Bone marrow changes in beta-thalassemia major: quantitative MR imaging findings and correlation with iron stores

Microvasculopathy-Related Hemorrhagic Tissue Deposition of Iron May Contribute to Fibrosis in Systemic Sclerosis: Hypothesis-Generating Insights from the Literature and Preliminary Findings

Microvascular wall abnormalities demonstrated by nailfold capillaroscopy in systemic sclerosis (SSc) may result in microhemorrhagic deposition of erythrocyte-derived iron. Such abnormalities precede fibrosis, which is orchestrated by myofibroblasts. Iron induces endothelial-to-mesenchymal transition in vitro, which is reversed by reactive oxygen species (ROS) scavengers. The conversion of quiescent fibroblasts into profibrotic myofibroblasts has also been associated with ROS-mediated activation of TGF-β1. Given that iron overload predisposes to ROS formation, we hypothesized that the uptake of erythrocyte-derived iron by resident cells promotes fibrosis. Firstly, we show that iron induces oxidative stress in skin-derived and synovial fibroblasts in vitro, as well as in blood mononuclear cells ex vivo. The biological relevance of increased oxidative stress was confirmed by showing the concomitant induction of DNA damage in these cell types. Similar results were obtained in vivo, following intravenous iron administration. Secondly, using magnetic resonance imaging we show an increased iron deposition in the fingers of a patient with early SSc and nailfold microhemorrhages. While a systematic magnetic resonance study to examine tissue iron levels in SSc, including internal organs, is underway, herein we propose that iron may be a pathogenetic link between microvasculopathy and fibrosis and an additional mechanism responsible for increased oxidative stress in SSc.

The added value of chemical shift imaging in evaluation of bone marrow changes in sickle cell disease

Background

The aim of this study was to assess the added value of chemical shift imaging when used with routine MRI study in evaluation of bone marrow changes in SCD. Forty-two patients with SCD and bone pain were included in the study; they underwent CSI and routine MRI study on the symptomatic anatomic part of the skeleton.

Results

Four patterns of diffuse bone marrow changes were recognized; they varied from persistent red marrow to diffuse hypointense patterns with abnormal signal loss percentage on CSI that suggest presence of iron overload (n = 28, 66.6%). Serum ferritin level was increasing in accordance to the degree of signal changes found on CSI with significant high negative correlation between the percentage of signal loss on CSI obtained from IP-OP/IP formula and serum ferritin level. In focal marrow lesions, all T1 hyperintense lesions demonstrated corresponding hyperintensity on IP and OP; the detection frequency on CSI was relatively higher on OP compared with IP images.

Conclusion

CSI has high diagnostic performance in detecting diffuse marrow changes and development of iron overload in SCD. In SCD-related focal marrow lesions, CSI could have a complementary role in detection of T1 hyperintensity and lesion conspicuity.

DXA and pQCT derived parameters in Indian children with beta thalassemia major - A case controlled study

Children with beta thalassemia major (BTM) are known to have reduced bone mass which increases incidence of non-traumatic fractures. Few studies have assessed prevalence of fractures and bone health in underprivileged children with BTM. Our objectives were to 1) determine prevalence of fractures in underprivileged Indian children with BTM, 2) assess size corrected bone density and bone geometry using Dual x-ray absorptiometry (DXA) and peripheral quantitative computerized tomography (pQCT) in these children and healthy controls 3) determine predictors of fractures in children with BTM 4) compare differences in bone density between children with BMT with and without fractures. Bone mineral content and areal bone mineral density (aBMD) of lumbar spine and whole body and vertebral fracture assessment (VFA) was performed by DXA in 334 children (3-18 years, 167 BTM + 167 controls). Volumetric BMD (vBMD) and bone geometry were assessed by pQCT (subset, 70 BTM, 70 healthy) at distal radius. Children with BTM had higher prevalence of vertebral and long bone fractures (p < 0.05). DXA aBMD was lower in children with BTM (p < 0.05), whereas, lumbar spine bone mineral apparent density (LSBMAD) was higher (p > 0.05). Children with BTM had lower total distal radial vBMD, cortical vBMD and strength strain index (SSI) at 66% site whereas, distal radial trabecular vBMD at 4% was higher (p < 0.05). On height adjustment, children with BTM had lower muscle area and cortical thickness and higher marrow area (p < 0.05) at 66% site. Age, body size, total body less head (TBLH) aBMD and strength strain index (SSI) were important predictors of fractures in children with BTM. Thus, children with BTM had higher prevalence of non-traumatic fractures. Despite lower areal and volumetric densities, they had higher LSBMAD and trabecular densities which may be attributed to erythroid hyperplasia and iron deposition due to inadequate transfusion and chelation. As LSBMAD is raised in these children, it is unlikely to identify BTM subjects at risk of fracture; VFA thus maybe useful in identifying asymptomatic vertebral fractures.

