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2.
  • Alamidi, Daniel, et al. (författare)
  • Variable Flip Angle 3D Ultrashort Echo Time (UTE) T-1 Mapping of Mouse Lung: A Repeatability Assessment
  • 2018
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 48:3, s. 846-852
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Lung T-1 is a potential translational biomarker of lung disease. The precision and repeatability of variable flip angle (VFA) T-1 mapping using modern 3D ultrashort echo time (UTE) imaging of the whole lung needs to be established before it can be used to assess response to disease and therapy. Purpose: To evaluate the feasibility of regional lung T-1 quantification with VFA 3D-UTE and to investigate long-and short-term T-1 repeatability in the lungs of naive mice. Field strength/Sequence: 3D free-breathing radial UTE (8 mu s) at 4.7T. Assessment: VFA 3D-UTE T-1 calculations were validated against T-1 values measured with inversion recovery (IR) in phantoms. Lung T-1 and proton density (S-0) measurements of whole lung and muscle were repeated five times over 1 month in free-breathing naive mice. Two consecutive T-1 measurements were performed during one of the imaging sessions. Statistical Tests: Agreement in T-1 between VFA 3D-UTE and IR in phantoms was assessed using Bland-Altman and Pearson's correlation analysis. The T-1 repeatability in mice was evaluated using coefficient of variation (CV), repeated-measures analysis of variance (ANOVA), and paired t-test. Results: Good T-1 agreement between the VFA 3D-UTE and IR methods was found in phantoms. T-1 in lung and muscle showed a 5% and 3% CV (1255 +/- 63 msec and 1432 +/- 42 msec, respectively, mean +/- SD) with no changes in T-1 or S-0 over a month. Consecutive measurements resulted in an increase of 2% in both lung T-1 and S-0. Data Conclusion: VFA 3D-UTE shows promise as a reliable T-1 mapping method that enables full lung coverage, high signal-to-noise ratio (similar to 25), and spatial resolution (300 mu m) in freely breathing animals. The precision of the VFA 3D-UTE method will enable better design and powering of studies.
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3.
  • Alsaqal, Salem, et al. (författare)
  • The Combination of MR Elastography and Proton Density Fat Fraction Improves Diagnosis of Nonalcoholic Steatohepatitis.
  • 2022
  • Ingår i: Journal of Magnetic Resonance Imaging. - : John Wiley & Sons. - 1053-1807 .- 1522-2586. ; 56:2, s. -379
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is rapidly increasing worldwide. It is subdivided into nonalcoholic fatty liver (NAFL) and the more aggressive form, nonalcoholic steatohepatitis (NASH), which carries a higher risk of developing fibrosis and cirrhosis. There is currently no reliable non-invasive method for differentiating NASH from NAFL.PURPOSE: To investigate the ability of magnetic resonance imaging (MRI)-based imaging biomarkers to diagnose NASH and moderate fibrosis as well as assess their repeatability.STUDY TYPE: Prospective.SUBJECTS: Sixty-eight participants (41% women) with biopsy-proven NAFLD (53 NASH and 15 NAFL). Thirty participants underwent a second MRI in order to assess repeatability.FIELD STRENGTH/SEQUENCE: 3.0 T; MR elastography (MRE) (a spin-echo echo-planar imaging [SE-EPI] sequence with motion-encoding gradients), MR proton density fat fraction (PDFF) and R2* mapping (a multi-echo three-dimensional gradient-echo sequence), T1 mapping (a single-point saturation-recovery technique), and diffusion-weighted imaging (SE-EPI sequence).ASSESSMENT: Quantitative MRI measurements were obtained and assessed alone and in combination with biochemical markers (cytokeratin-18 [CK18] M30, alanine transaminase [ALT], and aspartate transaminase [AST]) using logistic regression models. Models that could differentiate between NASH and NAFL and between moderate to advanced fibrosis (F2-4) and no or mild fibrosis (F0-1), based on the histopathological results, were identified.STATISTICAL TESTS: Independent samples t-test, Pearson's chi-squared test, area under the receiver operating characteristic curve (AUROC), Spearman's correlation, intra-individual coefficient of variation, and intraclass correlation coefficient (ICC). Statistical significance was set at P < 0.05.RESULTS: There was a significant difference between the NASH and NAFL groups with liver stiffness assessed with MRE, CK18 M30, and ALT, with an AUROC of 0.74, 0.76, and 0.70, respectively. Both MRE and PDFF contributed significantly to a bivariate model for diagnosing NASH (AUROC = 0.84). MRE could significantly differentiate between F2-4 and F0-1 (AUROC = 0.74). A model combining MRE with AST improved the diagnosis of F2-4 (AUROC = 0.83). The ICC for repeatability was 0.94 and 0.99 for MRE and PDFF, respectively.DATA CONCLUSION: MRE can potentially diagnose NASH and differentiate between fibrosis stages. Combining MRE with PDFF improves the diagnosis of NASH.LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 2.
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4.
  • Andersson, Thord, et al. (författare)
  • Consistent intensity inhomogeneity correction in water-fat MRI
  • 2015
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley-Blackwell. - 1053-1807 .- 1522-2586. ; 42:2
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To quantitatively and qualitatively evaluate the water-signal performance of the consistent intensity inhomogeneity correction (CIIC) method to correct for intensity inhomogeneitiesMETHODS: Water-fat volumes were acquired using 1.5 Tesla (T) and 3.0T symmetrically sampled 2-point Dixon three-dimensional MRI. Two datasets: (i) 10 muscle tissue regions of interest (ROIs) from 10 subjects acquired with both 1.5T and 3.0T whole-body MRI. (ii) Seven liver tissue ROIs from 36 patients imaged using 1.5T MRI at six time points after Gd-EOB-DTPA injection. The performance of CIIC was evaluated quantitatively by analyzing its impact on the dispersion and bias of the water image ROI intensities, and qualitatively using side-by-side image comparisons.RESULTS: CIIC significantly ( P1.5T≤2.3×10-4,P3.0T≤1.0×10-6) decreased the nonphysiological intensity variance while preserving the average intensity levels. The side-by-side comparisons showed improved intensity consistency ( Pint⁡≤10-6) while not introducing artifacts ( Part=0.024) nor changed appearances ( Papp≤10-6).CONCLUSION: CIIC improves the spatiotemporal intensity consistency in regions of a homogenous tissue type.
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5.
  • Berggren, Klas, et al. (författare)
  • Super-Resolution Cine Image Enhancement for Fetal Cardiac Magnetic Resonance Imaging
  • 2022
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 56:1, s. 223-231
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundFetal cardiac magnetic resonance imaging (MRI) improves the diagnosis of congenital heart defects, but is sensitive to fetal motion due to long image acquisition time. This may be overcome with faster image acquisition with low resolution, followed by image enhancement to provide clinically useful images.PurposeTo combine phase-encoding undersampling with super-resolution neural networks to achieve high-resolution fetal cine cardiac MR images with short acquisition time.Study TypeProspective.SubjectsTwenty-eight fetuses (gestational week 36 [interquartile range 33–38 weeks]).Field Strength/Sequence1.5 T, balanced steady-state free precession (bSSFP) cine sequence.AssessmentImages were acquired using fully sampled Doppler ultrasound-gated clinical bSSFP cine as reference, with equivalent cine sequences with decreased phase-encoding resolution (25%, 33%, and 50% of clinical standard). Two super-resolution methods based on convolutional neural networks were proposed and evaluated (phasrGAN and phasrresnet). Data were partitioned into training (36 cine slices), validation (3 cine slices), and test sets (67 cine slices) without overlap. Conventional reconstruction methods using bicubic interpolation and k-space zeropadding were used for comparison. Three blinded observers scored image quality between 1 and 10.Statistical TestsImage scores are reported as median [interquartile range] and were compared using Mann–Whitney's nonparametric test with P < 0.05 showing statistically significant differences.ResultsBoth proposed methods showed no significant difference in image quality compared to clinical images (8 [7–8.5]) down to 33% (phasrGAN 8 [6.5–8]; phasrresnet 8 [7–8], all P ≥ 0.19) phase-encoding resolution, i.e., up to three times faster image acquisition, whereas bicubic interpolation and k-space zeropadding showed significantly lower quality for 33% phase-encoding resolution (both 7 [6–8]).Data ConclusionSuper-resolution enhancement can be used for fetal cine cardiac MRI to reduce image acquisition time while maintaining image quality. This may lead to an improved success rate for fetal cine MR imaging, as the impact of fetal motion is lessened by shortened acquisitions.Level of Evidence1Technical EfficacyStage 2
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6.
  • Bergvall, Erik, et al. (författare)
  • A fast and highly automated approach to myocardial motion analysis using phase contrast magnetic resonance imaging.
  • 2006
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 23:5, s. 652-661
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To develop a fast and highly automated method for calculating two-dimensional myocardial motion and deformation using velocity encoded magnetic resonance imaging. Materials and Methods: Two-dimensional phase contrast magnetic resonance imaging was used to acquire time resolved velocity maps of the myocardium. Cardiac motion was calculated by an iterative integration-regularization scheme of low computational cost. Image segmentation was performed using active appearance models. Results: Validation of motion tracking was performed in N = 47 subjects using saturation grid-tagging and closely followed "tag-lines." Image segmentation was validated vs. manual delineation. Conclusion: The speed and limited user interaction gives the method good potential for use in clinical practice.
