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Evaluation of MR imaging with T1 and T2* mapping for the determination of hepatic iron overload. Eur Radiol 2012; 22:2478-86. [PMID: 22645044 DOI: 10.1007/s00330-012-2506-2] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 03/30/2012] [Accepted: 04/15/2012] [Indexed: 12/18/2022]
Abstract
OBJECTIVES To evaluate MRI using T1 and T2* mapping sequences in patients with suspected hepatic iron overload (HIO). METHODS Twenty-five consecutive patients with clinically suspected HIO were retrospectively studied. All underwent MRI and liver biopsy. For the quantification of liver T2* values we used a fat-saturated multi-echo gradient echo sequence with 12 echoes (TR = 200 ms, TE = 0.99 ms + n × 1.41 ms, flip angle 20°). T1 values were obtained using a fast T1 mapping sequence based on an inversion recovery snapshot FLASH sequence. Parameter maps were analysed using regions of interest. RESULTS ROC analysis calculated cut-off points at 10.07 ms and 15.47 ms for T2* in the determination of HIO with accuracy 88 %/88 %, sensitivity 84 %/89.5 % and specificity 100 %/83 %. MRI correctly classified 20 patients (80 %). All patients with HIO only had decreased T1 and T2* relaxation times. There was a significant difference in T1 between patients with HIO only and patients with HIO and steatohepatitis (P = 0.018). CONCLUSIONS MRI-based T2* relaxation diagnoses HIO very accurately, even at low iron concentrations. Important additional information may be obtained by the combination of T1 and T2* mapping. It is a rapid, non-invasive, accurate and reproducible technique for validating the evidence of even low hepatic iron concentrations. KEY POINTS • Hepatic iron overload causes fibrosis, cirrhosis and increases hepatocellular carcinoma risk. • MRI detects iron because of the field heterogeneity generated by haemosiderin. • T2* relaxation is very accurate in diagnosing hepatic iron overload. • Additional information may be obtained by T1 and T2* mapping.
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102
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Ibrahim ESH, Rana FN, Johnson KR, White RD. Assessment of cardiac iron deposition in sickle cell disease using 3.0 Tesla cardiovascular magnetic resonance. Hemoglobin 2012; 36:343-61. [PMID: 22563880 DOI: 10.3109/03630269.2012.679376] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Many patients with sickle cell disease receive blood transfusions as a life-saving treatment. However, excess transfusions may lead to increased body iron burden. Specifically, heart failure due to cardiac iron overload is the leading cause of death in these patients. The purpose of this study was to investigate the potential role of high-field 3.0-Tesla (T) cardiovascular magnetic resonance (CMR) for assessment of cardiac iron content by measuring the transverse relaxivity rate R2*. The R2* was measured in calibrated phantoms with different iron concentrations at 3.0T and 1.5T using optimized pulse sequences. Myocardial R2* was measured at 3.0T in a group of sickle cell disease patients with different disease stages, and the results were compared to the serum ferritin levels and hepatic R2*. The phantom R2* measurements at 3.0T were double those at 1.5T, and the measurements of both systems showed linear relationships with iron concentration. The 3.0T R2* was more sensitive than 1.5T in detecting low iron concentration. In patients, myocardial R2* had weak and good correlations with hepatic R2* and serum ferritin levels, respectively. Bland-Altman analysis showed low inter- and intra-observer variabilities. In conclusion, measuring myocardial R2* at 3.0T is a promising technique with high sensitivity and reproducibility for evaluating cardiac iron overload in sickle cell disease patients.
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Affiliation(s)
- El-Sayed H Ibrahim
- Department of Radiology, University of Florida College of Medicine, Jacksonville, Florida 32209, USA.