Dual-energy X-ray absorptiometry pitfalls in Thalassemia Major

BACKGROUND

Low mineral mass and reduced bone strength with increased fracture risk are the main causes of morbidity in Thalassemia Major (TM). The pathogenesis is multifactorial and includes ineffective erythropoiesis with medullary expansion, multiple endocrine dysfunctions, direct iron bone deposition, deferoxamine-induced bone dysplasia, and reduced physical activity associated with disease complications. Dual-energy X-ray absorptiometry (DXA) is the "gold standard" for bone mineral density (BMD) assessment and for bone strength and quality evaluation. This method identifies patients at greater risk of fragility fractures, guiding treatment and monitoring response to therapy. In TM, DXA shows limitations concerning BMD calculation accuracy and fracture risk prediction. One of the main challenges in the assessment of bone health in patients with TM is the accurate interpretation of densitometric results.

PURPOSE

This review investigates the major pitfalls in DXA implementation and interpretation in TM.

METHODS

Available literature has been assessed.

CONCLUSIONS

DXA shows limitations in assessing bone mineral "status" in TM, especially in the paediatric population, due to the peculiar characteristics of bone architecture and deformities associated with the disease. A radiological technique adjustment in this population is mandatory.

The utility of susceptibility-weighted imaging to evaluate the extent of iron accumulation in the choroid plexus of patients with β-thalassaemia major

AIM

To assess iron accumulation in the choroid plexus of β-thalassaemia patients using fast spin echo (FSE) T2-weighted, gradient echo (GRE) T2*-weighted, susceptibility-weighted imaging (SWI) and compare the results.

MATERIALS AND METHODS

Eighteen patients with transfusion-dependent β-thalassaemia and the control group underwent magnetic resonance imaging (MRI) examinations. Signal intensities were separately evaluated using a "number of hypointensity in the choroid plexus" (NHICP) grading system on axial FSE T2-weighted, GRE T2*-weighted, and SWI images. The NHICP grading system scores were compared using the chi-squared test. Spearman's correlation analysis was used to explore relationships between the variables and NHICP grading system scores.

RESULTS

The sensitivity of each technique was calculated: FSE T2-weighted imaging=0.17, GRE T2*-weighted imaging=0.48, and SWI=0.81. Three-sample test for equality of proportions showed that chi-squared=74.85, df=2, p<0.0001. All of the FSE T2-weighted, GRE T2*-weighted, and SWI images differed significantly in terms of their capacity to reveal iron accumulation in the choroid plexus. Of the three methods, SWI was the most sensitive.

CONCLUSIONS

SWI is useful for revealing iron deposition in the brains of β-thalassaemia patients, especially those in the early stages of disease, and it can be used to predict disease prognosis. The present study contributes to an understanding of the important role played by the choroid plexus in brain iron metabolism.

Iron overload detection using pituitary and hepatic MRI in thalassemic patients having short stature and hypogonadism

OBJECTIVE

to assess the growth and pubertal development among a group of patients with β-Thalassemia Major (β-TM) and to evaluate the role of the pituitary gland and liver MRI signal intensity (SI) reduction in assessing and predicting the clinical severity of growth and pubertal dysfunctions.

METHODS

Thirty-eight patients with β-TM were examined and divided into two groups: Group I patients were of normal height and puberty and Group II patients had short statures and hypogonadism. Laboratory investigations included serum ferritin, LH, FSH, prolactin, TSH, and basal and dynamic growth hormones. Pituitary and liver MRIs were performed to assess the pituitary to fat (P/F) and liver to muscle (L/M) signal intensities (SI), respectively. Fifteen healthy and sex- and age-matched subjects were included as controls.

