Quantification of iron concentration in the liver by MRI

An algorithmic approach to MR characterization of focal liver lesions in adults without cirrhosis

Diagnosing both known and incidental liver lesions in the non-cirrhotic liver on MRI can be challenging. The radiologist can often narrow the diagnosis toward a diagnostic category using various sequences. Using an organized framework to guide the reader's differential diagnosis can be helpful. We present a sequential approach to the diagnosis of focal liver lesions, by first assessing background liver parenchymal signal intensity, then comparing the T1-weighted signal intensity of the reference organ(s), followed by comparing the T2-weighted signal intensity characteristics of lesion to fluid/spleen, and finally confirming using additional sequences including dynamic contrast-enhanced imaging, hepatobiliary imaging, diffusion weighted imaging, as well as clinical and laboratory testing and additional modalities. Using this stepwise framework can sequentially guide the reader toward a diagnosis.

Hemochromatosis Affects the Distribution of 68 Ga-DOTATATE in the Liver and Spleen

ABSTRACT

Hemosiderosis is a chronic condition characterized by abnormal iron accumulation in tissues. In a PET scan of a 37-year-old woman, we observed an irregular distribution of 68 Ga-DOTATATE in the liver and spleen. Specifically, 68 Ga-DOTATATE appeared to be concentrated primarily in the peripheral regions of these organs, creating a distinctive "shell-like" appearance. This peculiar pattern may be attributed to the substantial accumulation of hemosiderin in the liver and spleen.

Non-invasive methods for iron overload evaluation in dysmetabolic patients

INTRODUCTION

Although hyperferritinemia may reflect the inflammatory status of patients with non-alcoholic fatty liver disease (NAFLD), approximately 33% of hyperferritinemia cases reflect real hepatic iron overload.

AIM

To evaluate a non-invasive method for assessing mild iron overload in patients with NAFLD using 3T magnetic resonance imaging (MRI) relaxometry, serum hepcidin, and the expression of ferritin subunits.

METHODS

This cross-sectional study assessed patients with biopsy-proven NAFLD. MRI relaxometry was performed using a 3T scanner in all patients, and the results were compared with iron content determined by liver biopsy. Ferritin, hepcidin, and ferritin subunits were assessed and classified according to ferritin levels and to siderosis identified by liver biopsy.

RESULTS

A total of 67 patients with NAFLD were included in the study. MRI revealed mild iron overload in all patients (sensitivity, 73.5%; specificity, 70%). For mild (grade 1) siderosis, the transverse relaxation rate (R2*) threshold was 58.9 s-1 and the mean value was 72.5 s-1 (SD, 33.9), while for grades 2/3 it was 88.2 s-1 (SD, 31.9) (p < 0.001). The hepcidin threshold for siderosis was > 30.2 ng/mL (sensitivity, 87%; specificity, 82%). Ferritin H and ferritin L subunits were expressed similarly in patients with NAFLD, regardless of siderosis. There were no significant differences in laboratory test results between the groups, including glucose parameters and liver function tests.

CONCLUSIONS

MRI relaxometry and serum hepcidin accurately assessed mild iron overload in patients with dysmetabolic iron overload syndrome.

Assessment of iron nanoparticle distribution in mouse models using ultrashort-echo-time MRI

Microscopic magnetic field inhomogeneities caused by iron deposition or tissue-air interfaces may result in rapid decay of transverse magnetization in MRI. The aim of this study is to detect and quantify the distribution of iron-based nanoparticles in mouse models by applying ultrashort-echo-time (UTE) sequences in tissues exhibiting extremely fast transverse relaxation. In 24 C57BL/6 mice (two controls), suspensions containing either non-oxidic Fe or AuFeO_x nanoparticles were injected into the tail vein at two doses (200 μg and 600 μg per mouse). Mice underwent MRI using a UTE sequence at 4.7 T field strength with five different echo times between 100 μs and 5000 μs. Transverse relaxation times T₂ * were computed for the lung, liver, and spleen by mono-exponential fitting. In UTE imaging, the MRI signal could reliably be detected even in liver parenchyma exhibiting the highest deposition of nanoparticles. In animals treated with Fe nanoparticles (600 μg per mouse), the relaxation time substantially decreased in the liver (3418 ± 1534 μs (control) versus 228 ± 67 μs), the spleen (2170 ± 728 μs versus 299 ± 97 μs), and the lungs (663 ± 101 μs versus 413 ± 99 μs). The change in transverse relaxation was dependent on the number and composition of the nanoparticles. By pixel-wise curve fitting, T₂ * maps were calculated showing nanoparticle distribution. In conclusion, UTE sequences may be used to assess and quantify nanoparticle distribution in tissues exhibiting ultrafast signal decay in MRI.

Determination of Non-Invasive Biomarkers for the Assessment of Fibrosis, Steatosis and Hepatic Iron Overload by MR Image Analysis. A Pilot Study

The reference diagnostic test of fibrosis, steatosis, and hepatic iron overload is liver biopsy, a clear invasive procedure. The main objective of this work was to propose HSA, or human serum albumin, as a biomarker for the assessment of fibrosis and to study non-invasive biomarkers for the assessment of steatosis and hepatic iron overload by means of an MR image acquisition protocol. It was performed on a set of eight subjects to determine fibrosis, steatosis, and hepatic iron overload with four different MRI sequences. We calibrated longitudinal relaxation times (T1 [ms]) with seven human serum albumin (HSA [%]) phantoms, and we studied the relationship between them as this protein is synthesized by the liver, and its concentration decreases in advanced fibrosis. Steatosis was calculated by means of the fat fraction (FF [%]) between fat and water liver signals in “fat-only images” (the subtraction of in-phase [IP] images and out-of-phase [OOP] images) and in “water-only images” (the addition of IP and OOP images). Liver iron concentration (LIC [µmol/g]) was obtained by the transverse relaxation time (T2* [ms]) using Gandon’s method with multiple echo times (TE) in T2-weighted IP and OOP images. The preliminary results showed that there is an inverse relationship (r = −0.9662) between the T1 relaxation times (ms) and HSA concentrations (%). Steatosis was determined with FF > 6.4% and when the liver signal was greater than the paravertebral muscles signal, and thus, the liver appeared hyperintense in fat-only images. Hepatic iron overload was detected with LIC > 36 µmol/g, and in these cases, the liver signal was smaller than the paravertebral muscles signal, and thus, the liver behaved as hypointense in IP images.

