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Transverse relaxometry with transmit field-constrained stimulated echo compensation

  • Reza BasiriEmail author
  • Paolo Federico
  • Robert Marc Lebel
Research Article

Abstract

Objective

Purely exponential decay is rarely observed in conventional mono-exponential T2 mapping due to transmit field inhomogeneity and calibration errors, which collectively introduce stimulated and indirect echo pathways. Stimulated echo correction (SEC) requires an additional fit parameter for the transmit field, resulting in greater uncertainty in T2 relative to mono-exponential fitting. The aim of this study was to develop an accurate and precise method for T2 mapping using SEC.

Methods

The proposed method, called two-step SEC (tSEC), leverages spatial correlations in the transmit field to reduce the number of fully independent fitting parameters from three to two. The method involves a two-pass fit: the first pass involves a fast but standard SEC fit. The initially estimated transmit field is smoothed and provided as a fixed input to the second pass.

Results

Simulations and in vivo experiments demonstrated up to 38% and 27% decreases in relative T2 variance with tSEC relative to SEC. Average T2 values were unchanged between tSEC and SEC fits. The proposed method uses the same input data as SEC and exponential fits, so it is applicable to existing data.

Discussion

The proposed method generates reliable and reproducible quantitative T2 maps and should be considered for future relaxometry studies.

Keywords

Magnetic resonance imaging Spin echo imaging Stimulated echo correction Relaxometry Extended phase graph 

Notes

Author contributions

RB: study conception and design, acquisition of data, analysis and interpretation of data, drafting of manuscript, and critical revision. PF: study conception and design, and critical revision. RML: study conception and design, acquisition of data, analysis and interpretation of data, and critical revision.

Compliance with ethical standards

Conflict of interest

Dr. Lebel is an employee of GE Healthcare. The remaining authors have no conflicts of interest or financial ties.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

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Copyright information

© European Society for Magnetic Resonance in Medicine and Biology (ESMRMB) 2019

Authors and Affiliations

  1. 1.Biomedical EngineeringUniversity of CalgaryCalgaryCanada
  2. 2.Hotchkiss Brain InstituteUniversity of CalgaryCalgaryCanada
  3. 3.Department of Clinical Neuroscience, Cumming School of MedicineUniversity of CalgaryCalgaryCanada
  4. 4.Department of RadiologyUniversity of CalgaryCalgaryCanada
  5. 5.GE HealthcareCalgaryCanada
  6. 6.Seaman Family Centre, Foothills Medical Centre, MRG 020ACalgaryCanada

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