GSTF-based pre-emphasis to investigate the possibilities of a perfectly balanced steady state-free precession sequence

• Applicant: Dr. Anne Slawig
• Subject Area: Medical Physics, Biomedical Technology ; Nuclear Medicine, Radiotherapy, Radiobiology
• Term: from 2020 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 446320484

The gradient system transfer function (GSTF) comprehensively describes the behaviour of a hardware system, like an MRI-scanner. It relates the input signal to the true output signal, which deviates due to hardware imperfections or induced eddy currents. Especially eddy currents can have a disastrous effect on image quality and their effect is most severe in cases of non-linear or non-cartesian read-out designs or incoherent undersampling.The balanced steady state free precession (bSSFP) -sequence is a very interesting candidate for the acceleration and quantification of MRI examinations, due to its inherently fast scan times, high signal yield and unique contrast. Unfortunately, this type of MR sequence is highly sensitive towards eddy current induced disturbances. Image artefacts arise if imperfect gradient waveforms are played out or dephasing occurs during the measurement. Nevertheless, as most novel imaging and acceleration procedures rely on a flexible read-out design, the combination of such designs with bSSFP is of major interest. The aim of this project is to investigate the possibilities of a GSTF-based pre-emphasis for bSSFP measurements. Such a pre-emphasis will allow implementing a perfectly balanced gradient scheme and a phase correction during the measurement, to avoid disruptions of the steady state and thereby image artefacts.Image quality of the pre-emphasized bSSFP-sequence will then be independent of read-out designs or undersampling patterns. Thus, opening a wide range of applications that require bSSFP in combination with acceleration techniques.Additionally, the signal behavior of an undisturbed bSSFP sequence will closely follow standard signal models. A model-based reconstruction can thus allow the deduction of quantitative tissue parameters from a bSSFP measurement.In conclusion, the GSTF-based pre-emphasis of bSSFP can help to solve two of the major drawbacks in MR imaging: long scan times and non-quantitative images.

• DFG Programme: Research Grants