Correlation of Serum Ferritin and Liver Iron Concentration with Transient Liver Elastography in Adult Thalassemia Intermedia Patients with Blood Transfusion

INTRODUCTION

Iron overload is a common feature of thalassemia intermedia due to regular blood transfusion and increased gastrointestinal iron absorption. Early detection and adequate iron chelator can decrease morbidity and mortality from iron overload. Liver iron concentration (LIC) by MRI T2* is the best non-invasive way to measure body iron stores. However, this method is expensive and not available nationwide in Indonesia. The aim of this study was to identify liver iron overload and correlation of transferrin saturation, serum ferritin, liver MRI T2* and LIC with transient liver elastography in adult thalassemia intermedia patients.

METHODS

This is a cross-sectional study of 45 patients with thalassemia intermedia with blood transfusion and with and without iron chelator therapy. The study was conducted at Cipto Mangunkusumo Hospital from August through October 2016. We performed measurements of transferrin saturation, serum ferritin level, transient liver elastography and liver MRI T2*. Pearson and Spearman correlation tests were used to evaluate the correlation between transient liver elastography with transferrin saturation, serum ferritin, liver MRI T2*and LIC.

RESULTS AND DISCUSSION

This study showed that 64.4% of study subjects are β-Hb E thalassemia intermedia. Furthermore, 84.4% of study subjects have regular transfusion. Based on liver MRI T2*all subjects suffered from liver iron overload, 48.9% had severe degree. Median value of liver MRI T2* was 1.6 ms. Mean serum ferritin was 2831 ng/mL, with median transferrin saturation of 66%. Mean of LIC corresponding to liver MRI T2* and mean liver stiffness measurement was 15.36±7.37 mg Fe/gr dry weight and 7.7±3.8 kPa, respectively. Liver stiffness correlated with serum ferritin (r=0.651; p=0.000), liver MRI T2* (r=-0.357; p=0.016), and LIC (r=0.433; p=0.003). No correlation was found between liver elastography and transferrin saturation (r=0.204; p=0.178).

CONCLUSION

Serum ferritin, liver MRI T2*and LIC correlated with liver elastography. No correlation was found between transferrin saturation and liver elastography.

Association of HFE Gene Mutations With Serum Ferritin Level and Heart and Liver Iron Overload in Patients With Transfusion-dependent Beta-Thalassemia

OBJECTIVE

This study was performed on patients with transfusion-dependent beta-thalassemia (TDT) to investigate the effect of HFE gene mutations of iron overload in a large group of patients with TDT major and its relationship with heart and liver T2* magnetic resonance imaging (MRI) level.

MATERIALS AND METHODS

In a cross-sectional study, a total of 253 patients with TDT who had regular blood transfusion were included in this study. HFE gene mutations including H63D and C282Y were evaluated in all patients through molecular assay. Heart and liver T2* MRI results, types, duration of iron therapy, and the demographic data including age, gender, serum ferritin level, blood transfusion, and splenectomy history of the included participants were also collected, using a questionnaire.

RESULTS

Homozygous and heterozygous H63D mutation was found in 39.5% of the patients and C282Y mutation was found only in 1 patient. Ferritin level was significantly higher in patients with H63D mutation in comparison with patients without this mutation (P=0.036). Although heart T2* MRI and also the liver T2* MRI in the patients with H63D was slightly higher, the difference was not statistically significant. No significant correlation was observed between serum ferritin level and heart and liver T2* MRI, and iron chelation regimen.

DISCUSSION

Heart and liver iron overload was not significantly different between patients with and without H63D mutation. As for serum ferritin, it was significantly higher among patients with H63D mutation compared with patients without this mutation. Hence, it is recommended to consider HFE gene mutations among patients with thalassemia to reach a better iron overload evaluation and management.

R2 and R2* MRI assessment of liver iron content in an undifferentiated diagnostic population with hyperferritinaemia, and impact on clinical decision making

PURPOSE

To confirm the linear correlation between Ferriscan® R2 (1/T2 Relaxomatry) and R2* (1/T2* Relaxometry) derived 3D Gradient echo (GRE) mDIXON-Quant sequence (Philips) with simultaneous production of a proton density fat fraction (PDFF) in undifferentiated patients with hyperferritinaemia, and to prospectively determine the clinical utility of this tool in these patients by recording the impact on clinical decision-making.

MATERIALS AND METHODS

Participants referred to a hospital haematology outpatient clinic for investigation and management of elevated serum ferritin (two serum ferritin levels > 500 μg/L 4 weeks apart) were included in the study.

EXCLUSION CRITERIA

contraindications to MRI; clinically relevant investigations for alternative causes of hyperferritinaemia pending; and terminal illness. Thirty-two participants were recruited: 27 men, 5 women. All MRIs performed at 1.5 T. For R2* quantification, 3D six echo GRE sequence (mDIXON-Quant) was acquired. R2 images were acquired over 20 min as dictated and reported by the licensee (Ferriscan®). Clinician interpretation and patient management based on R2* and liver iron content derived from R2 (LIC_R2) was recorded. Pearson's correlations, linear regression analyses, and ROC curves were calculated. P value <0.05 was considered significant.

RESULTS

A high degree of correlation between mean R2* and LIC_R2 was observed in this novel patient population (slope ± SE of 43.35 ± 1.88 s^-1 permg/g; 95 % CI 39.5-47.2; P < 0.001; R² = 0.87). Clinical decision making was amended in 14/32 (44 %) patients with hyperferritinaemia following the disclosure of R2* results to clinicians, compared with serum ferritin alone. Liver biopsy was avoided in one patient based on LIC_R2 and R2*. Unrecognised hepatic steatosis was diagnosed in one patient from the PDFF map.

