Limitations of Magnetic Resonance Imaging in Measurement of Hepatic Iron

Real-world complication burden and disease management paradigms in transfusion-related β-thalassaemia in Greece: Results from ULYSSES, an epidemiological, multicentre, retrospective cross-sectional study

Patients with transfusion-dependent beta (β)-thalassaemia experience a broad range of complications. ULYSSES, an epidemiological, multicentre, retrospective cross-sectional study, aimed to assess the prevalence and severity of treatment and disease complications, capture disease management and identify predictors of complications in patients with transfusion-dependent β-thalassaemia, treated in routine settings in Greece. Eligible patients were adults diagnosed with β-thalassaemia ≥12 months before enrolment and having received ≥6 red blood cell (RBC) units (excluding elective surgery) with no transfusion-free period ≥35 days in the 24 weeks before enrolment. Primary data were collected at a single visit and through chart review. Between Oct 21, 2019, and Jun 15, 2020, 201 eligible patients [median (interquartile range, IQR) age 45.7 (40.2-50.5) years; 75.6% > 40 years old; 64.2% female] were enrolled, a mean (standard deviation) of 42.9 (7.8) years after diagnosis. Median (IQR) age at diagnosis and RBC transfusion initiation were 0.8 (0.4-2.8) and 1.3 (1.0-5.0) years, respectively. From diagnosis to enrolment, patients had developed a median of six (range: 1-55) complications; 19.6% were grade ≥3. The most represented complications were endocrine/metabolic/nutrition disorders (91.5%), surgical/medical procedures (67.7%) and blood/lymphatic system disorders (64.7%). Real-world data generated by ULYSSES underscore the substantial complication burden of transfusion-dependent β-thalassaemia patients, routinely managed in Greece.

2021 Thalassaemia International Federation Guidelines for the Management of Transfusion-dependent Thalassemia

Beta-thalassemia and particularly its transfusion-dependent form (TDT) is a demanding clinical condition, requiring life-long care and follow-up, ideally in specialized centers and by multidisciplinary teams of experts. Despite the significant progress in TDT diagnosis and treatment over the past decades that has dramatically improved patients’ prognosis, its management remains challenging. On one hand, diagnostic and therapeutic advances are not equally applied to all patients across the world, particularly in several high-prevalence eastern regions. On the other, healthcare systems in low-prevalence western countries that have recently received large numbers of migrant thalassemia patients, were not ready to address patients’ special needs. Thalassaemia International Federation (TIF), a global patient-driven umbrella federation with 232 member-associations in 62 countries, strives for equal access to quality care for all patients suffering from thalassemia or other hemoglobinopathies in every part of the world by promoting education, research, awareness, and advocacy. One of TIF’s main actions is the development and dissemination of clinical practice guidelines for the management of these patients. In 2021, the fourth edition of TIF’s guidelines for the management of TDT was published. The full text provides detailed information on the management of TDT patients and the clinical presentation, pathophysiology, diagnostic approach, and treatment of disease complications or other clinical entities that may occur in these patients, while also covering relevant psychosocial and organizational issues. The present document is a summary of the 2021 TIF guidelines for TDT that focuses mainly on clinical practice issues and recommendations.

Analysis of MRI-derived spleen iron in the UK Biobank identifies genetic variation linked to iron homeostasis and hemolysis

The spleen plays a key role in iron homeostasis. It is the largest filter of the blood and performs iron reuptake from old or damaged erythrocytes. Despite this role, spleen iron concentration has not been measured in a large, population-based cohort. In this study, we quantify spleen iron in 41,764 participants of the UK Biobank by using magnetic resonance imaging and provide a reference range for spleen iron in an unselected population. Through genome-wide association study, we identify associations between spleen iron and regulatory variation at two hereditary spherocytosis genes, ANK1 and SPTA1. Spherocytosis-causing coding mutations in these genes are associated with lower reticulocyte volume and increased reticulocyte percentage, while these common alleles are associated with increased expression of ANK1 and SPTA1 in blood and with larger reticulocyte volume and reduced reticulocyte percentage. As genetic modifiers, these common alleles may explain mild spherocytosis phenotypes that have been observed clinically. Our genetic study also identifies a signal that co-localizes with a splicing quantitative trait locus for MS4A7, and we show this gene is abundantly expressed in the spleen and in macrophages. The combination of deep learning and efficient image processing enables non-invasive measurement of spleen iron and, in turn, characterization of genetic factors related to the lytic phase of the erythrocyte life cycle and iron reuptake in the spleen.

Biopsy-based optimization and calibration of a signal-intensity-ratio-based MRI method (1.5 Tesla) in a dextran-iron loaded mini-pig model, enabling estimation of very high liver iron concentrations

Objective

Magnetic resonance imaging (MRI)-based techniques for non-invasive assessing liver iron concentration (LIC) in patients with iron overload have a limited upper measuring range around 35 mg/g dry weight, caused by signal loss from accelerated T1-, T2-, T2* shortening with increasing LIC. Expansion of this range is necessary to allow evaluation of patients with very high LIC.

Aim

To assess measuring range of a gradient-echo R2* method and a T1-weighted spin-echo (SE), signal intensity ratio (SIR)-based method (TE = 25 ms, TR = 560 ms), and to extend the upper measuring range of the SIR method by optimizing echo time (TE) and repetition time (TR) in iron-loaded minipigs.

Methods

Thirteen mini pigs were followed up during dextran-iron loading with repeated percutaneous liver biopsies for chemical LIC measurement and MRIs for parallel non-invasive estimation of LIC (81 examinations) using different TEs and TRs.

Results

SIR and R2* method had similar upper measuring range around 34 mg/g and similar method agreement. Using TE = 12 ms and TR = 1200 ms extended the upper measuring range to 115 mg/g and yielded good method of agreement.

Discussion

The wider measuring range is likely caused by lesser sensitivity of the SE sequence to iron, due to shorter TE, leading to later signal loss at high LIC, allowing evaluation of most severe hepatic iron overload. Validation in iron-loaded patients is necessary.

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.

R2 relaxometry based MR imaging for estimation of liver iron content: A comparison between two methods

PURPOSE

To compare the reproducibility and accuracy of R2-relaxometry MRI for estimation of liver iron concentration (LIC) between in-house analysis and FDA-approved commercially available third party results.

METHODS

All MR studies were performed on a 1.5T scanner. Multi-echo spin-echo scans with a fixed TR and increasing TE values of 6 ms, 9 ms, 12 ms, 15 ms, and 18 ms (spaced at 3 ms intervals) were used. Post-processing of the images to calculate mean relaxivity, R2, included drawing of regions of interest to include the whole liver on mid-slice. The relationship between liver R2 values and estimated LIC calculated with in-house analysis and values reported by an external company (FerriScan^®, Resonance Health, Australia) were assessed with correlation coefficients and Bland-Altman difference plots. Continuous variables are presented as mean ± standard deviation. Significance was set at p value < 0.05.

