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Simultaneous quantitative susceptibility mapping (QSM) and R2* for high iron concentration quantification with 3D ultrashort echo time sequences: An echo dependence study.

ABSTRACT: PURPOSE:To evaluate the echo dependence of 3D ultrashort echo time (TE) quantitative susceptibility mapping (3D UTE-QSM) and effective transverse relaxation rate ( R2*) measurement in the setting of high concentrations of iron oxide nanoparticles. METHODS:A phantom study with iron concentrations ranging from 2 to 22?mM was performed using a 3D UTE Cones sequence. Simultaneous QSM processing with morphology-enabled dipole inversion (MEDI) and R2* single exponential fitting was conducted offline with the acquired 3D UTE data. The dependence of UTE-QSM and R2* on echo spacing (?TE) and first TE (TE1 ) was investigated. RESULTS:A linear relationship was observed between UTE-QSM measurement and iron concentration up to 22?mM only, with the minimal TE1 of 0.032 ms and ?TE of less than 0.1 ms. A linear relationship was observed between R2* and iron concentration up to 22?mM only when TE1 was less than 0.132 ms and ?TE was less than 1.2 ms. UTE-QSM with MEDI processing showed strong dependence on ?TE and TE1 , especially at high iron concentrations. CONCLUSION:UTE-QSM is more sensitive than R2* measurement to TE selection. Both an ultrashort TE1 and a small ?TE are needed to achieve accurate QSM for high iron concentrations. Magn Reson Med 79:2315-2322, 2018. © 2018 International Society for Magnetic Resonance in Medicine.

SUBMITTER: Lu X

PROVIDER: S-EPMC5811338 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Simultaneous quantitative susceptibility mapping (QSM) and R2* for high iron concentration quantification with 3D ultrashort echo time sequences: An echo dependence study.

Lu Xing X Ma Yajun Y Chang Eric Y EY He Qun Q Searleman Adam A von Drygalski Annette A Du Jiang J

Magnetic resonance in medicine 20180104 4

<h4>Purpose</h4>To evaluate the echo dependence of 3D ultrashort echo time (TE) quantitative susceptibility mapping (3D UTE-QSM) and effective transverse relaxation rate ( R2*) measurement in the setting of high concentrations of iron oxide nanoparticles.<h4>Methods</h4>A phantom study with iron concentrations ranging from 2 to 22 mM was performed using a 3D UTE Cones sequence. Simultaneous QSM processing with morphology-enabled dipole inversion (MEDI) and R2* single exponential fitting was cond ...[more]

PMID: 29314215

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Project description:BackgroundCurrent R2*-MRI techniques for measuring hepatic iron content (HIC) use various acquisition types and fitting models.PurposeTo evaluate the accuracy and precision of R2*-HIC acquisition and fitting methods.Study typeSignal simulations, phantom study, and prospective in vivo cohort.PopulationIn all, 132 patients (58/74 male/female, mean age 17.7 years).Field strength/sequence2D-multiecho gradient-echo (GRE) and ultrashort echo time (UTE) acquisitions at 1.5T.AssessmentSynthetic MR signals were created to mimic published GRE and UTE methods, using different R2* values (25-2000 s-1 ) and signal-to-noise ratios (SNR). Phantoms with varying iron concentrations were scanned at 1.5T. In vivo data were analyzed from 132 patients acquired at 1.5T. R2* was estimated by fitting using three signal models. Accuracy and precision of R2* measurements for UTE acquisition parameters (SNR, echo spacing [ΔTE], maximum echo time [TEmax ]) and fitting methods were compared for simulated, phantom, and in vivo datasets.Statistical testsR2* accuracy was determined from the relative error and by linear regression analysis. Precision was evaluated using coefficient of variation (CoV) analysis.ResultsIn simulations, all models had high R2* accuracy (error <5%) and precision (CoV <10%) for all SNRs, shorter ΔTE (≤0.5 msec), and longer TEmax (≥10.1 msec); except the constant offset model overestimated R2* at the lowest SNR. In phantoms and in vivo, all models produced similar R2* values for different SNRs and shorter ΔTEs (slopes: 0.99-1.06, R2 > 0.99, P < 0.001). In all experiments, R2* results degraded for high R2* values with longer ΔTE (≥1 msec). In vivo, shorter and longer TEmax gave similar R2* results (slopes: 1.02-1.06, R2 > 0.99, P < 0.001) for the noise subtraction model for 25≤R2*≤2000 s-1 . However, both quadratic and constant offset models, using shorter TEmax (≤4.7 msec) overestimated R2* and yielded high CoVs up to ∼170% for low R2* (<250 s-1 ).Data conclusionUTE with TEmax ≥ 10.1 msec and ΔTE ≤ 0.5 msec yields accurate R2* estimates over the entire clinical HIC range. Monoexponential fitting with noise subtraction is the most robust signal model to changes in UTE parameters and achieves the highest R2* accuracy and precision.Level of evidence2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1475-1488.