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Auboiroux V, Viallon M, Roland J, Hyacinthe JN, Petrusca L, Morel DR, Goget T, Terraz S, Gross P, Becker CD, Salomir R. ARFI-prepared MRgHIFU in liver: simultaneous mapping of ARFI-displacement and temperature elevation, using a fast GRE-EPI sequence. Magn Reson Med 2012; 68:932-46. [PMID: 22246646 DOI: 10.1002/mrm.23309] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Revised: 10/25/2011] [Accepted: 11/07/2011] [Indexed: 01/18/2023]
Abstract
MR acoustic radiation force imaging (ARFI) is an elegant adjunct to MR-guided high intensity focused ultrasound for treatment planning and optimization, permitting in situ assessment of the focusing and targeting quality. The thermal effect of high intensity focused ultrasound pulses associated with ARFI measurements is recommended to be monitored on line, in particular when the beam crosses highly absorbent structures or interfaces (e.g., bones or air-filled cavities). A dedicated MR sequence is proposed here, derived from a segmented gradient echo-echo planar imaging kernel by adding a bipolar motion encoding gradient with interleaved alternating polarities. Temporal resolution was reduced to 2.1 s, with in-plane spatial resolution of 1 mm. MR-ARFI measurements were executed during controlled animal breathing, with trans-costal successively steered foci, to investigate the spatial modulation of the focus intensity and the targeting offset. ARFI-induced tissue displacement measurements enabled the accurate localization, in vivo, of the high intensity focused ultrasound focal point in sheep liver, with simultaneous monitoring of the temperature elevation. ARFI-based precalibration of the focal point position was immediately followed by trans-costal MR-guided high intensity focused ultrasound ablation, monitored with a conventional proton resonance frequency shift MR thermometry sequence. The latter MR thermometry sequence had spatial resolution and geometrical distortion identical with the ARFI maps, hence no coregistration was required.
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104
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Taylor BA, Elliott AM, Hwang KP, Hazle JD, Stafford RJ. Correlation between the temperature dependence of intrinsic MR parameters and thermal dose measured by a rapid chemical shift imaging technique. NMR IN BIOMEDICINE 2011; 24:1414-1421. [PMID: 21721063 PMCID: PMC3190595 DOI: 10.1002/nbm.1707] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 12/23/2010] [Accepted: 02/15/2011] [Indexed: 05/31/2023]
Abstract
In order to investigate simultaneous MR temperature imaging and direct validation of tissue damage during thermal therapy, temperature-dependent signal changes in proton resonance frequency (PRF) shifts, R(2)* values, and T1-weighted amplitudes are measured from one technique in ex vivo tissue. Using a multigradient echo acquisition and the Stieglitz-McBride algorithm, the temperature sensitivity coefficients of these parameters are measured in each tissue at high spatiotemporal resolutions (1.6 x 1.6 x 4 mm 3,≤ 5sec) at the range of 25-61 °C. Non-linear changes in MR parameters are examined and correlated with an Arrhenius rate dose model of thermal damage. Using logistic regression, the probability of changes in these parameters is calculated as a function of thermal dose to determine if changes correspond to thermal damage. Temperature sensitivity of R(2)* and, in some cases, T1-weighted amplitudes are statistically different before and after thermal damage occurred. Significant changes in the slopes of R(2)* as a function of temperature are observed. Logistic regression analysis shows that these changes could be accurately predicted using the Arrhenius rate dose model (Ω = 1.01 ± 0.03), thereby showing that the changes in R(2)* could be direct markers of protein denaturation. Overall, by using a chemical shift imaging technique with simultaneous temperature estimation, R(2)* mapping and T1-W imaging, it is shown that changes in the sensitivity of R(2)* and, to a lesser degree, T1-W amplitudes are measured in ex vivo tissue when thermal damage is expected to occur. These changes could possibly be used for direct validation of thermal damage in contrast to model-based predictions.
