Hepatic Iron Quantification Research Articles

Reversal of Complications Following Intensive Combined Chelation in β-Thalassemia Major Patients.

Life-threatening sequelae in β-thalassemia major patients (TM), result from transfusion iron overload (Fe load). Combined chelation with desferrioxamine (DFO) and deferiprone (DFP) is well tolerated and produces a synergistic effect superior to either drug alone. Combination can place all TMp in negative net iron balance and effect significant reduction in Fe load. 50 TM (24 males, 26 females) aged 8–48 yrs, were switched from monotherapy with DFO, to an individually tailored regimen (DFO 40–60 mg/kg/day- DFP 75–100 mg/kg/day) for 5–6yrs. Fe load was evaluated by mean ferritin levels (MEIA) and non-invasive heart &hepatic iron quantification, by annual Signa-MRI 1.5 Tesla, multi-echo T2 sequences. The heart was evaluated by Echo Doppler. Endocrine function was assessed by:- thyroid: FT4, FT3 &TSH in TRH-test, - Gonads: estradiol, progesterone, testosterone, Free-testosterone levels &LHRH stimulation- Glucose tolerance: OGGT with glucose &insulin measurements at each time and area under the curve (AUC). Insulin sensitivity and beta-cell function were assessed by indices of homeostasis model assessment (ISIHOMA &SCHOMA). Subsequently, all patients survived, even though with DFO alone in the previous decade, mortality ranged from 13.3–14.3%. In patients who accepted the treatment well, a trend analysis (PROC MIXED in SAS), revealed a negative trend of ferritin over time (p<0.0001) with a rate of decline equal to −95 ng/ml/month and a cumulative decrease in 5 years. The mean Ferritin value at baseline, 3.421μg/L, decreased dramatically to 87μg/L. MRI measurements led to significant reduction (p<0.0001) of Fe load to virtually Fe free organs (T2Heart from 28,2msec to 38,1msec &T2Liver from 22,7msec to37,2msec). In 12/50 with pre-existing cardiac dysfunction on medication, symptoms reversed and heart medications were stopped. Ventricular dimensions and function normalized in Echo tests. Mean LVEF increased significantly (p<0.0001) from 54% to 72% with no new dysfunction nor deterioration of heart function. In 17/50 with hypothyroidism on replacement therapy, 7/17 (41%) discontinued therapy and their TSH, FT4 normalised and 4/17 reduced their thyroxin dose. Free thyroxin (FT4) was significantly increased in euthyroid patients. In 14/24 males who were initially on testosterone replacement therapy, 4/14(28.5%) discontinued therapy, whereas 10/24 increased their testosterone levels. In 19/26 females with secondary amenorrhea, 2 had spontaneous ovulation with subsequent normal births and 2 gave birth following in vitro fertilization. In 6/50 with Insulin-dependent Diabetes, insulin dose was reduced. Initially, 14/50 TMp had non- Insulin dependent Diabetes (glucose 0>126 mg/dl, 2h>200mg/dl), 16/50 had Impaired Glucose Tolerance (IGT: glucose 2h>140<200 mg/dl) and 3/50 had Impaired Fasting Glucose (glucose 0>100<126 mg/dl). Following intensive combined chelation, 9/14 (64%), 10/16 (67%) and 3/3 (100%) respectively, normalised their glucose metabolism (p <0.001). An improvement in the glucose AUC was also noted (ANOVA-GENERAL LINEAR MODEL: p<0.002) despite BMI increase (p<0,001). Additionally, insulin secretion increased (SCHOMA: p<0,05 and Friedman/Wilcoxon p<0,004) and insulin sensitivity reduced, (ISIHOMA: p<0,742). These results indicate that in our patient cohort, intensive combination dramatically improved survival and led to reversal of secondary iron overload sequelae.

Hepatic iron quantification by atomic absorption spectrophotometry: Full validation of an analytical method using a fast sample preparation

Atomic absorption spectrophotometry is considered the method of choice for hepatic iron quantification. The objective of the present study was to perform full validation assays of hepatic iron quantification by atomic absorption spectrophotometry, using a fast sample preparation procedure, following the guidelines from the International Conference on Harmonization. The following parameters were evaluated: specificity, linearity/range, precision, accuracy, limit of detection and limit of quantification. A good linear correlation was found (0.9948) in the concentration range evaluated (20‐ 120 ppb). The relative standard deviations were below 15% for accuracy, and below 10% for both day‐to‐day reproducibility and within‐days precision, and the repeatability of injections was 0.65%. Limit of detection was 2 ppb, and limit of quantification was 6 ppb. Fresh bovine liver tissue was used to evaluate the procedure of collecting samples by liver biopsies. These findings indicate that hepatic iron quantification by atomic absorption spectrophotometry can be reliably performed at the established conditions, and suggest the method is suitable for further use in clinical practice. Hepatic iron quantification by AAS is validated by the experiments performed in the present study.