CONCLUSION

We have confirmed the linear correlation between R2 and R2* in a real-world diagnostic population with hyperferritinaemia. Non-invasive assessment of liver iron content (LIC) by R2 and R2* MRI is a useful clinical tool and alters management in these patients.

Comparison of automated and manual protocols for magnetic resonance imaging assessment of liver iron concentration

Objective

To compare automated and manual magnetic resonance imaging protocols for estimating liver iron concentrations at 1.5 T.

Materials and Methods

Magnetic resonance imaging examination of the liver was performed in 53 patients with clinically suspected hepatic iron overload and in 21 control subjects. Liver iron concentrations were then estimated by two examiners who were blinded to the groups. The examiners employed automated T2* and T1 mapping, as well as manual T2* and signal-intensity-ratio method. We analyzed accuracy by using ROC curves. Interobserver and intraobserver agreement were analyzed by calculating two-way intraclass correlation coefficients.

Results

The area under the ROC curve (to discriminate between patients and controls) was 0.912 for automated T2* mapping, 0.934 for the signal-intensity-ratio method, 0.908 for manual T2*, and 0.80 for T1 mapping, the last method differing significantly from the other three. The level of interobserver and intraobserver agreement was good (intraclass correlation coefficient, 0.938-0.998; p < 0.05). Correlations involving T1 mapping, although still significant, were lower.

Conclusion

At 1.5 T, T2* mapping is a rapid tool that shows promise for the diagnosis of liver iron overload, whereas T1 mapping shows less accuracy. The performance of T1 mapping is poorer than is that of T2* methods.

Evaluation of liver iron overload with R2* relaxometry with versus without fat suppression: both are clinically accurate but there are differences

OBJECTIVES

To assess clinically relevant difference in hepatic iron quantification using R2* relaxometry with (FS) and without (non-FS) fat saturation for the evaluation of patients with suspected hepatic iron overload.

METHODS

We prospectively enrolled 134 patients who underwent 1.5-T MRI R2* relaxometry with FS and non-FS gradient echo sequences (12 echoes, initial TE = 0.99 ms). Proton density fat fraction for the quantification of steatosis was assessed. Linear regression analyses and Bland-Altman plots including Lin's concordance correlation coefficient were performed for correlation of FS R2* with non-FS R2*. Patients were grouped into 4 severity classes of iron overload (EASL based), and agreement was evaluated by contingency tables and the proportion of overall agreement.

RESULTS

A total of 41.8% of patients showed hepatic iron overload; 67.9% had concomitant steatosis; and 58.2% revealed no iron overload of whom 60.3% had steatosis. The mean R2* value for all FS data was 102.86 1/s, for non-FS 108.16 1/s. Linear regression resulted in an R-squared value of 0.99 (p < 0.001); Bland-Altman plot showed a mean R2* difference of 5.26 1/s (SD 17.82). The concordance correlation coefficient was only slightly lower for patients with steatosis compared with non-steatosis (0.988 vs. 0.993). The overall agreement between FS and non-FS R2* measurements was 94.8% using either method to classify patients according to severity of iron storage. No correlation between R2* and proton density fat fraction was found for both methods.

CONCLUSION

R2* relaxometry showed an excellent overall agreement between FS and non-FS acquisition. Both variants can therefore be used in daily routine. However, clinically relevant differences might result when switching between the two methods or during patient follow-up, when fat content changes over time. We therefore recommend choosing a method and keeping it straight in the context of follow-up examinations.

KEY POINTS

• Both variants of R2* relaxometry (FS and non-FS) may be used in daily routine. • Clinically relevant differences might result when switching between the two methods or during patient follow-up, when fat content changes over time. • It seems advisable choosing one method and keeping it straight in the context of follow-up examinations.

A positive influence of basal ganglia iron concentration on implicit sequence learning

Iron homeostasis is important for maintaining normal physiological brain functioning. In two independent samples, we investigate the link between iron concentration in the basal ganglia (BG) and implicit sequence learning (ISL). In Study 1, we used quantitative susceptibility mapping and task-related fMRI to examine associations among regional iron concentration measurements, brain activation, and ISL in younger and older adults. In Study 2, we examined the link between brain iron and ISL using a metric derived from fMRI in an age-homogenous sample of older adults. Three main findings were obtained. First, BG iron concentration was positively related to ISL in both studies. Second, ISL was robust for both younger and older adults, and performance-related activation was found in fronto-striatal regions across both age groups. Third, BG iron was positively linked to task-related BOLD signal in fronto-striatal regions. This is the first study investigating the relationship among brain iron accumulation, functional brain activation, and ISL, and the results suggest that higher brain iron concentration may be linked to better neurocognitive functioning in this particular task.

Serum ferritin levels and irregular use of iron chelators predict liver iron load in patients with major beta thalassemia: a cross-sectional study

Aim

To determine whether serum ferritin, liver transaminases, and regularity and type of iron chelation protocol can be used to predict liver iron load as assessed by T2* magnetic resonance imaging (MRI) in patients with beta thalassemia major (TM).

Methods

This cross-sectional study, conducted from March 1, 2014 to March 1, 2015, involved 90 patients with beta TM on regular packed red blood cell transfusion. Liver and cardiac iron load were evaluated with T2* MRI. Compliance with iron-chelating agents, deferoxamine or deferasirox, and regularity of their use, as well as serum ferritin and liver transaminase levels were assessed.

Results

Patients with high serum ferritin were 2.068 times (95% confidence interval 1.26-3.37) more likely to have higher liver or cardiac iron load. High serum aspartate aminotransferases and irregular use of iron chelating agents, but not their type, predicted higher cardiac iron load. In a multiple regression model, serum ferritin level was the only significant predictor of liver and myocardial iron load.

Conclusions

Higher serum ferritin strongly predicted the severity of cardiac and liver iron load. Irregular use of chelator drugs was associated with a higher risk of cardiac and liver iron load, regardless of the type of chelating agent.

Liver involvement in patients with Gaucher disease types I and III

Background & aims

Gaucher disease (GD) is a multisystemic disease. Liver involvement in GD is not well characterised and ranges from hepatomegaly to cirrhosis and hepatocellular carcinoma. We aim to describe, and assess the effect of treatment, on the hepatic phenotype of a cohort of patients with GD types I and II.

