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  • American Society of Hematology  (2)
  • 1
    In: Blood, American Society of Hematology, Vol. 112, No. 11 ( 2008-11-16), p. 3877-3877
    Abstract: Segmental distribution of T2* values can be assessed in heart iron overloaded patients by multislice, multiecho cardiovascular MRI. A significant heterogeneity in T2* segmental distribution was demonstrated in previous studies in thalassemia major (TM) patients [1] and may represent true heterogeneous iron density or could be generated by geometric and susceptibility artefacts. In this study we investigate the relationship between T2* heterogeneity and iron overload progression in a large patient population in order to understand if susceptibility artefact may account for inhomogeneous T2* values segmental distribution. 230 TM patients consecutively affered to our laboratory were studied. Informed consent was obtained for all of them. MRI was performed using a 1.5 T MR scanner (GE Signa, CV/i). For the measurements of myocardial T2*, a fast gradient echo-multiecho sequence (FA=25°, matrix=256×192, FOV=35×35 cm, thickness=8.0 mm, NEX=0.75) was used with ECG triggering. Each slice was acquired at nine echo times (2.2–20.3 ms, with echo spacing of 2.26 ms) in a single end-expiratory breath-hold. Three short axis views (basal, medium, and apical) of the left ventricle were obtained and analyzed using a custom-written, previous validated software (HIPPO MIOT®) The myocardium was automatically segmented into a 16-segments standardized heart model and the T2* value on each segment was calculated as well as the global T2* value. The level of heterogeneity of the T2* segmental distribution on each patient was evaluated by computing the coefficient of variation (CoV) as the standard deviation of the absolute value of differences between the segmental T2* values and the global T2* value divided by their means, and expressed as the percentage. A surrogate data sets was obtained stating that the inhomogeneous segmental distribution of T2* would be generated only by susceptibility artefacts that are additive in the R2* (1/T2*) domain. These artefacts were characterized in a previous study by the analysis of the segmental T2* distribution in normal subject [2]. In 45 (20%) TM patients, segmental T2* values were all below the lower limit of normal (20 ms). In 104 (45%) patients, T2* values were heterogeneous with respect to the normal threshold. Of these patients, 74% showed a normal T2* global value. Eighty-one (35%) patients had all normal segments. Figure 1 shows the distribution of heterogeneous T2* among the patients population. Figure 2 shows the CoV in myocardial T2* distribution vs. the global T2* values in patients and surrogate data. Patients were sorted using the global T2* values and averaged on a 20-point window to smooth the resulting graph. Mean and normal global T2* value for healthy subjects were assessed in a previous study. Montecarlo simulation was performed on 10,000 surrogate data sets. For surrogate data, the mean CoV values together with the mean⊠2SD limits are shown. T2* heterogeneity for patients without iron overload was compatible with the hypothesis that the heterogeneity was generated by additive susceptibility artefacts. Below the normal limit of global T2* the heterogeneity abruptly increased of about 10%. Starting from this level, the heterogeneity decreased linearly returning to 25% in patients with high iron overload levels. Figure 2 shows In conclusion, a large percentage of thalassemia major patients shows a significant heterogeneity of segmental distribution of T2* values in myocardium, measured by multislice multiecho T2* cardiac magnetic resonance. T2* segmental heterogeneity in TM patients cannot be explained by the effect of susceptibility artefacts, that are additive and should vanish at high iron overload levels. A possible interpretation is that a true heterogeneity in iron overload distribution is present in TM patients. This heterogeneity seems more important in the early development of iron overload and reduces when the iron overload level increases. Figure 1 Figure 1. Figure 2 Figure 2.
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    RVK:
    RVK:
    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2008
    detail.hit.zdb_id: 1468538-3
    detail.hit.zdb_id: 80069-7
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  • 2
    In: Blood, American Society of Hematology, Vol. 112, No. 11 ( 2008-11-16), p. 5420-5420
    Abstract: Iron induced cardiomiopathy is the main cause of mortality in thalassemic population. Thus, the improvement of chelation regimens, to reduce cardiac disease, has the highest priority. Efficient evaluation of cardiac iron status and careful epidemiologic assessment of thalassemic patients play an important role in this matter. T2* magnetic resonance imaging (MRI) is a unique technique to quantify myocardial iron overload and useful to tailor the chelation therapy. Effective and reproducible assessment of myocardial iron loading using the multislice multiecho T2* approach for segmental and global myocardial iron distribution, has been demonstrated at the MRI centre in Pisa [1,2] . Aim of this work is to build within the MIOT (Myocardial Iron Overload in Thalassemia) project a reliable network of haematological and paediatric centers specializing in thalassemia care and MRI centers able to perform feasible and reproducible heart and liver iron overload assessments for a consistent number of thalassemia patients in a standardized and robust manner. First, the transferability of the multislice multiecho T2* technique was assessed. Heart multislice multiecho T2* and liver multiecho T2* sequences were installed on 1.5 T MRI scanners (GE Healthcare) at six different sites in Italy. Five healthy subjects at each site (n=30) were scanned to verify the homogeneity of normal ranges (T2* lover limit of normal 20ms). Then, five thalassemia major (TM) patients were scanned at the reference site and were rescanned locally (n=25) within one month. T2* images were analysed using a previously validated software (HIPPO MIOT®). T2* values of healthy subjects showed inter-sites homogeneity. On TM patients, for global heart T2* values the correlation coefficient was 0.97, Coefficients of Variation (CoVs) ranged from 0.04 to 0.12 and Intraclass Coefficients (ICCs) ranged from 0.94 to 0.99. The mean CoV and ICC for segmental T2* distribution were 0.198 and 88, respectively. After the assessment of MRI technique reproducibility, patients enrolling started in September 2006. Since the project’s beginning, 695 thalassemia patients have been involved in the network. Six hundred and thirteen patients (88%) successfully underwent MRI examination. Each MRI center had a specific absorption capacity that seemed to remain constant over time, but the network was capable of sustaining an increasing number of patients due to continuous enrolment of new centers. The mean distance from the patients’ home locations to the MRI centers where the patients underwent the exams, which is considered an indicator of patient comfort, significantly decreased during the network’s evolution. In Figure, the average distances from the thalassemia centers which sent the patients for MRI examination are plotted versus time. With the activation of delocalized MRI centers, average distances tend to be comparable. In conclusion, the multislice multiecho T2* technique is transferable among scanners with good reproducibility. The MIOT network seems to be a robust and scalable system in which T2* MRI-based cardiac and liver iron overload assessment is available, accessible and reachable for a significant and increasing number of thalassemia patients in Italy, reducing the mean distance from the patients’ locations to the MRI sites. A solid, wide and homogeneous database will constitute an important scientific resource, shortening the time scale for diagnostic, prognostic and therapeutical evidence-based research on the management of thalassemia disease. Figure Figure
    Type of Medium: Online Resource
    ISSN: 0006-4971 , 1528-0020
    RVK:
    RVK:
    Language: English
    Publisher: American Society of Hematology
    Publication Date: 2008
    detail.hit.zdb_id: 1468538-3
    detail.hit.zdb_id: 80069-7
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
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