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  • Bjerner, Tomas, et al. (författare)
  • Evaluation of nonperfused myocardial ischemia with MRI and an intravascular USPIO contrast agent in an ex vivo pig model
  • 2000
  • Ingår i: Journal of Magnetic Resonance Imaging. - 1053-1807 .- 1522-2586. ; 12:6, s. 866-872
  • Tidskriftsartikel (refereegranskat)abstract
    • The ultrasmall superparamagnetic iron oxide (USPIO) preparation NC100150 Injection (Clariscan; Nycomed Imaging, Oslo, Norway) was tested for its ability to delineate nonperfused myocardium under steady-state conditions. An experimental animal model of focal myocardial ischemia induced by ligation of the distal part of the left anterior descending artery was used. The contrast agent was administered in four doses: 0, 4, 8, and 12 mg Fe/kg body weight. Magnetic resonance examination ex vivo, including T1-, T2-, and T2*-weighted sequences, was performed. Nonperfused myocardium was determined by fluorescein. The best delineation of nonperfused myocardium was found with a T1-weighted inversion recovery/turbo spin-echo sequence and doses of 4 and 8 mg Fe/kg body weight, where 95% of the volume was discernible at the dose of 4 mg Fe/kg body weight. The results suggest that steady-state imaging by T1-weighted sequence with the use of NC100150 Injection to delineate nonperfused myocardium is feasible. J. Magn. Reson. Imaging 2000;12:866-872.
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  • Briley Saebo, Karen, et al. (författare)
  • Long-term imaging effects in rat liver after a single injection of an iron oxide nanoparticle based MR contrast agent
  • 2004
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 20:4, s. 622-631
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To investigate the duration of liver R2* enhancement and pharmacokinetics following administration of an iron oxide nanoparticle in a rat model.MATERIALS AND METHODS: Rats were injected with 0, 1, 2, or 5 mg Fe/kg of NC100150 Injection, and quantitative in vivo 1/T2* liver measurements were obtained between 1 and 133 days after injection. The concentration of NC100150 Injection was determined by relaxometry methods in ex vivo rat liver homogenate.RESULTS: At all dose levels, 1/T2* remained greater than control values up to 63 days after injection. In the highest dose group, 1/T2* was above control levels during the entire 133 day time-course investigated. There were no quantifiable amounts of NC100150 Injection present 63 days after injection in any of the dose groups. The half-life of NC100150 Injection in rat liver was dose dependent. For the lowest dose group, the degradation of the particles could be defined by a mono-exponential function with a half-life of eight days. For the 2 and 5 mg Fe/kg dose groups, the degradation was bi-exponential with a fast initial decay of seven to eight days followed by a slow terminal decay of 43-46 days.CONCLUSION: NC100150 Injection exhibits prolonged 1/T2* enhancement in rat liver. The liver enhancement persisted at time points when the concentration of iron oxide particles present in the liver was below method detection limits. The prolonged 1/T2* enhancement is likely a result of the particle breakdown products and the induction of ferritin and hemosiderin with increasing iron cores/loading factors.
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  • Burtscher, Isabella M, et al. (författare)
  • Proton MR spectroscopy in clinical routine
  • 2001
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 13:4, s. 560-567
  • Tidskriftsartikel (refereegranskat)abstract
    • In vivo magnetic resonance spectroscopy (MRS) addresses metabolic pathways and their steady states in different tissue types. The brain has by tradition, and due to technical limitations in other organs, been one of the tissues most studied by MRS, and both 1H- and 31P-MRS have been used. Although 31P-MRS is outstanding for the evaluation of sources of metabolic energy in the brain, 1H-MRS has become the major clinically applied method in neurospectroscopy, as it provides information on markers of neuronal function, myelin, cell membranes, and metabolic active compounds. Furthermore, MR sensitivity is much greater for protons than it is for phosphorus and 1H-MRS, therefore allowing better spatial resolution. This review focuses on neurospectroscopy and diagnostic insights into diverse neurological problems provided by 1H-MRS applied as a clinical tool.
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  • Bustamante, Mariana, et al. (författare)
  • Automatic Time-Resolved Cardiovascular Segmentation of 4D Flow MRI Using Deep Learning
  • 2023
  • Ingår i: Journal of Magnetic Resonance Imaging. - Hoboken, NJ, United States : John Wiley & Sons. - 1053-1807 .- 1522-2586. ; 57:1, s. 191-203
  • Tidskriftsartikel (refereegranskat)abstract
    • Background Segmenting the whole heart over the cardiac cycle in 4D flow MRI is a challenging and time-consuming process, as there is considerable motion and limited contrast between blood and tissue.Purpose To develop and evaluate a deep learning-based segmentation method to automatically segment the cardiac chambers and great thoracic vessels from 4D flow MRI. Study Type Retrospective.Subjects A total of 205 subjects, including 40 healthy volunteers and 165 patients with a variety of cardiac disorders were included. Data were randomly divided into training (n = 144), validation (n = 20), and testing (n = 41) sets.Field Strength/Sequence A 3 T/time-resolved velocity encoded 3D gradient echo sequence (4D flow MRI).Assessment A 3D neural network based on the U-net architecture was trained to segment the four cardiac chambers, aorta, and pulmonary artery. The segmentations generated were compared to manually corrected atlas-based segmentations. End-diastolic (ED) and end-systolic (ES) volumes of the four cardiac chambers were calculated for both segmentations.Statistical tests Dice score, Hausdorff distance, average surface distance, sensitivity, precision, and miss rate were used to measure segmentation accuracy. Bland-Altman analysis was used to evaluate agreement between volumetric parameters.Results The following evaluation metrics were computed: mean Dice score (0.908 +/- 0.023) (mean +/- SD), Hausdorff distance (1.253 +/- 0.293 mm), average surface distance (0.466 +/- 0.136 mm), sensitivity (0.907 +/- 0.032), precision (0.913 +/- 0.028), and miss rate (0.093 +/- 0.032). Bland-Altman analyses showed good agreement between volumetric parameters for all chambers. Limits of agreement as percentage of mean chamber volume (LoA%), left ventricular: 9.3%, 13.5%, left atrial: 12.4%, 16.9%, right ventricular: 9.9%, 15.6%, and right atrial: 18.7%, 14.4%; for ED and ES, respectively.Data conclusion The addition of this technique to the 4D flow MRI assessment pipeline could expedite and improve the utility of this type of acquisition in the clinical setting. Evidence Level 4Technical Efficacy Stage 1
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  • Bustamante, Mariana, et al. (författare)
  • Using Deep Learning to Emulate the Use of an External Contrast Agent in Cardiovascular 4D Flow MRI
  • 2021
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 54:3, s. 777-786
  • Tidskriftsartikel (refereegranskat)abstract
    • Background Although contrast agents would be beneficial, they are seldom used in four-dimensional (4D) flow magnetic resonance imaging (MRI) due to potential side effects and contraindications. Purpose To develop and evaluate a deep learning architecture to generate high blood-tissue contrast in noncontrast 4D flow MRI by emulating the use of an external contrast agent. Study Type Retrospective. Subjects Of 222 data sets, 141 were used for neural network (NN) training (69 with and 72 without contrast agent). Evaluation was performed on the remaining 81 noncontrast data sets. Field Strength/Sequences Gradient echo or echo-planar 4D flow MRI at 1.5 T and 3 T. Assessment A cyclic generative adversarial NN was trained to perform image translation between noncontrast and contrast data. Evaluation was performed quantitatively using contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), structural similarity index (SSIM), mean squared error (MSE) of edges, and Dice coefficient of segmentations. Three observers performed a qualitative assessment of blood-tissue contrast, noise, presence of artifacts, and image structure visualization. Statistical Tests The Wilcoxon rank-sum test evaluated statistical significance. Kendalls concordance coefficient assessed interobserver agreement. Results Contrast in the regions of interest (ROIs) in the NN enhanced images increased by 88%, CNR increased by 63%, and SNR improved by 48% (all P < 0.001). The SSIM was 0.82 +/- 0.01, and the MSE of edges was 0.09 +/- 0.01 (range [0,1]). Segmentations based on the generated images resulted in a Dice similarity increase of 15.25%. The observers managed to differentiate between contrast MR images and our results; however, they preferred the NN enhanced images in 76.7% of cases. This percentage increased to 93.3% for phase-contrast MR angiograms created from the NN enhanced data. Visual grading scores were blood-tissue contrast = 4.30 +/- 0.74, noise = 3.12 +/- 0.98, and presence of artifacts = 3.63 +/- 0.76. Image structures within and without the ROIs resulted in scores of 3.42 +/- 0.59 and 3.07 +/- 0.71, respectively (P < 0.001). Data Conclusion The proposed approach improves blood-tissue contrast in MR images and could be used to improve data quality, visualization, and postprocessing of cardiovascular 4D flow data. Evidence Level 3 Technical Efficacy Stage 1
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14.
  • Calamante, Fernando, et al. (författare)
  • MR System Operator: Recommended Minimum Requirements for Performing MRI in Human Subjects in a Research Setting
  • 2015
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 41:4, s. 899-902
  • Forskningsöversikt (refereegranskat)abstract
    • This article is intended to provide guidelines for the minimum level of safety and operational knowledge that an MR system operator should exhibit in order to safely perform an MR procedure in a human subject in a research setting. This article represents the position of the International Society for Magnetic Resonance in Medicine (ISMRM) regarding this important topic and was developed by members of this society's MR Safety Committee. J. Magn. Reson. Imaging 2015;41:899-902. (c) 2014 Wiley Periodicals, Inc.