Project description:ObjectivesMRI-based R2* mapping may enable reliable and rapid quantification of liver iron concentration (LIC). However, the performance and reproducibility of R2* across acquisition protocols remain unknown. Therefore, the objective of this work was to evaluate the performance and reproducibility of complex confounder-corrected R2* across acquisition protocols, at both 1.5 T and 3.0 T.MethodsIn this prospective study, 40 patients with suspected iron overload and 10 healthy controls were recruited with IRB approval and informed written consent and imaged at both 1.5 T and 3.0 T. For each subject, acquisitions included four different R2* mapping protocols at each field strength, and an FDA-approved R2-based method performed at 1.5 T as a reference for LIC. R2* maps were reconstructed from the complex data acquisitions including correction for noise effects and fat signal. For each subject, field strength, and R2* acquisition, R2* measurements were performed in each of the nine liver Couinaud segments and the spleen. R2* measurements were compared across protocols and field strength (1.5 T and 3.0 T), and R2* was calibrated to LIC for each acquisition and field strength.ResultsR2* demonstrated high reproducibility across acquisition protocols (p > 0.05 for 96/108 pairwise comparisons across 2 field strengths and 9 liver segments, ICC > 0.91 for each field strength/segment combination) and high predictive ability (AUC > 0.95 for four clinically relevant LIC thresholds). Calibration of R2* to LIC was LIC = - 0.04 + 2.62 × 10-2 R2* at 1.5 T and LIC = 0.00 + 1.41 × 10-2 R2* at 3.0 T.ConclusionsComplex confounder-corrected R2* mapping enables LIC quantification with high reproducibility across acquisition protocols, at both 1.5 T and 3.0 T.Key points• Confounder-corrected R2* of the liver provides reproducible R2* across acquisition protocols, including different spatial resolutions, echo times, and slice orientations, at both 1.5 T and 3.0 T. • For all acquisition protocols, high correlation with R2-based liver iron concentration (LIC) quantification was observed. • The calibration between confounder-corrected R2* and LIC, at both 1.5 T and 3.0 T, is determined in this study.

Project description:BACKGROUND:Quantitative MRI of patellar tendinopathy (PT) can be challenging due to spatial variation of T2 * relaxation times. PURPOSE:1) To compare T2 * quantification using a standard approach with analysis in specific tissue compartments of the patellar tendon. 2) To evaluate test-retest reliability of different methods for fitting ultrashort echo time (UTE)-relaxometry data. STUDY TYPE:Prospective. SUBJECTS:Sixty-five athletes with PT. FIELD STRENGTH/SEQUENCE:3D UTE scans covering the patellar tendon were acquired using a 3.0T scanner and a 16-channel surface coil. ASSESSMENT:Voxelwise median T2 * was quantified with monoexponential, fractional-order, and biexponential fitting. We applied two methods for T2 * analysis: first, a standard approach by analyzing all voxels covering the proximal patellar tendon. Second, within subregions of the patellar tendon, by using thresholds on biexponential fitting parameter percentage short T2 * (0-30% for mostly long T2 *, 30-60% for mixed T2 *, and 60-100% for mostly short T2 *). STATISTICAL TESTS:Average test-retest reliability was assessed in three athletes using coefficients-of-variation (CV) and coefficients-of-repeatability (CR). RESULTS:With standard image analysis, we found a median [interquartile range, IQR] monoexponential T2 * of 6.43 msec [4.32-8.55] and fractional order T2 * 4.39 msec [3.06-5.78]. The percentage of short T2 * components was 52.9% [35.5-69.6]. Subregional monoexponential T2 * was 13.78 msec [12.11-16.46], 7.65 msec [6.49-8.61], and 3.05 msec [2.52-3.60] and fractional order T2 * 11.82 msec [10.09-14.44], 5.14 msec [4.25-5.96], and 2.19 msec [1.82-2.64] for 0-30%, 30-60%, and 60-100% short T2 *, respectively. Biexponential component short T2 * was 1.693 msec [1.417-2.003] for tissue with mostly short T2 * and long T2 * of 15.79 msec [13.47-18.61] for mostly long T2 *. The average CR (CV) was 2 msec (15%), 2 msec (19%) and 10% (22%) for monoexponential, fractional order and percentage short T2 *, respectively. DATA CONCLUSION:Patellar tendinopathy is characterized by regional variability in binding states of water. Quantitative multicompartment T2 * analysis in PT can be facilitated using a voxel selection method based on using biexponential fitting parameters. LEVEL OF EVIDENCE:1 TECHNICAL EFFICACY STAGE: 1 J. Magn. Reson. Imaging 2020;52:420-430.