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Affiliation(s)
- Brian A. Taylor
- Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas
- The University of Texas Graduate School of Biomedical Sciences, Houston, Texas
| | - Andrew M. Elliott
- Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas
| | - Ken-Pin Hwang
- Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas
- Applied Science Laboratory, GE Healthcare, Waukesha, Wisconsin
| | - John D. Hazle
- Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas
| | - R. Jason Stafford
- Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas
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105
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Meloni A, Positano V, Keilberg P, De Marchi D, Pepe P, Zuccarelli A, Campisi S, Romeo MA, Casini T, Bitti PP, Gerardi C, Lai ME, Piraino B, Giuffrida G, Secchi G, Midiri M, Lombardi M, Pepe A. Feasibility, reproducibility, and reliability for the T*2 iron evaluation at 3 T in comparison with 1.5 T. Magn Reson Med 2011; 68:543-51. [PMID: 22127999 DOI: 10.1002/mrm.23236] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 09/06/2011] [Accepted: 09/06/2011] [Indexed: 12/11/2022]
Abstract
This study aimed to determine the feasibility, reproducibility, and reliability of the multiecho T*(2) Magnetic resonance imaging technique at 3 T for myocardial and liver iron burden quantification and the relationship between T*(2) values at 3 and 1.5 T. Thirty-eight transfusion-dependent patients and 20 healthy subjects were studied. Cardiac segmental and global T*(2) values were calculated after developing a correction map to compensate the artifactual T*(2) variations. The hepatic T*(2) value was determined over a region of interest. The intraoperator and interoperator reproducibility for T*(2) measurements at 3 T was good. A linear relationship was found between patients' R *2 (1000/T*(2) ) values at 3 and 1.5 T. Segmental correction factors were significantly higher at 3 T. A conversion formula returning T*(2) values at 1.5 T from values at 3 T was proposed. A good diagnostic reliability for T*(2) assessment at 3 T was demonstrated. Lower limits of normal for 3 T T*(2) values were 23.3 ms, 21.1 ms, and 11.7 ms, for the global heart, mid-ventricular septum, and liver, respectively. In conclusion, T*(2) quantification of iron burden in the mid-ventricular septum, global heart, and no heavy-moderate livers resulted to be feasible, reproducible, and reliable at 3 T. Segmental heart T*(2) analysis at 3 T may be challenging due to significantly higher susceptibility artifacts.
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Affiliation(s)
- Antonella Meloni
- CMR Unit, Fondazione G Monasterio CNR-Regione Toscana and Institute of Clinical Physiology, Pisa, Italy.
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Cheung JS, Au WY, Ha SY, Kim D, Jensen JH, Zhou IY, Cheung MM, Wu Y, Guo H, Khong PL, Brown TR, Brittenham GM, Wu EX. Reduced transverse relaxation rate (RR2) for improved sensitivity in monitoring myocardial iron in thalassemia. J Magn Reson Imaging 2011; 33:1510-6. [PMID: 21591022 DOI: 10.1002/jmri.22553] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To evaluate the reduced transverse relaxation rate (RR2), a new relaxation index which has been shown recently to be primarily sensitive to intracellular ferritin iron, as a means of detecting short-term changes in myocardial storage iron produced by iron-chelating therapy in transfusion-dependent thalassemia patients. MATERIALS AND METHODS A single-breathhold multi-echo fast spin-echo sequence was implemented at 3 Tesla (T) to estimate RR2 by acquiring signal decays with interecho times of 5, 9 and 13 ms. Transfusion-dependent thalassemia patients (N = 8) were examined immediately before suspending iron-chelating therapy for 1 week (Day 0), after a 1-week suspension of chelation (Day 7), and after a 1-week resumption of chelation (Day 14). RESULTS The mean percent changes in RR2, R2, and R2* off chelation (between Day 0 and 7) were 11.9 ± 8.9%, 5.4 ± 7.7% and -4.4 ± 25.0%; and, after resuming chelation (between Day 7 and 14), -10.6 ± 13.9%, -8.9 ± 8.0% and -8.5 ± 24.3%, respectively. Significant differences in R2 and RR2 were observed between Day 0 and 7, and between Day 7 and 14, with the greatest proportional changes in RR2. No significant differences in R2* were found. CONCLUSION These initial results demonstrate that significant differences in RR2 are detectable after a single week of changes in iron-chelating therapy, likely as a result of superior sensitivity to soluble ferritin iron, which is in close equilibrium with the chelatable cytosolic iron pool. RR2 measurement may provide a new means of monitoring the short-term effectiveness of iron-chelating agents in patients with myocardial iron overload.
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Affiliation(s)
- Jerry S Cheung
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
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107
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Kruer MC, Boddaert N, Schneider SA, Houlden H, Bhatia KP, Gregory A, Anderson JC, Rooney WD, Hogarth P, Hayflick SJ. Neuroimaging features of neurodegeneration with brain iron accumulation. AJNR Am J Neuroradiol 2011; 33:407-14. [PMID: 21920862 DOI: 10.3174/ajnr.a2677] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
NBIA characterizes a class of neurodegenerative diseases that feature a prominent extrapyramidal movement disorder, intellectual deterioration, and a characteristic deposition of iron in the basal ganglia. The diagnosis of NBIA is made on the basis of the combination of representative clinical features along with MR imaging evidence of iron accumulation. In many cases, confirmatory molecular genetic testing is now available as well. A number of new subtypes of NBIA have recently been described, with distinct neuroradiologic and clinical features. This article outlines the known subtypes of NBIA, delineates their clinical and radiographic features, and suggests an algorithm for evaluation.
