MO-G-18C-01: BEST IN PHYSICS (IMAGING) - Novel Correction of Signal Modulation and Motion Artifacts in Temporal Bone BSSFP MRI.
PURPOSE
Phase cycled balanced steady state free precession (bSSFP) magnetic resonance (MR) images demonstrate high contrast in the temporal bone region, but are limited by motion artifacts stemming from globe motion, CSF and carotid artery pulsation, and by signal loss/modulation typical of bSSFP imaging of complex tissue environments. We sought to generate images delineating the fine morphology of temporal bone structures while minimizing signal loss and motion artifacts.


METHODS
Four axial 3D bSSFP MR images with Δθ = 0°, 90°, 180°, and 270° phase cycling respectively were acquired with a Philips Ingenia 3T MRI scanner in 2.3 minutes of total scan time. Other parameters included a 30° flip angle applied with a transmit/receive radiofrequency head coil, TE/TR = 4.2/2.1ms, receiver bandwidth = 890 Hz/pixel, and 180/180/120 matrix size and 1/1/1 mm voxel size along frequency/phase/slice directions. Complex image data were input into the Geometric Solution (GS) algorithm for calculation of artifact-free bSSFP signal on a pixel-by-pixel basis. SNR was improved by linearizing the solution in a second-pass regional optimization.


RESULTS
The GS eliminated the bSSFP signal intensity modulations while minimizing motion artifacts present in the original four images. The efficacy of the GS is validated through comparison with a complex average of the four original bSSFP images; unlike the GS, the complex average only moderates artifacts.


CONCLUSION
The GS represents a novel method of correcting bSSFP MRI signal modulation and motion artifacts while maintaining contrast near the temporal bone. The technique is fast, easy to implement, and requires minimal post-processing. This technique may inspire early clinical adoption, as it overcomes two major artifactual obstacles which have historically limited the widespread use of bSSFP MRI.