Project description:PurposeTo evaluate three-dimensional (3D) ultrashort echo time (UTE) MRI regarding image quality and suitability for functional image analysis using gradient-echo sequences in breath-hold and with self-navigation.Materials and methodsIn this prospective exploratory study, 10 patients (mean age, 21 years; age range, 5-58 years; five men) and 10 healthy control participants (mean age, 25 years; age range, 10-39 years; five men) underwent 3D UTE MRI at 3.0 T. Imaging was performed with a prototypical stack-of-spirals 3D UTE sequence during single breath holds (echo time [TE], 0.05 msec) and with a self-navigated "Koosh ball" 3D UTE sequence at free breathing (TE, 0.03 msec). Image quality was rated on a four-point Likert scale. Edge sharpness was calculated. After semiautomated segmentation, fractional ventilation was calculated from MRI signal intensity (FVSI) and volume change (FVVol). The air volume fraction (AVF) was estimated from relative signal intensity (aortic blood signal intensity was used as a reference). Means were compared between techniques and participants. The Wilcoxon signed rank test and Spearman rank correlation were used for statistical analyses.ResultsImage quality ratings were equal for both techniques. However, stack-of-spirals breath-hold UTE was more susceptible to motion and aliasing artifacts. Mean FVSI was higher during breath hold than at free breathing (mean ± standard deviation in milliliters of gas per milliliters of parenchyma, 0.17 mL/mL ± 0.06 [minimum, 0.07; maximum, 0.34] vs 0.11 mL/mL ± 0.03 [minimum, 0.06; maximum, 0.17], P = .016). Mean FVSI and FVVol were in good agreement (mean difference: at breath hold, -0.008 [95% confidence interval {CI}: 0.007, -0.024]; ρ = 0.97 vs free breathing, -0.004 [95% CI: 0.007, -0.016]; ρ = 0.91). AVF correlated between both techniques (ρ = 0.94).ConclusionBreath-hold and self-navigated 3D UTE sequences yield proton density-weighted images of the lungs that are similar in quality, and both techniques are suitable for functional image analysis.Supplemental material is available for this article.© RSNA, 2020.

Project description:BackgroundComputed tomography (CT) and spirometry are the current standard methods for assessing lung anatomy and pulmonary ventilation, respectively. However, CT provides limited ventilation information and spirometry only provides global measures of lung ventilation. Thus, a method that can enable simultaneous examination of lung anatomy and ventilation is of clinical interest.PurposeTo develop and test a 4D respiratory-resolved sparse lung MRI (XD-UTE: eXtra-Dimensional Ultrashort TE imaging) approach for simultaneous evaluation of lung anatomy and pulmonary ventilation.Study typeProspective.PopulationIn all, 23 subjects (11 volunteers and 12 patients, mean age = 63.6 ± 8.4).Field strength/sequence3T MR; a prototype 3D golden-angle radial UTE sequence, a Cartesian breath-hold volumetric-interpolated examination (BH-VIBE) sequence.AssessmentAll subjects were scanned using the 3D golden-angle radial UTE sequence during normal breathing. Ten subjects underwent an additional scan during alternating normal and deep breathing. Respiratory-motion-resolved sparse reconstruction was performed for all the acquired data to generate dynamic normal-breathing or deep-breathing image series. For comparison, BH-VIBE was performed in 12 subjects. Lung images were visually scored by three experienced chest radiologists and were analyzed by two observers who segmented the left and right lung to derive ventilation parameters in comparison with spirometry.Statistical testsNonparametric paired two-tailed Wilcoxon signed-rank test; intraclass correlation coefficient, Pearson correlation coefficient.ResultsXD-UTE achieved significantly improved image quality compared both with Cartesian BH-VIBE and radial reconstruction without motion compensation (P < 0.05). The global ventilation parameters (a sum of the left and right lung measures) were in good correlation with spirometry in the same subjects (correlation coefficient = 0.724). There were excellent correlations between the results obtained by two observers (intraclass correlation coefficient ranged from 0.8855-0.9995).Data conclusionSimultaneous evaluation of lung anatomy and ventilation using XD-UTE is demonstrated, which have shown good potential for improved diagnosis and management of patients with heterogeneous lung diseases.Level of evidence2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:411-422.

Dataset Information

Simultaneous quantitative susceptibility mapping (QSM) and R2* for high iron concentration quantification with 3D ultrashort echo time sequences: An echo dependence study.

Publications

Simultaneous quantitative susceptibility mapping (QSM) and R2* for high iron concentration quantification with 3D ultrashort echo time sequences: An echo dependence study.

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