Artifactual microhemorrhage generated by susceptibility weighted image processing

Abstract

Purpose To report that artifactual microhemorrhages are introduced by the 2D homodyne filtering method of generating susceptibility weighted images (SWI) when open-ended fringelines (OEF) are present in phase data. Materials and Methods SWI data from 28 traumatic brain injury (TBI) patients was obtained on a 3T clinical Siemens scanner using both the product 3D gradient echo sequence (GRE) with GRAPPA acceleration and an in-house developed segmented echo planar imaging (sEPI) sequence without GRAPPA acceleration. SWI processing included (1) 2D Homodyne method implemented on the scanner console and (2) a 3D Fourier-based phase unwrapping followed by 3D high pass filtering. Original and enhanced magnitude and phase images were carefully reviewed for sites of type III OEFs and microhemorrhages by a neuroradiologist on a PACS workstation. Results Nineteen of 28 (68%) phase datasets acquired using GRAPPA-accelerated GRE acquisition demonstrated type III OEFs. In SWI images, artifactual microhemorrhages were found on 17 of 19 (89%) cases generated using 2D homodyne processing. Application of a 3D Fourier-based unwrapping method prior HP filtering minimized the appearance of the phase singularities in the enhanced phase, and did not generate microhemorrhage-like artifacts in magnitude images. Conclusion The 2D homodyne filtering method may introduce artifacts mimicking intracranial microhemorrhages in SWI images when type III OEFs are present in phase images. Such artifacts could lead to overestimation of pathology, e.g. TBI. This work demonstrates that 3D phase unwrapping methods minimize this artifact. However, methods to properly combine of phase across coils are needed to eliminate this artifact.

Susceptibility‐weighted imaging: current status and future directions

“…Proper reconstruction of the phase images from a gradient echo sequence is critical for both SWI and QSM, as any noise or artifact in the phase images will be propagated into the final results during the phase unwrapping and/or background phase removal . Although SWI and QSM may be largely affected when severe signal cancelation occurs because of improper combination, local cusp artifacts could also be misinterpreted as microbleeds .…”

Segmented 3D Echo Planar Acquisition for Rapid Susceptibility‐Weighted Imaging: Application to Microhemorrhage Detection in Traumatic Brain Injury

“…CMBs in the context of trauma often line up along parenchymal veins, potentially to the extent that individual hemorrhages are difficult to distinguish 36 . Because there is no reference standard or pathologic proof in this study, it is impossible to completely exclude the presence of artefactual microhemorrhages leading to an inaccurate microhemorrhage count 37 …”

“…36 Because there is no reference standard or pathologic proof in this study, it is impossible to completely exclude the presence of artefactual microhemorrhages leading to an inaccurate microhemorrhage count. 37 Other approaches to accelerate image acquisition, for example, SENSE, GRAPPA, CAIPIRINHA that can be applied to 3D GRE acquisitions sequences depend on the number of individual coil elements and provide acceleration factors typically in the range of 2-4, 38 potentially more than 10 when combining multiple techniques. 39 The combined acceleration factor may be close to the acceleration provided by the echo train in segEPI, which was 15 in this work.…”

ENLIVE: An Efficient Nonlinear Method for Calibrationless and Robust Parallel Imaging

“…For example, as Li et al . 31 have shown, phase singularities can appear as artifactual microhemorrhage in susceptibility weighted imaging. NLINV and ENLIVE guarantee smooth sensitivities, but this then traps the algorithm in a local minimum and creates a hole instead 32 .…”