Non-invasive assessment of hepatic iron overload: are we finally there?

Iron excess in tissues can lead to toxicity and organ disease. The liver, as the primary site of body iron deposition, is also a principal target for its toxicity. Heavy iron overload in humans is usually associated with a genetically determined disturbance of iron homeostasis (i.e. hereditary hemochromatosis, HH) or with intensive transfusion regimens associated with hereditary anemia (i.e. bthalassemia). Liver biopsy is the most accurate method for assessing hepatic iron burden and provides important information on underlying liver damage and diseases. However, it entails the risk for potential complications while accurate iron measurements may be biased by sampling variability in advanced chronic disease. Therefore, at least within a diagnostic workup, costs and benefits of liver biopsy should be carefully considered. In hereditary hemochromatosis, a positive genetic test for HFE or other hemochromatosis gene mutations (transferrin receptor 2, hemojuvelin, hepcidin) may allow to avoid liver biopsy in most symptomatic patients, whereas histology remains essential in homozygotes with abnormal transaminases, hepatomegaly or serum ferritin higher than 1000 ng/ml [1]. In recent years, the potential role of mild iron overload as factor of comorbidity in the progression of several hepatic disorders (e.g. viral hepatitis, alcoholic liver disease, nonalcoholic fatty liver disease, porphyria cutanea tarda) has been increasingly recognized. In fact, accurate evaluation of hepatic iron content is now regarded as an important clinical manoeuvre in the management of chronic non-HH liver disease. Due to safety concerns of liver biopsy, non-invasive methods to measure hepatic iron content have been, therefore, devised. Serum ferritin may be a good surrogate marker for evaluating iron stores but suffers from low specificity. High sensitivity has been reported for the superconducting quantum interference device (SQUID) that measures magnetic susceptibilities [2]. SQUID, however, is not widely available and requires experienced operators. Computed tomography shows attenuation of the liver in the presence of excess iron, but seems to suffer of low sensitivity and specificity particular at mild iron overload grades and in the presence of fat [3]. Magnetic resonance has been intensively exploited, until recently, as a sensitive and specific tool for assessing hepatic iron overload [4‐9]. Due to the paramagnetic properties of iron, its increased hepatic content decreases both the T2 relaxation time and the liver signal’s intensity (SI): this gives the typical dark liver at MRI. Gradient-recalled-echo (GRE) techniques have been shown to be more accurate in quantifying mild iron overload states than spin-echo sequences due to higher sensitivity to field inhomogeneities induced by paramagnetic substances. Most published studies agree on the fact that MRI is accurate in assessing a moderate-severe iron overload but a validated and cost effective method for taking advantage of MRI in quantifying also low grades of iron stores was still missing. In addition, an ideal method should also be simple and easy to be standardized in order to be transferred and applied to different machines. Gandon and coworkers seem to have taken a fundamental step toward this end [7]. They studied 174 patients by both percutaneous liver biopsy with biochemical assessment of hepatic iron concentration and MRI of the liver with various GRE sequences on a 1.5 T magnet. They calculated liver iron concentration by evaluating the correlation between liver to muscle (L/M) signal intensity ratio and developed an algorithm to calculate magnetic resonance hepatic iron concentration. Data obtained in a study group (nZ139) that included patients with suspected iron overload or patients managed for hepatitis C, were then applied to a validation group (nZ35). A highly

MR quantification of hepatic iron concentration.

To evaluate the accuracy of magnetic resonance (MR) imaging in the quantification of hepatic iron concentration. Between April 1999 and June 2001, 112 patients were recruited prospectively. All had undergone liver biopsy and hepatic iron concentration quantification with spectrophotometry, followed by MR imaging. MR imaging involved use of four gradient-echo sequences and one spin-echo sequence. Signal intensity (SI) was measured on images obtained with each sequence by means of regions of interest placed in the liver and paraspinal muscle to obtain the liver-to-muscle SI ratio. The relationship between hepatic iron concentration and SI ratio for each sequence was analyzed with multiple linear regression. Receiver operating characteristic analysis was performed to find the diagnostic thresholds. Sixty-eight patients had normal hepatic iron levels (<36 micromol/g), 23 had hemosiderosis (36-80 micromol/g), and 21 had hemochromatosis (>80 micromol/g). With all sequences, an inverse linear relationship between iron concentration and SI ratio was apparent. The authors generated a mathematic model to estimate the iron concentrations from MR imaging data (r = 0.937). For estimated concentrations of more than 85 micromol/g, the positive predictive value for hemochromatosis was 100%; for those less than 40 micromol/g, the negative predictive value for hemochromatosis was 100%. For estimated concentrations of more than 58 micromol/g, the positive predictive value for iron overload was 100%; for those less than 20 micromol/g, the negative predictive value for iron overload was 100%. MR imaging is a useful and noninvasive diagnostic tool for quantification of hepatic iron concentration.