Methods

Retrospective study based on the review of the medical files of the Gaucher Reference Centre of the Hospital de Clínicas de Porto Alegre, Brazil. Data from all GD types I and III patients seen at the centre since 2003 were analysed. Variables were compared as pre- (“baseline”) and post-treatment (“follow-up”).

Results

Forty-two patients (types I: 39, III: 3; female: 22; median age: 35 y; enzyme replacement therapy: 37; substrate reduction therapy: 2; non-treated: 3; median time on treatment-MTT: 124 months) were included. Liver enzyme abnormalities, hepatomegaly, and steatosis at baseline were seen in 19/28 (68%), 28/42 (67%), and 3/38 patients (8%), respectively; at follow-up, 21/38 (55%), 15/38 (39%) and 15/38 (39%). MRI iron quantification showed overload in 7/8 patients (treated: 7; MTT: 55 months), being severe in 2/7 (treated: 2/2; MTT: 44.5 months). Eight patients had liver biopsy (treated: 6; MTT: 58 months), with fibrosis in 3 (treated: 1; time on treatment: 108 months) and steatohepatitis in 2 (treated: 2; time on treatment: 69 and 185 months). One patient developed hepatocellular carcinoma.

Conclusions

GD is a heterogeneous disease that causes different patterns of liver damage even during treatment. Although treatment improves the hepatocellular damage, it is associated with an increased rate of steatosis. This study highlights the importance of a follow-up of liver integrity in these patients.

A new molecular probe: An NRP-1 targeting probe for the grading diagnosis of glioma in nude mice

Magnetic resonance molecular imaging, as a safe imaging technology, provides a new idea for the early qualitative and hierarchical diagnosis of gliomas. The purpose of this study was to design and evaluate the value of neuropilin-1 (NRP-1) targeting molecular probes in the hierarchical diagnosis of gliomas. First, we created an NRP-1 targeted magnetic resonance molecular probe (USPIO-PEG-tLyP-1) by combining the polypeptide tLyP-1 with ultra-small superparamagnetic iron oxide nanoparticles (USPIONs), detecting the physical properties by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Second, in vivo experiments, we established two different degrees of malignant gliomas in-situ in nude mice by injecting U87 and CHG-5 cells. Then, to detect the binding ability of the probe with different grades of tumour tissues, we injected the probe into the tumour-bearing mice through the tail vein. Next, MRI was performed before injection, and 6 h, 12 h, 24 h after injection, and we found significantly more iron particles in the tumour tissues of U87 tumour-bearing mice than in tumour tissues of CHG-5 tumour-bearing mice. The signal intensities of the T2-weighted images of the tumour tissues of each group as well as microscopic observations by Prussian blue staining indicated that the binding ability of this molecular probe to U87 glioma (HGG) with high NRP-1 expression was significantly greater than that of CHG-5 glioma (LGG) with low NRP-1 expression (P < 0.01). Therefore, this study confirms that the novel molecular probe USPIO-PEG-tLyP-1 can be used for the grading diagnosis by MRI for gliomas of high and low grade with different NRP-1 expression levels.

Practical guide to quantification of hepatic iron with MRI

Abstract

Our intention is to demystify the MR quantification of hepatic iron (i.e., the liver iron concentration) and give you a step-by-step approach by answering the most pertinent questions. The following article should be more of a manual or guide for every radiologist than a classic review article, which just summarizes the literature. Furthermore, we provide important background information for professional communication with clinicians. The information regarding the physical background is reduced to a minimum. After reading this article, you should be able to perform adequate MR measurements of the LIC with 1.5-T or 3.0-T scanners.

Key Points

• MRI is widely accepted as the primary approach to non-invasively determine liver iron concentration (LIC).

• This article is a guide for every radiologist to perform adequate MR measurements of the LIC.

• When using R2* relaxometry, some points have to be considered to obtain correct measurements—all explained in this article.

Liver MRI susceptibility-weighted imaging (SWI) compared to T2* mapping in the presence of steatosis and fibrosis

PURPOSE

To show that both susceptibility-weighted imaging (SWI) and T2*-mapping are dependent on liver steatosis, which should be taken into account when using these parameters to grade liver fibrosis and cirrhosis.

METHODS

In this prospective study, a total of 174 patients without focal liver disease underwent multiparametric MRI at 3 T including SWI, T1- and T2* mapping, proton density fat fraction (PDFF) quantification and MR elastography. SWI, T2* and T1 were measured in the liver (4 locations), as well as in paraspinal muscles, to calculate the liver-to-muscle ratio (LMR). Liver and LMR values were compared among patients with different steatosis grades (PDFF < 5%, 5-10%, 10-20% and >20%), patients with normal, slightly increased and increased liver stiffness (<2.8 kPa, 2.8-3.5 kPa and >3.5 kPa, respectively). ANOVA with Bonferroni-corrected post hoc tests as well as a multivariate analysis were used to compare values among groups and parameters.

RESULTS

SWI and T2* both differed significantly among groups with different steatosis grades (p < 0.001). However, SWI allowed a better differentiation among liver fibrosis grades (p < 0.001) than did T2* (p = 0.05). SWI LMR (p < 0.001) and T2* LMR (p = 0.036) showed a similar performance in differentiating among liver fibrosis grades.

CONCLUSION

SWI and T2*-mapping are strongly dependent on the liver steatosis grades. Nevertheless, both parameters are useful predictors for liver fibrosis when using a multiparametric approach.

Predicting gastroesophageal varices through spleen magnetic resonance elastography in pediatric liver fibrosis

BACKGROUND

A recent retrospective study confirmed that hepatic stiffness and splenic stiffness measured with magnetic resonance elastography (MRE) are strongly associated with the presence of esophageal varices. In addition, strong correlations have been reported between splenic stiffness values measured with MRE and hepatic venous pressure gradients in animal models. However, most studies have been conducted on adult populations, and previous pediatric MRE studies have only demonstrated the feasibility of MRE in pediatric populations, while the actual clinical application of spleen MRE has been limited.