RESULTS

474 studies from 175 patients were included in the study (mean age 10.4 ± 4.2 years (range 1-18 years); 254 studies from girls, 220 studies from boys). LIC ranged from 0.6 to 43 mg/g dry tissue, covering a broad range from normal levels to extremely high iron levels. Linearity between proprietary and in-house methods was excellent across the observed range for R2 (31.5 to 334.8 s^-1); showing a correlation coefficient of r = 0.87, p < 0.001. Bland-Altman R2 difference plot between the two methods shows a mean bias of + 21.5 s^-1 (range - 47.0 to + 90.0 s^-1 between two standard deviations). LIC reported by FerriScan^® compared with LIC estimated in-house with R2 as reported by FerriScan^® agreed strongly, (r = 1.0, p < 0.001).

CONCLUSION

R2 relaxometry MR imaging for liver iron concentration estimation is reproducible between proprietary FDA-approved commercial software and in-house analysis methods.

Comparative Efficacy and Safety of Oral Iron Chelators and their Novel Combination in Children with Thalassemia

OBJECTIVE

To compare the efficacy and safety of oral iron chelators (Deferiprone and Deferasirox) when used singly and in combination in multi-transfused children with thalassemia.

DESIGN

Prospective comparative study.

SETTING

Thalassemia Center of a medical college affiliated hospital.

PARTICIPANTS AND INTERVENTION

49 multi-transfused children with thalassemia with a mean (SD) age 11.6 (6.21) y received daily chelation therapy with either deferiprone alone (75 mg/kg/day in 3 divided doses), deferasirox alone (30 mg/kg/day single dose) or their daily combination (same dose as monotherapy) for 12 months.

OUTCOME MEASURES

Serum ferritin levels at the start of study, after 6 months and after 12 months. MRI T2* of liver and heart initially and after 6 months of follow up. 24-hour urinary iron excretion values at the outset and after 12 months of chelation therapy. At every visit for blood transfusion, all patients were clinically assessed for any adverse effects; liver and renal functions were monitored 6-monthly.

RESULTS

After 12 months of respective chelation therapy, serum ferritin values decreased from a mean of 3140.5 ng/mL to 2910.0 ng/mL in deferiprone alone group, 3859.2 ng/mL to 3417.4 ng/mL in deferasirox alone group and from 3696.5 ng/mL to 2572.1 ng/mL in the combination group. The combination therapy was more efficacious in causing fall in serum ferritin levels compared to deferiprone and deferasirox monotherapy (P= 0.035 and 0.040, respectively). Results of MRI T2 were equivocal. Combined drug usage produced maximum negative iron balance in the body by maximally increasing the iron excretion in urine from 61.1 umol/day to 343.3 umol/day (P = 0.002). No significant adverse reactions were noticed in either the monotherapy or the combination group.

CONCLUSION

Oral combination therapy of deferiprone and deferasirox appears to be an efficacious and safe modality to reduce serum ferritin in multi-transfused children with thalassemia.

Efficacy of hepatic T2* MRI values and serum ferritin concentration in predicting thalassemia major classification for hematopoietic stem cell transplantation

Liver biopsy has been performed for many decades for classifying the patients with TM. Meanwhile, using non-invasive methods such as T2* MRI technique has been recently much more considered to determine the hepatic iron overload. Ninety-three pediatric HSCT candidates with TM who underwent liver biopsy were included in this study. Hepatic T2* MRI values and serum ferritin concentrations were assessed to investigate and determine the useful method in detection of patients with TM class III whom received different conditioning regimens, in comparison with class I and II. Twenty (21.5%) patients were categorized as class III. Hepatic T2* MRI could detect TM class III patients with 60% sensitivity and 87.67% specificity (LR+: 4.867, accuracy: 81.72%), while predictive feature of ferritin values for distinguishing patients with TM class III was not statistically significant (p-value >0.01). Combination of T2*MRI with age (T2*-age) could detect TM class III with 85% sensitivity and 72.6% specificity (LR+: 3.1, accuracy: 75.27%).T2*-age may be considered as an alternative and non-invasive method to liver biopsy for differentiation and classification of patients with TM before transplantation.

Diagnostic value of MRI proton density fat fraction for assessing liver steatosis in chronic viral C hepatitis

OBJECTIVE

To assess the diagnostic performance of a T1-independent, T2*-corrected multiecho magnetic resonance imaging (MRI) technique for the quantification of hepatic steatosis in a cohort of patients affected by chronic viral C hepatitis, using liver biopsy as gold standard.

METHODS

Eighty-one untreated patients with chronic viral C hepatitis were prospectively enrolled. All included patients underwent MRI, transient elastography, and liver biopsy within a time interval <10 days.

RESULTS

Our cohort of 77 patients included 43/77 (55.8%) males and 34/77 (44.2%) females with a mean age of 51.31 ± 11.27 (18-81) years. The median MRI PDFF showed a strong correlation with the histological fat fraction (FF) (r = 0.754, 95% CI 0.637 to 0.836, P < 0.0001), and the correlation was influenced by neither the liver stiffness nor the T2* decay. The median MRI PDFF result was significantly lower in the F4 subgroup (P < 0.05). The diagnostic accuracy of MRI PDFF evaluated by AUC-ROC analysis was 0.926 (95% CI 0.843 to 0.973) for S ≥ 1 and 0.929 (95% CI 0.847 to 0.975) for S = 2.

CONCLUSIONS

Our MRI technique of PDFF estimation allowed discriminating with a good diagnostic accuracy between different grades of hepatic steatosis.

T2* imaging of the heart: methods, applications, and outcomes

This review describes and discusses the rationale, technique, applications, and impact of cardiovascular magnetic resonance (CMR) T2* imaging, principally in the assessment of iron loading within the heart, and highlights how this robust imaging strategy has transformed disease outcome.Until recently, no simple noninvasive measurement was available to reliably indicate severe cardiac iron loading before the development of overt cardiac dysfunction or heart failure. Consequently, the majority of patients with transfusion-dependent anemias, such as β-thalassemia major, died prematurely of cardiovascular complications of severe iron overload.The magnetic properties of particulate iron disrupt magnetic field homogeneity in the CMR environment and consequently influence the CMR parameter T2*, which describes signal decay relating to both field inhomogeneity and loss of spin coherence. There is a direct relationship between T2* and myocardial iron concentration, enabling this to be used to identify and quantify myocardial iron load. Single breath-hold gradient-echo sequences in which a single midventricular short-axis myocardial slice is acquired at multiple echo times enables a myocardial T2* value to be measured from the rate of exponential decay. The application of T2* CMR to assessing cardiac iron loading is rapid, reproducible, extensively validated, and now widely performed. Data have highlighted the profound predictive power of this imaging technique and moreover its ability to inform management strategies such that, over a relatively short duration, outcome has been dramatically improved, and the disease course in β-thalassemia major transformed.

T2(∗) MRI changes in the heart and liver of ex-thalassemic patients after hematopoietic stem cell transplantation

BACKGROUND

Non-invasive methods like MRI-based techniques have been considered recently for assessment of liver and heart status in patients with thalassemia major (TM). The purpose of this study is to examine the alterations of hepatic and myocardial T2(∗) MRI values in TM patients after hematopoietic stem cell transplantation (HSCT) just before starting chelation therapy.

