Susceptibility-weighted imaging in acute-stage pediatric convulsive disorders

Diagnostic Accuracy of SWAN in the Diagnosis of Low-Flow Brain Vascular Malformations in Childhood

Purpose The main objective of this study is to demonstrate the diagnostic accuracy of susceptibility-weighted angiography (SWAN) in the diagnosis of slow-flow cerebral vascular malformations, especially developmental venous anomaly (DVA). We also aimed to determine the prevalence of DVAs identified by SWAN at 1.5 T.

Methods We retrospectively evaluated 1,760 axial SWAN images for the diagnosis of low-flow vascular anomaly. Among them were 305 patients who underwent contrast-enhanced examination due to different indications. Postcontrast images were analyzed by different radiologists who were blinded to patients. The presence of DVA and other features such as location, length, depth, and direction of drainage vein was evaluated.

Results Twenty-six patients with DVA had both SWAN and postcontrast images. There were four false-negative patients with SWAN. The sensitivity of the SWAN sequence was 84.6%. In addition, totally 77 DVA (4.36%), 2 capillary telangiectasia (0.11%), and 2 cavernous malformations (0.11%) were detected in 1,760 patients.

Conclusion SWAN is an effective method for the diagnosis of developmental venous anomalies and other low-flow cerebral vascular malformations. Especially in the pediatric age, susceptibility-weighted imaging sequences are useful to limit contrast use.

Simultaneous feedback control for joint field and motion correction in brain MRI

T2*-weighted gradient-echo sequences count among the most widely used techniques in neuroimaging and offer rich magnitude and phase contrast. The susceptibility effects underlying this contrast scale with B₀, making T2*-weighted imaging particularly interesting at high field. High field also benefits baseline sensitivity and thus facilitates high-resolution studies. However, enhanced susceptibility effects and high target resolution come with inherent challenges. Relying on long echo times, T2*-weighted imaging not only benefits from enhanced local susceptibility effects but also suffers from increased field fluctuations due to moving body parts and breathing. High resolution, in turn, renders neuroimaging particularly vulnerable to motion of the head. This work reports the implementation and characterization of a system that aims to jointly address these issues. It is based on the simultaneous operation of two control loops, one for field stabilization and one for motion correction. The key challenge with this approach is that the two loops both operate on the magnetic field in the imaging volume and are thus prone to mutual interference and potential instability. This issue is addressed at the levels of sensing, timing, and control parameters. Performance assessment shows the resulting system to be stable and exhibit adequate loop decoupling, precision, and bandwidth. Simultaneous field and motion control is then demonstrated in examples of T2*-weighted in vivo imaging at 7T.

Susceptibility-Based Neuroimaging: Standard Methods, Clinical Applications, and Future Directions

The evaluation of neuropathologies using MRI methods that leverage tissue susceptibility have become standard practice, especially to detect blood products or mineralization. Additionally, emerging MRI techniques have the ability to provide new information based on tissue susceptibility properties in a robust and quantitative manner. This paper discusses these advanced susceptibility imaging techniques and their clinical applications.