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Whole liver phase‐based R2 mapping in liver iron overload within a breath‐hold.

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Title: Whole liver phase‐based R2 mapping in liver iron overload within a breath‐hold.
Authors: Tamada, Daiki1 (AUTHOR) dtamada@wisc.edu, Navaratna, Ruvini1,2 (AUTHOR), Weaver, Jayse Merle1,2 (AUTHOR), Hernando, Diego1,2 (AUTHOR), Reeder, Scott B.1,2,3,4,5 (AUTHOR)
Source: Magnetic Resonance in Medicine. Jul2025, Vol. 94 Issue 1, p183-198. 16p.
Subjects: Iron overload, Bloch equations, Liver, Volunteers, Iron
Abstract: Purpose: Diagnosis and treatment monitoring of iron overload increasingly relies on non‐invasive MRI‐based measurement of liver iron concentration (LIC). Liver R2 mapping is known to correlate well with LIC. However, traditional spin‐echo based R2 mapping methods have drawbacks such as long acquisition times and limited volumetric coverage. In this work, we present an optimized phase‐based R2 mapping method to quantify whole‐liver R2 in iron overload patients within a single breathhold. Theory and Methods: A recently developed phase‐based R2 mapping method is optimized in this study to improve estimation of high R2 values using reduced TR, spatial averaging, and R1 correction. Using Bloch equation simulations, the proposed optimization method was evaluated. Furthermore, the impact of fat on R2 bias was investigated through simulations. The feasibility of the optimized phase‐based R2 method was assessed in healthy volunteers and patients with iron overload and compared to reference STEAM‐MRS R2 measurements. Results: Simulations demonstrate that a shorter TR extends the dynamic range of R2 estimation to higher values and that averaging of signal phase before R2 estimation is necessary when R2 is high. Phantom experiments also demonstrate reduced phase‐based R2 bias using R1 correction. Good agreement (1.5 T: r2 = 0.76, 3.0 T: r2 = 0.70) between the modified phase‐based R2 method and reference STEAM R2 was found in healthy volunteers and iron overload patients over a wide range of LIC values. Conclusion: This study demonstrates the feasibility of the proposed phase‐based R2 method to accurately measure whole‐liver R2 mapping in severe iron overloaded patients during a single breathhold. [ABSTRACT FROM AUTHOR]
Copyright of Magnetic Resonance in Medicine is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Whole liver phase‐based R2 mapping in liver iron overload within a breath‐hold.
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  Data: <searchLink fieldCode="AR" term="%22Tamada%2C+Daiki%22">Tamada, Daiki</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> dtamada@wisc.edu</i><br /><searchLink fieldCode="AR" term="%22Navaratna%2C+Ruvini%22">Navaratna, Ruvini</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Weaver%2C+Jayse+Merle%22">Weaver, Jayse Merle</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Hernando%2C+Diego%22">Hernando, Diego</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Reeder%2C+Scott+B%2E%22">Reeder, Scott B.</searchLink><relatesTo>1,2,3,4,5</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Magnetic+Resonance+in+Medicine%22">Magnetic Resonance in Medicine</searchLink>. Jul2025, Vol. 94 Issue 1, p183-198. 16p.
– Name: Subject
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  Data: <searchLink fieldCode="DE" term="%22Iron+overload%22">Iron overload</searchLink><br /><searchLink fieldCode="DE" term="%22Bloch+equations%22">Bloch equations</searchLink><br /><searchLink fieldCode="DE" term="%22Liver%22">Liver</searchLink><br /><searchLink fieldCode="DE" term="%22Volunteers%22">Volunteers</searchLink><br /><searchLink fieldCode="DE" term="%22Iron%22">Iron</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Purpose: Diagnosis and treatment monitoring of iron overload increasingly relies on non‐invasive MRI‐based measurement of liver iron concentration (LIC). Liver R2 mapping is known to correlate well with LIC. However, traditional spin‐echo based R2 mapping methods have drawbacks such as long acquisition times and limited volumetric coverage. In this work, we present an optimized phase‐based R2 mapping method to quantify whole‐liver R2 in iron overload patients within a single breathhold. Theory and Methods: A recently developed phase‐based R2 mapping method is optimized in this study to improve estimation of high R2 values using reduced TR, spatial averaging, and R1 correction. Using Bloch equation simulations, the proposed optimization method was evaluated. Furthermore, the impact of fat on R2 bias was investigated through simulations. The feasibility of the optimized phase‐based R2 method was assessed in healthy volunteers and patients with iron overload and compared to reference STEAM‐MRS R2 measurements. Results: Simulations demonstrate that a shorter TR extends the dynamic range of R2 estimation to higher values and that averaging of signal phase before R2 estimation is necessary when R2 is high. Phantom experiments also demonstrate reduced phase‐based R2 bias using R1 correction. Good agreement (1.5 T: r2 = 0.76, 3.0 T: r2 = 0.70) between the modified phase‐based R2 method and reference STEAM R2 was found in healthy volunteers and iron overload patients over a wide range of LIC values. Conclusion: This study demonstrates the feasibility of the proposed phase‐based R2 method to accurately measure whole‐liver R2 mapping in severe iron overloaded patients during a single breathhold. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Magnetic Resonance in Medicine is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1002/mrm.30461
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 16
        StartPage: 183
    Subjects:
      – SubjectFull: Iron overload
        Type: general
      – SubjectFull: Bloch equations
        Type: general
      – SubjectFull: Liver
        Type: general
      – SubjectFull: Volunteers
        Type: general
      – SubjectFull: Iron
        Type: general
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      – TitleFull: Whole liver phase‐based R2 mapping in liver iron overload within a breath‐hold.
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          Name:
            NameFull: Tamada, Daiki
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            NameFull: Navaratna, Ruvini
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            NameFull: Weaver, Jayse Merle
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            NameFull: Hernando, Diego
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            NameFull: Reeder, Scott B.
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            – D: 01
              M: 07
              Text: Jul2025
              Type: published
              Y: 2025
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