PROCEDURE

The study included fifty-two TM patients with mean age of 7.6years who were referred to our center for HSCT. Before HSCT, patients underwent liver biopsy to determine fibrosis stage based on the Lucarelli classification. Hepatic and myocardial T2(∗) values before and 6months after transplantation were measured and analyzed.

RESULTS

There was not a statistically significant increase in myocardial T2(∗) values after HSCT (p-value=0.35). Hepatic T2(∗) values significantly decreased after HSCT (p-value <0.001), showing the liver status has been worsened. In subgroup analysis, post-HSCT hepatic T2(∗) values (adjusted for baseline values) were significantly higher in patients with graft-versus-host disease (GvHD) compared to non-GvHD patients (p-value=0.04).

CONCLUSIONS

The issue of iron overload is still remained as the main problem in ex-thalassemic patients after HSCT. We found T2(∗) MRI technique a quite beneficial method for following up the patients after transplantation. Obviously, planning large controlled trials associated with liver biopsy results after transplantation is required.

Diabetes mellitus in patients with thalassemia major

BACKGROUND

Diabetes mellitus is a major endocrinopathy for patients with thalassemia major. Although diabetes mellitus is multifactorial, iron loading is its primary cause and its management poses a clinical challenge. Detecting the pre-diabetes stage is critical because clinical diabetes can potentially be reversed or prevented.

PROCEDURE

Patients with thalassemia major who received regular blood transfusion therapy from 1994 to 2010 were evaluated for the incidence of diabetes mellitus and glucose dysregulation. The association between patients' clinical, biochemical, and image parameters was also evaluated.

RESULTS

The patients with diabetes were significantly older, had higher ferritin levels, a smaller pancreas volume, and lower cardiac T2* magnetic resonance imaging (MRI) values than the patients without diabetes. The pancreas T2* MRI values were higher in the patients without diabetes, but the difference was not statistically significant. The liver iron concentration did not differ between the patients with and without diabetes. The prevalence of hepatitis C infection and hypogonadism was also higher in the patients with diabetes. In the patients without diabetes, the cardiac T2* MRI values were higher in patients with normal fasting glucose levels (P = 0.03), and the homeostasis model assessment of insulin resistance level was associated with hepatitis C infection (P = 0.024, r = 0.32) and hypogonadism (P = 0.034, r = 0.301).

CONCLUSIONS

Fasting glucose and insulin levels were appropriate screening tools for evaluating glucose dysregulation and complemented the MRI findings. The cardiac T2* and pancreas volumes were significant predictors of diabetes.

Diagnostic value of real-time elastography in the assessment of hepatic fibrosis in patients with liver iron overload

OBJECTIVE

The objective of our prospective monocentric work was to determine the diagnostic value of real-time elastography (RTE) in the assessment of liver fibrosis in patients with iron overload, using transient elastography (TE) as reference standard.

METHODS

Sixty-seven consecutive patients with MRI detectable iron overload (T2*<6.3 ms) were enrolled. TE and RTE were performed on the same day as MRI. Elastograms were acquired by an experienced operator and analyzed by calculating the elastic ratio between perihepatic soft tissues and liver parenchyma. An elliptical ROI of 1cm(2) (Z1) was positioned in the liver parenchyma and a smaller elliptical ROI of 2mm(2) (Z2) was positioned in a homogeneously soft (red) region of the diaphragm, which was considered as internal control to calculate the elastic ratio Z2/Z1.

RESULTS

Seven patients were excluded because of invalid TE or RTE examinations. The remaining 60 patients were 57% males and 43% females (mean age: 42 [21-76] years), including 37 homozygous-β-thalassemics, 13 patients with β-thalassemia intermedia, 6 with primary hemochromatosis, and 4 with myelodysplastic syndrome. Increasing elastic ratios were significantly correlated with increasing TE values (r=0.645, 95% CI 0.468-0.772, P<0.0001). The mean elastic ratios for each METAVIR group were as follows: F0/1 = 1.9 ± 0.4; F2 = 2.2 ± 0.4; F3 = 2.9 ± 0.5; F4 = 3.2 ± 0.4. The diagnostic accuracy of RTE for F ≥ 2 evaluated by AUC-ROC analysis was 0.798 (95% CI 0.674-0.890). The diagnostic accuracy of RTE for F ≥ 3 was 0.909 (95% CI 0.806-0.968). At a cut-off ≥ 2.75, RTE showed a sensitivity of 70% (95% CI 45.7-88.1) and a specificity of 97.5% (95% CI 86.8-99.9).

CONCLUSIONS

In patients with MRI-detectable liver iron-overload RTE allows to discriminate between F0/1-F2 and F3-F4 with a reasonable diagnostic accuracy.

Quantitative assessment of lesion detection accuracy, resolution, and reconstruction algorithms in neutron stimulated emission computed tomography

We present a quantitative analysis of the image quality obtained using filtered back-projection (FBP) with Ram-Lak filtering and maximum likelihood-expectation maximization (ML-EM)-with no post-reconstruction filtering in either case-in neutron stimulated emission computed tomography (NSECT) imaging using Monte Carlo simulations in the context of clinically relevant models of liver iron overload. The ratios of pixel intensities for several regions of interest and lesion shape detection using an active-contours segmentation algorithm are assessed for accuracy across different scanning configurations and reconstruction algorithms. The modulation transfer functions (MTFs) are also computed for the cases under study and are applied to determine a minimum detectable lesion spacing as a form of sensitivity analysis. The accuracy of NSECT imaging in measuring relative tissue concentration is presented for simulated clinical liver cases. When using the 15th iteration, ML-EM provides at least 25% better resolution than FBP and proves to be highly robust under low-signal high-noise conditions prevalent in NSECT. However, FBP gives more accurate lesion pixel intensity ratios and size estimates in some cases; due to advantages provided by both reconstruction algorithms, it is worth exploring the development of an algorithm that is a hybrid of the two. We also show that NSECT imaging can be used to accurately detect 3-cm lesions in backgrounds that are a significant fraction (one-quarter) of the concentration of the lesion, down to a 4-cm spacing between lesions.

Measurement of liver iron overload: noninvasive calibration of MRI-R2* by magnetic iron detector susceptometer

An accurate assessment of body iron accumulation is essential for the diagnosis and therapy of iron overload in diseases such as thalassemia or hemochromatosis. Magnetic iron detector susceptometry and MRI are noninvasive techniques capable of detecting iron overload in the liver. Although the transverse relaxation rate measured by MRI can be correlated with the presence of iron, a calibration step is needed to obtain the liver iron concentration. Magnetic iron detector provides an evaluation of the iron overload in the whole liver. In this article, we describe a retrospective observational study comparing magnetic iron detector and MRI examinations performed on the same group of 97 patients with transfusional or congenital iron overload. A biopsy-free linear calibration to convert the average transverse relaxation rate in iron overload (R(2) = 0.72), or in liver iron concentration evaluated in wet tissue (R(2) = 0.68), is presented. This article also compares liver iron concentrations calculated in dry tissue using MRI and the existing biopsy calibration with liver iron concentrations evaluated in wet tissue by magnetic iron detector to obtain an estimate of the wet-to-dry conversion factor of 6.7 ± 0.8 (95% confidence level).