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  • Cibis, Merih, et al. (författare)
  • Creating Hemodynamic Atlases of Cardiac 4D Flow MRI
  • 2017
  • Ingår i: Journal of Magnetic Resonance Imaging. - : WILEY. - 1053-1807 .- 1522-2586. ; 46:5, s. 1389-1399
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: Hemodynamic atlases can add to the pathophysiological understanding of cardiac diseases. This study proposes a method to create hemodynamic atlases using 4D Flow magnetic resonance imaging (MRI). The method is demonstrated for kinetic energy (KE) and helicity density (Hd). Materials and Methods: Thirteen healthy subjects underwent 4D Flow MRI at 3T. Phase-contrast magnetic resonance cardioangiographies (PC-MRCAs) and an average heart were created and segmented. The PC-MRCAs, KE, and Hd were nonrigidly registered to the average heart to create atlases. The method was compared with 1) rigid, 2) affine registration of the PC-MRCAs, and 3) affine registration of segmentations. The peak and mean KE and Hd before and after registration were calculated to evaluate interpolation error due to nonrigid registration. Results: The segmentations deformed using nonrigid registration overlapped (median: 92.3%) more than rigid (23.1%, P amp;lt; 0.001), and affine registration of PC-MRCAs (38.5%, P amp;lt; 0.001) and affine registration of segmentations (61.5%, P amp;lt; 0.001). The peak KE was 4.9 mJ using the proposed method and affine registration of segmentations (P50.91), 3.5 mJ using rigid registration (P amp;lt; 0.001), and 4.2 mJ using affine registration of the PC-MRCAs (P amp;lt; 0.001). The mean KE was 1.1 mJ using the proposed method, 0.8 mJ using rigid registration (P amp;lt; 0.001), 0.9 mJ using affine registration of the PC-MRCAs (P amp;lt; 0.001), and 1.0 mJ using affine registration of segmentations (P50.028). The interpolation error was 5.262.6% at mid-systole, 2.863.8% at early diastole for peak KE; 9.669.3% at mid-systole, 4.064.6% at early diastole, and 4.964.6% at late diastole for peak Hd. The mean KE and Hd were not affected by interpolation. Conclusion: Hemodynamic atlases can be obtained with minimal user interaction using nonrigid registration of 4D Flow MRI. Level of Evidence: 2 Technical Efficacy: Stage 1
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  • Covaciu, Lucian, et al. (författare)
  • Human brain MR spectroscopy thermometry using metabolite aqueous-solution calibrations
  • 2010
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 31:4, s. 807-814
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To estimate absolute brain temperature using proton MR spectroscopy ((1)H-MRS) and mean brain-body temperature difference of healthy human volunteers. MATERIALS AND METHODS: Chemical shift difference between temperature-dependent water spectral line position and temperature-stable metabolite spectral reference was used for the estimations of absolute brain temperature. Temperature calibrations constants were obtained from the spectra of the N-acetyl aspartate (NAA line at approximately 2.0 ppm), glycero-phosphocholine (GPC line at approximately 3.2 ppm), and creatine (Cr line at approximately 3.0 ppm) aqueous solutions with pH values within physiologically pertinent ranges. Single-voxel PRESS sequence (TR/TE 2000/80 ms) was used for this purpose. Brain temperature was determined by averaging the temperatures computed from water-Cho, water-Cr, and water-NAA chemical shift differences. RESULTS: The mean brain temperature of 18 healthy volunteers was 38.1 +/- 0.4 degrees C and mean brain-body (rectal) temperature difference was 1.3 +/- 0.4 degrees C. CONCLUSION: Improved accuracy of the temperature constants and averaging the temperatures computed from water-Cho, water-Cr, and water-NAA chemical shift differences increased the reliability of the brain temperature estimations.
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  • Covarrubias, Yesenia, et al. (författare)
  • Pilot study on longitudinal change in pancreatic proton density fat fraction during a weight-loss surgery program in adults with obesity
  • 2019
  • Ingår i: Journal of Magnetic Resonance Imaging. - : WILEY. - 1053-1807 .- 1522-2586. ; 50:4, s. 1092-1102
  • Tidskriftsartikel (refereegranskat)abstract
    • Background Quantitative-chemical-shift-encoded (CSE)-MRI methods have been applied to the liver. The feasibility and potential utility CSE-MRI in monitoring changes in pancreatic proton density fat fraction (PDFF) have not yet been demonstrated. Purpose To use quantitative CSE-MRI to estimate pancreatic fat changes during a weight-loss program in adults with severe obesity and nonalcoholic fatty liver disease (NAFLD). To explore the relationship of reduction in pancreatic PDFF with reductions in anthropometric indices. Study Type Prospective/longitudinal. Population Nine adults with severe obesity and NAFLD enrolled in a weight-loss program. Field Strength/Sequence CSE-MRI fat quantification techniques and multistation-volumetric fat/water separation techniques were performed at 3 T. Assessment PDFF values were recorded from parametric maps colocalized across timepoints. Statistical Tests Rates of change of log-transformed variables across time were determined (linear-regression), and their significance assessed compared with no change (Wilcoxon test). Rates of change were correlated pairwise (Spearmans correlation). Results Mean pancreatic PDFF decreased by 5.7% (range 0.7-17.7%) from 14.3 to 8.6%, hepatic PDFF by 11.4% (2.6-22.0%) from 14.8 to 3.4%, weight by 30.9 kg (17.3-64.2 kg) from 119.0 to 88.1 kg, body mass index by 11.0 kg/m(2) (6.3-19.1 kg/m(2)) from 44.1 to 32.9 kg/m(2), waist circumference (WC) by 25.2 cm (4.0-41.0 cm) from 133.1 to 107.9 cm, HC by 23.5 cm (4.5-47.0 cm) from 135.8 to 112.3 cm, visceral adipose tissue (VAT) by 2.9 L (1.7-5.7 L) from 7.1 to 4.2 L, subcutaneous adipose tissue (SCAT) by 4.0 L (2.9-7.4 L) from 15.0 to 11.0 L. Log-transformed rate of change for pancreatic PDFF was moderately correlated with log-transformed rates for hepatic PDFF, VAT, SCAT, and WC (rho = 0.5, 0.47, 0.45, and 0.48, respectively), although not statistically significant. Data Conclusion Changes in pancreatic PDFF can be estimated by quantitative CSE-MRI in adults undergoing a weight-loss surgery program. Pancreatic and hepatic PDFF and anthropometric indices decreased significantly. Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019;50:1092-1102.
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19.
  • de Boer, Anneloes, et al. (författare)
  • Consensus-Based Technical Recommendations for Clinical Translation of Renal Phase Contrast MRI
  • 2022
  • Ingår i: Journal of Magnetic Resonance Imaging. - : John Wiley & Sons. - 1053-1807 .- 1522-2586. ; 55:2, s. 323-335
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Phase-contrast (PC) MRI is a feasible and valid noninvasive technique to measure renal artery blood flow, showing potential to support diagnosis and monitoring of renal diseases. However, the variability in measured renal blood flow values across studies is large, most likely due to differences in PC-MRI acquisition and processing. Standardized acquisition and processing protocols are therefore needed to minimize this variability and maximize the potential of renal PC-MRI as a clinically useful tool.PURPOSE: To build technical recommendations for the acquisition, processing, and analysis of renal 2D PC-MRI data in human subjects to promote standardization of renal blood flow measurements and facilitate the comparability of results across scanners and in multicenter clinical studies.STUDY TYPE: Systematic consensus process using a modified Delphi method.POPULATION: Not applicable.SEQUENCE FIELD/STRENGTH: Renal fast gradient echo-based 2D PC-MRI.ASSESSMENT: An international panel of 27 experts from Europe, the USA, Australia, and Japan with 6 (interquartile range 4-10) years of experience in 2D PC-MRI formulated consensus statements on renal 2D PC-MRI in two rounds of surveys. Starting from a recently published systematic review article, literature-based and data-driven statements regarding patient preparation, hardware, acquisition protocol, analysis steps, and data reporting were formulated.STATISTICAL TESTS: Consensus was defined as ≥75% unanimity in response, and a clear preference was defined as 60-74% agreement among the experts.RESULTS: Among 60 statements, 57 (95%) achieved consensus after the second-round survey, while the remaining three showed a clear preference. Consensus statements resulted in specific recommendations for subject preparation, 2D renal PC-MRI data acquisition, processing, and reporting.DATA CONCLUSION: These recommendations might promote a widespread adoption of renal PC-MRI, and may help foster the set-up of multicenter studies aimed at defining reference values and building larger and more definitive evidence, and will facilitate clinical translation of PC-MRI.LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 1.
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21.
  • Diaz, Sandra, et al. (författare)
  • Hyperpolarized (3)He apparent diffusion coefficient MRI of the lung: Reproducibility and volume dependency in healthy volunteers and patients with emphysema.
