PURPOSE: To evaluate the impact of MR gradient system imperfections and limitations for the quantitative mapping of short T2* signals performed by ultrashort echo time (UTE) acquisition approach. MATERIALS AND METHODS: The measurement of short T2* signals from a phantom and a healthy volunteer study (8 subjects of average age 28 ± 4 years) were performed on a 3T scanner. The characteristics of the gradient system were obtained using calibration method performed directly on the measured subject or phantom. This information was used to calculate the actual sampling trajectory with the help of a parametric eddy current model. The actual sample positions were used to reconstruct corrected images and compared with uncorrected data. RESULTS: Comparison of both approaches, i.e., without and with correction of k-space sampling trajectories revealed substantial improvement when correction was applied. The phantom experiments demonstrate substantial in-plane signal intensity variations for uncorrected sampling trajectories. In the case of the volunteer study, this led to significant differences in relative proton density (RPD) estimation between the uncorrected and corrected data (P = 0.0117 by Wilcoxon matched-pairs test) and provides for about ~15% higher values for short T2* components of white matter (WM) in the case of uncorrected images. CONCLUSION: The imperfection of the applied gradients could induce errors in k-space data sampling which further propagates into the fidelity of the UTE images and jeopardizes precision of quantification. However, the study proved that measurement of gradient errors together with correction of sample positions can contribute to increased accuracy and unbiased characterization of short T2* signals.

Biological Resources Imaging Laboratory Mark Wainwright Analytical Centre Level 4 Lowy Cancer Research Centre UNSW Australia Sydney NSW 2052 Australia

Central European Institute of Technology Masaryk University Brno Czech Republic

Central European Institute of Technology Masaryk University Brno Czech Republic; Department of Neurology University Hospital Brno Jihlavska 20 62500 Brno Czech Republic

Central European Institute of Technology Masaryk University Brno Czech Republic; University of Alberta Department of Oncology Division of Medical Physics 8303 112 Street NW Edmonton AB T6G 2T4 Canada

Institute of Scientific Instruments of the Czech Academy of Sciences Brno Czech Republic

Citace poskytuje Crossref.org