Functional magnetic resonance imaging of the liver: parametric assessments beyond morphology

There is growing interest in exploring and using functional imaging techniques to provide additional information on structural alterations in the liver, which often occur late in the disease process. This article presents a summary of the different functional MR imaging techniques currently in use, focusing on dynamic contrast-enhanced MR imaging, diffusion-weighted MR imaging, MR spectroscopy, in- and oppose-phase MR imaging, and T2*-weighted imaging. For each technique, the biologic underpinning for the technique is explained, the clinical applications surveyed, and the challenges for their application enumerated. Developing and less frequently used techniques such as MR elastography, blood oxygenation level dependent imaging, dynamic susceptibility contrast-enhanced MR imaging, and diffusion-tensor imaging are reviewed. The challenges widespread adoption of functional MR imaging and the translation of such techniques to high field strengths are also discussed.

Polystyrene microsphere-ferritin conjugates: a robust phantom for correlation of relaxivity and size distribution

In vivo iron load must be monitored to prevent complications from iron overload diseases such as hemochromatosis or transfusion-dependent anemias. While liver biopsy is the gold standard for determining in vivo iron load, MRI offers a noninvasive approach. MR phantoms have been reported that estimate iron concentration in the liver and mimic relaxation characteristics of in vivo deposits of hemosiderin. None of these phantoms take into account the size distribution of hemosiderin, which varies from patient to patient based on iron load. We synthesized stable and reproducible microsphere-ferritin conjugates (ferribeads) of different sizes that are easily characterized for several parameters that are necessary for modeling such as iron content and bead fraction. T(1) s and T(2) s were measured on a 1.41-T low-resolution NMR spectrometer and followed a size-dependent trend. Ferribeads imaged at 4.7 and 14.1 T showed that signal intensities are dependent on the distribution of ferritin around the bead rather than the iron concentration alone. These particles can be used to study the effects of particle size, ferritin distribution, and bead fraction on proton relaxation and may be of use in mimicking hemosiderin in a phantom for estimating iron concentration.

Hepatic iron overload in children with sickle cell anemia on chronic transfusion therapy

Hepatic iron overload is a serious complication of chronic transfusion therapy in patients with sickle cell disease (SCD). No firm consensus has been reached with regard to correlation between hepatic iron content (HIC) and variables including age, number of transfusions, and serum iron makers. Also, the role of HIC in determining hepatic injury is not well established. There is scarcity of data on chronically transfused children with SCD and no other confounding liver pathology. We aimed to further explore relationships between these variables in a cohort of children with SCD on chronic transfusion therapy naive to chelation. Liver biopsies obtained before starting chelation therapy from 27 children with sickle cell anemia receiving chronic transfusion therapy were evaluated for histologic scoring and determination of HIC. Average serum ferritin and iron saturation values were determined for 6 months before biopsy. Duration and total volume of transfusion were obtained from the medical records. All children were negative for human immunodeficiency virus, hepatitis B virus, and hepatitis C virus infections. Mean age at biopsy was 10.95+/-3.34 years. Mean duration and total volume of transfusions were 50.0+/-26.6 months and 17.4+/-9.6 L, respectively. Pearson product-moment bivariate correlation coefficients indicated significant correlations between HIC and histologic iron score, serum ferritin, iron saturation, age, and transfusion volume. After adjusting for transfusion volume, a significant correlation was only seen between HIC and transfusion volume. Mean HIC was 21.8+/-10.4 mg/g dry weight, with fibrosis observed in 10 patients and lobular inflammation in 9. HIC was higher in biopsies with fibrosis (28.2+/-3.8 mg/g) than biopsies without fibrosis (17.6+/-18.3 mg/g; P=0.012). HIC did not differ between biopsies with lobular inflammation (25.5+/-4.0 mg/g) and biopsies without inflammation (19.9+/-2.5 mg/g; P=0.22). These findings show that transfusion volume provides more insight on hepatic iron overload than serum iron markers.

T2* relaxometry in liver, pancreas, and spleen in a healthy cohort of one hundred twenty-nine subjects-correlation with age, gender, and serum ferritin

OBJECTIVE

To assess T2* values of liver, pancreas, and spleen in a healthy cohort and to compare the gained values with serum ferritin levels and anthropometric data. In addition, the relationship of T2* between the 3 organs was investigated.

MATERIALS AND METHODS

One hundred twenty-nine healthy subjects (85 women, 44 men) were examined on a 1.5-T magnetic resonance whole-body unit. Age ranged from 20 to 70 years (mean age, 47.9 +/- 11.4 years). A multislice fat-saturated breath-hold 2D multiecho gradient-echo sequence was applied for T2* measurement. To assess T2* values of the liver, pancreas, and spleen, T2* maps were calculated. The correlation of organ T2* with serum ferritin and anthropometric data (age, gender, body mass index) was investigated.

RESULTS

Measurement of T2* was feasible in all volunteers. A gender-related analysis revealed significant higher hepatic and splenic T2* values for women than for men (P < 0.01). For the pancreas, these differences could not be found. A significant negative correlation was found between hepatic T2*, splenic T2*, and serum ferritin (r = -0.62 liver, r = -0.64 spleen; P < 0.0001). In contrast, no such relationship was found for pancreatic T2* (r = -0.15). For women, a statistically significant age-dependent increase was found for splenic T2* values.

CONCLUSION

Using a fast quantitative T2* magnetic resonance imaging technique, it was possible to gain insights into the iron metabolism of a healthy cohort. Gender- and age-related differences concerning T2* and serum ferritin levels were found in the liver and spleen, but not in the pancreas.

Near-Field High-Energy Spectroscopic Gamma Imaging Using a Rotation Modulation Collimator

Certain trace elements are vital to the body and elemental imbalances can be indicators of certain diseases including cancer and liver diseases. Neutron Stimulated Emission Computed Tomography (NSECT) is being developed as spectroscopic imaging technique to non-invasively and non-destructively measure and image elemental concentrations within the body. A region of interest is illuminated via a high-energy beam of neutrons that scatter inelastically with elemental nuclei within the body. The excited nuclei then relax by emitting characteristic gamma rays. Acquiring the gamma spectrum in a tomographic manner allows not only the identification of elements, but also the formation of images representing spatial distributions of specific elements. We are developing a high-energy position-sensitive gamma camera that allows full illumination of the entire region of interest. Because current scintillation crystal based position-sensitive gamma cameras operate in too low of an energy range, we are adapting high-energy gamma imaging techniques used in space-based imaging. A High Purity Germanium (HPGe) detector provides high-resolution energy spectra while a rotating modulation collimator (RMC) placed in front of the detector modulates the incoming signal to provide spatial information. The purpose of this manuscript is to describe the near-field RMC geometry, which varies greatly from the infinite-focus space-based applications, and how it modulates the incident gamma flux. A simple geometric model is presented and then used to reconstruct two-dimensional planar images of both simulated point sources and extended sources.

