Susceptibility-weighted Angiography Research Articles

Management of carotid stenosis in women: Consensus document

The Neuro Image by Scully et al.1 attempted to show that the new T2* susceptibility-weighted angiography (SWAN) MRI is more sensitive to show microbleeds not visualized on T2*-GRE. SWAN MRI may not be a familiar term to all neurologists. ESI techniques have recently gained popularity for being more sensitive in showing paramagnetic tissues compared with the standard T2*-GRE. This was initially commercialized as susceptibility-weighted imaging (SWI) by Siemens (Malvern, PA) MRI. SWI uses additional phase information to increase the sensitivity.2 We previously reported evidence for higher sensitivity of SWI over GRE.3 Since then, it is gradually replacing T2*-GRE in clinical imaging, especially in settings where Siemens MRI is used. Due to licensing and patent issues, different MRI vendors are often forced to slightly modify a sequence technique to avoid infringement. To provide an equivalent ESI technique, General Electric (Milwaukee, WI) modified the T2*-GRE by multiecho acquisition and postprocessing reconstruction as weighted average in its MRI and called it SWAN. Similarly, Philips (Andover, MA) MRI uses a different postprocessing technique called phase difference enhanced imaging (PADRE) to combine the phase information. The different ESI are probably superior to T2*-GRE. It would be interesting to compare ESI techniques from different vendors, comparing apples to apples.

Susceptibility-weighted angiography for the detection of high-flow intracranial vascular lesions: preliminary study

Susceptibility-weighted magnetic resonance imaging (MRI) sequences may demonstrate various signal intensities of draining veins in cases of high-flow vascular malformation (HFVM), including arteriovenous malformation (AVM) and dural arteriovenous fistula (dAVF). Our objective was to evaluate susceptibility-weighted angiography (SWAN) for the detection of HFVM. Fifty-eight consecutive patients with a suspected intracranial vascular malformation were explored with SWAN and post-contrast MRI sequences at 3 T. The diagnosis of slow-flow vascular malformation (SFVM), including developmental venous anomaly (DVA) or brain capillary telangiectasia (BCT), was based on MRI. Patients with suspected HFVM underwent digital subtraction angiography (DSA). SWAN images were analysed by three blinded readers according to a three-point scale of the venous signal. Thirty-one patients presented 35 SFVM (26 DVA and 9 BCT) that systematically appeared hypointense on SWAN images. In patients with atypical MRI findings, DSA revealed one patient with an atypical DVA and 26 patients with HFVM (22 AVM and 4 dAVF). SWAN revealed at least one venous hyperintensity in all patients with HFVM. Agreement between readers was excellent. SWAN appears reliable for characterising blood flow dynamics in brain veins. In clinical practice, SWAN can routinely rule out HFVM in patients with atypical brain veins.

SWAN MRI revealing multiple microhemorrhages secondary to septic emboli from mucormycosis

A 77-year-old man with myelodysplastic syndrome presented with fever and acute renal failure, followed by right-sided hemiparesis, neglect, and aphasia. Neuroimaging revealed a left parietal-occipital ICH with extensive edema. T2-star susceptibility weighted angiography (SWAN) revealed multiple

Iron deposition of the deep grey matter in patients with multiple sclerosis and neuromyelitis optica: A control quantitative study by 3D-enhanced susceptibility-weighted angiography (ESWAN)

Previous studies have detected abnormal iron deposition in the deep grey matter (DGM) of multiple sclerosis (MS). The regional specificity of the DGM iron deposition in neuromyelitis optica (NMO) is still unclear. We compared the differences in the DGM iron concentration between MS and NMO patients. We enrolled 42 relapsing-remitting MS (RRMS) patients, 42 NMO patients and 42 healthy controls undergoing brain conventional MRI and three-dimensional (3D)-enhanced T(2)*-weighted angiography (ESWAN) sequences. We obtained the mean phase values (MPVs) for ESWAN-filtered phase images. An analysis of covariance (ANCOVA) was used to compare MPVs among three groups. The correlations of MPVs changes with disease duration and expanded disability status scale (EDSS) were analyzed. The RRMS patients had higher DGM iron concentration than did the NMO and control groups, but only the bilateral substantia nigra (SN) showed a significant statistical difference among three groups (p<0.05). In the RRMS group, the iron concentration in the bilateral head of the caudate nucleus (HCN) (left: p<0.0001; right: p=0.0134) and the dentate nucleus (DN) (p<0.05 for both) were correlated with disease duration. In the NMO group, no correlation was found between the DGM iron concentration and disease duration (p>0.05). Furthermore, no correlations were found between the DGM iron concentration and EDSS (p>0.05). We confirm the iron concentration in the DGM iron content of MS patients is more than NMO patients and healthy controls in the same age range. Furthermore, the disease duration was found to be a significant contributor to patients with MS.