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Affiliation(s)
- M C Kruer
- Department of Pediatrics, Sanford Children's Research Center, University of South Dakota Sanford College of Medicine, Sioux Falls, South Dakota 57104, USA.
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108
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Ghugre NR, Wood JC. Relaxivity-iron calibration in hepatic iron overload: probing underlying biophysical mechanisms using a Monte Carlo model. Magn Reson Med 2010; 65:837-47. [PMID: 21337413 DOI: 10.1002/mrm.22657] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 08/26/2010] [Accepted: 09/01/2010] [Indexed: 01/20/2023]
Abstract
Iron overload is a serious condition for patients with β-thalassemia, transfusion-dependent sickle cell anemia, and inherited disorders of iron metabolism. MRI is becoming increasingly important in noninvasive quantification of tissue iron, overcoming the drawbacks of traditional techniques (liver biopsy). Effective transverse relaxation rate (1/effective transverse relaxation time) rises linearly with iron while transverse relaxation rate (1/T2) has a curvilinear relationship in human liver. Although recent work has demonstrated clinically valid estimates of human liver iron, the calibration varies with MRI sequence, field strength, iron chelation therapy, and organ imaged, forcing recalibration in patients. To understand and correct these limitations, a thorough understanding of the underlying biophysics is of critical importance. Toward this end, a Monte Carlo-based approach, using human liver as a "model" tissue system, was used to determine the contribution of particle size and distribution on MRI signal relaxation. Relaxivities were determined for hepatic iron concentrations ranging from 0.5 to 40 mg iron per gram dry tissue weight. Model predictions captured the linear and curvilinear relationship of effective transverse relaxation rate and transverse relaxation rate with hepatic iron concentrations, respectively, and were within in vivo confidence bounds; contact or chemical exchange mechanisms were not necessary. A validated and optimized model will aid understanding and quantification of iron-mediated relaxivity in tissues where biopsy is not feasible (heart and spleen).
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Affiliation(s)
- Nilesh R Ghugre
- Division of Cardiology, Department of Radiology, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California 90027-0034, USA
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109
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Manka R, Paetsch I, Schnackenburg B, Gebker R, Fleck E, Jahnke C. BOLD cardiovascular magnetic resonance at 3.0 tesla in myocardial ischemia. J Cardiovasc Magn Reson 2010; 12:54. [PMID: 20860792 PMCID: PMC2954934 DOI: 10.1186/1532-429x-12-54] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Accepted: 09/22/2010] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND The purpose of this study was to determine the ability of blood oxygen level dependent (BOLD) cardiovascular magnetic resonance (CMR) to detect stress-inducible myocardial ischemic reactions in the presence of angiographically significant coronary artery disease (CAD). METHODS Forty-six patients (34 men; age 65 ± 9 years,) with suspected or known coronary artery disease underwent CMR at 3Tesla prior to clinically indicated invasive coronary angiography. BOLD CMR was performed in 3 short axis slices of the heart at rest and during adenosine stress (140 μg/kg/min) followed by late gadolinium enhancement (LGE) imaging. In all 16 standard myocardial segments, T2* values were derived at rest and under adenosine stress. Quantitative coronary angiography served as the standard of reference and defined normal myocardial segments (i.e. all 16 segments in patients without any CAD), ischemic segments (i.e. supplied by a coronary artery with ≥50% luminal narrowing) and non-ischemic segments (i.e. supplied by a non-significantly stenosed coronary artery in patients with significant CAD). RESULTS Coronary angiography demonstrated significant CAD in 23 patients. BOLD CMR at rest revealed significantly lower T2* values for ischemic segments (26.7 ± 11.6 ms) compared to normal (31.9 ± 11.9 ms; p < 0.0001) and non-ischemic segments (31.2 ± 12.2 ms; p = 0.0003). Under adenosine stress T2* values increased significantly in normal segments only (37.2 ± 14.7 ms; p < 0.0001). CONCLUSIONS Rest and stress BOLD CMR at 3Tesla proved feasible and differentiated between ischemic, non-ischemic, and normal myocardial segments in a clinical patient population. BOLD CMR during vasodilator stress identified patients with significant CAD.