  • 2008
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 27, s. 763-770
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To measure the apparent diffusion coefficient (ADC) of hyperpolarized (HP) (3)He gas using diffusion weighted MRI in healthy volunteers and patients with emphysema and examine the reproducibility and volume dependency. MATERIALS AND METHODS: A total of eight healthy volunteers and 16 patients with emphysema were examined after inhalation of HP (3)He gas mixed with nitrogen (N(2)) during breathhold starting from functional residual capacity (FRC) in supine position. Coronal diffusion-sensitized MR images were acquired. Each subject was imaged on three separate days over a seven-day period and received two different volumes (6% and 15% of total lung capacity [TLC]) of HP (3)He each day. ADC maps and histograms were calculated. The mean and standard deviation (SD) of the ADC at different days and volumes were compared. RESULTS: The reproducibility of the mean ADC and SD over several days was good in both healthy volunteers and patients (SD range of 0.003-0.013 cm(2)/second and 0.001-0.009 cm(2)/second at 6% and 15% of TLC for healthy volunteers, and a SD range of 0.001-0.041 cm(2)/second and 0.001-0.011 cm(2)/second, respectively, for patients). A minor but significant increase in mean ADC with increased inhaled gas volume was observed in both groups. CONCLUSION: Mean ADC and SD of HP (3)He MRI is reproducible and discriminates well between healthy controls and patients with emphysema at the higher gas volume. This method is robust and may be useful to gain new insights into the pathophysiology and course of emphysema. J. Magn. Reson. Imaging 2008. (c) 2008 Wiley-Liss, Inc.
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22.
  • Dicks, Demetrius L., et al. (författare)
  • Persistent Decline in Longitudinal and Radial Strain After Coronary Microembolization Detected on Velocity Encoded Phase Contrast Magnetic Resonance Imaging
  • 2009
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 30:1, s. 69-76
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To use velocity-encoded phase contrast (PC) MRI in assessing the effect of coronary microembolization on longitudinal and radial myocardial strain. Materials and Methods: A combined X-ray and MR system (XMR) was used for selective left anterior descending artery catheterization and microinfarct assessment in swine (n = 6). The embolized area at risk was defined on perfusion MRI followed by administration of a 7500 count (size = 100-300 mu m) of the embolic agent. Quantification of strain and microinfarction was performed at 1 h and 1 week using PC-MRI and delayed enhancement (DE) MRI, respectively. At postmortem, sliced hearts were stained to define microinfarction. Results: Baseline longitudinal and radial strain did not differ between area-at-risk and remote myocardium. The embolized territory (area at risk) showed significant decline in longitudinal strain from -11.5 +/- 3.2% to 1.8 +/- 2.5% at 1 h (P < 0.05) and -3.9 +/- 1.1% at 1 week (P < 0.05). Similarly, regional radial strain progressively declined from 23.6 +/- 2.5% at baseline to 12.5 +/- 3.7% at 1 h (P < 0.05) and 4.8 +/- 5.0% at 1 week (P < 0.01). The size of microinfarction was not significantly different between DE-MRI and histochemical staining. Conclusion: PC-MRI is sensitive in assessing changes in regional longitudinal and radial strain after coronary embolization. Longitudinal and radial strain of the hyperenhanced patchy microinfarction demonstrates persistent decline over the course of 1 week.
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23.
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24.
  • Dunås, Tora, et al. (författare)
  • Accuracy of blood flow assessment in cerebral arteries with 4D flow MRI : Evaluation with three segmentation methods
  • 2019
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 50:2, s. 511-518
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Accelerated 4D flow MRI allows for high‐resolution velocity measurements with whole‐brain coverage. Such scans are increasingly used to calculate flow rates of individual arteries in the vascular tree, but detailed information about the accuracy and precision in relation to different postprocessing options is lacking.Purpose: To evaluate and optimize three proposed segmentation methods and determine the accuracy of in vivo 4D flow MRI blood flow rate assessments in major cerebral arteries, with high‐resolution 2D PCMRI as a reference.Study Type: Prospective.Subjects: Thirty‐five subjects (20 women, 79 ± 5 years, range 70–91 years).Field Strength/Sequence: 4D flow MRI with PC‐VIPR and 2D PCMRI acquired with a 3 T scanner.Assessment: We compared blood flow rates measured with 4D flow MRI, to the reference, in nine main cerebral arteries. Lumen segmentation in the 4D flow MRI was performed with k‐means clustering using four different input datasets, and with two types of thresholding methods. The threshold was defined as a percentage of the maximum intensity value in the complex difference image. Local and global thresholding approaches were used, with evaluated thresholds from 6–26%.Statistical Tests: Paired t‐test, F‐test, linear correlation (P < 0.05 was considered significant) along with intraclass correlation (ICC).Results: With the thresholding methods, the lowest average flow difference was obtained for 20% local (0.02 ± 15.0 ml/min, ICC = 0.97, n = 310) or 10% global (0.08 ± 17.3 ml/min, ICC = 0.97, n = 310) thresholding with a significant lower standard deviation for local (F‐test, P = 0.01). For all clustering methods, we found a large systematic underestimation of flow compared with 2D PCMRI (16.1–22.3 ml/min).Data Conclusion: A locally adapted threshold value gives a more stable result compared with a globally fixed threshold. 4D flow with the proposed segmentation method has the potential to become a useful reliable clinical tool for assessment of blood flow in the major cerebral arteries.Level of Evidence: 2Technical Efficacy: Stage 2
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25.
  • Dyverfeldt, Petter, 1980-, et al. (författare)
  • Assessment of fluctuating velocities in disturbed cardiovascular blood flow : in vivo feasibility of generalized phase-contrast MRI
  • 2008
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 28:3, s. 655-663
  • Tidskriftsartikel (refereegranskat)abstract
    • PurposeTo evaluate the feasibility of generalized phase-contrast magnetic resonance imaging (PC-MRI) for the noninvasive assessment of fluctuating velocities in cardiovascular blood flow.Materials and MethodsMultidimensional PC-MRI was used in a generalized manner to map mean flow velocities and intravoxel velocity standard deviation (IVSD) values in one healthy aorta and in three patients with different cardiovascular diseases. The acquired data were used to assess the kinetic energy of both the mean (MKE) and the fluctuating (TKE) velocity field.ResultsIn all of the subjects, both mean and fluctuating flow data were successfully acquired. The highest TKE values in the patients were found at sites characterized by abnormal flow conditions. No regional increase in TKE was found in the normal aorta.ConclusionPC-MRI IVSD mapping is able to detect flow abnormalities in a variety of human cardiovascular conditions and shows promise for the quantitative assessment of turbulence. This approach may assist in clarifying the role of disturbed hemodynamics in cardiovascular diseases.
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26.
  • Dyverfeldt, Petter, et al. (författare)
  • Hemodynamic aspects of mitral regurgitation assessed by generalized phase-contrast MRI
  • 2011
  • Ingår i: Journal of Magnetic Resonance Imaging. - : John Wiley and Sons. - 1053-1807 .- 1522-2586. ; 33:3, s. 582-588
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: Mitral regurgitation creates a high velocity jet into the left atrium (LA), contributing both volume andpressure; we hypothesized that the severity of regurgitation would be reflected in the degree of LA flowdistortion.Material and Methods: Three-dimensional cine PC-MRI was applied to determine LA flow patterns andturbulent kinetic energy (TKE) in seven subjects (five patients with posterior mitral leaflet prolapse, two normalsubjects). In addition, the regurgitant volume and the time-velocity profiles in the pulmonary veins weremeasured.Results: The LA flow in the mitral regurgitation patients was highly disturbed with elevated values of TKE.Peak TKE occurred consistently at late systole. The total LA TKE was closely related to the regurgitant volume.LA flow patterns were characterized by a pronounced vortex in proximity to the regurgitant jet. In some patients,pronounced discordances were observed between individual pulmonary venous inflows, but these could not berelated to the direction of the flow jet or parameters describing global LA hemodynamics.Conclusion: PC-MRI permits investigations of atrial and pulmonary vein flow patterns and TKE in significantmitral regurgitation, reflecting the impact of the highly disturbed blood flow that accompanies this importantvalve disease.
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27.
  • Dyverfeldt, Petter, et al. (författare)
  • Reduction of motion artifacts in carotid MRI using free-induction decay navigators
  • 2014
  • Ingår i: Journal of Magnetic Resonance Imaging. - : John Wiley & Sons. - 1053-1807 .- 1522-2586. ; 40:1, s. 214-220
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE:To develop a framework for prospective free-induction decay (FID)-based navigator gating for suppression of motion artifacts in carotid magnetic resonance imaging (MRI) and to assess its capability in vivo.MATERIALS AND METHODS:An FID-navigator, comprising a spatially selective low flip-angle sinc-pulse followed by an analog-to-digital converter (ADC) readout, was added to a conventional turbo spin-echo (TSE) sequence. Real-time navigator processing delivered accept/reject-and-reacquire decisions to the sequence. In this Institutional Review Board (IRB)-approved study, seven volunteers were scanned with a 2D T2-weighted TSE sequence. A reference scan with volunteers instructed to minimize motion as well as nongated and gated scans with volunteers instructed to perform different motion tasks were performed in each subject. Multiple image quality measures were employed to quantify the effect of gating.RESULTS:There was no significant difference in lumen-to-wall sharpness (2.3 ± 0.3 vs. 2.3 ± 0.4), contrast-to-noise ratio (CNR) (9.0 ± 2.0 vs. 8.5 ± 2.0), or image quality score (3.1 ± 0.9 vs. 2.6 ± 1.2) between the reference and gated images. For images acquired during motion, all image quality measures were higher (P < 0.05) in the gated compared to nongated images (sharpness: 2.3 ± 0.4 vs. 1.8 ± 0.5, CNR: 8.5 ± 2.0 vs. 7.2 ± 2.0, score: 2.6 ± 1.2 vs. 1.8 ± 1.0).CONCLUSION:Artifacts caused by the employed motion tasks deteriorated image quality in the nongated scans. These artifacts were alleviated with the proposed FID-navigator.