Clinical Value of 3D T2*-weighted Imaging with Multi-echo Acquisition: Comparison with Conventional 2D T2*-weighted Imaging and 3D Phase-sensitive MR Imaging

Susceptibility-weighted angiography (SWAN) is a state-of-the-art 3-dimensional (3D) T₂*-weighted imaging (T₂*WI) technique with multiple echo acquisitions, but its clinical utility remains to be determined. We compared the utility of susceptibility-weighting sequences among SWAN, 3D phase-sensitive magnetic resonance (MR) imaging (PSI), and conventional 2-dimensional (2D) T₂*WI in routine clinical practice. Our results indicate that SWAN can achieve susceptibility weighting more effectively than conventional 2D T₂*WI and as effectively as PSI and requires a much shorter scan time than PSI.

MR Imaging Findings in Intracranial Dural Arteriovenous Fistula Shunt with Retrograde Cortical Venous Drainage Using Susceptibility-Weighted Angiography

We read with special interest the article of Noguchi et al entitled “Intracranial Dural Arteriovenous Fistula with Retrograde Cortical Venous Drainage: Use of Susceptibility-Weighted Imaging in Combination with Dynamic Susceptibility Contrast Imaging.”[1][1] The authors reported the use of SWI

Susceptibility-weighted angiography (SWAN) of cerebral veins and arteries compared to TOF-MRA

High resolution, non-contrast imaging of both cerebral veins and arteries by use of gradient echo T2 star weighted angiography (SWAN) is a new method for susceptibility-weighted imaging with short acquisition times. We assessed the potential of this sequence for the depiction of both cerebral veins and arteries. 15 healthy volunteers were included in the study. MRI was performed on a 3T MR scanner using the following sequences: (1) a 3D multi-echo gradient echo T2 star weighted angiography (SWAN), (2) an arterial 3D TOF MR angiography and (3) a venous 2D TOF. With regard to the SWAN sequence, both MinIP and MIP images were reconstructed and systematically compared to MIP reconstructions of the artTOF and the venTOF. To suggest possible clinical implications of our findings, we additionally included two illustrative cases. With regard to the visualization of the cerebral veins, the MinIP reconstructions of the SWAN sequence were considerably superior compared to the venTOF. Concerning the depiction of the main segments of the big cerebral arteries the value of the MIP reconstructions of the SWAN was comparable to that of the artTOF with limitations in the homogenity and in the depiction of smaller arteries. SWAN allows for high-resolution visualization of both cerebral veins and arteries in one sequence without application of contrast agent and with significantly shortened scan time compared to the combined scan time of TOF-MRA and TOF-MRV. By use of either MinIP or MIP reconstructions, the arteries can be distinguished from the veins.

Presence of a central vein within white matter lesions on susceptibility weighted imaging: a specific finding for multiple sclerosis?

Susceptibility weighted imaging depicts the perivenous extent of multiple sclerosis white matter lesions (MS-WML) in vivo by directly visualizing their centrally running vein. The aim of this study was to investigate the specificity of this finding for MS. Fifteen patients with MS and 15 patients with microangiopathic white matter lesions (mWML) underwent 3T MRI, including a fluid-attenuated inversion recovery sequence (FLAIR) and a susceptibility weighted angiography (SWAN). All WMLs were identified on FLAIR and assigned to one of the following localizations: supratentorial peripheral, supratentorial periventricular, or infratentorial. Subsequently, the presence of a central vein within these lesions was assessed on SWAN. A total of 711 MS-WMLs and 1,119 m-WMLs were identified on FLAIR, all of which could also be visualized on SWAN. A central vein was detectable in 80% of the MS-WMLs and in 78% of the m-WMLs (in 73% and 76% of the peripheral, in 92% and 94% of the periventricular, and in 71% and 75% of the infratentorial MS-WMLs and m-WMLs, respectively). With regard to the supratentorial peripheral lesions, significantly more m-WMLs showed a central vein compared to the MS-WMLs. For the other localizations, there was no significant difference between the groups with regard to the percentage of lesions with central vein. Our results indicate that the detection of a central vein within a WML should not be considered a specific finding for MS; it is also found in WMLs of other etiologies.