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Affiliation(s)
- Robert Manka
- Department of Internal Medicine/Cardiology, German Heart Institute, Berlin, Germany
| | - Ingo Paetsch
- Department of Internal Medicine/Cardiology, German Heart Institute, Berlin, Germany
- Department of Cardiology, University Hospital RWTH Aachen, Germany
| | | | - Rolf Gebker
- Department of Internal Medicine/Cardiology, German Heart Institute, Berlin, Germany
| | - Eckart Fleck
- Department of Internal Medicine/Cardiology, German Heart Institute, Berlin, Germany
| | - Cosima Jahnke
- Department of Internal Medicine/Cardiology, German Heart Institute, Berlin, Germany
- Department of Cardiology, University Hospital RWTH Aachen, Germany
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Holbrook AB, Santos JM, Kaye E, Rieke V, Pauly KB. Real-time MR thermometry for monitoring HIFU ablations of the liver. Magn Reson Med 2010; 63:365-73. [PMID: 19950255 DOI: 10.1002/mrm.22206] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A high-resolution and high-speed pulse sequence is presented for monitoring high-intensity focused ultrasound ablations in the liver in the presence of motion. The sequence utilizes polynomial-order phase saturation bands to perform outer volume suppression, followed by spatial-spectral excitation and three readout segmented echo-planar imaging interleaves. Images are processed with referenceless thermometry to create temperature-rise images every frame. The sequence and reconstruction were implemented in RTHawk and used to image stationary and moving sonications in a polyacrylamide gel phantom (62.4 acoustic W, 50 sec, 550 kHz). Temperature-rise images were compared between moving and stationary experiments. Heating spots and corresponding temperature-rise plots matched very well. The stationary sonication had a temperature standard deviation of 0.15 degrees C compared to values of 0.28 degrees C and 0.43 degrees C measured for two manually moved sonications at different velocities. Moving the phantom (while not heating) with respect to the transducer did not cause false temperature rises, despite susceptibility changes. The system was tested on nonheated livers of five normal volunteers. The mean temperature rise was -0.05 degrees C, with a standard deviation of 1.48 degrees C. This standard deviation is acceptable for monitoring high-intensity focused ultrasound ablations, suggesting real-time imaging of moving high-intensity focused ultrasound sonications can be clinically possible.
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Affiliation(s)
- Andrew B Holbrook
- Department of Bioengineering, Stanford University, Stanford, California, USA.
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111
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Abstract
Accurate evaluation of iron overload is necessary to establish the diagnosis of hemochromatosis and guide chelation treatment in transfusion-dependent anemia. The liver is the primary site for iron storage in patients with hemochromatosis or transfusion-dependent anemia, therefore, liver iron concentration (LIC) accurately reflects total body iron stores. In the past 20 years, magnetic resonance imaging (MRI) has emerged as a promising method for measuring LIC in a variety of diseases. We review the potential role of MRI in LIC determination in the most important disorders that are characterized by iron overload, that is, thalassemia major, other hemoglobinopathies, acquired anemia, and hemochromatosis. Most studies have been performed in thalassemia major and MRI is currently a widely accepted method for guiding chelation treatment in these patients. However, the lack of correlation between liver and cardiac iron stores suggests that both organs should be evaluated with MRI, since cardiac disease is the leading cause of death in this population. It is also unclear which MRI method is the most accurate since there are no large studies that have directly compared the different available techniques. The role of MRI in the era of genetic diagnosis of hemochromatosis is also debated, whereas data on the accuracy of the method in other hematological and liver diseases are rather limited. However, MRI is a fast, non-invasive and relatively accurate diagnostic tool for assessing LIC, and its use is expected to increase as the role of iron in the pathogenesis of liver disease becomes clearer.
