Christof Boehm1, Maximilian N. Diefenbach1,2, Sophia Kronthaler1, Jakob Meineke3, Kilian Weiss4, Marcus R. Makowski1, and Dimitrios C. Karampinos1
1Department of Diagnostic and Interventional Radiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany, 2Division of Infectious Diseases and Tropical Medicine, University Hospital, LMU Munich, Munich, Germany, 3Philips Research Lab, Hamburg, Germany, 4Philips Healthcare, Hamburg, Germany
1Department of Diagnostic and Interventional Radiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany, 2Division of Infectious Diseases and Tropical Medicine, University Hospital, LMU Munich, Munich, Germany, 3Philips Research Lab, Hamburg, Germany, 4Philips Healthcare, Hamburg, Germany
The use of in-phase echo times (a) introduces quantification bias in the fieldmap and QSM, (b) limits the estimation of valuable fat fraction information and (c) shows no clear advantages when compared to standard water–fat echo times for body QSM.
Figure 4: In vivo healthy liver results show a reduced contrast between high and low PDFF regions in the field- and χ-map. The susceptibility map within the liver (box) shows a significant underestimation when using in-phase echoes, although the liver fat content is negligible. Further, when using in-phase echo times the overall sharpness and contrast is reduced in the χ-map, the depiction of fine structures such as vessels is limited (left arrow), the susceptibility values are heterogeneously distributed within the liver and more BFR artifacts are apparent (bottom right arrow).
Figure 2: Numerical simulation results of the lumbar spine. In-phase echo times induce a 24% higher error in the fieldmap and 44% higher error in the susceptibility map when compared to standard water–fat separation echo times. The overall contrast of the QSM map is reduced using in-phase echo times and the intervertebral disc region shows an artefactual paramagnetic increase (arrow). When Laplacian unwrapping is additionally performed on the field-map based on the water–fat separation echo times, the estimated susceptibility-map does not change significantly.