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T1-mapping in the heart: accuracy and precision.

Kellman P, Hansen MS - J Cardiovasc Magn Reson (2014)

Bottom Line: Both T1 and ECV measures have been shown to have important prognostic significance.The accuracy of inversion recovery techniques is affected significantly by magnetization transfer (MT).Despite this, the estimate of apparent T1 using inversion recovery is a sensitive measure, which has been demonstrated to be a useful tool in characterizing tissue and discriminating disease.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA. kellman@nih.gov.

ABSTRACT
The longitudinal relaxation time constant (T1) of the myocardium is altered in various disease states due to increased water content or other changes to the local molecular environment. Changes in both native T1 and T1 following administration of gadolinium (Gd) based contrast agents are considered important biomarkers and multiple methods have been suggested for quantifying myocardial T1 in vivo. Characterization of the native T1 of myocardial tissue may be used to detect and assess various cardiomyopathies while measurement of T1 with extracellular Gd based contrast agents provides additional information about the extracellular volume (ECV) fraction. The latter is particularly valuable for more diffuse diseases that are more challenging to detect using conventional late gadolinium enhancement (LGE). Both T1 and ECV measures have been shown to have important prognostic significance. T1-mapping has the potential to detect and quantify diffuse fibrosis at an early stage provided that the measurements have adequate reproducibility. Inversion recovery methods such as MOLLI have excellent precision and are highly reproducible when using tightly controlled protocols. The MOLLI method is widely available and is relatively mature. The accuracy of inversion recovery techniques is affected significantly by magnetization transfer (MT). Despite this, the estimate of apparent T1 using inversion recovery is a sensitive measure, which has been demonstrated to be a useful tool in characterizing tissue and discriminating disease. Saturation recovery methods have the potential to provide a more accurate measurement of T1 that is less sensitive to MT as well as other factors. Saturation recovery techniques are, however, noisier and somewhat more artifact prone and have not demonstrated the same level of reproducibility at this point in time.This review article focuses on the technical aspects of key T1-mapping methods and imaging protocols and describes their limitations including the factors that influence their accuracy, precision, and reproducibility.

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Imperfect inversion combined with the influence of SSFP readout alters the apparent T1* of the myocardium.
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Figure 11: Imperfect inversion combined with the influence of SSFP readout alters the apparent T1* of the myocardium.

Mentions: Adiabatic inversion pulses used to mitigate inhomogeneity of transmit B1 field strength do not achieve perfect inversion as a result of transverse relaxation (T2) during the pulse [40]. Imperfect adiabatic inversion leads to an error in estimating T1 (Figure 11) since the Look-Locker correction (B/A-1) of the apparent T1* assumes ideal inversion. Furthermore, the inversion efficiency may lead to a T2-dependent error in the T1 estimate. An optimized pulse design [40] with improved inversion efficiency can reduce this error as well as achieve a reduced T2-dependence. Empirical correction (T1 ≈ T1*(B/A-1)/α) for imperfect adiabatic inversion (α) may be used to further improve T1-measurement accuracy.


T1-mapping in the heart: accuracy and precision.

Kellman P, Hansen MS - J Cardiovasc Magn Reson (2014)

Imperfect inversion combined with the influence of SSFP readout alters the apparent T1* of the myocardium.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3927683&req=5

Figure 11: Imperfect inversion combined with the influence of SSFP readout alters the apparent T1* of the myocardium.
Mentions: Adiabatic inversion pulses used to mitigate inhomogeneity of transmit B1 field strength do not achieve perfect inversion as a result of transverse relaxation (T2) during the pulse [40]. Imperfect adiabatic inversion leads to an error in estimating T1 (Figure 11) since the Look-Locker correction (B/A-1) of the apparent T1* assumes ideal inversion. Furthermore, the inversion efficiency may lead to a T2-dependent error in the T1 estimate. An optimized pulse design [40] with improved inversion efficiency can reduce this error as well as achieve a reduced T2-dependence. Empirical correction (T1 ≈ T1*(B/A-1)/α) for imperfect adiabatic inversion (α) may be used to further improve T1-measurement accuracy.

Bottom Line: Both T1 and ECV measures have been shown to have important prognostic significance.The accuracy of inversion recovery techniques is affected significantly by magnetization transfer (MT).Despite this, the estimate of apparent T1 using inversion recovery is a sensitive measure, which has been demonstrated to be a useful tool in characterizing tissue and discriminating disease.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA. kellman@nih.gov.

ABSTRACT
The longitudinal relaxation time constant (T1) of the myocardium is altered in various disease states due to increased water content or other changes to the local molecular environment. Changes in both native T1 and T1 following administration of gadolinium (Gd) based contrast agents are considered important biomarkers and multiple methods have been suggested for quantifying myocardial T1 in vivo. Characterization of the native T1 of myocardial tissue may be used to detect and assess various cardiomyopathies while measurement of T1 with extracellular Gd based contrast agents provides additional information about the extracellular volume (ECV) fraction. The latter is particularly valuable for more diffuse diseases that are more challenging to detect using conventional late gadolinium enhancement (LGE). Both T1 and ECV measures have been shown to have important prognostic significance. T1-mapping has the potential to detect and quantify diffuse fibrosis at an early stage provided that the measurements have adequate reproducibility. Inversion recovery methods such as MOLLI have excellent precision and are highly reproducible when using tightly controlled protocols. The MOLLI method is widely available and is relatively mature. The accuracy of inversion recovery techniques is affected significantly by magnetization transfer (MT). Despite this, the estimate of apparent T1 using inversion recovery is a sensitive measure, which has been demonstrated to be a useful tool in characterizing tissue and discriminating disease. Saturation recovery methods have the potential to provide a more accurate measurement of T1 that is less sensitive to MT as well as other factors. Saturation recovery techniques are, however, noisier and somewhat more artifact prone and have not demonstrated the same level of reproducibility at this point in time.This review article focuses on the technical aspects of key T1-mapping methods and imaging protocols and describes their limitations including the factors that influence their accuracy, precision, and reproducibility.

Show MeSH
Related in: MedlinePlus