Tilted quantitative susceptibility mapping at oblique MRI (tiltQSM).

Area of Science:

• Medical Imaging
• Biophysics
• Computational Neuroscience

Background:

• Quantitative Susceptibility Mapping (QSM) is crucial for analyzing MRI phase images.
• Oblique acquisition in MRI introduces artifacts, complicating accurate QSM.
• Existing QSM methods require phase images acquired perpendicular to the main magnetic field (B0).

Purpose of the Study:

• To develop and validate a method (tiltQSM) for accurate QSM from oblique MRI phase images.
• To address the "oblique effect" caused by tilted acquisition planes.
• To provide a preprocessing solution for QSM reconstruction in non-standard MRI orientations.

Main Methods:

• Proposed two matrix-based methods: rotData (phase image rotation) and rotKernel (dipole kernel rotation).
• Implemented tiltQSM as a preprocessing subroutine for regular QSM pipelines.
• Validated tiltQSM using numerical simulations, phantom studies, and in vivo human brain MRI at 3T with axial slice tilting.

Main Results:

• tiltQSM achieved high spatial correlation (>0.90) for tilt angles below 10°.
• Performance was assessed considering both the oblique effect and MRI anisotropy.
• Voxel anisotropy due to image matrix rotation can degrade tiltQSM performance.

Conclusions:

• tiltQSM effectively corrects for the oblique effect in QSM from tilted MRI.
• Recommended practice is to acquire MRI phase images with minimal obliqueness (<10°) for optimal QSM.
• tiltQSM offers a viable solution for QSM in challenging oblique acquisition scenarios.