AIM

To assess the utility of splenic stiffness measurements by MRE to predict gastroesophageal varices in children.

METHODS

We retrospectively reviewed abdominal MRE images taken on a 3T system in pediatric patients. Patients who had undergone Kasai operations for biliary atresia were selected for the Kasai group, and patients with normal livers and spleens were selected for the control group. Two-dimensional spin-echo echo-planar MRE acquisition centered on the liver, with a pneumatic driver at 60 Hz and a low amplitude, was performed to obtain hepatic and splenic stiffness values. Laboratory results for aspartate aminotransferase to platelet ratio index (APRI) were evaluated within six months of MRE, and the normalized spleen size ratio was determined with the upper normal size limit. All Kasai group patients underwent gastroesophageal endoscopy during routine follow-up. The Mann-Whitney U test, Kendall's tau b correlation and diagnostic performance analysis using the area under the curve (AUC) were performed for statistical analysis.

RESULTS

The median spleen MRE value was 5.5 kPa in the control group (n = 9, age 9-18 years, range 4.7-6.4 kPa) and 8.6 kPa in the Kasai group (n = 22, age 4-18 years, range 5.0-17.8 kPa). In the Kasai group, the APRI, spleen size ratio and spleen MRE values were higher in patients with portal hypertension (n = 11) than in patients without (n = 11) (all P < 0.001) and in patients with gastroesophageal varices (n = 6) than in patients without (n = 16) (all P < 0.05), even though their liver MRE values were not different. The APRI (τ = 0.477, P = 0.007), spleen size ratio (τ = 0.401, P = 0.024) and spleen MRE values (τ = 0.426, P = 0.016) also correlated with varices grades. The AUC in predicting gastroesophageal varices was 0.844 at a cut-off of 0.65 (100% sensitivity and 75% specificity) for the APRI, and 0.844 at a cut-off of 9.9 kPa (83.3% sensitivity and 81.3% specificity) for spleen MRE values.

CONCLUSION

At a cut-off of 9.9 kPa, spleen MRE values predicted gastroesophageal varices as well as the APRI and spleen size ratio in biliary atresia patients after the Kasai operation. However, liver MRE values were not useful for this purpose.

MRI for Iron Overload in Thalassemia

MRI is a key tool in the current management of patients with thalassemia. Given its capability of assessing iron overload in different organs noninvasively and without contrast, it has significant advantages over other metrics, including serum ferritin. Liver iron concentration can be measured either with relaxometry methods T2*/T2 or signal intensity ratio techniques. Myocardial iron can be assessed in the same examination through T2* imaging. In this review, we focus on showing how MRI evaluates iron in both organs and the clinical applications as well as practical approaches to using this tool by clinicians taking care of patients with thalassemia.

Imaging features of thalassaemia

This article highlights the range of osseous findings that can be encountered as well as the imaging features of extramedullary haematopoiesis. As iron overload remains a major cause of morbidity and mortality in these disorders, we also discuss the MRI evaluation of hepatic and cardiac hemosiderosis, to aid in the optimization of iron chelation therapy. Future imaging use will be dictated by evolving clinical needs, such as in screening for emerging morbidities, including hepatic fibrosis and hepatocellular carcinoma.

Hemochromatosis: pathophysiology, evaluation, and management of hepatic iron overload with a focus on MRI

Hereditary hemochromatosis (HH) is an autosomal recessive disorder that occurs in approximately 1 in 200-250 individuals. Mutations in the HFE gene lead to excess iron absorption. Excess iron in the form of non-transferrin-bound iron (NTBI) causes injury and is readily uptaken by cardiomyocytes, pancreatic islet cells, and hepatocytes. Symptoms greatly vary among patients and include fatigue, abdominal pain, arthralgias, impotence, decreased libido, diabetes, and heart failure. Untreated hemochromatosis can lead to chronic liver disease, fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Many invasive and noninvasive diagnostic tests are available to aid in diagnosis and treatment. MRI has emerged as the reference standard imaging modality for the detection and quantification of hepatic iron deposition, as ultrasound (US) is unable to detect iron overload and computed tomography (CT) findings are nonspecific and influenced by multiple confounding variables. If caught and treated early, HH disease progression can significantly be altered. Area covered: The data on Hemochromatosis, iron overload, and MRI were gathered by searching PubMed. Expert commentary: MRI is a great tool for diagnosis and management of iron overload. It is safe, effective, and a standard protocol should be included in diagnostic algorithms of future treatment guidelines.

Incidentally Detected Transfusion-associated Iron Overload in 3 Children After Cancer Chemotherapy

Iron overload is a potential long-term complication among cancer survivors who received transfusions during treatment. Although there are screening guidelines for iron overload in pediatric survivors of hematopoietic stem cell transplant, these do not call for screening of other pediatric oncology patients. In our practice we incidentally discovered 3 patients in a population of 168 cancer survivors over the span of 17 years who were treated for cancer without hematopoietic stem cell transplant who had iron overload. The 3 patients had elevated liver iron on magnetic resonance imaging T2* and 2 received therapeutic phlebotomy. These cases, and others like them, suggest that collaborative groups should consider revisiting the literature to establish screening and treatment guidelines for iron overload after cancer therapy.

Demystifying liver iron concentration measurements with MRI

This Editorial comment refers to the article: Non-invasive measurement of liver iron concentration using 3-Tesla magnetic resonance imaging: validation against biopsy. D'Assignies G, et al. Eur Radiol Nov 2017.

KEY POINTS

• MRI is a widely accepted reliable tool to determine liver iron concentration. • MRI cannot measure iron directly, it needs calibration. • Calibration curves for 3.0T are rare in the literature. • The study by d'Assignies et al. provides valuable information on this topic. • Evaluation of liver iron overload should no longer be restricted to experts.

