brain parenchyma.

Figure 2: Correlation of signal intensity ratio of the thrombus with aneurysm wall thickness (p<0.01).

Figure 3: MPRAGE shows low signal intensity pattern of thrombus in aneurysm No. 6 (white asterisk (WA): intraluminal thrombus; double daggers: brain parenchyma). Green box indicates area of histopathological specimen (A). WA indicates intraluminal thrombus (B-E). Red blood cells in the thrombus (WA) and thin aneurysm wall (black asterisk) in HE staining (B). Loss of elastic fibers in aneurysm wall layer in Verhoeff-Van Gieson staining (black asterisk) (C). A few macrophages (WA) in the thrombus in CD68 (D). Limited iron deposition (WA) in the thrombus stained with Prussian blue (F).

Figure 4: MPRAGE shows high signal intensity pattern in Aneurysm No. 15 (white asterisk: intraluminal thrombus; double daggers: brain parenchyma). Green box indicates area of histopathological specimen (A). White asterisk (WA) indicates intraluminal thrombus (B-E). Abundant red blood cells in the thrombus (WA) in HE staining (B). Thick aneurysm wall layer in Verhoeff-Van Gieson staining (black asterisk) (C). Abundant macrophages (WA) in the thrombus in CD68 immunostaining (D). Limited iron deposition (WA) in the thrombus stained with Prussian blue (F).

Proc. Intl. Soc. Mag. Reson. Med. 28 (2020)
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