Dataset Information

B₀ and B₁ inhomogeneities in the liver at 1.5 T and 3.0 T.

ABSTRACT:

Purpose

The purpose of this work is to characterize the magnitude and variability of B₀ and B₁ inhomogeneities in the liver in large cohorts of patients at both 1.5 T and 3.0 T.

Methods

Volumetric B₀ and B₁ maps were acquired over the liver of patients presenting for routine abdominal MRI. Regions of interest were drawn in the nine Couinaud segments of the liver, and the average value was recorded. Magnitude and variation of measured averages in each segment were reported across all patients.

Results

A total of 316 B₀ maps and 314 B₁ maps, acquired at 1.5 T and 3.0 T on a variety of GE Healthcare MRI systems in 630 unique exams, were identified, analyzed, and, in the interest of reproducible research, de-identified and made public. Measured B₀ inhomogeneities ranged (5th-95th percentiles) from -31.7 Hz to 164.0 Hz for 3.0 T (-14.5 Hz to 81.3 Hz at 1.5 T), while measured B₁ inhomogeneities (ratio of actual over prescribed flip angle) ranged from 0.59 to 1.13 for 3.0 T (0.83 to 1.11 at 1.5 T).

Conclusion

This study provides robust characterization of B₀ and B₁ inhomogeneities in the liver to guide the development of imaging applications and protocols. Field strength, bore diameter, and sex were determined to be statistically significant effects for both B₀ and B₁ uniformity. Typical clinical liver imaging at 3.0 T should expect B₀ inhomogeneities ranging from approximately -100 Hz to 250 Hz (-50 Hz to 150 Hz at 1.5 T) and B₁ inhomogeneities ranging from approximately 0.4 to 1.3 (0.7 to 1.2 at 1.5 T).

SUBMITTER: Roberts NT

PROVIDER: S-EPMC7869971 | biostudies-literature | 2021 Apr

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

B<sub>0</sub> and B<sub>1</sub> inhomogeneities in the liver at 1.5 T and 3.0 T.

Roberts Nathan T NT Hinshaw Louis A LA Colgan Timothy J TJ Ii Takanori T Hernando Diego D Reeder Scott B SB

Magnetic resonance in medicine 20201026 4

<h4>Purpose</h4>The purpose of this work is to characterize the magnitude and variability of B<sub>0</sub> and B<sub>1</sub> inhomogeneities in the liver in large cohorts of patients at both 1.5 T and 3.0 T.<h4>Methods</h4>Volumetric B<sub>0</sub> and B<sub>1</sub> maps were acquired over the liver of patients presenting for routine abdominal MRI. Regions of interest were drawn in the nine Couinaud segments of the liver, and the average value was recorded. Magnitude and variation of measured ave ...[more]

PMID: 33107109

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Project description:Background MRI is a standard of care tool to measure liver iron concentration (LIC). Compared with regulatory-approved R2 MRI, R2* MRI has superior speed and is available in most MRI scanners; however, the cross-vendor reproducibility of R2*-based LIC estimation remains unknown. Purpose To evaluate the reproducibility of LIC via single-breath-hold R2* MRI at both 1.5 T and 3.0 T with use of a multicenter, multivendor study. Materials and Methods Four academic medical centers using MRI scanners from three different vendors (three 1.5-T scanners, one 2.89-T scanner, and two 3.0-T scanners) participated in this prospective cross-sectional study. Participants with known or suspected liver iron overload were recruited to undergo multiecho gradient-echo MRI for R2* mapping at 1.5 T and 3.0 T (2.89 T or 3.0 T) on the same day. R2* maps were reconstructed from the multiecho images and analyzed at a single center. Reference LIC measurements were obtained with a commercial R2 MRI method performed using standardized 1.5-T spin-echo imaging. R2*-versus-LIC calibrations were generated across centers and field strengths using linear regression and compared using F tests. Receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic performance of R2* MRI in the detection of clinically relevant LIC thresholds. Results A total of 207 participants (mean age, 38 years ± 20 [SD]; 117 male participants) were evaluated between March 2015 and September 2019. A linear relationship was confirmed between R2* and LIC. All calibrations within the same field strength were highly reproducible, showing no evidence of statistically significant center-specific differences (P > .43 across all comparisons). Calibrations for 1.5 T and 3.0 T were generated, as follows: for 1.5 T, LIC (in milligrams per gram [dry weight]) = -0.16 + 2.603 × 10-2 R2* (in seconds-1); for 2.89 T, LIC (in milligrams per gram) = -0.03 + 1.400 × 10-2 R2* (in seconds-1); for 3.0 T, LIC (in milligrams per gram) = -0.03 + 1.349 × 10-2 R2* (in seconds-1). Liver R2* had high diagnostic performance in the detection of clinically relevant LIC thresholds (area under the ROC curve, >0.98). Conclusion R2* MRI enabled accurate and reproducible quantification of liver iron overload over clinically relevant ranges of liver iron concentration (LIC). The data generated in this study provide the necessary calibrations for broad clinical dissemination of R2*-based LIC quantification. ClinicalTrials.gov registration no.: NCT02025543 © RSNA, 2022 Online supplemental material is available for this article.