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28.
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29.
  • Ebbers, Tino, et al. (författare)
  • Improving Computation of Cardiovascular Relative Pressure Fields From Velocity MRI
  • 2009
  • Ingår i: JOURNAL OF MAGNETIC RESONANCE IMAGING. - : Wiley. - 1053-1807 .- 1522-2586. ; 30:1, s. 54-61
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To evaluate a multigrid-based solver for the pressure Poisson equation (PPE) with Galerkin coarsening, which works directly on the specified domain, for the computation of relative pressure fields from velocity MRI data. Materials and Methods: We compared the proposed structure-defined Poisson solver to other popular Poisson solvers working on unmodified rectangular and modified quasirectangular domains using synthetic and in vitro phantoms in which the mathematical solution of the pressure field is known, as well as on in vivo MRI velocity measurements of aortic blood flow dynamics. Results: All three PPE solvers gave accurate results for convex computational domains. Using a rectangular or quasirectangular domain on a more complicated domain, like a c-shape, revealed a systematic underestimation of the pressure amplitudes, while the proposed PPE solver, working directly on the specified domain, provided accurate estimates of the relative pressure fields. Conclusion: Popular iterative approaches with quasirectangular computational domains can lead to significant systematic underestimation of the pressure amplitude. We suggest using a multigrid-based PPE solver with Galerkin coarsening, which works directly on the structure-defined computational domain. This solver provides accurate estimates of the relative pressure fields for both simple and complex geometries with additional significant improvements with respect to execution speed.
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30.
  • Erdogmus, Deniz, et al. (författare)
  • Image construction methods for phased array magnetic resonance imaging
  • 2004
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 20:2, s. 306-314
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose To study image construction in phased array magnetic resonance imaging (MRI) systems from a statistical signal processing point of view. Materials and Methods Three new approaches for image combination with multiple coils are proposed: 1) one based on the singular value decomposition of the measurement matrix, which is asymptotically optimal in the signal-to-noise ratio sense; 2) one based on a maximum-likelihood formulation, incorporating a priori information on the coil sensitivities in a Bayesian manner; and 3) one based on a least-squares formulation, which incorporates a smoothness constraint on the coil sensitivities. Results Numerical examples using synthetic and real data are presented to illustrate the performance of these new approaches. Results on the synthetic data show improvement in signal-to-error ratio, while results on the real data (a 4.7 T four-coil image of a cat spinal cord) show that the proposed methods can improve the SNR in the final image by up to 3 dB in the regions of interest compared to conventional sum-of-squares processing. Conclusion It is demonstrated that phased array MRI reconstruction performance can be improved by the use of more elaborate statistical signal processing algorithms. J. Magn. Reson. Imaging 2004;20:306–314. © 2004 Wiley-Liss, Inc.
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31.
  • Eriksson, Rolf, et al. (författare)
  • Contrast enhancement of manganese-hydroxypropyl-tetraacetic acid, an MR contrast agent with potential for detecting differences in myocardial blood flow
  • 2006
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 24:4, s. 858-863
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To determine whether the contrast agent MnHPTA has potential for detecting differences in myocardial blood flow. Materials and Methods: R1 in the myocardium was calculated from MR signal intensity measurements in 18 pigs after intravenous injection of 5, 15, or 25 mu mol MnHPTA/kg body weight. Measurements were made in each animal after administration at rest and during dobutamine-induced stress. Results: A difference of approximately 0.1 see(-1) in the R1 increase between rest and stress still remained 31 minutes after administration of 25 mu mol MnHPTA/kg body weight. When two consecutive MnHPTA injections were performed, the second injection induced a lower R1 increase than the corresponding first injection. Conclusion: MnHPTA at a dose of 25 mu mol/kg body weight (b.w.) has the potential to detect perfusion differences in myocardium. When two consecutive injections of MnHPTA were administered, the RI change after the second injection was affected by the earlier administration. Therefore, a protocol including more than one administration is not ideal for this contrast agent.
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32.
  • Eriksson, Rolf, et al. (författare)
  • Dobutamine-induced stress affects intracellular uptake of manganese : a quantitative magnetic resonance imaging study in pigs
  • 2004
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 21:4, s. 360-364
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To determine whether there are differences in increase in longitudinal relaxation rate (DeltaR1) in the myocardium between bolus administration of Mn(2+) ions during rest and during dobutamine-induced stress and, additionally, to determine whether there are differences in DeltaR1 between bolus injection and infusion of Mn(2+) ions during dobutamine-induced stress. MATERIALS AND METHODS: Pigs were divided into three groups with six pigs in each group. All animals received 15 mumol MnCl(2)/kg of body weight (b.w.) intravenously either as a bolus injection (groups 1 and 2) or as an infusion over one minute (group 3). The animals in groups 2 and 3 were subjected to dobutamine stress before injection of MnCl(2), while those in group 1 were not given dobutamine. T1 was quantified in the myocardium and left ventricular blood pool before contrast injection and repeatedly during a one-hour postinjection period. RESULTS: A significant difference in DeltaR1 between the groups with and the group without dobutamine stress was noted in the myocardium up to 45 minutes after contrast agent injection. No such significant difference was found between pigs that received the contrast agent as a bolus injection compared to infusion. CONCLUSION: Dobutamine stress increases uptake of manganese ions in the myocardium. This increase was independent of whether the contrast agent was administered as a bolus injection or as an infusion.
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33.
  • Eriksson, Rolf, et al. (författare)
  • Uptake of MnCl2 and mangafodipir trisodium in the myocardium : a magnetic resonance imaging study in pigs
  • 2004
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 19:5, s. 564-569
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To examine the changes in the longitudinal relaxation times (DeltaR1) induced in pig myocardium and blood following injections of 5, 10, and 15 micromol mangafodipir trisodium (Mn-DPDP) or MnCl2/kg of body weight (b.w.). MATERIALS AND METHODS: Twelve pigs were divided into two groups, one group receiving MnCl2 and the other receiving Mn-DPDP. Three consecutive doses of contrast agent (5, 10, and 15 micromol/kg of b.w.) were injected in each animal with a 40-minute time interval between each dose. Measurements of T1 in blood and myocardium were made 5, 15, 25, and 35 minutes after each injection. Additionally, relaxivity measurements in blood samples were performed. RESULTS: An increase in myocardial R1 was observed for both contrast agents at all concentration levels tested. This increase peaked 5 minutes after injection and then declined. An increase could still be detected 35 minutes after injection. The effect was larger when using MnCl2 than when using Mn-DPDP. CONCLUSION: The dissociation kinetics of Mn2+ from the DPDP ligand limits the relaxation increase of Mn-DPDP relative to that of MnCl2. On the other hand, the toxicity of MnCl2 may exclude it from clinical use.
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34.
  • Escobar Kvitting, John-Peder, et al. (författare)
  • In Vitro Assessment of Flow Patterns and Turbulence Intensity in Prosthetic Heart Valves Using Generalized Phase-Contrast MRI
  • 2010
  • Ingår i: JOURNAL OF MAGNETIC RESONANCE IMAGING. - : John Wiley and Sons, Ltd. - 1053-1807 .- 1522-2586. ; 31:5, s. 1075-1080
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To assess in vitro the three-dimensional mean velocity field and the extent and degree of turbulence intensity (TI) in different prosthetic heart valves using a generalization of phase-contrast MRI (PC-MRI). Materials and Methods: Four 27-mm aortic valves (Bjork-Shiley Monostrut tilting-disc, St. Jude Medical Standard bileaflet, Medtronic Mosaic stented and Freestyle stentless porcine valve) were tested under steady inflow conditions in a Plexiglas phantom. Three-dimensional PC-MRI data were acquired to measure the mean velocity field and the turbulent kinetic energy (TKE), a direction-independent measure of TI. Results: Velocity and TI estimates could be obtained up and downstream of the valves, except where metallic structure in the valves caused signal void. Distinct differences in the location, extent, and peak values of velocity and TI were observed between the valves tested. The maximum values of TKE varied between the different valves: tilting disc, 100 J/m(3); bileaflet, 115 J/m(3); stented, 200 J/m(3); stentless, 145 J/m(3). Conclusion: The TI downstream from a prosthetic heart valve is dependent on the specific valve design. Generalized PC-MRI can be used to quantify velocity and TI downstream from prosthetic heart valves, which may allow assessment of these aspects of prosthetic valvular function in postoperative patients.
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35.
