Dataset Information

Controlled saturation magnetization transfer for reproducible multivendor variable flip angle T₁ and T₂ mapping.

ABSTRACT:

Purpose

The widespread clinical application of quantitative MRI has been hindered by a lack of reproducibility across sites and vendors. Previous work has attributed this to incorrect B₁ mapping or insufficient spoiling conditions. We recently proposed the controlled saturation magnetization transfer (CSMT) framework and hypothesized that the lack of reproducibility can also be attributed to magnetization transfer effects. This work seeks to validate this hypothesis and demonstrate that reproducible multivendor single-pool relaxometry can be achieved with the CSMT approach.

Methods

Three healthy volunteers were scanned on scanners from 3 vendors (GE Healthcare, Philips, Siemens). An extensive set of images necessary for joint T₁ and T₂ estimation were acquired with (1) each vendor default RF pulses and spoiling conditions; (2) harmonized RF spoiling; and (3) harmonized RF spoiling and CSMT pulses. Different subsets of images were used to generate 6 different T₁ and T₂ maps for each subject's data from each vendor. Cross-protocol, cross-vendor, and test/retest variability were estimated.

Results

Harmonized RF spoiling conditions are insufficient to ensure good cross-vendor reproducibility. Controlled saturation magnetization transfer allows cross-protocol variability to be reduced from 18.3% to 4.0%. Whole-brain variability using the same protocol was reduced from a maximum of 19% to 4.5% across sites. Both CSMT and native vendor RF conditions have a reported variability of less than 5% for repeat measures on the same vendor.

Conclusion

Magnetization transfer effects are a major contributor to intersite/intrasite variability of T₁ and T₂ estimation. Controlled saturation magnetization transfer stabilizes these effects, paving the way for the use of single-pool T₁ and T₂ as a reliable source for clinical diagnosis across sites.

SUBMITTER: A G Teixeira RP

PROVIDER: S-EPMC7154666 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Publications

Controlled saturation magnetization transfer for reproducible multivendor variable flip angle T<sub>1</sub> and T<sub>2</sub> mapping.

A G Teixeira Rui Pedro RP Neji Radhouene R Wood Tobias C TC Baburamani Ana A AA Malik Shaihan J SJ Hajnal Joseph V JV

Magnetic resonance in medicine 20191217 1

<h4>Purpose</h4>The widespread clinical application of quantitative MRI has been hindered by a lack of reproducibility across sites and vendors. Previous work has attributed this to incorrect B<sub>1</sub> mapping or insufficient spoiling conditions. We recently proposed the controlled saturation magnetization transfer (CSMT) framework and hypothesized that the lack of reproducibility can also be attributed to magnetization transfer effects. This work seeks to validate this hypothesis and demons ...[more]

PMID: 31846122

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Project description:Quantitative proton density (PD) maps measure the amount of free water, which is important for non-invasive tissue characterization in pathology and across lifespan. PD mapping requires the estimation and subsequent removal of factors influencing the signal intensity other than PD. These factors include the T1, T2* relaxation effects, transmit field inhomogeneities, receiver coil sensitivity profile (RP) and the spatially invariant factor that is required to scale the data. While the transmit field can be reliably measured, the RP estimation is usually based on image post-processing techniques due to limitations of its measurement at magnetic fields higher than 1.5 T. The post-processing methods are based on unified bias-field/tissue segmentation, fitting the sensitivity profile from images obtained with different coils, or on the linear relationship between T1 and PD. The scaling factor is derived from the signal within a specific tissue compartment or reference object. However, these approaches for calculating the RP and scaling factor have limitations particularly in severe pathology or over a wide age range, restricting their application. We propose a new approach for PD mapping based on a multi-contrast variable flip angle acquisition protocol and a data-driven estimation method for the RP correction and map scaling. By combining all the multi-contrast data acquired at different echo times, we are able to fully correct the MRI signal for T2* relaxation effects and to decrease the variance and the entropy of PD values within tissue class of the final map. The RP is determined from the corrected data applying a non-parametric bias estimation, and the scaling factor is based on the median intensity of an external calibration object. Finally, we compare the signal intensity and homogeneity of the multi-contrast PD map with the well-established effective PD (PD*) mapping, for which the RP is based on concurrent bias field estimation and tissue classification, and the scaling factor is estimated from the mean white matter signal. The multi-contrast PD values homogeneity and accuracy within the cerebrospinal fluid (CSF) and deep brain structures are increased beyond that obtained using PD* maps. We demonstrate that the multi-contrast RP approach is insensitive to anatomical or a priori tissue information by applying it in a patient with extensive brain abnormalities and for whole body PD mapping in post-mortem foetal imaging.

Dataset Information

Controlled saturation magnetization transfer for reproducible multivendor variable flip angle T₁ and T₂ mapping.

Purpose

Methods

Results

Conclusion

Publications

Controlled saturation magnetization transfer for reproducible multivendor variable flip angle T<sub>1</sub> and T<sub>2</sub> mapping.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Dataset Information

Controlled saturation magnetization transfer for reproducible multivendor variable flip angle T1 and T2 mapping.

Purpose

Methods

Results

Conclusion

Publications

Controlled saturation magnetization transfer for reproducible multivendor variable flip angle T<sub>1</sub> and T<sub>2</sub> mapping.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Controlled saturation magnetization transfer for reproducible multivendor variable flip angle T₁ and T₂ mapping.