Theory of nonexponential NMR signal decay in liver with iron overload or superparamagnetic iron oxide particles.

A quantitative theory is proposed for the nonexponential NMR proton signal decay observed in liver with iron overload or superparamagnetic iron oxide particles. This effect occurs for Carr-Purcell-Meiboom-Gill (CPMG) sequences and is argued to be a direct consequence of the strong magnetic field inhomogeneities generated by the iron, rather than being due to tissue compartments. An approximate mathematical form is given for the signal decay, which is fit to experimental data for samples of rat liver with iron oxide particles, for samples of marmoset liver with hemosiderosis, and for in vivo human liver with hereditary hemochromatosis. The fitting parameters obtained are consistent with the pattern of iron deposition determined from histology. For the case of hereditary hemochromatosis, a good correlation is found between a parameter characterizing the nonexponential decay and the iron concentration. Implications for practical MR quantification of hepatic iron are discussed.

Correlation of Liver Density by Magnetic Resonance Imaging and Hepatic Iron Levels

The diagnosis of hemochromatosis requires liver biopsy and the quantification of hepatic iron. Magnetic resonance imaging (MRI) of the liver shows a characteristic decrease in tissue signal intensity in iron overload states, but its role in the diagnosis of hemochromatosis has not been fully delineated. Forty-three patients (31 men and 12 women) were referred for the evaluation of hemochromatosis based upon a fasting transferrin saturation > 55% and/or a serum ferritin > 400 ng/ml in males or > 300 ng/ml in females. Each patient prospectively underwent MRI of the liver prior to percutaneous liver biopsy and quantitative hepatic iron determination. Homozygous hemochromatosis was diagnosed in 10 patients based upon an hepatic iron/age index > or = 2. MRI was performed with a 1.5 Tesla system using standard spin-echo sequences (T1; TR = 300-500 ms, TE = 13-17 ms, PD; TR = 2,000-2,600 ms, TE = 30 ms). Signal intensity values were blindly determined for regions of interest in liver and skeletal muscle at T1 and proton density. Ratios of liver to muscle (LM) for T1 and proton density (PD) calculated from these values showed a significant correlation with quantitative iron by multiple regression analysis. The LMPD ratio provided the best correlation with hepatic iron (r = -0.6946; p < 0.001). Linear regression analysis also provides an equation that can be used to predict hepatic iron based upon the LMPD ratio; micrograms/g of hepatic iron = (-5,174 x LMPD) + 9,932. All patients with LMPD ratios of > 0.5 had hepatic iron/age indices of < 2.0, thereby excluding homozygous hemochromatosis. These results suggest that LMPD ratios derived from MRI of the liver can accurately predict hepatic iron content. These ratios can be clinically useful in the evaluation of hemochromatosis among patients who either refuse or have contraindications to liver biopsy.

Liver Iron Stores in Patients With Non-Insulin-Dependent Diabetes Mellitus

Iron overload such as that in idiopathic hemochromatosis is a well-established, albeit rare, cause of non-insulin-dependent diabetes mellitus (NIDDM). Most patients with NIDDM have no recognized cause of their disease. Investigators have proposed that subclinical iron overload may cause diabetes mellitus in a substantial number of patients with NIDDM. The aim of the current study was to evaluate hepatic iron stores in autopsy specimens from a group of community residents with NIDDM. Fifteen patients with NIDDM and 17 age-matched control subjects were identified from a review of medical records of decreased residents of Olmsted County, Minnesota. Formalin-fixed liver tissue was analyzed for iron concentration by flameless atomic absorption spectrophotometry, and distribution of hepatic iron was determined histochemically. No significant difference was found in either the distribution or the mean amount of hepatic iron between the diabetic and the control group (1,303 versus 1,349 micrograms Fe/g dry weight; P = 0.87). Thus, the mean difference was -46 micrograms Fe/g dry weight (confidence interval, -631 to 540). Because hepatic iron quantification is the definitive means of assessing total body iron stores, our results suggest that NIDDM is typically not associated with a substantial level of iron overload.

