Retrospective correction of bias in diffusion tensor imaging arising from coil combination mode

• Published in: Magnetic resonance imaging Vol. 37; pp. 203 - 208
• Main Authors: Sakaie, Ken, Lowe, Mark
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01.04.2017
• Subjects: Adaptive combine; Algorithms; Bias; Brain - diagnostic imaging; Coil combination; Diffusion tensor imaging; Diffusion Tensor Imaging - instrumentation; Diffusion Tensor Imaging - methods; DTI; Female; Humans; Image Processing, Computer-Assisted - methods; Male; Radiology; Retrospective correction; Retrospective Studies; Sum of squares; DTI; Adaptive combine; Retrospective correction; Coil combination; Sum of squares; Diffusion tensor imaging
• ISSN: 0730-725X; 1873-5894; 1873-5894
• DOI: 10.1016/j.mri.2016.12.004

To quantify and retrospectively correct for systematic differences in diffusion tensor imaging (DTI) measurements due to differences in coil combination mode. Multi-channel coils are now standard among MRI systems. There are several options for combining signal from multiple coils during image reconstruction, including sum-of-squares (SOS) and adaptive combine (AC). This contribution examines the bias between SOS- and AC-derived measures of tissue microstructure and a strategy for limiting that bias. Five healthy subjects were scanned under an institutional review board-approved protocol. Each set of raw image data was reconstructed twice—once with SOS and once with AC. The diffusion tensor was calculated from SOS- and AC-derived data by two algorithms—standard log-linear least squares and an approach that accounts for the impact of coil combination on signal statistics. Systematic differences between SOS and AC in terms of tissue microstructure (axial diffusivity, radial diffusivity, mean diffusivity and fractional anisotropy) were evaluated on a voxel-by-voxel basis. SOS-based tissue microstructure values are systematically lower than AC-based measures throughout the brain in each subject when using the standard tensor calculation method. The difference between SOS and AC can be virtually eliminated by taking into account the signal statistics associated with coil combination. The impact of coil combination mode on diffusion tensor-based measures of tissue microstructure is statistically significant but can be corrected retrospectively. The ability to do so is expected to facilitate pooling of data among imaging protocols. •Coil combination is a key step in image reconstruction from multichannel coils.•Bias in diffusion tensor imaging due to coil combination is quantified.•Substantial reduction in bias can be achieved retrospectively.•Limiting bias is expected to enable effective pooling of data.