Experimental detection of iron overload in liver through neutron stimulated emission spectroscopy

Iron overload disorders have been the focus of several quantification studies involving non-invasive imaging modalities. Neutron spectroscopic techniques have demonstrated great potential in detecting iron concentrations within biological tissue. We are developing a neutron spectroscopic technique called neutron stimulated emission computed tomography (NSECT), which has the potential to diagnose iron overload in the liver at clinically acceptable patient dose levels through a non-invasive scan. The technique uses inelastic scatter interactions between atomic nuclei in the sample and incoming fast neutrons to non-invasively determine the concentration of elements in the sample. This paper discusses a non-tomographic application of NSECT investigating the feasibility of detecting elevated iron concentrations in the liver. A model of iron overload in the human body was created using bovine liver tissue housed inside a human torso phantom and was scanned with a 5 MeV pulsed beam using single-position spectroscopy. Spectra were reconstructed and analyzed with algorithms designed specifically for NSECT. Results from spectroscopic quantification indicate that NSECT can currently detect liver iron concentrations of 6 mg g(-1) or higher and has the potential to detect lower concentrations by optimizing the acquisition geometry to scan a larger volume of tissue. The experiment described in this paper has two important outcomes: (i) it demonstrates that NSECT has the potential to detect clinically relevant concentrations of iron in the human body through a non-invasive scan and (ii) it provides a comparative standard to guide the design of iron overload phantoms for future NSECT liver iron quantification studies.

R2 relaxometry with MRI for the quantification of tissue iron overload in beta-thalassemic patients

PURPOSE

To evaluate the usefulness of a time-efficient MRI method for the quantitative determination of tissue iron in the liver and heart of beta-thalassemic patients using spin-spin relaxation rate, R2, measurements.

MATERIALS AND METHODS

Images were obtained at 1.5 T from aqueous Gd-DTPA solutions (0.106-8 mM) and from the liver and heart of 46 beta-thalassemic patients and 10 controls. The imaging sequence used was a respiratory-triggered 16-echo Carr-Purcell-Meiboom-Gill (CPMG) spin-echo (SE) pulse sequence (TR = 2000 msec, TE(min) = 5 msec, echo spacing (ES) = 5 msec, matrix = 192 x 256, slice thickness = 10 mm). Liver iron concentration (LIC) measurements were obtained for 22 patients through biopsy specimens excised from the relevant liver segment. Biopsy specimens were also evaluated regarding iron grade and fibrosis. Serum ferritin (SF) measurements were obtained in all patients.

RESULTS

A statistically significant difference was found between patients and healthy controls in mean liver (P < 0.004) and myocardium (P < 0.004) R2 values. The R2 values correlated well with Gd DTPA concentration (r = 0.996, P < 0.0001) and LIC (r = 0.874, P < 0.0001). A less significant relationship (r = 0.791, P < 0.0001) was found between LIC measurements and SF levels. R2 measurements appear to be significantly affected (P = 0.04) by different degrees of hepatic fibrosis. The patients' liver R2 values did not correlate with myocardial R2 values (r = 0.038, P < 0.21).

CONCLUSION

Tissue iron deposition in beta-thalassemic patients may be adequately quantified using R2 measurements obtained with a 16-echo MRI sequence with short ES (5 msec), even in patients with a relatively increased iron burden.

Use of the oral chelator deferiprone in the treatment of iron overload in patients with Hb H disease

Seventeen non-transfusion-dependent Chinese haemoglobin H (Hb H) disease patients (age 29-76 years) with serum ferritin >900 microg/l were treated with deferiprone for up to 18 months. One patient withdrew and data from 16 patients were analysed. Sixteen other Hb H patients with ferritin <900 microg/l, matched for age and genotype, acted as controls. Treatment was well tolerated except for mild arthralgia. Serum ferritin fell with treatment, reaching significance at 6 and 18 months (from 1492.3 +/- 901.4 to 519.4 +/- 405.4 microg/l at 18 months, P = 0.0008). Nine of 16 patients had levels below 397 microg/l before 18 months. Serum ferritin remained stable 6 months after stopping treatment. In contrast, there was no change in ferritin levels in the control group. Magnetic resonance imaging was used for measurement of liver iron content. Spin echo T(1)-signal intensity ratio (T(1)-SIR) and gradient echo T(2)-signal intensity ratio (T(2)-SIR) increased with treatment. T(2)-SIR rose from 0.17 +/- 0.08 pretreatment to 0.58 +/- 0.50 at 2 years (P = 0.0055). Improvement occurred in 12 of 16 patients, reaching normal in three patients. Using echocardiography, peak early diastolic : late diastolic blood flow (E/A) remained unchanged with treatment, but isovolumic relaxation time (IVRT) was prolonged at 2 years indicating mild impairment of diastolic function. All systolic function parameters were normal. A longer treatment period is desirable to demonstrate improvement in cardiac function.

MRI R2 and R2* mapping accurately estimates hepatic iron concentration in transfusion-dependent thalassemia and sickle cell disease patients

Measurements of hepatic iron concentration (HIC) are important predictors of transfusional iron burden and long-term outcome in patients with transfusion-dependent anemias. The goal of this work was to develop a readily available, noninvasive method for clinical HIC measurement. The relaxation rates R2 (1/T2) and R2* (1/T2*) measured by magnetic resonance imaging (MRI) have different advantages for HIC estimation. This article compares noninvasive iron estimates using both optimized R2 and R2* methods in 102 patients with iron overload and 13 controls. In the iron-overloaded group, 22 patients had concurrent liver biopsy. R2 and R2* correlated closely with HIC (r2 > or = .95) for HICs between 1.33 and 32.9 mg/g, but R2 had a curvilinear relationship to HIC. Of importance, the R2 calibration curve was similar to the curve generated by other researchers, despite significant differences in technique and instrumentation. Combined R2 and R2* measurements did not yield more accurate results than either alone. Both R2 and R2* can accurately measure hepatic iron concentration throughout the clinically relevant range of HIC with appropriate MRI acquisition techniques.

Magnetic resonance screening of iron status in transfusion-dependent β-thalassaemia patients

The clinical utility of dual sequence (T1- and T2-weighted) magnetic resonance (MR) imaging in estimating liver iron concentration (LIC) in 32 transfusion-dependent beta-thalassaemia major (24 females; age 18.5+/-5.9 years) patients on desferrioxamine was evaluated. Signal intensity ratios (SIR) between liver, spleen and pancreas to psoas muscle were determined on both sequences. Relationships between clinical and MR parameters, and accuracy of SIR thresholds in determining adequacy of chelation from LIC were analysed. Liver T1- and T2-SIR were related to LIC (P < 0.001). T1-SIR < 0.60 predicted severe iron overload (LIC > 15 mg/g) with sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 100%, 87%, 33% and 100% respectively. T2-SIR < 0.1 yielded 100% sensitivity, 93% specificity, 50% PPV and 100% NPV. T1-SIR > or = 1.1 predicted LIC < 7 mg/g with 69% sensitivity, 88% specificity, 85% PPV and 74% NPV. T2-SIR > or = 0.20 yielded 56.5% sensitivity, 94% specificity, 90% PPV and 71% NPV. LIC correlated with liver T1-SIR, liver T2-SIR and serum ferritin (r = -0.76, -0.65, 0.47, respectively; P < 0.01). Serum ferritin was inversely related to liver T1-SIR, liver T2-SIR and spleen T2-SIR (r = -0.35, -0.43, -0.40, respectively; P < 0.05). Mean total transfusion burden was not related to any MR parameter. Although neither MR sequence was a highly accurate predictor of LIC, SIR thresholds are useful to determine presence of iron overload and adequacy of chelation treatment.

