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