Project description:BackgroundRecent multicenter, multivendor MRI-based R2* vs. liver iron concentration (LIC) calibrations (i.e., MCMV calibrations) may facilitate broad clinical dissemination of R2*-based LIC quantification. However, these calibrations are based on a centralized offline R2* reconstruction, and their applicability with vendor-provided R2* maps is unclear.PurposeTo determine R2* ranges of agreement between the centralized and three MRI vendors' R2* reconstructions.Study typeProspective.SubjectsTwo hundred and seven subjects (mean age 37.6 ± 19.6 years; 117 male) with known or suspected iron overload from four academic medical centers.Field strength/sequenceStandardized multiecho spoiled gradient echo sequence at 1.5 T and 3.0 T for R2* mapping and a multiple spin-echo sequence at 1.5 T for LIC quantification. MRI vendors: GE Healthcare, Philips Healthcare, and Siemens Healthineers.AssessmentR2* maps were generated using both the centralized and vendor reconstructions, and ranges of agreement were determined. R2*-LIC linear calibrations were determined for each site, field strength, and reconstruction and compared with the MCMV calibrations.Statistical testsBland-Altman analysis to determine ranges of agreement. Linear regression, analysis of covariance F tests, and Tukey's multiple comparison testing to assess reproducibility of calibrations across sites and vendors. A P value <0.05 was considered significant.ResultsThe upper limits of R2* ranges of agreement were approximately 500, 375, and 330 s-1 for GE, Philips, and Siemens reconstructions, respectively, at 1.5 T and approximately 700 and 800 s-1 for GE and Philips, respectively, at 3.0 T. Within the R2* ranges of agreement, vendor R2*-LIC calibrations demonstrated high reproducibility (no significant differences between slopes or intercepts; P ≥ 0.06) and agreed with the MCMV calibrations (overlapping 95% confidence intervals).Data conclusionBased on the determined upper limits, R2* measurements obtained from vendor-provided R2* maps may be reliably and practically used to quantify LIC less than approximately 8-13 mg/g using the MCMV calibrations and similar acquisition parameters as this study.Evidence level1 TECHNICAL EFFICACY: Stage 3.

Dataset Information

B₀ and B₁ inhomogeneities in the liver at 1.5 T and 3.0 T.

Purpose

Methods

Results

Conclusion

Publications

B<sub>0</sub> and B<sub>1</sub> inhomogeneities in the liver at 1.5 T and 3.0 T.

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Tweets

Dataset Information

B0 and B1 inhomogeneities in the liver at 1.5 T and 3.0 T.

Purpose

Methods

Results

Conclusion

Publications

B<sub>0</sub> and B<sub>1</sub> inhomogeneities in the liver at 1.5 T and 3.0 T.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

B₀ and B₁ inhomogeneities in the liver at 1.5 T and 3.0 T.