  • Fagan, A. J., et al. (författare)
  • 7T MR Safety
  • 2021
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 53:2333-346, s. 333-346
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetic resonance imaging and spectroscopy (MRI/MRS) at 7T represents an exciting advance in MR technology, with intriguing possibilities to enhance image spatial, spectral, and contrast resolution. To ensure the safe use of this technology while still harnessing its potential, clinical staff and researchers need to be cognizant of some safety concerns arising from the increased magnetic field strength and higher Larmor frequency. The higher static magnetic fields give rise to enhanced transient bioeffects and an increased risk of adverse incidents related to electrically conductive implants. Many technical challenges remain and the continuing rapid pace of development of 7T MRI/MRS is likely to present further challenges to ensuring safety of this technology in the years ahead. The recent regulatory clearance for clinical diagnostic imaging at 7T will likely increase the installed base of 7T systems, particularly in hospital environments with little prior ultrahigh-field MR experience. Informed risk/benefit analyses will be required, particularly where implant manufacturer-published 7T safety guidelines for implants are unavailable. On behalf of the International Society for Magnetic Resonance in Medicine, the aim of this article is to provide a reference document to assist institutions developing local institutional policies and procedures that are specific to the safe operation of 7T MRI/MRS. Details of current 7T technology and the physics underpinning its functionality are reviewed, with the aim of supporting efforts to expand the use of 7T MRI/MRS in both research and clinical environments. Current gaps in knowledge are also identified, where additional research and development are required. Level of Evidence 5 Technical Efficacy 2
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36.
  • Fokkinga, Ella, et al. (författare)
  • Advanced Diffusion-Weighted MRI for Cancer Microstructure Assessment in Body Imaging, and Its Relationship With Histology
  • Ingår i: Journal of Magnetic Resonance Imaging. - 1053-1807.
  • Forskningsöversikt (refereegranskat)abstract
    • Diffusion-weighted magnetic resonance imaging (DW-MRI) aims to disentangle multiple biological signal sources in each imaging voxel, enabling the computation of innovative maps of tissue microstructure. DW-MRI model development has been dominated by brain applications. More recently, advanced methods with high fidelity to histology are gaining momentum in other contexts, for example, in oncological applications of body imaging, where new biomarkers are urgently needed. The objective of this article is to review the state-of-the-art of DW-MRI in body imaging (ie, not including the nervous system) in oncology, and to analyze its value as compared to reference colocalized histology measurements, given that demonstrating the histological validity of any new DW-MRI method is essential. In this article, we review the current landscape of DW-MRI techniques that extend standard apparent diffusion coefficient (ADC), describing their acquisition protocols, signal models, fitting settings, microstructural parameters, and relationship with histology. Preclinical, clinical, and in/ex vivo studies were included. The most used techniques were intravoxel incoherent motion (IVIM; 36.3% of used techniques), diffusion kurtosis imaging (DKI; 16.7%), vascular, extracellular, and restricted diffusion for cytometry in tumors (VERDICT; 13.3%), and imaging microstructural parameters using limited spectrally edited diffusion (IMPULSED; 11.7%). Another notable category of techniques relates to innovative b-tensor diffusion encoding or joint diffusion-relaxometry. The reviewed approaches provide histologically meaningful indices of cancer microstructure (eg, vascularization/cellularity) which, while not necessarily accurate numerically, may still provide useful sensitivity to microscopic pathological processes. Future work of the community should focus on improving the inter-/intra-scanner robustness, and on assessing histological validity in broader contexts. Level of Evidence: NA. Technical Efficacy: Stage 2.
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37.
  • Fredriksson, Alexandru Grigorescu, et al. (författare)
  • 4D flow MRI can detect subtle right ventricular dysfunction in primary left ventricular disease.
  • 2016
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley-Blackwell. - 1053-1807 .- 1522-2586. ; 43:3, s. 558-565
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To investigate whether 4D flow magnetic resonance imaging (MRI) can detect subtle right ventricular (RV) dysfunction in primary left ventricular (LV) disease.MATERIALS AND METHODS: 4D flow and morphological 3T MRI data were acquired in 22 patients with mild ischemic heart disease who were stratified into two groups based on LV end-diastolic volume index (EDVI): lower-LVEDVI and higher-LVEDVI, as well as in 11 healthy controls. The RV volume was segmented at end-diastole (ED) and end-systole (ES). Pathlines were emitted from the ED volume and traced forwards and backwards in time to ES. The blood volume was separated into flow components. The Direct Flow (DF) component was defined as RV inflow passing directly to outflow. The kinetic energy (KE) of the DF component was calculated. Echocardiographic conventional RV indices were also assessed.RESULTS: The higher-LVEDVI group had larger LVEDVI and lower LV ejection fraction (98 ± 32 ml/m(2) ; 48 ± 13%) compared to the healthy (67 ± 12, P = 0.002; 64 ± 7, P < 0.001) and lower-LVEDI groups (62 ± 10; 68 ± 7, both P < 0.001). The RV 4D flow-specific measures "DF/EDV volume-ratio" and "DF/EDV KE-ratio at ED" were lower in the higher-LVEDVI group (38 ± 5%; 52 ± 6%) compared to the healthy (44 ± 6; 65 ± 7, P = 0.018 and P < 0.001) and lower-LVEDVI groups (44 ± 6; 64 ± 7, P = 0.011 and P < 0.001). There was no difference in any of the conventional MRI and echocardiographic RV indices between the three groups.CONCLUSION: We found that in primary LV disease mild impairment of RV function can be detected by 4D flow-specific measures, but not by the conventional MRI and echocardiographic indices. J. Magn. Reson. Imaging 2015.
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38.
  • Fredriksson, Alexandru Grigorescu, et al. (författare)
  • Turbulent kinetic energy in the right ventricle : Potential MR marker for risk stratification of adults with repaired Tetralogy of Fallot
  • 2018
  • Ingår i: Journal of Magnetic Resonance Imaging. - Hoboken : John Wiley & Sons. - 1053-1807 .- 1522-2586. ; 47:4, s. 1043-1053
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To assess right ventricular (RV) turbulent kinetic energy (TKE) in patients with repaired Tetralogy of Fallot (rToF) and a spectrum of pulmonary regurgitation (PR), as well as to investigate the relationship between these 4D flow markers and RV remodeling.Materials and Methods: Seventeen patients with rToF and 10 healthy controls were included in the study. Patients were divided into two groups based on PR fraction: one lower PR fraction group (11%) and one higher PR fraction group (>11%). Field strength/sequences: 3D cine phase contrast (4D flow), 2D cine phase contrast (2D flow), and balanced steady-state free precession (bSSFP) at 1.5T. Assessment: The RV volume was segmented in the morphologic short-axis images and TKE parameters were computed inside the segmented RV volume throughout diastole. Statistical tests: One-way analysis of variance with Bonferroni post-hoc test; unpaired t-test; Pearson correlation coefficients; simple and stepwise multiple regression models; intraclass correlation coefficient (ICC).Results: The higher PR fraction group had more remodeled RVs (140 6 25 vs. 107 6 22 [lower PR fraction, P < 0.01] and 93 6 15 ml/m2[healthy, P < 0.001] for RV end-diastolic volume index [RVEDVI]) and higher TKE values (5.95 6 3.15 vs. 2.23 6 0.81 [lower PR fraction, P < 0.01] and 1.91 6 0.78 mJ [healthy, P < 0.001] for Peak Total RV TKE). Multiple regression analysis between RVEDVI and 4D/2D flow parameters showed that Peak Total RV TKE was the strongest predictor of RVEDVI (R25 0.47, P 5 0.002).Conclusion: The 4D flow-specific TKE markers showed a slightly stronger association with RV remodeling than conventional 2D flow PR parameters. These results suggest novel hemodynamic aspects of PR in the development of late complications after ToF repair.
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39.
  • Gifford, Aliya, et al. (författare)
  • Canine body composition quantification using 3 tesla fat–water MRI
  • 2014
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 39:2, s. 485-491
  • Tidskriftsartikel (refereegranskat)abstract
    • PurposeTo test the hypothesis that a whole-body fat–water MRI (FWMRI) protocol acquired at 3 Tesla combined with semi-automated image analysis techniques enables precise volume and mass quantification of adipose, lean, and bone tissue depots that agree with static scale mass and scale mass changes in the context of a longitudinal study of large-breed dogs placed on an obesogenic high-fat, high-fructose diet.Materials and MethodsSix healthy adult male dogs were scanned twice, at weeks 0 (baseline) and 4, of the dietary regiment. FWMRI-derived volumes of adipose tissue (total, visceral, and subcutaneous), lean tissue, and cortical bone were quantified using a semi-automated approach. Volumes were converted to masses using published tissue densities.ResultsFWMRI-derived total mass corresponds with scale mass with a concordance correlation coefficient of 0.931 (95% confidence interval = [0.813, 0.975]), and slope and intercept values of 1.12 and −2.23 kg, respectively. Visceral, subcutaneous and total adipose tissue masses increased significantly from weeks 0 to 4, while neither cortical bone nor lean tissue masses changed significantly. This is evidenced by a mean percent change of 70.2% for visceral, 67.0% for subcutaneous, and 67.1% for total adipose tissue.ConclusionFWMRI can precisely quantify and map body composition with respect to adipose, lean, and bone tissue depots. The described approach provides a valuable tool to examine the role of distinct tissue depots in an established animal model of human metabolic disease.
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40.