Evaluation of myocardial iron by magnetic resonance imaging during iron chelation therapy with deferrioxamine: indication of close relation between myocardial iron content and chelatable iron pool

Evaluation of myocardial iron during iron chelation therapy is not feasible by repeated endomyocardial biopsies owing to the heterogeneity of iron distribution and the risk of complications. Recently, we described a noninvasive method based on magnetic resonance imaging. Here, the method was used for repeated estimation of the myocardial iron content during iron chelation with deferrioxamine in 14 adult nonthalassemic patients with transfusional iron overload. We investigated the repeatability of the method and the relationship between the myocardial iron estimates and iron status. The repeatability coefficient (2sD) was 2.8 micromol/g in the controls (day-to-day) and 4.0 micromol/g in the patients (within-day). Myocardial iron estimates were elevated in 10 of all 14 patients at first examination, but normalized in 6 patients after 6 to 18 months of treatment. If liver iron declined below 350 micromol/g all but one of the myocardial iron estimates were normal or nearly normal. At start (R2 = 0.69, P =.0014) and still after 6 months of iron chelation (R2 = 0.76, P =.001), the estimates were significantly and more closely related to the urinary iron excretion than to liver iron or serum ferritin levels. In conclusion, our preliminary data, which may only pertain to patients with acquired anemias, suggest the existence of a critical liver iron concentration, above which elevated myocardial iron is present, but its extent seems related to the size of the chelatable iron pool, as reflected by the urinary iron excretion. This further supports the concept of the labile iron pool as the compartment directly involved in transfusional iron toxicity.

Noninvasive measurement of iron: report of an NIDDK workshop

An international workshop on the noninvasive measurement of iron was conducted by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) on April 17, 2001, to assess the current state of the science and to identify areas needing further investigation. The workshop concluded that a clear clinical need is evident for quantitative, noninvasive, safe, accurate, and readily available means of measuring body storage iron to improve the diagnosis and management of patients with iron overload from such disorders as hereditary hemochromatosis, thalassemia major, sickle cell disease, aplastic anemia, and myelodysplasia, among others. Magnetic resonance imaging (MRI) potentially provides the best available technique for examining the 3-dimensional distribution of excess iron in the body, but further research is needed to develop means of making measurements quantitative. Biomagnetic susceptometry provides the only noninvasive method to measure tissue iron stores that has been calibrated, validated, and used in clinical studies, but the complexity, cost, and technical demands of the liquid-helium-cooled superconducting instruments required at present have restricted clinical access to the method. The workshop identified basic and clinical research opportunities for deepening our understanding of the physical properties of iron and iron toxicity, for further investigation of MRI as a method for quantitative determinations of tissue iron, especially in liver, heart and brain, and for development of improved methods and more widely available instrumentation for biomagnetic susceptometry.

Liver density measured by DEXA correlates with serum ferritin in patients with beta-Thalassemia Major

Patients with beta-Thalassemia Major have a requirement for repeated blood transfusion, which ultimately results in liver iron- and whole body iron-overload. These patients are also at risk of reduced bone mineral density (BMD). Seventeen patients (9 female, age 19-32 yr) were referred for bone density estimations of the hip, spine, and whole body. As well as calculating the usual indices of body composition, we superimposed regions of interest over the liver, and expressed the result as "BMD" (g/cm2). This was compared with the serum ferritin as a noninvasive indication of total body iron status. Twelve patients were studied at least twice, more than 18 mo apart. This group showed a significantly below average BMD (T-spine -2.1, T-femoral neck -1.2, T-whole body -1.7, p < 0.001). The group's hepatic density correlated significantly with initial serum ferritin (r = 0.90, p < 0.001). Changes in individual liver density did not correlate significantly with changes in ferritin levels (p = 0.15), possibly due to wide variability in individual results. DEXA may be a useful noninvasive technique for estimating liver-iron concentration.

Evaluation of iron overload by single voxel MRS measurement of liver T2

PURPOSE

To overcome the difficulty of poor signal-to-noise ratio of magnetic resonance imaging (MRI) in evaluating heavy iron overload by using a single voxel magnetic resonance spectroscopy (MRS) technique.

MATERIALS AND METHODS

A single voxel STEAM pulse sequence with a minimum TE of 1.5 msec and a sampling volume of 36.6 cm(3) was developed and applied to 1/T2 measurement of the liver in 14 patients with thalassemia whose liver iron concentration was determined through biopsy.

RESULTS

The iron level ranged from 0.23 to 37.15 mg Fe/g dry tissue with a median value of 18.06. In all cases, strong MR signals were obtained. 1/T2 was strongly correlated with the liver iron concentration (r = 0.95, P < 0.00005).

CONCLUSION

The single voxel MRS measurement of T2 in liver iron overload overcomes the difficulty of lack of detectable signals in conventional MRI when the iron level is high. There is an excellent correlation between the iron level and 1/T2.

MR imaging of iron depositional disease

This article discusses the physiology of iron metabolism in humans. The pathophysiology and MR imaging findings of disorders that result in iron deposition in the liver are described. Emphasis is placed on genetic, clinical, and imaging findings of hemochromatosis. Radiologists should familiarize themselves with the patterns of iron deposition on MR images in order to suggest a potential etiology, which may not be known at the time of imaging.

Liver iron estimation in beta-thalassaemia: comparison of MRI biochemical assay and histological grading

AIMS

The aims of the study were to compare the efficacy of magnetic resonance imaging (MRI), biochemical assay and histological grading in estimating liver iron content, and to evaluate the value of liver to muscle signal intensity ratio (L/M ratio) on spin-echo T1-weighted images in this role.

MATERIALS AND METHODS

Thirty-nine homozygous beta-thalassaemics had their L/M ratio measured on MRI, followed by ultrasound-guided liver biopsies with histological grading of iron storage and biochemical quantification of liver iron concentration (LIC-b) using atomic absorption spectrophotometry.

RESULTS

A significant difference in L/M ratios between the four grades of iron storage on histology was observed (P < 0.001). The coefficient of correlation was -0.67 between L/M ratio and LIC-b ranging from 2 to 21.6 mg/g dry weight. Specific values of L/M ratio reliably reflected liver iron content at clinically important levels. A L/M ratio of < 0.6 has 86% sensitivity and 100% specificity in the prediction of grade 3 or 4 iron storage histologically and 81% sensitivity and 81% specificity in predicting LIC-b > 15 mg/g. A L/M ratio of > 0.8 predicts a histological iron storage grading of 0 or 1 with a 100% sensitivity and 74% specificity.

CONCLUSION

L/M ratio on MRI is of value as a non-invasive alternative to repeated liver biopsies for estimating liver iron content at clinically important thresholds.

