Michael Nicholas Hoff PhD, Presenter: Nothing to Disclose

Qing-San Xiang, Abstract Co-Author: Nothing to Disclose

Gregory James Wilson PhD, Abstract Co-Author: Nothing to Disclose

Jalal Badi Andre MD, Abstract Co-Author: Consultant, Hobbitview, Inc Research Grant, Koninklijke Philips NV

The high tissue/fluid contrast of high resolution balanced steady state free precession (bSSFP) MRI is ideal for imaging the fine detail of the inner ear. However, images are often plagued by signal modulation and dark bands due to magnetic field inhomogeneity, and ghosting artifacts due to arterial and CSF pulsation. Previously, the best bSSFP banding reduction was achieved with a complex sum (CS) of radiofrequency (RF) phase cycled images; here a novel geometric solution (GS) of four phase cycled images demonstrates the ability to eliminate banding near the temporal bone and cisternal regions, with improved motion-ghosting mitigation relative to the CS.

Four incrementally RF phase cycled 3D axial bSSFP images were acquired at 3T using a 180/180/120 matrix size and 1/1/1 mm voxel size along frequency/phase/slice directions. Complex data were input pixel-by-pixel into an expression which calculates the GS. SNR was improved through a second pass regional linearization solution, and results were compared with the CS of the four phase cycled images.

The attached figure depicts four phase cycled (∆θ = 0°, 90°, 180°, and 270°) axial magnitude images of the temporal bone (a-d) and foramen magnum (g-j), and the corresponding CS (e & k) and GS (f & l). The original phase cycled bSSFP images demonstrate banding, spuriously bright signal regions, and periodic motion artifact along the phase encoding direction stemming from globe motion, CSF pulsation, and carotid arterial flow. Colored arrows in the CS show residual banding in the globes (green) and CSF (yellow), erroneous contrast in the nasopharynx and prevertebral space (blue), and residual vascular and CSF flow artifact (red). Equivalently colored arrows in the GS indicate that nearly all artifacts are eliminated relative to the CS.

The GS removes the dependence of bSSFP signal on field inhomogeneity in the temporal bone and adjacent structures; unlike the CS, it yields reliable contrast without banding. The GS further achieves high noise immunity, typified by its insensitivity to motion-ghosting artifacts present in the original phase cycled images.

A novel geometric solution eliminates banding due to field inhomogeneity and reduces motion artifacts due to arterial/CSF pulsation in balanced steady state free precession MRI of the temporal bone.

Hoff, M, Xiang, Q, Wilson, G, Andre, J, Balanced Steady-state Free Precession MRI of the Temporal Bone with a Novel Geometric Solution for Banding Correction and Motion Artifact Reduction.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14008247.html