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112
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Cohen B, Ziv K, Plaks V, Harmelin A, Neeman M. Ferritin nanoparticles as magnetic resonance reporter gene. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2010; 1:181-8. [PMID: 20049789 DOI: 10.1002/wnan.11] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Dynamic imaging of gene expression in live animals is among the exciting challenges of molecular imaging. To achieve that, one of the approaches is to use reporter genes that encode for the synthesis of easily detectable products. Such reporter genes can be designed to be expressed under the control of the regulatory elements included in a promoter region of a gene of interest, thus allowing the use of the same reporter gene for the detection of multiple genes. The most commonly used reporter genes include the firefly light-generating enzyme luciferase and the green fluorescent protein detectable by bioluminescence and fluorescence optical imaging, respectively. Over the last years a number of studies demonstrated the ability to use the iron-binding protein ferritin as a reporter gene that allows the detection of gene expression by magnetic resonance imaging (MRI). MRI provides high spatial resolution and soft tissue contrast for deep tissues along with a large arsenal of functional and anatomical contrast mechanisms that can be correlated with gene expression, and can potentially be translated into clinical use.
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Affiliation(s)
- Batya Cohen
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel
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113
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Cobb JG, Paschal CB. Improved in vivo measurement of myocardial transverse relaxation with 3 Tesla magnetic resonance imaging. J Magn Reson Imaging 2009; 30:684-9. [PMID: 19711419 DOI: 10.1002/jmri.21877] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
PURPOSE To develop practical methods at 3 Tesla (T) for measuring myocardial transverse relaxation in normal human myocardium. MATERIALS AND METHODS Ten healthy volunteers were investigated with four multi-echo, turbo spin-echo (TSE) methods. Each method traded acquired phase encoding lines per image for echo-image sample points obtained along the T(2) decay curve. Four multi-echo turbo field-echo (TFE) methods were also tested. The TFE methods highlighted differences between achievable receiver bandwidth and echo time constraints versus the number of sample points obtained along the T(2) (*) decay curve. RESULTS Measured transverse relaxation values were consistent in reported means across all scan methods. T(2) for the ventricular septum was measured as 58.8 +/- 7.7 ms (N = 10). T(2) (*) for the ventricular septum was 31.6 +/- 5.8 ms (N = 10). The variation of mean T(2) or T(2) (*) within an region of interest improved significantly with increases in acquired echoes. Therefore, four or more echoes may provide for clear distinctions between regions of altered tissue composition within a subject. CONCLUSION These results suggest that the 4-echo methods are best suited for measuring variations in transverse relaxation values in the mid-ventricular septum.
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Affiliation(s)
- Jared Guthrie Cobb
- Vanderbilt University, Department of Biomedical Engineering, Nashville, Tennessee, USA.
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114
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Improved SNR efficiency in gradient echo coronary MRA with high temporal resolution using parallel imaging. Magn Reson Med 2009; 62:1211-20. [DOI: 10.1002/mrm.22114] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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115
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Guo H, Au WY, Cheung JS, Kim D, Jensen JH, Khong PL, Chan Q, Chan KC, Tosti C, Tang H, Brown TR, Lam WWM, Ha SY, Brittenham GM, Wu EX. Myocardial T2 quantitation in patients with iron overload at 3 Tesla. J Magn Reson Imaging 2009; 30:394-400. [PMID: 19629983 DOI: 10.1002/jmri.21851] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To investigate the feasibility of measuring myocardial T2 at 3 Tesla for assessment of tissue iron in thalassemia major and other iron overloaded patients. MATERIALS AND METHODS A single-breathhold electrocardiogram-triggered black-blood multi-echo spin-echo (MESE) sequence with a turbo factor of 2 was implemented at 3 Tesla (T). Myocardial and liver T2 values were measured with three repeated breathholds in 8 normal subjects and 24 patients. Their values, together with the T2 values measured using a breathhold multi-echo gradient-echo sequence, were compared with those at 1.5T in the same patients. RESULTS At 3T, myocardial T2 was found to be 39.6 +/- 7.4 ms in normal subjects. In patients, it ranged from 12.9 to 50.1 ms. "T2 and T2(*) [corrected] were observed to correlate in heart (rho = 0.93, P [corrected] < 0.0001) and liver (rho = 0.95, P < 0.0001). Myocardial T2 and T2 at 3T were also highly correlated with the 1.5T measurements. Preliminary results indicated that myocardial T2 quantitation was relatively insensitive to B1 variation, and reproducible with 3.2% intra-exam and 3.8% inter-exam variations. CONCLUSION Myocardial T2 quantitation is feasible at 3T. Given the substantially decreased T2 and increased B0 inhomogeneity, the rapid myocardial T2 measurement protocol demonstrated here may present a robust alternative to study cardiac iron overload at 3T.