The mechanisms of systemic iron homeostasis and etiology, diagnosis, and treatment of hereditary hemochromatosis

Hereditary hemochromatosis (HH) is a group of genetic iron overload disorders that manifest with various symptoms, including hepatic dysfunction, diabetes, and cardiomyopathy. Classic HH type 1, which is common in Caucasians, is caused by bi-allelic mutations of HFE. Severe types of HH are caused by either bi-allelic mutations of HFE2 that encodes hemojuvelin (type 2A) or HAMP that encodes hepcidin (type 2B). HH type 3, which is of intermediate severity, is caused by bi-allelic mutations of TFR2 that encodes transferrin receptor 2. Mutations of SLC40A1 that encodes ferroportin, the only cellular iron exporter, causes either HH type 4A (loss-of-function mutations) or HH type 4B (gain-of-function mutations). Studies on these gene products uncovered a part of the mechanisms of the systemic iron regulation; HFE, hemojuvelin, and TFR2 are involved in iron sensing and stimulating hepcidin expression, and hepcidin downregulates the expression of ferroportin of the target cells. Phlebotomy is the standard treatment for HH, and early initiation of the treatment is essential for preventing irreversible organ damage. However, because of the rarity and difficulty in making the genetic diagnosis, a large proportion of patients with non-HFE HH might have been undiagnosed; therefore, awareness of this disorder is important.

Progression of liver fibrosis can be controlled by adequate chelation in transfusion-dependent thalassemia (TDT)

A substantial proportion of patients with transfusion-dependent beta-thalassemia major suffer from chronic liver disease. Iron overload resulting from repeated transfusions and HCV infection has been implicated in the development of liver fibrosis. Hepatic siderosis and fibrosis were assessed in 99 transfusion-dependent thalassemia (TDT) patients using transient elastography (TE) and liver iron concentration (LIC) assessed by T2*MRI at baseline and after 4 years. Data were analyzed retrospectively. At baseline, the overall mean liver stiffness measurement (LSM) was 7.4 ± 3.2 kPa and the mean LIC was 4.81 ± 3.82 mg/g dw (n = 99). Data available at 4 ± 1.5 years showed a significant reduction in LSM (6.6 ± 3.2 kPa, p 0.017) and hepatic siderosis measured by LIC (3.65 ± 3.45 mg/g dw, p 0.001). This result was confirmed when considering patients with iron overload at the time of the first measurement (n = 41) and subjects treated with a stable dose of deferasirox over the entire period of observation (n = 39). A reduction of LSM, yet not statistically significant, was achieved in patients on combined deferoxamine + deferiprone, while the group on deferoxamine (n = 11) remained stable over time. HCV-RNA positivity was found in 33 patients at T0, 20 of which were treated during the observation period. Patients who underwent anti-HCV therapy showed a more evident reduction in LSM (9 ± 3 vs 7 ± 3.1 kPa, p 0.016). Adequate chelation therapy is mandatory in order to prevent liver disease progression in TDT. Patients could benefit from regular non-invasive assessment of liver fibrosis by TE to indirectly monitor treatment adequacy and therapeutic compliance.

Ultra-short echo time images quantify high liver iron

PURPOSE

1.5T gradient echo-based R2∗ estimates are standard-of-care for assessing liver iron concentration (LIC). Despite growing popularity of 3T, echo time (TE) limitations prevent 3T liver iron quantitation in the upper half of the clinical range (LIC ⪆20 mg/g). In this work, a 3D radial pulse sequence was assessed to double the dynamic range of 3T LIC estimates.

THEORY AND METHODS

The minimum TE limits the dynamic range of pulse sequences to estimate R2∗. 23 chronically-transfused human volunteers were imaged with 1.5T Cartesian gradient echo (1.5T-GRE), 3T Cartesian gradient echo (3T-GRE), and 3T ultrashort TE radial (3T-UTE) pulse sequences; minimum TEs were 0.96, 0.76, and 0.19 ms, respectively. R2∗ was estimated with an exponential signal model, normalized to 1.5T equivalents, and converted to LIC. Bland-Altman analysis compared 3T-based estimates to 1.5T-GRE.

RESULTS

LIC by 3T-GRE was unbiased versus 1.5T-GRE for LIC ≤ 25 mg/g (sd = 9.6%); 3T-GRE failed to quantify LIC > 25 mg/g. At high iron loads, 3T-UTE was unbiased (sd = 14.5%) compared to 1.5T-GRE. Further, 3T-UTE estimated LIC up to 50 mg/g, exceeding 1.5T-GRE limits.

CONCLUSION

3T-UTE imaging can reliably estimate high liver iron burdens. In conjunction with 3T-GRE, 3T-UTE allows clinical LIC estimation across a wide range of liver iron loads. Magn Reson Med 79:1579-1585, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

T2* Mapping from Multi-Echo Dixon Sequence on Gadoxetic Acid-Enhanced Magnetic Resonance Imaging for the Hepatic Fat Quantification: Can It Be Used for Hepatic Function Assessment?

Objective

To evaluate the diagnostic value of T2^* mapping using 3D multi-echo Dixon gradient echo acquisition on gadoxetic acid-enhanced liver magnetic resonance imaging (MRI) as a tool to evaluate hepatic function.

Materials and Methods

This retrospective study was approved by the IRB and the requirement of informed consent was waived. 242 patients who underwent liver MRIs, including 3D multi-echo Dixon fast gradient-recalled echo (GRE) sequence at 3T, before and after administration of gadoxetic acid, were included. Based on clinico-laboratory manifestation, the patients were classified as having normal liver function (NLF, n = 50), mild liver damage (MLD, n = 143), or severe liver damage (SLD, n = 30). The 3D multi-echo Dixon GRE sequence was obtained before, and 10 minutes after, gadoxetic acid administration. Pre- and post-contrast T2^* values, as well as T2^* reduction rates, were measured from T2^* maps, and compared among the three groups.

Results

There was a significant difference in T2^* reduction rates between the NLF and SLD groups (−0.2 ± 4.9% vs. 5.0 ± 6.9%, p = 0.002), and between the MLD and SLD groups (3.2 ± 6.0% vs. 5.0 ± 6.9%, p = 0.003). However, there was no significant difference in both the pre- and post-contrast T2^* values among different liver function groups (p = 0.735 and 0.131, respectively). A receiver operating characteristic (ROC) curve analysis showed that the area under the ROC curve for using T2^* reduction rates to differentiate the SLD group from the NLF group was 0.74 (95% confidence interval: 0.63–0.83).