RESULTS

Both patient groups had significantly elevated serum ferritin and significantly decreased prolactin and IGF1 compared to control subjects. Group II showed a significant reduction in LH, FSH, and IGF1 and a significant increase in ferritin in comparison with Group I and the control group, and it had a highly significant reduction in both P/F and L/M SI in comparison with Group I (p<0.001 and 0.008, respectively). The reduced P/F ratio was significantly correlated with FSH and LH, and a cutoff for a P/F ratio ≥0.94 was obtained to differentiate between Group I and II.

CONCLUSION

MRI in conjunction with the P/F signal intensity ratio is a useful and noninvasive tool for the early diagnosis of pituitary iron overload.

Tissue Iron Distribution Assessed by MRI in Patients with Iron Loading Anemias

Bone marrow, spleen, liver and kidney proton transverse relaxation rates (R2), together with cardiac R2* from patients with sickle cell disease (SCD), paroxysmal nocturnal hemoglobinuria (PNH) and non-transfusion dependent thalassemia (NTDT) have been compared with a control group. Increased liver and bone marrow R2 values for the three groups of patients in comparison with the controls have been found. SCD and PNH patients also present an increased spleen R2 in comparison with the controls. The simultaneous measurement of R2 values for several tissue types by magnetic resonance imaging (MRI) has allowed the identification of iron distribution patterns in diseases associated with iron imbalance. Preferential liver iron loading is found in the highly transfused SCD patients, while the low transfused ones present a preferential iron loading of the spleen. Similar to the highly transfused SCD group, PNH patients preferentially accumulate iron in the liver. A reduced spleen iron accumulation in comparison with the liver and bone marrow loading has been found in NTDT patients, presumably related to the differential increased intestinal iron absorption. The correlation between serum ferritin and tissue R2 is moderate to good for the liver, spleen and bone marrow in SCD and PNH patients. However, serum ferritin does not correlate with NTDT liver R2, spleen R2 or heart R2*. As opposed to serum ferritin measurements, tissue R2 values are a more direct measurement of each tissue's iron loading. This kind of determination will allow a better understanding of the different patterns of tissue iron biodistribution in diseases predisposed to tissue iron accumulation.

Liver iron and serum ferritin levels are misleading for estimating cardiac, pancreatic, splenic and total body iron load in thalassemia patients: factors influencing the heterogenic distribution of excess storage iron in organs as identified by MRI T2*

A comparative assessment of excess storage iron distribution in the liver, heart, spleen and pancreas of β-thalassemia major (β-ΤΜ) patients has been carried out using magnetic resonance imaging (MRI) relaxation times T2*. The β-ΤΜ patients (8-40 years, 11 males, 9 females) had variable serum ferritin levels (394-5603 μg/L) and were treated with deferoxamine (n = 10), deferiprone (n = 5) and deferoxamine/deferiprone combination (n = 5). MRI T2* assessment revealed that excess iron is not proportionally distributed among the organs but is stored at different concentrations in each organ and the distribution is different for each β-ΤΜ patient. There is random variation in the distribution of excess storage iron from normal to severe levels in each organ among the β-ΤΜ patients by comparison to the same organs of ten normal volunteers. The correlation of serum ferritin with T2* was for spleen (r = -0.81), liver (r = -0.63), pancreas (r = -0.33) and none with heart. Similar trend was observed in the correlation of liver T2* with the T2* of spleen (r = 0.62), pancreas (r = 0.61) and none with heart. These studies contradict previous assumptions that serum ferritin and liver iron concentration is proportional to the total body iron stores in β-ΤΜ and especially cardiac iron load. The random variation in the concentration of iron in the organs of β-ΤΜ patients appears to be related to the chelation protocol, organ function, genetic, dietary, pharmacological and other factors. Monitoring of the iron load for all the organs is recommended for each β-ΤΜ patient.

