Insufficient slow-flow suppression mimicking aneurysm wall enhancement in magnetic resonance vessel wall imaging: a phantom study

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>MR vessel wall imaging (VWI) is increasingly performed in clinical settings to support treatment decision-making regarding intracranial aneurysms. Aneurysm wall enhancement after contrast agent injection is expected to be related to aneurysm instability and rupture status. However, the authors hypothesize that slow-flow artifacts mimic aneurysm wall enhancement. Therefore, in this phantom study they assess the effect of slow flow on wall-like enhancement by using different MR VWI techniques.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>The authors developed an MR-compatible aneurysm phantom model, which was connected to a pump to enable pulsatile inflow conditions. For VWI, 3D turbo spin echo sequences—both with and without motion-sensitized driven equilibrium (MSDE) and delay alternating with nutation for tailored excitation (DANTE) preparation pulses—were performed using a 3-T MR scanner. VWI was acquired both before and after Gd contrast agent administration by using two different pulsatile inflow conditions (2.5 ml/sec peak flow at 77 and 48 beats per minute). The intraluminal signal intensity along the aneurysm wall was analyzed to assess the performance of slow-flow suppression.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>The authors observed wall-like enhancement after contrast agent injection, especially in low pump rate settings. Preparation pulses, in particular the DANTE technique, improved the performance of slow-flow suppression.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>Near-wall slow flow mimics wall enhancement in VWI protocols. Therefore, VWI should be carefully interpreted. Preparation pulses improve slow-flow suppression, and therefore the authors encourage further development and clinical implementation of these techniques.</jats:p></jats:sec>

High-Resolution Vessel Wall Magnetic Resonance Imaging of Small Unruptured Intracranial Aneurysms

“…The low positive predictive value of AWE and aneurysm instability may be partially explained by the insufficient slow-flow suppression by the currently available HR VW-MRI sequences. A phantom-based study by Cornelissen et al showed that slow flow along the aneurysm wall mimics AWE [ 39 ]. Thus, caution must be taken when interpreting HR VW-MRI studies.…”

Multimodal validation of focal enhancement in intracranial aneurysms as a surrogate marker for aneurysm instability

“…Cornelissen et al assumed that wall enhancement is not causally linked with inflammatory processes but rather attributable to method-inherent failure of blood signal suppression in low-flow conditions [ 40 , 41 ]. The results of our study suggest that inflammatory changes probably add to the extent of wall enhancement, and that even without convincing proof of a causal link, wall enhancement indicates the presence of a hemodynamic environment promoting inflammatory and degenerative processes and might therefore still serve as a surrogate marker for aneurysm wall instability.…”

Comprehensive review of imaging of intracranial aneurysms and angiographically negative subarachnoid hemorrhage

“…38 Advanced MRA techniques and vessel wall imaging have theoretical roles in aneurysm risk assessment, but they remain investigational. 17,25 Imaging is important in determining which therapeutic options are optimal for individual aneurysms. Although DSA remains the gold standard for imaging UIAs, CTA and MRA are more often being used to make surgical decisions without DSA due to their greater availability and noninvasiveness.…”