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Quantitative Mapping of Specific Ventilation in the Human Lung using Proton Magnetic Resonance Imaging and Oxygen as a Contrast Agent
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Flexible proton density (PD) mapping using multi-contrast variable flip angle (VFA) data.

Sara Lorio1, Tim M Tierney2, Amy McDowell1

  • 1UCL Great Ormond Street Institute of Child Health, University College London, London, UK.

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|November 23, 2018
PubMed
Summary
This summary is machine-generated.

This study introduces a novel multi-contrast MRI method for accurate quantitative proton density (PD) mapping. The new approach improves tissue characterization by correcting for magnetic field variations and enhancing map homogeneity, especially in challenging cases.

Keywords:
Anatomical malformationBiophysical tissue propertiesPost-mortem MRIProton densityQuantitative MRI

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Area of Science:

  • Magnetic Resonance Imaging (MRI)
  • Quantitative Imaging
  • Biomedical Engineering

Background:

  • Quantitative proton density (PD) mapping is crucial for non-invasive tissue characterization but is hindered by factors like T1/T2* relaxation and receiver coil sensitivity profiles (RP).
  • Current methods for estimating RP and scaling factors have limitations, particularly in severe pathologies or across wide age ranges, restricting their clinical applicability.
  • Accurate PD mapping requires robust correction for signal influences beyond proton density itself.

Purpose of the Study:

  • To develop and validate a new, data-driven approach for quantitative proton density (PD) mapping using a multi-contrast variable flip angle acquisition protocol.
  • To improve the accuracy and homogeneity of PD maps by effectively correcting for T2* relaxation, transmit field inhomogeneities, and receiver coil sensitivity profiles (RP).
  • To demonstrate the robustness and insensitivity of the proposed method to anatomical variations or prior tissue information.

Main Methods:

  • A multi-contrast variable flip angle acquisition protocol was employed to gather comprehensive MRI data.
  • A data-driven method was developed for estimating receiver coil sensitivity profile (RP) correction and map scaling.
  • The proposed method combines multi-contrast data to fully correct for T2* relaxation effects and reduce PD value variance and entropy.

Main Results:

  • The multi-contrast approach successfully corrected MRI signals for T2* relaxation effects.
  • The proposed method demonstrated increased homogeneity and accuracy of PD values in cerebrospinal fluid (CSF) and deep brain structures compared to established PD* mapping.
  • The multi-contrast RP approach proved insensitive to anatomical information, validated in a patient with extensive brain abnormalities and in post-mortem fetal imaging.

Conclusions:

  • The proposed multi-contrast quantitative proton density (PD) mapping method offers improved accuracy and homogeneity over existing techniques.
  • This novel approach overcomes limitations of previous methods, enabling reliable PD mapping across diverse pathologies and age groups.
  • The data-driven, multi-contrast strategy enhances the utility of quantitative MRI for tissue characterization in various clinical and research applications.