The importance of spleen, spleen iron, and splenectomy for determining total body iron load, ferrikinetics, and iron toxicity in thalassemia major patients

The importance of spleen, spleen iron and splenectomy has been investigated in 28 male and 19 female β-thalassemia major (β-ΤΜ), adult patients. In one study, an increase from about five (615 g; 19.5 × 11.0 × 6.0 cm) to twenty (2030 g; 25.0 × 17.5 × 12.0 cm) times higher than the normal size and weight of spleen has been observed in twenty patients following splenectomy. In a second study, the mean size for the liver (19.4 cm, range 13.5-26.0 cm) and spleen (15.6 cm, range 7.0-21.0 cm) measured by magnetic resonance imaging (MRI) and by ultrasound imaging for spleen (15.1 cm, range 9.0-21.0 cm) of 16 patients indicated that on average the spleen is about 80% of the size of the liver. In the third study, comparison of the iron load using MRI T(2)* and iron grading of stained biopsies indicated that substantial but variable amounts of excess iron are stored in the spleen (0-40%) in addition to that in the liver. Following splenectomy, total body iron storage capacity is reduced, whereas serum ferritin (p = 0.0085) and iron concentration in other organs appears to increase despite the reduction in the rate of transfusions (p = 0.0001) and maintenance of hemoglobin levels (p = 0.1748). Spleen iron seems to be cleared faster than liver iron using effective chelation protocols. Spleen iron is a major constituent of the total body iron load in β-ΤΜ patients and should be regularly monitored and targeted for chelation. Normalization of the body iron stores at an early age could maintain the spleen in near normal capacity and secondary effects such as cardiac and other complications could be avoided.

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

PURPOSE

To assess the performance and results of R(2) relaxometry using a fat-suppressed (FS) multiecho sequence and compare these to conventional R(2) relaxometry in estimating tissue iron overload.

MATERIALS AND METHODS

Relaxation rate values (R(2)=1/T2) of the liver, spleen, pancreas and vertebral bone marrow (VBM) were estimated in 21 patients with β-thalassemia major, using a respiratory-triggered 16-echo Carr-Purcell-Meiboom-Gill (CPMG) spin-echo sequence before (R(2)) and after (R(2) FS) the application of chemically selective fat suppression.

RESULTS

Hepatic and splenic R(2) FS values correlated with respective R(2) values (r=0.98 and r=0.96, P<.001), whereas correlations between R(2) FS and R(2) values for pancreas and VBM were not statistically significant. Bland-Altman plots show disagreement between R(2) and R(2) FS values, particularly for pancreas and VBM. Hepatic, pancreatic and VBM R(2) FS values correlated with serum ferritin (r=0.88, P<.001; r=0.51, P<.003; and r=0.75, P<.002, respectively). Hepatic R(2) FS values correlated with splenic R(2) FS (r=0.77, P<.03), pancreatic R(2) FS (r=0.61, P<.006) and VBM R(2) FS values (r=0.70, P<.001), whereas pancreatic R(2) FS values correlated also with VMB R(2) FS values. On the contrary, among the R(2) values of the above tissues, obtained without fat suppression, only hepatic R(2) values correlated with serum ferritin, whereas no correlation was documented between hepatic and pancreatic or VBM R(2) values. The application of fat suppression did not improve breathing or flow artifacts.

CONCLUSION

Application of fat suppression in the standard CPMG sequence improved the capability of MRI in noninvasive quantification of iron, particularly in lipid-rich tissues, such as vertebral bone marrow (VBM) and pancreas.

Characterization of low bone mass in young patients with thalassemia by DXA, pQCT and markers of bone turnover