Quantification of hepatic iron with CT and MRI: Practical considerations

The diagnostic efficacy of magnetic resonance (MR) and computed tomography (CT) for detection and quantification of hepatic iron was assessed in a series of patients under investigation for clinical or biochemical evidence of hepatic iron overload. Thirty patients underwent MR imaging (SE 30,60/1000 or SE 30,60/2000) at 0.5 Tesla with calculation of hepatic T2 and liver to paraspinous muscles signal intensity ratios. Twenty-nine patients also had measurement of hepatic attenuation on noncontrast CT images. Results of these imaging studies were correlated in all patients with quantitative iron determination from liver biopsy specimens. The best predictor of liver iron among parameters studied was the ratio of the signal intensities of liver and paraspinous muscle (L/M) on a SE 60/1000 sequence. Both MR using L/M ratios and CT were sensitive methods for detection of severe degrees of hepatic iron overload with 100% of patients with hepatic iron on biopsy &gt; 600 μg/100 mg liver dry weight detected on the basis of L/M &lt; 0.6 or CT attenuation &gt; 70 Hounsfield units (HU). The MR parameter, however, was more specific than CT (100 vs 50%) and showed a higher degree of correlation with quantitated hepatic iron from biopsy. T2 measurements showed poor correlation with hepatic iron, due to difficulty in obtaining precise T2 measurements in vivo when the signal intensity is low. None of the parameters utilized was sensitive for detecting mild or moderate degrees of hepatic iron overload. We conclude that MR and CT are sensitive techniques for noninvasive detection of severe hepatic iron overload, with MR providing greater specificity than CT. Lesser degrees of iron deposition, however, may go undetected by our current imaging techniques.

Hepatic iron overload: Diagnosis and quantification by noninvasive imaging

The diagnostic efficacy of magnetic resonance (MR) and computed tomography (CT) for detection and quantification of hepatic iron was assessed in a series of patients under investigation for clinical or biochemical evidence of hepatic iron overload. Thirty patients underwent MR imaging (SE 30,60/1000 or SE 30,60/2000) at 0.5 Tesla with calculation of hepatic T2 and liver to paraspinous muscle signal intensity ratios. Twenty-nine patients also had measurement of hepatic attenuation on noncontrast CT images. Results of these imaging studies were correlated in all patients with quantitative iron determination from liver biopsy specimens. The best predictor of liver iron among parameters studied was the ratio of the signal intensities of liver and paraspinous muscle (L/M) on a SE 60/1000 sequence. Both MR using L/M ratios and CT were sensitive methods for detection of severe degrees of hepatic iron overload with 100% of patients with hepatic iron on biopsy greater than 600 micrograms/100 mg liver dry weight detected on the basis of L/M less than 0.6 or CT attenuation greater than 70 Hounsfield units (HU). The MR parameter, however, was more specific than CT (100 vs 50%) and showed a higher degree of correlation with quantitated hepatic iron from biopsy. T2 measurements showed poor correlation with hepatic iron, due to difficulty in obtaining precise T2 measurements in vivo when the signal intensity is low. None of the parameters utilized was sensitive for detecting mild or moderate degrees of hepatic iron overload. We conclude that MR and CT are sensitive techniques for noninvasive detection of severe hepatic iron overload, with MR providing greater specificity than CT.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatic iron overload: Diagnosis and quantification by noninvasive imaging

The diagnostic efficacy of magnetic resonance (MR) and computed tomography (CT) for detection and quantification of hepatic iron was assessed in a series of patients under investigation for clinical or biochemical evidence of hepatic iron overload. Thirty patients underwent MR imaging (SE 30,60/1000 or SE 30,60/2000) at 0.5 Tesla with calculation of hepatic T2 and liver to paraspinous muscle signal intensity ratios. Twenty-nine patients also had measurement of hepatic attenuation on noncontrast CT images. Results of these imaging studies were correlated in all patients with quantitative iron determination from liver biopsy specimens. The best predictor of liver iron among parameters studied was the ratio of the signal intensities of liver and paraspinous muscle (L/M) on a SE 60/1000 sequence. Both MR using L/M ratios and CT were sensitive methods for detection of severe degrees of hepatic iron overload with 100% of patients with hepatic iron on biopsy > 600 Μg/ 100 mg liver dry weight detected on the basis of L/M 70 Hounsfield units (HU). The MR parameter, however, was more specific than CT (100 vs 50%) and showed a higher degree of correlation with quantitated hepatic iron from biopsy. T2 measurements showed poor correlation with hepatic iron, due to difficulty in obtaining precise T2 measurements in vivo when the signal intensity is low. None of the parameters utilized was sensitive for detecting mild or moderate degrees of hepatic iron overload.