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Affiliation(s)
- Hua Guo
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
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Heinrichs U, Utting JF, Frauenrath T, Hezel F, Krombach GA, Hodenius MA, Kozerke S, Niendorf T. MyocardialT2*mapping free of distortion using susceptibility-weighted fast spin-echo imaging: A feasibility study at 1.5 T and 3.0 T. Magn Reson Med 2009; 62:822-8. [DOI: 10.1002/mrm.22054] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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117
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Abstract
OBJECTIVE With recent advances in technology, advanced MRI methods such as diffusion-weighted and perfusion-weighted MRI, MR elastography, chemical shift-based fat-water separation, and MR spectroscopy can now be applied to liver imaging. We will review the respective roles of these techniques for assessment of chronic liver disease. CONCLUSION MRI plays an increasingly important role in assessment of patients with chronic liver disease because of the lack of ionizing radiation and the possibility of performing multiparametric imaging.
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Affiliation(s)
- Bachir Taouli
- Department of Radiology New York University Medical Center 560 First Avenue New York, NY, 10016
| | - Richard L. Ehman
- Department of Radiology Mayo Clinic 200 First St. SW Rochester, MN, 55905
| | - Scott B. Reeder
- Department of Radiology, Medical Physics and Biomedical Engineering University of Wisconsin 600 Highland Ave, CSC E1/374 Madison, WI 53792-3252
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Song R, Lin W, Chen Q, Asakura T, Wehrli FW, Song HK. Relationships between MR transverse relaxation parameters R*(2), R(2) and R'(2) and hepatic iron content in thalassemic mice at 1.5 T and 3 T. NMR IN BIOMEDICINE 2008; 21:574-580. [PMID: 18041805 DOI: 10.1002/nbm.1227] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Assessment of hepatic iron concentration is important in the management of patients with thalassemia. The goal of this study was to investigate the relationships between the three MR transverse relaxation rates, R*(2), R(2) and R'(2), and hepatic iron content in a mouse model of thalassemia at 1.5 and 3 T field strengths. A GESFIDE (gradient-echo sampling of free induction decay and echo) pulse sequence was used to measure the three parameters efficiently in a single scan in a study examining the livers of normal and thalassemic mice, including a subgroup of the latter that were subjected to periodic transfusions. The results showed that R*(2), R(2) and R'(2) all correlated closely with liver iron concentration at both 1.5 T and 3 T, with correlation coefficients ranging from 0.72 to 0.79. High degrees of correlation (r = 0.93-0.99) were also observed among the three MR parameters at both field strengths. It can be concluded that the three rates could all be effective for assessing hepatic iron concentration and that imaging at higher fields may not offer any advantages over that at lower fields.
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Affiliation(s)
- Ruitian Song
- Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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Virtanen JM, Komu ME, Parkkola RK. Quantitative liver iron measurement by magnetic resonance imaging: in vitro and in vivo assessment of the liver to muscle signal intensity and the R2* methods. Magn Reson Imaging 2008; 26:1175-82. [PMID: 18524528 DOI: 10.1016/j.mri.2008.01.028] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 12/10/2007] [Accepted: 01/28/2008] [Indexed: 10/22/2022]
Abstract
PURPOSE To evaluate the liver-to-muscle signal intensity and R2* methods to gain a transferable, clinical application for liver iron measurement. MATERIALS AND METHODS Sixteen liver phantoms and 33 human subjects were examined using three 1.5-T MRI scanners from two different vendors. Phantom-to-muscle and liver-to-muscle signal intensity ratios were analyzed to determine MRI estimated phantom and hepatic iron concentration (M-PIC and M-HIC, respectively). R2* was calculated for the phantoms and the liver of human subjects. Seven patients' biochemical hepatic iron concentration was obtained. RESULTS M-PIC and R2* results of three scanners correlated linearly to phantom iron concentrations (r=0.984 to 0.989 and r=0.972 to 0.981, respectively), and no significant difference between the scanners was found (P=.482 and P=.846, respectively) in vitro. The patients' R2* correlated linearly to M-HIC of the standard scanner (r=0.981). M-HIC values did not differ from those obtained from the biopsy specimens (P=.230). The difference in M-HIC was significant, but the difference in R2* was not significant between the scanners (P<.0001 and P=.505, respectively) in vivo. CONCLUSION Both methods, M-HIC and R2*, are reliable iron concentration indicators with linear dependence on iron concentration in vivo and in vitro. The R2* method was found to be comparable among different scanners. Transferability testing is needed for the use of the methods at various scanners.