Previous reports using dual x-ray absorptiometry (DXA) suggest that up to 70% of adults with thalassemia major (Thal) have low bone mass. However, few studies have controlled for body size and pubertal delay, variables known to affect bone mass in this population. In this study, bone mineral content and areal density (BMC, aBMD) of the spine and whole body were assessed by DXA, and volumetric BMD and cortical geometries of the distal tibia by peripheral quantitative computed tomography (pQCT) in subjects with Thal (n = 25, 11 male, 10 to 30 years) and local controls (n=34, 15 male, 7 to 30 years). Z-scores for bone outcomes were calculated from reference data from a large sample of healthy children and young adults. Fasting blood and urine were collected, pubertal status determined by self-assessment and dietary intake and physical activity assessed by written questionnaires. Subjects with Thal were similar in age, but had lower height, weight and lean mass index Z-scores (all p < 0.001) compared to controls. DXA aBMD was significantly lower in Thal compared to controls at all sites. Adult Thal subjects (> 18 years, n = 11) had lower tibial trabecular vBMD (p = 0.03), cortical area, cortical BMC, cortical thickness, periosteal circumference and section modulus Z-scores (all p < 0.01) compared to controls. Cortical area, cortical BMC, cortical thickness, and periosteal circumference Z-scores (p = 0.02) were significantly lower in young Thal (≤ 18 years, n = 14) compared to controls. In separate multivariate models, tibial cortical area, BMC, and thickness and spine aBMD and whole body BMC Z-scores remained lower in Thal compared to controls after adjustment for gender, lean mass and/or growth deficits (all p < 0.01). Tanner stage was not predictive in these models. Osteocalcin, a marker of bone formation, was significantly reduced in Thal compared to controls after adjusting for age, puberty and whole body BMC (p=0.029). In summary, we have found evidence of skeletal deficits that cannot be dismissed as an artifact of small bone size or delayed maturity alone. Given that reduced bone density and strength are associated with increased risk of fracture, therapies focused on increasing bone formation and bone size in younger patients are worthy of further evaluation.

[Relaxation times T1, T2, and T2* of apples, pears, citrus fruits, and potatoes with a comparison to human tissues]

The aim of the project was a systematic assessment of relaxation times of different fruits and vegetables and a comparison to values of human tissues. Results provide an improved basis for selection of plant phantoms for development of new MR techniques and sequences. Vessels filled with agar gel are mostly used for this purpose, preparation of which is effortful and time-consuming. In the presented study apples, (malus, 8 species), pears, (pyrus, 2 species), citrus fruits (citrus, 5 species) and uncooked potatoes (solanum tuberosum, 8 species) from the supermarket were examined which are easily available nearly all-the-year. T1, T2 and T2* relaxation times of these nature products were measured on a 1.5 Tesla MR system with adapted examination protocols and mono-exponential fitting, and compared to literature data of human parenchyma tissues, fatty tissue and body fluid (cerebrospinal fluid). Resulting values were as follows: apples: T1: 1486-1874 ms, T2: 163-281 ms, T2*: 2.3-3.2 ms; pears: T1: 1631-1969 ms, T2: 119-133 ms, T2* : 10.1-10.6 ms, citrus fruits (pulp) T1: 2055-2632 ms, T2: 497-998 ms, T2* : 151-182 ms; citrus fruits (skin) T1: 561-1669 ms, T2: 93-119 ms; potatoes: T1: 1011-1459 ms, T2: 166 - 210 ms, T2* : 20 - 30 ms. All T1-values of the examined objects (except for potatoes and skins of citrus fruits) were longer than T1 values of human tissues. Also T2 values (except for pears and skins of citrus fruits) of the fruits and the potatoes tended to be longer. T2* values of apples, pears and potatoes were shorter than in healthy human tissue. Results show relaxation values of many fruits to be not exactly fitting to human tissue, but with suitable selection of the fruits and optionally with an adaption of measurement parameters one can achieve suitable contrast and signal characteristics for some purposes.

Quantitative computed tomography is unreliable for measurement of bone mineral density in inadequately chelated adolescent patients with β-thalassemia major: a case-control study

BACKGROUND

Utility of quantitative computed tomography (QCT) for assessment of bone mineral density (BMD) in patients with thalassemia is not fully established. Majority of patients with thalassemia in India receive suboptimal iron chelation. There is paucity of data on BMD in this population. Aim was to assess BMD by lumbar QCT in adolescent patients with transfusion dependent β-thalassemia major and compare with controls.

PROCEDURE

Study was conducted prospectively, over 15 months. Single energy QCT was performed through first three lumbar vertebrae.

RESULTS

Forty-five patients were enrolled (age: 10-19 years). Thirty-eight normal siblings of patients with thalassemia patients served as controls. Forty percent patients weighed <3rd percentile, 64% were stunted, and 40% had suboptimal sexual maturity scores. Eighteen (40%) patients were on iron chelation with deferiprone. Mean serum ferritin was 2,800 ± 1,473 ng/ml. Mean BMD (mg/cu mm) of cases and controls was 194.5 ± 27.1 and 170.4 ± 28.84, respectively (P = 0.0002). The mean BMD of patients with ferritin <2,000 ng/ml and those with a higher ferritin was 181.2 ± 14.9 and 196.7 ± 25, respectively (P = 0.07). The finding of increased BMD in patients with thalassemia is in stark contrast to published reports. Patients had several risk factors for low BMD, including growth retardation, delayed puberty, and iron overload.