Indirect evidence for the potential ability of magnetic resonance imaging to evaluate the myocardial iron content in patients with transfusional iron overload

The purpose of this study was to evaluate the potential ability of magnetic resonance imaging (MRI) for evaluation of myocardial iron deposits. The applied MRI technique has earlier been validated for quantitative determination of the liver iron concentration. The method involves cardiac gating and may, therefore, also be used for simultaneous evaluation of myocardial iron. The tissue signal intensities were measured from spin echo images and the myocardium/muscle signal intensity ratio was determined. The SI ratio was converted to tissue iron concentration values based on a modified calibration curve from the liver model. The crucial steps of the method were optimized; i.e. recognition and selection of the myocardial slice for analysis and positioning of the regions of interest (ROIs) within the myocardium and the skeletal muscle. This made the myocardial MRI measurements sufficiently reproducible. We applied this method in 41 multiply transfused patients. Our data demonstrate significant positive linear relationships between different iron store parameters and the MRI-derived myocardial iron concentration, which was significantly related to the serum ferritin concentration (rho=0.62, P<0.0001) and to the MRI-determined liver iron concentration (rho=0.36, P=0.02). The myocardial MRI iron concentrations demonstrated also a significant positive correlation with the number of blood units given (rho=0.45, P=0.005) and the aminotransferase serum concentration (rho=0.54, P=0.0008). Our data represents indirect evidence for the ability of MRI techniques based on myocardium/muscle signal intensity ratio measurements to evaluate myocardial iron overload.

In vivo investigation of hepatic iron overload in rats using T2 maps: quantification at high intensity field (4.7-T)

In vivo quantitation of hepatic iron content is useful in diagnosis and staging of several iron related diseases. We used an experimental model of hepatic iron overload to determine the correlation between iron content and T2 relaxation time in rat liver. Experiments were carried out at 4.7T for high signal-to-noise ratio (SNR) using a spin-echo multiecho sequence with six echoes and minimum echo-time of 5.5 msec. The liver iron content was determined ex vivo by atomic absorption spectrophotometry (AAS). T2 maps were calculated in order to evaluate the space distribution of the iron content. We found good linear correlation between the in vivo liver transversal relaxation rate and the iron content within the range explored (106-4538 microg Fe/g liver wet wt.). T2 maps revealed that the decrease in T2 is not homogeneous through the liver parenchyma. This finding represents a physiological limitation to obtaining better correlation between T2 and iron content.

Noninvasive methods for quantitative assessment of transfusional iron overload in sickle cell disease

Because optimal management of iron chelation therapy in patients with sickle cell disease and transfusional iron overload requires accurate determination of the magnitude of iron excess, a variety of techniques for evaluating iron overload are under development, including measurement of serum ferritin iron levels, x-ray fluorescence of iron, magnetic resonance imaging, computed tomography, and measurement of magnetic susceptibility. The most promising methods for noninvasive assessment of body iron stores in patients with sickle cell anemia and transfusional iron overload are based on measurement of hepatic magnetic susceptibility, either using superconducting quantum interference device (SQUID) susceptometry or, potentially, magnetic resonance susceptometry.

Secondary iron overload

Transfusion therapy for inherited anemias and acquired refractory anemias both improves the quality of life and prolongs survival. A consequence of chronic transfusion therapy is secondary iron overload, which adversely affects the function of the heart, the liver and other organs. This session will review the use of iron chelating agents in the management of transfusion-induced secondary iron overload. In Section I Dr. John Porter describes techniques for the administration of deferoxamine that exploit the pharmacokinetic properties of the drug and minimize potential toxic side effects. The experience with chelation therapy in patients with thalassemia and sickle cell disease will be reviewed and guidelines will be suggested for chelation therapy of chronically transfused adults with refractory anemias. In Section II Dr. Nancy Olivieri examines the clinical consequences of transfusion-induced secondary iron overload and suggests criteria useful in determining the optimal timing of the initiation of chelation therapy. Finally, Dr. Olivieri discusses the clinical trials evaluating orally administered iron chelators.

Iron overload and iron-chelating therapy in hemoglobin E-beta thalassemia

Whereas hemoglobin (Hb) E-beta thalassemia is recognized as probably the most common serious hemoglobinopathy worldwide, its natural history remains poorly defined. The interaction of hemoglobin E and beta-thalassemia result in a wide spectrum of clinical disorders, some indistinguishable from thalassemia major and some milder and not transfusion-dependent. Partially as a result of this wide range of phenotypes, clear guidelines for approaches to transfusion and to iron-chelating therapy for patients with Hb E-beta thalassemia have not been developed. By contrast, data that have accumulated during the past 10 years in patients with beta-thalassemia permit a quantitative approach to the management of iron overload and provide guidelines for the control of body iron burden in individual patients treated with iron-chelating therapy. These guidelines may be applicable to patients with Hb E-beta thalassemia. Preliminary evidence from our studies of iron loading in affected patients with Hb E-beta thalassemia in Sri Lanka suggest that this disorder may be associated with variable, but accelerated, gastrointestinal iron absorption, and that the iron loading associated with chronic transfusions in patients with Hb E-beta thalassemia is similar to that observed in patients with beta-thalassemia. These data, in the only cohort of patients with Hb E-beta thalassemia to have undergone quantitative assessment of body iron burden, suggest that the principles that guide assessment of iron loading and initiation of chelating therapy in patients with beta-thalassemia may be generally applicable to those with Hb E-beta thalassemia. Further quantitative studies in both nontransfused and transfused patients will be necessary to permit firm conclusions.

Magnetic resonance imaging (MRI) and diseases of the liver and biliary tract. Part 1. Basic principles, MRI in the assessment of diffuse and focal hepatic disease

Magnetic resonance imaging (MRI) relies on the physical properties of unpaired protons in tissues to generate images. Unpaired protons behave like tiny bar magnets and will align themselves in a magnetic field. Radiofrequency pulses will excite these aligned protons to higher energy states. As they return to their original state, they will release this energy as radio waves. The frequency of the radio waves depends on the local magnetic field and by varying this over a subject, it is possible to build the images we are familiar with. In general, MRI has not been sufficiently sensitive or specific in the assessment of diffuse liver disease for clinical use. However, because of the specific characteristics of fat and iron, it may be useful in the assessment of hepatic steatosis and iron overload. Magnetic resonance imaging is useful in the assessment of focal liver disease, particularly in conjunction with contrast agents. Haemangiomas have a characteristic bright appearance on T2 weighted images because of the slow flowing blood in dilated sinusoids. Focal nodular hyperplasia (FNH) has a homogenous appearance, and enhances early in the arterial phase after gadolinium injection, while the central scar typically enhances late. Hepatic adenomas have a more heterogenous appearance and also enhance in the arterial phase, but less briskly than FNH. Hepatocellular carcinoma is similar to an adenoma, but typically occurs in a cirrhotic liver and has earlier washout of contrast. The appearance of metastases depends on the underlying primary malignancy. Overall, MRI appears more sensitive and specific than computed tomography with contrast for the detection and evaluation of malignant lesions.

Genetic and clinical features of hemoglobin H disease in Chinese patients

BACKGROUND

Normally, one pair of each of the two alpha-globin genes, alpha1 and alpha2, resides on each copy of chromosome 16. In hemoglobin H disease, three of these four alpha-globin genes are affected by a deletion, a mutation, or both. We studied the alpha1-globin gene abnormalities and the clinical and hematologic features of Chinese patients with hemoglobin H disease in Hong Kong.