Conclusion

Incorporation of T2^* mapping using 3D multi-echo Dixon GRE sequence in gadoxetic acid-enhanced liver MRI protocol may provide supplemental information for liver function deterioration in patients with SLD.

Evaluation of Iron Deposition in the Adrenal Glands of β Thalassemia Major Patients Using 3-Tesla MRI

Background

Beta-thalassemia major (β-TM) patients need blood transfusions, which result in iron deposition. To regulate chelation therapy, iron load has to be measured. With MRI, the amount of signal loss and T2* decay time shortening are used for iron quantification.

Objectives

The aim was to measure adrenal iron load with T2* relaxometry using MRI, and to compare it with liver and cardiac iron and serum ferritin, and to find out whether adrenal iron could be predicted from those parameters.

Patients and Methods

Between October 2014 and March 2015, MRI was performed in 21 patients with β-TM, recieving blood transfusions and chelation therapy. The control group (n = 11) included healthy volunteers with no known history of adrenal, hematologic, chronic disease, and blood transfusion.

Results

Among patients, there was no significant correlation between plasma ferritin and adrenal T2*. Significant difference was detected among T2* values of adrenals between the patient and control groups. There was no significant correlation between adrenal gland and liver T2* in β-TM patients, moderate correlation was detected between adrenal T2* and cardiac T2*.

Conclusion

Adrenal iron in β-TM can be reliably measured in 3 Tesla MRI. The results highlight the absence of correlation between adrenal iron deposition both with serum ferritin and hepatic iron.

Magnetic Resonance Elastography and Other Magnetic Resonance Imaging Techniques in Chronic Liver Disease: Current Status and Future Directions

Recent advances in the noninvasive imaging of chronic liver disease have led to improvements in diagnosis, particularly with magnetic resonance imaging (MRI). A comprehensive evaluation of the liver may be performed with the quantification of the degree of hepatic steatosis, liver iron concentration, and liver fibrosis. In addition, MRI of the liver may be used to identify complications of cirrhosis, including portal hypertension, ascites, and the development of hepatocellular carcinoma. In this review article, we discuss the state of the art techniques in liver MRI, namely, magnetic resonance elastography, hepatobiliary phase MRI, and liver fat and iron quantification MRI. The use of these advanced techniques in the management of chronic liver diseases, including nonalcoholic fatty liver disease, will be elaborated.

On the R2⁎ relaxometry in complex multi-peak multi-Echo chemical shift-based water-fat quantification: Applications to the neuromuscular diseases

PURPOSE

Investigation of the feasibility of the R₂^⁎ mapping techniques by using latest theoretical models corrected for confounding factors and optimized for signal to noise ratio.

THEORY AND METHODS

The improvement of the performance of state of the art magnetic resonance imaging (MRI) relaxometry algorithms is challenging because of a non-negligible bias and still unresolved numerical instabilities. Here, R₂^⁎ mapping reconstructions, including complex fitting with multi-spectral fat-correction by using single-decay and double-decay formulation, are deeply studied in order to investigate and identify optimal configuration parameters and minimize the occurrence of numerical artifacts. The effects of echo number, echo spacing, and fat/water relaxation model type are evaluated through both simulated and in-vivo data. We also explore the stability and feasibility of the fat/water relaxation model by analyzing the impact of high percentage of fat infiltrations and local transverse relaxation differences among biological species.

RESULTS

The main limits of the MRI relaxometry are the presence of bias and the occurrence of artifacts, which significantly affect its accuracy. Chemical-shift complex R₂^⁎-correct single-decay reconstructions exhibit a large bias in presence of a significant difference in the relaxation rates of fat and water and with fat concentration larger than 30%. We find that for fat-dominated tissues or in patients affected by extensive iron deposition, MRI reconstructions accounting for multi-exponential relaxation time provide accurate R₂^⁎ measurements and are less prone to numerical artifacts.

CONCLUSIONS

Complex fitting and fat-correction with multi-exponential decay formulation outperforms the conventional single-decay approximation in various diagnostic scenarios. Although it still lacks of numerical stability, which requires model enhancement and support from spectroscopy, it offers promising perspectives for the development of relaxometry as a reliable tool to improve tissue characterization and monitoring of neuromuscular disorders.

Comparison between different software programs and post-processing techniques for the MRI quantification of liver iron concentration in thalassemia patients

PURPOSE

In magnetic resonance imaging (MRI) relaxometry, various software programs are available to perform R2* measurements and to estimate the liver iron concentration (LIC). The main objective of our study was to compare R2* LIC values, obtained with three different software programs based on specific decay models and calibration curves, with LIC estimates provided by R2-relaxometry (FerriScan).

METHODS

This retrospective study included 15 patients with 15 baseline MRIs and 34 serial examinations. R2* LIC estimates were calculated using the FuncTool, CMRtools/Thalassemia Tools and Quanta Hematology programs. Longitudinal LIC changes (ΔLIC) were calculated using the subset of 34 serial MRIs.

RESULTS

After Bland-Altman analysis on baseline data, Quanta Hematology, which employs the monoexponential-plus-constant fit, produced the lowest mean difference [0.01 ± 0.14 log(mg/gdw)] with the closest limits of agreement. In the longitudinal setting, Quanta Hematology again gave the lowest mean difference between R2 and R2* LIC (0.1 ± 2.6 mg/gdw). Using FerriScan as reference, the value of concordant directional ΔLIC changes was the same for all programs (27/34, 85.7 %).

CONCLUSIONS

R2* LICs are higher than R2 LICs at iron levels <7 mg/gdw, while R2 LIC averages higher than R2* LIC with increasing iron load. The monoexponential-plus-constant model provided the best agreement with R2 LIC estimates.