CONCLUSION

Single energy QCT of lumbar vertebrae is not reliable for measurement of BMD in inadequately chelated patients with β-thalassemia major. The deposition of iron in bone tissue may result in increased X-ray attenuation values of trabecular bone.

Deferoxamine versus combined therapy for chelating liver, spleen and bone marrow iron in beta-thalassemic patients: a quantitative magnetic resonance imaging study

We used magnetic resonance imaging (MRI) to compare the effect of iron chelation on liver, spleen and bone marrow. We examined 21 beta-thalassemic patients undergoing deferoxamine (DFO) (9/21) or combined therapy [DFO and deferiprone (L1), 12/21] with two abdominal MRI studies using T1-w/Pd-w/T2*-wGRE and T1-wTSE sequences. Changes in serum ferritin (DF%), and liver, spleen and marrow to paraspinous muscles signal intensity ratios (SI) in T1-wTSE sequence were calculated as D%=[(2(nd)value-1(st) value)/1(st) value] x100%. Negative DF% and positive D(SI)% indicated reduction of iron. Although 17/21 (80.9%) patients demonstrated reduction in ferritin, only 8/21 (38%), 7/21 (33.3%) and 7/21 (33.3%) patients had decreased liver, spleen and marrow iron. Patients undergoing combined therapy showed significantly greater reduction (Student's t-test, p < 0.05) or less increase (t-test, p <0.05) in iron stores. Combined therapy is more effective than DFO for removing and preventing liver, spleen and bone marrow iron accumulation in beta-thalassemic patients. Magnetic resonance imaging is valuable for organ-specific monitoring of chelation therapy.

Assessment of iron distribution between liver, spleen, pancreas, bone marrow, and myocardium by means of R2 relaxometry with MRI in patients with beta-thalassemia major

PURPOSE

To investigate the correlation between the degree of hepatic, splenic, pancreatic, vertebral bone marrow (VBM), and myocardial siderosis, as expressed by relaxation rate (R2 = 1/T2) values, in patients with thalassemia.

MATERIALS AND METHODS

R2 relaxation rate values of liver, spleen, VBM, pancreas, and myocardium were estimated in 68 consecutive transfusion-dependent patients with beta-thalassemia major and 10 healthy controls using a respiratory triggered 16-echo Carr-Purcell-Meiboom-Gill (CPMG) spin echo sequence.

RESULTS

Hepatic R2 values were significantly increased in all 68 patients; VBM, pancreatic, and myocardial R2 values were increased in 67/68, 35/47, and 47/61 patients, whereas five patients showed decreased pancreatic R2 attributed to fatty degeneration. Of the 39 nonsplenectomized patients, splenic R2 values were decreased in 30 and normal in nine patients. Hepatic R2 values correlated with splenic (r = 0.63, P < 0.001), VBM (r = 0.52, P < 0.001), but not with myocardial and pancreatic R2 values.

CONCLUSION

Despite positive correlations between the degree of hepatic, splenic, and VBM siderosis, as expressed by respective R2 values, there was variability of iron distribution patterns in thalassemic patients. Unpredictable patterns of iron distribution may be seen, such as normal signal of the spleen in the presence of siderotic liver, resembling primary hemochromatosis. Fatty degeneration of the pancreas was not uncommon.

Spleen R2 and R2* in iron-overloaded patients with sickle cell disease and thalassemia major

PURPOSE

To evaluate the magnetic properties of the spleen in chronically transfused, iron-overloaded patients with sickle cell disease (SCD) and thalassemia major (TM) and to compare splenic iron burdens to those in the liver, heart, pancreas, and kidneys.

MATERIALS AND METHODS

A retrospective analysis of 63 TM and 46 SCD patients was performed. Spleen R2 and R2* values were calculated from spin-echo and gradient-echo images collected between April 2004 and September 2007.

