Arjen Lindenholz

83 Comparison of 3T Intracranial Vessel Wall MRI Sequences 4 Introduction High-resolution intracranial vessel wall magnetic resonance imaging (MRI) plays an increasing role in diagnosing intracranial vascular diseases. 1,2 The main advantage of this imaging technique compared with lumen-based methods such as CT-angiography and digital subtraction angiography (DSA), is the visualization of the vessel wall itself, including the detection of vessel wall lesions that do not necessarily show or only subtle luminal narrowing. 3-7 Intracranial vessel wall imaging can be used for the detection and characterization of plaque burden in intracranial atherosclerotic disease, which is known to be one of the most important contributing factors of ischemic stroke and may be detected in an early stage. 8-10 It can also be helpful in the differentiation of other vascular diseases, such as vasculitis and reversible vasoconstriction syndrome, with, for instance, visualization of vessel wall enhancement. 11 Furthermore, intracranial vessel wall imaging may aid in the diagnosis of aneurysm rupture and intracranial dissection, though this is less supported in the literature. 12-14 Intracranial vessel wall MRI requires a high spatial resolution to visualize the thin vessel wall and potential accompanying vessel wall lesions. Currently, most 3D-acquired vessel wall sequences use a voxel size between 0.4 and 0.7 mm, though this is larger than the normal diameter of the intracranial vessel walls. 2,15 In addition, a high signal-to-noise-ratio (SNR) and contrast-to-noise-ratio (CNR) are required to delineate the vessel wall from surrounding tissue (i.e., blood, cerebrospinal fluid (CSF) and parenchyma). 1,2,16 At higher magnetic field strengths, a higher spatial resolution and/or SNR can be achieved. Therefore, vessel wall MR imaging is currently performed at 3T and higher field strengths. However, with high spatial resolution, the SNR is still limited and the total scan duration is long. Recently published intracranial vessel wall MRI sequences have scan durations ranging from 5.0 to 10.2 minutes. 16-22 To assess vessel wall lesions, one needs pre- and postcontrast acquisitions to evaluate contrast enhancement of the vessel walls. For a complete examination, other sequences, such as Time-of-Flight (TOF) MR angiography, Diffusion Weighted Imaging (DWI) and T 2 -Fluid-attenuated Inversion-Recovery (FLAIR) images may also be needed, resulting in a long total scan duration. With longer scan durations, motion artifacts may increase, especially in neurologically impaired patients. Ideally, total scan duration of the pre- and postcontrast vessel wall sequence should be reduced without sacrificing image quality. In this study, SNR and CNR of one earlier reported intracranial vessel wall sequence 23,24 was compared with 6 variations, which includes another previously reported sequence, 19 with different trade-offs between scan duration, resolution, and contrast. Subsequently, pre- and postcontrast images of the fastest vessel wall variant were compared with the current variant that is used in our daily clinical practice. 24