METHODS

We assessed the clinical features, hematologic values, serum ferritin levels, and liver function of 114 patients with hemoglobin H disease. We also performed echocardiography and magnetic resonance imaging of the liver and examined the two pairs of alpha-globin genes.

RESULTS

Hemoglobin H disease in 87 of the 114 patients (76 percent) was due to the deletion of three of the four alpha-globin genes (--/-alpha), a combination termed the deletional type of hemoglobin H. The remaining 27 patients (24 percent) had the nondeletional type of hemoglobin H disease, in which two alpha-globin genes are deleted and a third is mutated (--/alphaalphaT). All 87 patients with the deletional type of hemoglobin H were double heterozygotes in whom there was a deletion of both alpha-globin genes from one chromosome, plus a deletion of the alpha1 or alpha2 gene from the other chromosome (--/alpha- or --/-alpha). A variety of mutated alpha-globin genes was found in the patients with nondeletional type of hemoglobin H disease. Patients with the nondeletional type of the H disease had more symptoms at a younger age, more severe hemolytic anemia, and larger spleens and were more likely to require transfusions than patients with deletional hemoglobin H disease. The severity of iron overload was not related to the genotype.

CONCLUSIONS

Chinese patients in Hong Kong with the nondeletional type of hemoglobin H disease have more severe disease than those with the deletional type of the disease. Iron overload is a major cause of disability in both forms of the disease.

Hepatic iron concentration and total body iron stores in thalassemia major

BACKGROUND AND METHODS

We tested the usefulness of measuring the hepatic iron concentration to evaluate total body iron stores in patients who had been cured of thalassemia major by bone marrow transplantation and who were undergoing phlebotomy treatment to remove excess iron.

RESULTS

We began treatment with phlebotomy a mean (+/-SD) of 4.3+/-2.7 years after transplantation in 48 patients without hepatic cirrhosis. In the group of 25 patients with liver-biopsy samples that were at least 1.0 mg in dry weight, there was a significant correlation between the decrease in the hepatic iron concentration and total body iron stores (r=0.98, P<0.001). Assuming that the hepatic iron concentration is reduced to zero with complete removal of body iron stores during phlebotomy, the amount of total body iron stores (in milligrams per kilogram of body weight) is equivalent to 10.6 times the hepatic iron concentration (in milligrams per gram of liver, dry weight). With the use of this equation, we could reliably estimate total body iron stores as high as 250 mg per kilogram of body weight, with a standard error of less than 7.9.

CONCLUSIONS

The hepatic iron concentration is a reliable indicator of total body iron stores in patients with thalassemia major. In patients with transfusion-related iron overload, repeated determinations of the hepatic iron concentration can provide a quantitative means of measuring the long-term iron balance.

Transfusional hemochromatosis: quantitative relation of MR imaging pituitary signal intensity reduction to hypogonadotropic hypogonadism

PURPOSE

To assess the relationship between magnetic resonance (MR) imaging pituitary signal intensity reduction in patients with transfusional hemochromatosis and the clinical manifestation of hypogonadotropic hypogonadism.

MATERIALS AND METHODS

Pituitary MR imaging at 0.5 T was performed in 38 consecutive patients affected by secondary hemochromatosis and in 20 healthy volunteers. Serum ferritin levels were estimated in the affected population. Twenty (53%) of the 38 patients had hypogonadotropic hypogonadism diagnosed. Pituitary-to-fat signal intensity ratios were calculated from coronal gradient-echo (GRE) T2*-weighted MR images. The relationship between the quantitative reduction of the pituitary-to-fat signal intensity ratio and the clinical manifestation of pituitary dysfunction was assessed in the affected population. Signal intensity reduction in the anterior lobe of the pituitary gland was also correlated with the serum ferritin level.

RESULTS

The degree of reduction of the pituitary-to-fat signal intensity ratio correlated with the presence of hypogonadotropic hypogonadism, with a sensitivity of 90%, a specificity of 89%, and an overall accuracy of 89%. In addition, the reduction of pituitary signal intensity was greater in patients with higher ferritin levels (r = -0.55, r(2) = -0.30, P <.001).

CONCLUSION

The degree of signal intensity reduction, measured as the pituitary-to-fat signal intensity ratio for GRE T2*-weighted images, in patients with secondary hemochromatosis correlates with the severity of pituitary dysfunction.

The use of skin Fe levels as a surrogate marker for organ Fe levels, to monitor treatment in cases of iron overload

A system based on the detection of K-shell x-ray fluorescence (XRF) has been used to investigate whether a correlation exists between the concentration of iron in the skin and the concentration of iron in the liver, as the degree of iron loading increases. The motivation behind this work is to develop a non-invasive method of determining the extent of the body's iron stores via measurements on the skin, in order to monitor the efficacy of chelation therapy administered to patients with beta-thalassaemia. Sprague-Dawley rats were iron loaded via injections of iron dextran and subsequently treated with the iron chelator CP94. The non-haem iron concentrations of the liver, heart and spleen were determined using bathophenanthroline sulphonate as the chromogen reagent. Samples of abdominal skin were taken and the iron concentrations determined using XRF. A strong correlation between the skin iron concentration and the liver iron concentration has been demonstrated (R2 = 0.86). Similar correlations exist for the heart and the spleen. These results show that this method holds great potential as a tool in the diagnosis and treatment of hereditary haemochromatosis and beta-thalassaemia.

Qualitative and quantitative magnetic resonance imaging in haemoglobin H disease: screening for iron overload

OBJECTIVES

To evaluate the clinical utility of magnetic resonance imaging (MRI) in screening for iron overload in non-transfusion dependent Haemoglobin (Hb) H disease.

PATIENTS AND METHODS

Thirty-six non-transfusion dependent HbH patients were evaluated with axial spin echo T1 and gradient echo T2 MRI of the abdomen and heart. The ratios of signal intensities (SIR) of the liver, spleen, pancreas and heart to paraspinous muscles were calculated. SIR <1 was taken as indicative of iron overload. Qualitative grading (0-4 scale) of iron overload was also performed. The relationship between T1 and T2 SIR and serum ferritin, and that between qualitative grading and serum ferritin were examined using standard statistical methods. Comparisons were also made between qualitative grading and quantitative T1 and T2 SIR data in diagnosing iron overload. Six patients underwent liver biopsies.

RESULTS

T2 SIR was more sensitive in detecting iron overload than T1 SIR. Thirty-three livers, 13 spleens, six pancreas and one heart were diagnosed as having iron overload with T2 SIR, including three patients with normal serum ferritin. A positive diagnosis by T2 SIR was more closely related to that of qualitative grading than T1 SIR. Serum ferritin was negatively correlated with hepatic SIR (T1 and T2), and with T2 SIR of the spleen and pancreas, even after adjustment for age. Liver haemosiderosis was confirmed in all six patients who underwent liver biopsies. Liver iron concentration of only one and a half times the normal was found in one patient with positive MR findings.

CONCLUSION

MR is a non-invasive, effective method for early detection of iron overload particularly in the liver and spleen. Qualitative grading and quantitative T2 SIR data are equivalent in diagnosing iron overload. Routine screening of non-transfusion dependent HbH patients will identify high risk patients in whom early therapeutic intervention may prevent further complications and morbidity.