RESULTS

The spleen showed a different R2-R2* relationship than that previously established for the liver. At high iron concentrations (R2* > 300 Hz), spleen R2 was lower than predicted for liver. The proportion of splenic to hepatic iron content was greater in SCD patients compared with TM patients (23.8% vs. 13.8%). A weak association was found between splenic and liver iron-this association was stronger in SCD patients. Little correlation was found between splenic iron and extrahepatic R2* values.

CONCLUSION

For spleen and liver tissue with the same R2* value, splenic R2 was significantly lower than hepatic R2, particularly for R2* > approximately 300 Hz. Splenic iron levels have little predictive value for R2* values of heart, pancreas, and kidney.

Non-invasive assessment of tissue iron overload

In recent years, there has been increasing interest in non-invasive iron measurement, especially of the liver and heart, in patients with iron overload. Serum ferritin still remains an essential monitoring parameter in intervals between liver iron measurements; however, confounding factors such as inflammation, chelation treatment changes and the specific disease have to be taken into account. Liver iron measurements can now routinely be performed in clinical applications either by quantitative magnetic resonance imaging (MRI) using the transverse magnetic relaxation rate R(2) or R(2)* (1/T(2)*) or by biomagnetic liver susceptometry. For iron measurements in the heart, the single-breathhold multi-echo MRI-R(2)* method has become a standard modality and is now applied in clinical settings beyond research studies. In other tissues like the pancreas, pituitary, and brain, different MRI methods are employed, but their clinical benefit has yet to be proven.

MRI evaluation of tissue iron burden in patients with beta-thalassaemia major

beta-Thalassaemia major is a hereditary haemolytic anaemia that is treated with multiple blood transfusions. A major complication of this treatment is iron overload, which leads to cell death and organ dysfunction. Chelation therapy, used for iron elimination, requires effective monitoring of the body burden of iron, for which serum ferritin levels and liver iron content measured in liver biopsies are used as markers, but are not reliable. MRI based on iron-induced T2 relaxation enhancement can be used for the evaluation of tissue siderosis. Various MR protocols using signal intensity ratio and mainstream relaxometry methods have been used, sometimes with discrepant results. Relaxometry methods using multiple echoes achieve better sampling of the time domain in which relaxation mechanisms take place and lead to more precise results. In several studies the MRI parameters of liver siderosis have failed to correlate with those of other affected organs, underlining the necessity for MRI iron evaluation in individual organs. Most studies have included children in the evaluated population, but MRI data on very young children are lacking. Wider application of relaxometry methods is indicated, with the establishment of universally accepted MRI protocols, and further studies, including young children, are needed.

Liver, bone marrow, pancreas and pituitary gland iron overload in young and adult thalassemic patients: a T2 relaxometry study

Thirty-seven patients with beta-thalassemia major, including 14 adolescents (15.2 +/- 3.0 years) and 23 adults (26.4 +/- 6.9 years), were studied. T2 relaxation time (T2) of the liver, bone marrow, pancreas and pituitary gland was measured in a 1.5-Tesla magnetic resonance (MR) imager, using a multiecho spin-echo sequence (TR/TE 2,000/20, 40, 60, 80, 100, 120, 140, 160 ms). Pituitary gland height was evaluated in a midline sagittal scan of a spin-echo sequence (TR/TE, 500/20 ms). The T2 of the pituitary gland was higher in adolescents (59.4 +/- 15 ms) than in adults (45.3 +/- 10.4 ms), P < 0.05. The T2 of the pancreas was lower in adolescents (43.6 +/- 10.3 ms) than in adults (54.4 +/- 10.4 ms). No difference among groups was found in the T2 of the liver and bone marrow. There was no significant correlation of the T2 among the liver, pancreas, pituitary gland and bone marrow. There was no significant correlation between serum ferritin and T2 of the liver, pancreas and bone marrow. Pituitary T2 showed a significant correlation with pituitary gland height (adolescents: R = 0.63, adults: R = 0.62, P < 0.05) and serum ferritin (adolescents: R = -0.60, adults: R = -0.50, P < 0.05). In conclusion, iron overload evaluated by T2 is organ specific. After adolescence, age-related T2 changes are predominantly associated with pituitary siderosis and fatty degeneration of the pancreas. Pituitary size decreases with progressing siderosis.