Hepatic Iron Concentration: Noninvasive Estimation by Means of MR Imaging Techniques

Bonkovsky, Herbert L.; Rubin, Richard B.; Cable, Edward Earl; Davidoff, Ashley; Rijcken, Tammo H. Pels; Stark, David D.

doi:10.1148/radiology.212.1.r99jl35227

Cited by 143 publications

(111 citation statements)

References 29 publications

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“…Currently, a liver biopsy is used for assessment of cirrhosis, which increases the risk for hepatocellular carcinoma, or to identify concomitant diseases. Determination of the hepatic iron concentration by magnetic resonance imaging is increasingly recognized as a valuable diagnostic tool in patients with increased serum iron indices (195)(196)(197)(198)(199) and might be useful to establish iron overload in those patients without a pathognomonic HFE genotype and substantially increased ferritin concentrations (Ͼ500 g/L). This technology is now available in many medical centers and might improve the diagnostic procedure by allowing a reliable and noninvasive assessment of hepatic iron, provided that the proper software and calibration techniques are used.…”

Section: Clinical and Molecular Diagnosis Of Hereditary Forms Of Hhmentioning

confidence: 99%

Hereditary Hemochromatosis: Genetic Complexity and New Diagnostic Approaches

et al. 2006

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Since the discovery of the hemochromatosis gene (HFE) in 1996, several novel gene defects have been detected, explaining the mechanism and diversity of iron-overload diseases. At least 4 main types of hereditary hemochromatosis (HH) have been identified. Surprisingly, genes involved in HH encode for proteins that all affect pathways centered around liver hepcidin synthesis and its interaction with ferroportin, an iron exporter in enterocytes and macrophages. Hepcidin concentrations in urine negatively correlate with the severity of HH. Cytokine-mediated increases in hepcidin appear to be an important causative factor in anemia of inflammation, which is characterized by sequestration of iron in the macrophage system. For clinicians, the challenge is now to diagnose HH before irreversible damage develops and, at the same time, to distinguish progressive iron overload from increasingly common diseases with only moderately increased body iron stores, such as the metabolic syndrome. Understanding the molecular regulation of iron homeostasis may be helpful in designing innovative and reliable DNA and protein tests for diagnosis. Subsequently, evidence-based diagnostic strategies must be developed, using both conventional and innovative laboratory tests, to differentiate between the various causes of distortions of iron metabolism. This review describes new insights in mechanisms of iron overload, which are needed to understand new developments in diagnostic medicine.

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Section: Clinical and Molecular Diagnosis Of Hereditary Forms Of Hhmentioning

confidence: 99%

Hereditary Hemochromatosis: Genetic Complexity and New Diagnostic Approaches

et al. 2006

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“…20 In the absence of a theoretical understanding of the effects of iron on MRI, empirical efforts to estimate hepatic iron concentrations have used a variety of instruments, magnetic field strengths, imaging sequences (spin-echo, gradient recalled-echo), and parameters (T1 and T2 relaxation times, and signal intensity ratios as measured in proton, T1-, T2-, or T2*-weighted images), but no standard or generally accepted method has been adopted for clinical application. To date, MRI has been more useful as a screening technique for the detection of marked iron overload 20 than as a means for quantitative measurement. In particular, with increasing iron concentrations, the signal intensity of the liver is reduced to such an extent that discrimination between different concentrations becomes impossible, 21 at least with current technology.…”

Section: Detection Of Iron Overload By Magnetic Resonance Imaginingmentioning

confidence: 99%

Noninvasive measurement of iron: report of an NIDDK workshop

Brittenham

Badman

2003

Blood

255

188

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“…Magnetic induction methods have been tried previously for the characterization of the paramagnetic and diamagnetic properties of biological tissues [13] but the sensitivity is considerably low. To our knowledge, the only noninvasive measurement method so far tested for hepatic iron overload in humans is based on SQUIDs [14], [15] or on MRI [16]. However, also much simpler magnetic sensors are studied to allow the detection of physiological and pathophysiological iron concentrations in human subjects [17], [18].…”

Section: Example 2: Determination Of Excess Iron Stores In Liver Tmentioning

confidence: 99%

“…is derived from the change of the mutual inductance M between EXC and gradiometer coil (15) Since at a constant number of turns is proportional to , one can also write (16) The term is much more complicated to estimate. In the simplest approach, we assume C to be essentially determined by the capacitance between the individual windings, thus neglecting the shield.…”

Section: B Thermal Mismatch Of the Gradiometer Coilsmentioning

confidence: 99%

Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations

Scharfetter

Casañas

Rosell

2003

IEEE Trans. Biomed. Eng.

120

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Abstract-Magnetic induction spectroscopy (MIS) aims at the contactless measurement of the passive electrical properties (PEP), , and of biological tissues via magnetic fields at multiple frequencies. Whereas previous publications focus on either the conductive or the magnetic aspect of inductive measurements, this article provides a synthesis of both concepts by discussing two different applications with the same measurement system: 1) monitoring of brain edema and 2) the estimation of hepatic iron stores in certain pathologies. We derived the equations to estimate the sensitivity of MIS as a function of the PEP of biological objects. The system requirements and possible systematic errors are analyzed for a MIS-channel using a planar gradiometer (PGRAD) as detector. We studied 4 important error sources: 1) moving conductors near the PGRAD; 2) thermal drifts of the PGRAD-parameters; 3) lateral displacements of the PGRAD; and 4) phase drifts in the receiver. All errors were compared with the desirable resolution. All errors affect the detected imaginary part (mainly related to ) of the measured complex field much less than the real part (mainly related to and ). Hence, the presented technique renders possible the resolution of (patho-) physiological changes of the electrical conductivity when applying highly resolving hardware and elaborate signal processing. Changes of the magnetic permeability and permittivity in biological tissues are more complicated to deal with and may require chopping techniques, e.g., periodic movement of the object.Index Terms-Brain edema, impedance spectroscopy, iron overload, magnetic induction tomograpy, passive electrical properties of tissue.

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Hepatic Iron Concentration: Noninvasive Estimation by Means of MR Imaging Techniques

Abstract: MR imaging with these parameters is a rapid, noninvasive, and accurate modality for estimation of hepatic iron concentration; it is sufficiently accurate and precise to obviate liver biopsy for the purpose of measuring hepatic iron concentration.

Cited by 143 publications

References 29 publications

Hereditary Hemochromatosis: Genetic Complexity and New Diagnostic Approaches

Hereditary Hemochromatosis: Genetic Complexity and New Diagnostic Approaches

Noninvasive measurement of iron: report of an NIDDK workshop

Biological tissue characterization by magnetic induction spectroscopy (MIS): requirements and limitations

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