  • Glans, Anton, et al. (författare)
  • Maintaining Image Quality While Reducing Acoustic Noise and Switched Gradient Field Exposure During Lumbar MRI
  • 2021
  • Ingår i: Journal of Magnetic Resonance Imaging. - : John Wiley & Sons. - 1053-1807 .- 1522-2586. ; 54:1, s. 315-325
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: MR-generated acoustic noise can contribute to patient discomfort and potentially be harmful. One way to reduce this noise is by altering the gradient output and/or waveform using software optimization. Such modifications might influence image quality and switched gradient field exposure, and different techniques appear to affect sound pressure levels (SPLs) to various degrees.Purpose: To evaluate SPLs, image quality, switched gradient field exposure, and participants' perceived noise levels during two different acoustic noise reduction (ANR) techniques, Quiet Suite (QS) and Whisper Mode (WM), and to compare them with conventional T2-weighted turbo spin echo (T2W TSE) of the lumbar spine.Design: Prospective.Subjects: Forty adults referred for lumbar MRI.Field strength/sequence: Conventional T2W TSE, T2W TSE with QS, and T2W TSE with WM were acquired at 1.5 T.Assessment: Peak SPL (A-weighted decibels, dBA), perceived noise levels (Borg CR10®-scale), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), three radiologists' qualitative assessments in image quality on an ordinal scale 1-4, switched gradient field exposure (% general public), and gradient currents were measured. Interobserver reliability was reported as percentage agreement.Statistical tests: Repeated measures ANOVA, Friedman's ANOVA, and Wilcoxon's Signed-Rank Test for acoustic noise measurements and image quality assessments.Results: Mean peak SPLs were 89.9 dBA, 74.3 dBA, and 78.8 dBA for conventional, QS, and WM, respectively (P < 0.05). Participants perceived QS as the quietest and conventional as the loudest sequence (P < 0.05). No qualitative differences in image quality were seen (P > 0.05), although QS showed significantly improved SNR and CNR (P < 0.05). Switched gradient field exposure was reduced by 66% and 48% for QS and WM, respectively.Data conclusion: Without degrading image quality, both QS and WM are viable ANR techniques in lumbar T2W TSE. QS provided the lowest SPL, the lowest gradient field exposure and was perceived as the most silent among the three sequences.Level of evidence: 1 TECHNICAL EFFICACY STAGE: 5.
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41.
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42.
  • Good, Elin, 1983-, et al. (författare)
  • Quantitative Magnetic Resonance Imaging Assessment of the Relationships Between Fat Fraction and R2*Inside Carotid Plaques, and Circulating Lipoproteins
  • 2022
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 55:4, s. 1260-1270
  • Tidskriftsartikel (refereegranskat)abstract
    • Background Lipid-rich necrotic core (LRNC) and intraplaque hemorrhage (IPH) are morphological features of high-risk atherosclerotic plaques. However, their relationship to circulating lipoproteins is unclear. Purpose To study associations between changes in lipoproteins vs. changes in LRNC (represented by fat fraction [FF]) and IPH (represented by R2*). Study Type Prospective. Subjects Fifty-two patients with carotid plaques, 33 males (63.5%), mean age 72 (+/- 5). Field Strength/Sequence Four-point fast gradient Dixon magnetic resonance imaging (MRI) was used to quantify FF and R2* (to measure IPH) inside plaques and in vessel wall. Turbo-spin echo was used for T-1 weighted sequences to guide manual segmentation. Assessment Carotid MRI and serum lipid levels were assessed at baseline and at 1-year follow-up. For patients, lipid-lowering therapy was customized to reduce low-density lipoprotein (LDL) levels below 1.8 mmol/L. Segmentation was performed with one set of regions of interest for the plaque and one for the vessel wall at the location of the plaque. Thereby MRI data for FF, R2*, and volumes in plaque- and vessel-wall segmentations could be obtained from baseline and follow-up, as well as changes over the study year. Statistical Tests Pearson correlation coefficient for correlations. Paired samples t-test for changes over time. Significance at P < 0.05, 95% confidence interval. Results LDL decreased significantly (2.19-1.88 mmol/L, Z - 2.9), without correlation to changes in plaque composition, nor to the significant reduction in vessel-wall volume (-106.3 mm(3)). Plaque composition remained unchanged, FF +8.5% (P = 0.366) and R2* +3.5% (P = 0.304). Compared to plaque segmentations, R2* was significantly lower in the vessel-wall segmentations both at baseline (-9.3%) and at follow-up (-9.1%). Data Conclusion The absence of correlations between changes in lipoproteins and changes in plaque composition indicates more complex relationships between these parameters than previously anticipated. The significant differences in both R2* and volume dynamics comparing plaque segmentations and vessel-wall segmentations suggest differences in their pathobiology of atherosclerosis. Level of Evidence 1 Technical Efficacy Stage 4
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43.
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44.
  • Gärdin, Anna, et al. (författare)
  • T2 * relaxation time in Achilles tendinosis and controls and its correlation with clinical score
  • 2016
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 43:6, s. 1417-1422
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To investigate if the T2 * of Achilles tendons can discriminate between chronic Achilles tendinosis and healthy controls; to correlate with clinical score; to evaluate its short-term repeatability; and to estimate minimal detectable change.MATERIALS AND METHODS: Twenty patients, with chronic mid-portion Achilles tendinosis, and 10 controls without history of Achilles tendon symptoms, were examined with a 3T MR scanner with a 3D flash ultrashort time to echo sequence with five different echo times. The sequence was run twice to test repeatability. The tendon border was delineated on axial slices at three different levels in the calculated T2 * maps. The clinical severity of Achilles tendinosis was measured by a VISA-A questionnaire.RESULTS: There was a significant difference in mean T2 * between symptomatic and control tendons (P < 0.001). In patients with unilateral symptoms no significant difference in T2 * was found between symptomatic and contralateral asymptomatic tendons (P = 0.19). There was no significant correlation between clinical severity and T2 * (r = -0.28, P = 0.22). The short-term repeatability of T2 * showed a coefficient of variation of 18%, a least significant change of 50%, and the intraclass correlation coefficient had an average consistency of 0.99.CONCLUSION: T2 * may help to differentiate between chronic Achilles tendinosis and healthy controls but was not associated with the clinical score. However, and notably, the reproducibility of the method was low and the number of patients was small.
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45.
  • Hangaard, Stine, et al. (författare)
  • Delayed Gadolinium-Enhanced MRI of Menisci and Cartilage (dGEMRIM/dGEMRIC) in Obese Patients With Knee Osteoarthritis : Cross-Sectional Study of 85 Obese Patients With Intra-articular Administered Gadolinium Contrast
  • 2018
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807. ; 48:6, s. 1700-1706
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Early cartilage changes in knee osteoarthritis (OA) can be assessed by both intravenous (i.v.) and intra-articular (i.a.) delayed gadolinium-enhanced MRI of cartilage (dGEMRIC). Purpose: To examine the relationship between i.a. dGEMRIC and delayed gadolinium-enhanced MRI of menisci (dGEMRIM), and to investigate if the approach can be used to assess the morphological degeneration of menisci in obese patients with knee OA. Study Type: Cross-sectional. Population: Eighty-five obese patients with knee OA. Field Strength/Sequences: 1.5T. Inversion recovery sequence with four inversion times. Assessment: T1 relaxation times were calculated for posterior weight-bearing femoral cartilage and the posterior horns of the menisci. Meniscus degeneration sum score (0–2) was assessed as increased signal/no signal (1/0) and tear/no tear (1/0). Statistical Tests: T1 relaxation times were compared using Student's t-test. Comparison of cartilage and meniscus T1 relaxation times was done by regression analysis. Analysis of variance (ANOVA) was used for comparison of meniscal T1 relaxation times among the three summed morphological scores (0–2). Statistical analyses were performed with a level of significance at 0.05. Results: For lateral menisci, morphology sum scores of 0, 1, and 2 were found in 13, 58, and 14 patients and for medial menisci in 2, 30, and 30 patients, respectively. Mean T1 relaxation times were 441 msec, 480 msec, and 497 msec for cartilage, lateral menisci, and medial menisci, respectively. T1 relaxation times for the menisci were similar (P = 0.53), and a weak correlation was found between dGEMRIC and dGEMRIM in the lateral compartments (R = 0.26). Comparing dGEMRIM between different morphology sum scores showed no differences (P > 0.4). Data Conclusion: I.a. dGEMRIM showed no correlation between the degree of meniscal degeneration and meniscus T1 relaxation times. I.a. dGEMRIM do not seem to deliver useful information about meniscus degeneration to be suitable for clinical applications, but i.a. dGEMRIC may still be considered an alternative contrast-saving method for cartilage. Level of Evidence: 3. Technical Efficacy: Stage 3. J. Magn. Reson. Imaging 2018;00:000–000.
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46.
  • Hansson, Boel, et al. (författare)
  • Subjectively Reported Effects Experienced in an Actively Shielded 7T MRI: A Large-Scale Study.