Morbidity and mortality of adult patients with congenital dyserythropoietic anemia type I

Congenital dyserythropoietic anemia type I (CDAI) is a rare autosomal recessive disease characterized by macrocytic anemia, ineffective erythropoiesis, and secondary hemochromatosis. To better define the natural history of the disease among adult patients, we studied 32 Bedouin patients (median age 34 yr; range 21-60) all carrying the same CDAN1 founder mutation. Follow-up studies included complete blood count, blood chemistry, abdominal ultrasound, echocardiography, and T2*MRI. Main complications were due to anemia and ineffective erythropoiesis [osteoporosis (8/9, 89%), cholelithiasis (21/30, 70%), pulmonary arterial hypertension (PAH) (6/25, 24%)] and iron overload [hypothyroidism (9/24, 38%), and diabetes mellitus (6/32, 19%)]. T2* MRI revealed increased liver iron but no cardiac iron (13/13). Anemia improved in the majority of patients who underwent splenectomy (5/6). Three patients died (9%) at the age of 46-56 due to PAH (1) and sepsis (2). All previously underwent splenectomy. Analyzing both our patients and the 21 patients previously described by Heimpel et al. (Blood 107:334, 2006), we conclude that adults with CDA I suffer significant morbidity and mortality. Careful monitoring of iron overload and prompt iron chelation therapy is mandatory. Due to possible complications and inconsistent response to splenectomy α-interferon, transfusion therapy or stem cell transplantation should be considered as alternatives to this procedure in severely affected patients.

MRI Measurements of Iron Load in Transfusion-Dependent Patients: Implementation, Challenges, and Pitfalls

Magnetic resonance imaging (MRI) has played a key role in studies of iron overload in transfusion-dependent patients, providing insights into the relations among liver and cardiac iron loading, iron chelator dose, and morbidity. Currently, there is rapid uptake of these methods into routine clinical practice as part of the management strategy for iron overload in regularly transfused patients. Given the manifold methods of data acquisition and analysis, there are several potential pitfalls that may result in inappropriate decision making. Herein, we review the challenges of establishing suitable MRI techniques for tissue iron measurement in regularly transfused patients.

Metrology Standards for Quantitative Imaging Biomarkers

Although investigators in the imaging community have been active in developing and evaluating quantitative imaging biomarkers (QIBs), the development and implementation of QIBs have been hampered by the inconsistent or incorrect use of terminology or methods for technical performance and statistical concepts. Technical performance is an assessment of how a test performs in reference objects or subjects under controlled conditions. In this article, some of the relevant statistical concepts are reviewed, methods that can be used for evaluating and comparing QIBs are described, and some of the technical performance issues related to imaging biomarkers are discussed. More consistent and correct use of terminology and study design principles will improve clinical research, advance regulatory science, and foster better care for patients who undergo imaging studies.

The history of MR imaging as seen through the pages of radiology

The first reports in Radiology pertaining to magnetic resonance (MR) imaging were published in 1980, 7 years after Paul Lauterbur pioneered the first MR images and 9 years after the first human computed tomographic images were obtained. Historical advances in the research and clinical applications of MR imaging very much parallel the remarkable advances in MR imaging technology. These advances can be roughly classified into hardware (eg, magnets, gradients, radiofrequency [RF] coils, RF transmitter and receiver, MR imaging-compatible biopsy devices) and imaging techniques (eg, pulse sequences, parallel imaging, and so forth). Image quality has been dramatically improved with the introduction of high-field-strength superconducting magnets, digital RF systems, and phased-array coils. Hybrid systems, such as MR/positron emission tomography (PET), combine the superb anatomic and functional imaging capabilities of MR imaging with the unsurpassed capability of PET to demonstrate tissue metabolism. Supported by the improvements in hardware, advances in pulse sequence design and image reconstruction techniques have spurred dramatic improvements in imaging speed and the capability for studying tissue function. In this historical review, the history of MR imaging technology and developing research and clinical applications, as seen through the pages of Radiology, will be considered.

Magnetic resonance imaging correlates of bee sting induced multiple organ dysfunction syndrome: A case report

Occasionally systemic complications with high risk of death, such as multiple organ dysfunction syndrome (MODS), can occur following multiple bee stings. This case study reports a patient who presented with MODS, i.e., acute kidney injury, hepatic and cardiac dysfunction, after multiple bee stings. The standard clinical findings were then correlated with magnetic resonance imaging (MRI) findings, which demonstrates that MRI may be utilized as a simpler tool to use than other multiple diagnostics.

Taurine supplementation reduces oxidative stress and protects the liver in an iron-overload murine model

We previously demonstrated that iron overload induces liver damage by causing the formation of reactive oxygen species (ROS). Taurine is a potent free radical scavenger that attenuates the damage caused by excessive oxygen free radicals. Therefore, the aim of the present study was to investigate whether taurine could reduce the hepatotoxicity of iron overload with regard to ROS production. Mice were intraperitoneally injected with iron 5 days/week for 13 weeks to achieve iron overload. It was found that iron overload resulted in liver dysfunction, increased apoptosis and elevated oxidative stress. Taurine supplementation increased liver taurine levels by 40% and led to improved liver function, as well as a reduction in apoptosis, ROS formation and mitochondrial swelling and an attenuation in the loss of the mitochondrial membrane potential. Treatment with taurine mediated a reduction in oxidative stress in iron-overloaded mice, attenuated liver lipid peroxidation, elevated antioxidant enzyme activities and maintained reduced glutathione levels. These results indicate that taurine reduces iron-induced hepatic oxidative stress, preserves liver function and inhibits hepatocyte apoptosis. Therefore, taurine may be a potential therapeutic drug to reduce liver damage caused by iron overload.

Magnetic resonance imaging of the pediatric liver: imaging of steatosis, iron deposition, and fibrosis

Traditionally, many diffuse diseases of the liver could only be diagnosed by liver biopsy. Although still considered the gold standard, liver biopsy is limited by its small sample size, invasive nature, and subjectivity of interpretation. There have been significant advances in functional magnetic resonance (MR) imaging of the liver. These advances now provide radiologists with the tools to evaluate the liver at the molecular level, allowing quantification of hepatic fat and iron, and enabling the identification of liver fibrosis at its earliest stages. These methods provide objective measures of diffuse liver processes and aid hepatologists in the diagnosis and management of liver disease.