Susceptibility-weighted imaging of the brain: Does gadolinium administration matter?

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Abstract

Objective

Susceptibility-weighted MR imaging (SWI) is usually obtained without administration of intravenous gadolinium (Gd). However, it is occasionally necessary to perform SWI after Gd is injected. The effects of Gd on SWI have not been systematically examined. The aim of this prospective study was to investigate whether performing SWI after Gd would influence the diagnostic image quality, parenchymal signal and vascular enhancement. An additional aim is to suggest potential future applications for Gd-enhanced SWI.

Methods

SWI was performed in 31 subjects before and after Gd administration. 17 cases were examined in a 1.5 T scanner and the remaining 14 were scanned at 3 T. The pre- and post-Gd images were analysed for signal changes in the cerebral grey matter (GM), white matter (WM) as well as for enhancement in the superficial and deep venous system. The visibility of the veins was graded on subtraction maps.

Results

The Gd-enhanced images showed no image quality degradation and no significant signal intensity change in the GM and WM as compared to the pre-Gd images (p > 0.05). After Gd-administration significant enhancement of the venous sinuses was noticed (p < 0.005), while the deep and cortical veins were poorly enhanced as confirmed by the calculated subtraction maps. The results showed no significant difference at variable MRI field strengths.

Conclusion

It is possible to perform SWI after Gd injection without information loss or signal change in the parenchyma. The most significant difference is the enhancement of the cerebral venous sinuses. Potential future applications are discussed.

Introduction

Susceptibility-weighted imaging (SWI) has been introduced to the clinical arena in the beginning of this decade [1], [2]. This technique exploits the susceptibility differences between the tissues. It is thus extremely sensitive for parenchymal bleeds and calcifications, which are depicted as areas of signal loss. SWI can illuminate small vessels and veins in the brain, an advantage utilized for venous thrombosis, arteriovenous malformations and stroke. The two types of images most commonly used in clinical practice are the SWI and the reconstructed mini-IP (minimum intensity projection) images. Numerous excellent reviews of this technique and its clinical applications have been recently published [3], [4], [5]. SWI is traditionally performed without intravenous Gadolinium (Gd). In the daily clinical routine a radiologist might face a situation, when she/he decides to obtain SWI images after Gd has been already injected. However, it may be argued that the paramagnetic contrast medium could negatively influence SWI data, e.g. due to T2 shortening and additional signal loss.

The aim of this study is to clarify whether SWI after Gd-administration would degrade or significantly alter the image information regarding the: (1) signal change in the cerebral grey and white matter and the (2) enhancement of intracranial veins. (3) An additional aim is to suggest potential future applications for Gd-enhanced SWI.

Section snippets

Materials and methods

From January to June 2010, 31 adult subjects were prospectively studied; 17 were scanned in a single 1.5-T MRI (Magnetom Avanto, Siemens, Erlangen, Germany) and 14 individuals in a single 3-T scanner (Magnetom Verio, Siemens, Erlangen, Germany) equipped with a 12-channel head coil. The included subjects were scanned for clinical indications according to the routine guidelines in our institution. In all subjects, Gd-administration was clinically indicated. SWI was performed before and after

Results

Proper quality SWI images were obtained in all 31 studied subjects (13 females, 18 males) aged between 21 and 83 (mean 54, median 60).

Discussion

Susceptibility weighted imaging is a rather new MRI technique currently implemented on clinical MRI scanners. It is a fully velocity compensated, long echo, RF spoiled, high-resolution, 3D gradient echo (GRE) sequence. SWI takes advantage of the susceptibility differences between tissues, leading to phase differences (phase) and cause a signal loss (magnitude). SWI is more sensitive than conventional T2*-GRE technique for detection of parenchymal microbleeds, traumatic shearing injuries, small

Conclusions

SWI can be performed after Gd has been injected. The combination of pre- and post-Gd SWI images has several potential future clinical and radiological applications.

Acknowledgement

We thank Martin Zbinden, Support Center for Advanced Imaging (SCAN), Institute of Diagnostic and Interventional Neuroradiology, University Bern for statistical advice.

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1

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