  • 2020
  • Ingår i: Journal of magnetic resonance imaging : JMRI. - : Wiley. - 1522-2586 .- 1053-1807. ; 52:4, s. 1265-1276
  • Tidskriftsartikel (refereegranskat)abstract
    • Ultrahigh-field (UHF) MRI advances towards clinical use. Patient compliance is generally high, but few large-scale studies have investigated the effects experienced in 7T MRI systems, especially considering peripheral nerve stimulation (PNS) and caregiving.To evaluate the quantity, the intensity, and subjective experiences from short-term effects, focusing on the levels of comfort and compliance of subjects.Prospective.In all, 954 consecutive MRIs in 801 subjects for 3years.7T.After the 7T examination, a questionnaire was used to collect data.Descriptive statistics, Spearman's rank correlation, Mann-Whitney U-test, and t-test.The majority (63%) of subjects agreed that the MRI experience was comfortable and 93% would be willing to undergo future 7T MRI as a patient (5% undecided) and 82% for research purposes (12% undecided). The most common short-term effects experienced were dizziness (81%), inconsistent movement (68%), PNS (63%), headache (40%), nausea (32%), metallic taste (12%), and light flashes (8%). Of the subjects who reported having PNS (n = 603), 44% experienced PNS as "not uncomfortable at all," 45% as "little or very little uncomfortable," and 11% as "moderate to very much uncomfortable." Scanner room temperature was experienced more comfortable before (78%) than during (58%) examinations, and the noise level was acceptable by 90% of subjects. Anxiety before the examination was reported by 43%. Patients differed from healthy volunteers regarding an experience of headache, metallic taste, dizziness, or anxiety. Room for improvement was pointed out after 117 examinations concerning given information (n = 73), communication and sound system (n = 35), or nursing care (n = 15).Subjectively reported effects occur in actively shielded 7T MRI and include physiological responses and individual psychological issues. Although leaving room for improvement, few subjects experienced these effects being so uncomfortable that they would lead to aversion to future UHF examinations.1 TECHNICAL EFFICACY: Stage 5.
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47.
  • Haraldsson, Henrik, 1977-, et al. (författare)
  • Improved estimation and visualization of two-dimensional myocardial strain rate using MR velocity mapping
  • 2008
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 28:3, s. 604-611
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To estimate regional myocardial strain rate, with reduced sensitivity to noise and velocities outside the region of interest, and provide a visualization of the spatial variation of the obtained tensor field within the myocardium. Materials and Methods: Myocardial velocities were measured using two-dimensional phase contrast velocity mapping. Velocity gradients were estimated using normalized convolution and the calculated 2D strain rate tensor field was visualized using a glyph representation. Validation utilized a numerical phantom with known strain rate distribution. Strain rate glyph visualizations were created for normal myocardium in both systole and diastole and compared to a patient with an anteroseptal infarction. Results: In the phantom study the strain rate calculated with normalized convolution showed a very good agreement with the analytic solution, while traditional methods for gradient estimation were shown to be sensitive to both noise and surrounding velocity data. Normal myocardium showed a homogenous strain rate distribution, while a heterogeneous strain rate can be clearly seen in the patient data. Conclusion: The proposed approach for quantification and visualization of the regional myocardial strain rate can provide an objective measure of regional myocardial contraction and relaxation that may be valuable for the assessment of myocardial heart disease. © 2008 Wiley-Liss, Inc.
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48.
  • Haris, Kostas, et al. (författare)
  • Free-breathing fetal cardiac MRI with doppler ultrasound gating, compressed sensing, and motion compensation
  • 2020
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 51:1, s. 260-272
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Fetal cardiovascular MRI complements ultrasound to assess fetal cardiovascular pathophysiology.PURPOSE: To develop a free-breathing method for retrospective fetal cine MRI using Doppler ultrasound (DUS) cardiac gating and tiny golden angle radial sampling (tyGRASP) for accelerated acquisition capable of detecting fetal movements for motion compensation.STUDY TYPE: Feasibility study.SUBJECTS: Nine volunteers (gestational week 34-40). Short-axis and four-chamber views were acquired during maternal free-breathing and breath-hold.FIELD STRENGTH/SEQUENCE: 1.5T cine balanced steady-state free precession.ASSESSMENT: A self-gated reconstruction method was improved for clinical application by using 1) retrospective DUS gating, and 2) motion detection and rejection/correction algorithms for compensating for fetal motion. The free-breathing reconstructions were qualitatively and quantitatively assessed, and DUS-gating was compared with self-gating in breath-hold reconstructions. A scoring of 1-4 for overall image quality, cardiac, and extracardiac diagnostic quality was used.STATISTICAL TESTS: Friedman's test was used to assess differences in qualitative scoring between observers. A Wilcoxon matched-pairs signed rank test was used to assess differences between breath-hold and free-breathing acquisitions and between observers' quantitative measurements.RESULTS: In all cases, 111 free-breathing and 145 breath-hold acquisitions, the automatically calculated DUS-based cardiac gating signal provided reconstructions of diagnostic quality (median score 4, range 1-4). Free-breathing did not affect the DUS-based cardiac gated retrospective radial reconstruction with respect to image or diagnostic quality (all P > 0.06). Motion detection with rejection/correction in k-space produced high-quality free-breathing DUS-based reconstructions [median 3, range (2-4)], whereas free-breathing self-gated methods failed in 80 out of 88 cases to produce a stable gating signal.DATA CONCLUSION: Free-breathing fetal cine cardiac MRI based on DUS gating and tyGRASP with motion compensation yields diagnostic images. This simplifies acquisition for the pregnant woman and thus could help increase fetal cardiac MRI acceptance in the clinic.LEVEL OF EVIDENCE: 2 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019.
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49.
  • Haris, Kostas, et al. (författare)
  • Self-gated fetal cardiac MRI with tiny golden angle iGRASP : A feasibility study
  • 2017
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 46:1, s. 207-217
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To develop and assess a technique for self-gated fetal cardiac cine magnetic resonance imaging (MRI) using tiny golden angle radial sampling combined with iGRASP (iterative Golden-angle RAdial Sparse Parallel) for accelerated acquisition based on parallel imaging and compressed sensing.MATERIALS AND METHODS: Fetal cardiac data were acquired from five volunteers in gestational week 29-37 at 1.5T using tiny golden angles for eddy currents reduction. The acquired multicoil radial projections were input to a principal component analysis-based compression stage. The cardiac self-gating (CSG) signal for cardiac gating was extracted from the acquired radial projections and the iGRASP reconstruction procedure was applied. In all acquisitions, a total of 4000 radial spokes were acquired within a breath-hold of less than 15 seconds using a balanced steady-state free precession pulse sequence. The images were qualitatively compared by two independent observers (on a scale of 1-4) to a single midventricular cine image from metric optimized gating (MOG) and real-time acquisitions.RESULTS: For iGRASP and MOG images, good overall image quality (2.8 ± 0.4 and 2.6 ± 1.3, respectively, for observer 1; 3.6 ± 0.5 and 3.4 ± 0.9, respectively, for observer 2) and cardiac diagnostic quality (3.8 ± 0.4 and 3.4 ± 0.9, respectively, for observer 1; 3.6 ± 0.5 and 3.6 ± 0.9, respectively, for observer 2) were obtained, with visualized myocardial thickening over the cardiac cycle and well-defined myocardial borders to ventricular lumen and liver/lung tissue. For iGRASP, MOG, and real time, left ventricular lumen diameter (14.1 ± 2.2 mm, 14.2 ± 1.9 mm, 14.7 ± 1.1 mm, respectively) and wall thickness (2.7 ± 0.3 mm, 2.6 ± 0.3 mm, 3.0 ± 0.4, respectively) showed agreement and no statistically significant difference was found (all P > 0.05). Images with iGRASP tended to have higher overall image quality scores compared with MOG and particularly real-time images, albeit not statistically significant in this feasibility study (P > 0.99 and P = 0.12, respectively).CONCLUSION: Fetal cardiac cine MRI can be performed with iGRASP using tiny golden angles and CSG. Comparison with other fetal cardiac cine MRI methods showed that the proposed method produces high-quality fetal cardiac reconstructions.LEVEL OF EVIDENCE: 2 J. Magn. Reson. Imaging 2017.
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50.
  • Hawezi, Zana, et al. (författare)
  • In vivo transport of Gd-DTPA(2-) in human knee cartilage assessed by depth-wise dGEMRIC analysis.
  • 2011
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 34, s. 1352-1358
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To investigate the transport of Gd-DTPA(2-) in different layers of femoral knee cartilage in vivo. MATERIALS AND METHODS: T(1) measurements (1.5 Tesla) were performed in femoral knee cartilage of 23 healthy volunteers. The weight-bearing central cartilage was analyzed before contrast and at eight time points after an intravenous injection of Gd-DTPA(2-) : 12-60 min (4 volunteers) and 1-4 h (19 volunteers). Three regions of interest were segmented manually: deep, middle, and superficial. RESULTS: Before contrast injection, a depth-wise variation of T(1) was observed with 50% higher values in the superficial region compared with the deep region. In the deep region, the uptake of Gd-DTPA(2-) was not detected until 36 min and the concentration increased until 240 min, whereas in the superficial region, the uptake was seen already at 12 min and the concentration decreased after 180 min (P < 0.01). There was a difference between medial and lateral compartment regarding bulk, but not superficial Gd-DTPA(2-) concentration. The bulk gadolinium concentration was negatively related to the cartilage thickness (r = -0.68; P < 0.01). CONCLUSION: The depth-wise and thickness dependent variations in Gd-DTPA(2) transport influence the interpretation of bulk dGEMRIC analysis in vivo. In thick cartilage, incomplete penetration of Gd-DTPA(2) will yield a falsely too long T(1) . J. Magn. Reson. Imaging 2011;. © 2011 Wiley-Liss, Inc.
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