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Affiliation(s)
- Johanna M Virtanen
- Medical Imaging Centre of Southwest Finland, Turku University Hospital, FI-20520 Turku, Finland.
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Wood JC, Ghugre N. Magnetic resonance imaging assessment of excess iron in thalassemia, sickle cell disease and other iron overload diseases. Hemoglobin 2008; 32:85-96. [PMID: 18274986 DOI: 10.1080/03630260701699912] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Patients with transfusion-dependent anemia develop cardiac and endocrine toxicity from iron overload. Classically, serum ferritin and liver biopsy have been used to monitor patient response to chelation therapy. Recently, magnetic resonance imaging (MRI) has proven effective in detecting and quantifying iron in the heart and liver. Tissue iron is paramagnetic and increases the MRI relaxation rates R2 and R2* in a quantifiable manner. This review outlines the principles and validation of non invasive iron estimation by MRI, as well as discussing some of the technical considerations necessary for accurate measurements. Specifically, the use of R2 or R2* methods, choice of echo times, appropriate model for data fitting, the use of a pixel-wise or region-based measurement, and the choice of field strength are discussed.
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Affiliation(s)
- John C Wood
- Children's Hospital of Los Angeles, University of Southern California Keck School of Medicine, Los Angeles, California 90027, USA.
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Mamtani M, Kulkarni H. Influence of iron chelators on myocardial iron and cardiac function in transfusion-dependent thalassaemia: a systematic review and meta-analysis. Br J Haematol 2008; 141:882-90. [PMID: 18355381 DOI: 10.1111/j.1365-2141.2008.07122.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Iron chelators have dramatically prolonged the life expectancy of patients with transfusion-dependent thalassaemia, but their precise clinical benefit in reducing the myocardial iron burden and improving cardiac function is unknown. This systematic review and meta-analysis included published clinical trials that assessed the efficacy of iron chelators in regularly transfused patients of thalassaemia major for two commonly reported outcomes - myocardial iron content and left ventricular ejection fraction (LVEF). The meta-analysis of 392 patients for myocardial iron content and 291 patients for LVEF showed that (i) iron chelators reduced cardiac iron content by 23.9% (95% confidence interval 17.3-29.8%); (ii) there was no significant difference between the amount of iron reduced by deferoxamine and deferiprone (P = 0.9504); and (iii) LVEF was not significantly influenced by iron chelators - summary Hedge's g 0.13 (95% confidence interval -0.10-0.36). A significant publication bias existed for LVEF (Egger's P = 0.049) but not for myocardial iron (Egger's P = 0.871). Our results indicate that iron chelators significantly reduce myocardial iron content. Further, the choice of deferoxamine versus deferiprone may rest on factors other than their efficacy to reduce cardiac iron load.
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Cardiac T2* and lipid measurement at 3.0 T-initial experience. Eur Radiol 2007; 18:800-5. [DOI: 10.1007/s00330-007-0814-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Revised: 09/06/2007] [Accepted: 10/23/2007] [Indexed: 01/12/2023]
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Abstract
PURPOSE OF REVIEW To highlight recent advances in magnetic resonance imaging estimation of somatic iron overload. This review will discuss the need and principles of magnetic resonance imaging-based iron measurements, the validation of liver and cardiac iron measurements, and the key institutional requirements for implementation. RECENT FINDINGS Magnetic resonance imaging assessment of liver and cardiac iron has achieved critical levels of availability, utility, and validity to serve as the primary endpoint of clinical trials. Calibration curves for the magnetic resonance imaging parameters R2 and R2* (or their reciprocals, T2 and T2*) have been developed for the liver and the heart. Interscanner variability for these techniques has proven to be on the order of 5-7%. SUMMARY Magnetic resonance imaging assessment of tissue iron is becoming increasingly important in the management of transfusional iron load because it is noninvasive, relatively widely available and offers a window into presymptomatic organ dysfunction. The techniques are highly reproducible within and across machines and have been chemically validated in the liver and the heart. These techniques will become the standard of care as industry begins to support the acquisition and postprocessing software.
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Affiliation(s)
- John C Wood
- Divisions of Pediatric Cardiology and Radiology, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA.
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