Preferential patterns of myocardial iron overload by multislice multiecho T*2 CMR in thalassemia major patients

T*₂ multislice multiecho cardiac MR allows quantification of the segmental distribution of myocardial iron overload. This study aimed to determine if there were preferential patterns of myocardial iron overload in thalassemia major. Five hundred twenty‐three thalassemia major patients underwent cardiac MR. Three short‐axis views of the left ventricle were acquired and analyzed using a 16‐segment standardized model. The T*₂ value on each segment was calculated, as well as the global value. Four main circumferential regions (anterior, septal, inferior, and lateral) were defined. Significant segmental variability was found in the 229 patients with significant myocardial iron overload (global T*₂ <26 ms), subsequently divided into two groups: severe (global T*₂ <10 ms) and mild to moderate (global T*₂ between 10 and 26 ms) myocardial iron overload. A preferential pattern of iron store in anterior and inferior regions was detected in both groups. This pattern was preserved among the slices. The pattern could not be explained by additive susceptibility artifacts, negligible in heavily iron‐loaded patients. A significantly higher T*₂ value in the basal slice was found in patients with severe iron overload. In conclusion, a segmental T*₂ cardiac MR approach could identify early iron deposit, useful for tailoring chelation therapy and preventing myocardial dysfunction in the clinical setting. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Feasibility, reproducibility, and reliability for the T*2 iron evaluation at 3 T in comparison with 1.5 T

This study aimed to determine the feasibility, reproducibility, and reliability of the multiecho T*₂ Magnetic resonance imaging technique at 3 T for myocardial and liver iron burden quantification and the relationship between T*₂ values at 3 and 1.5 T. Thirty‐eight transfusion‐dependent patients and 20 healthy subjects were studied. Cardiac segmental and global T*₂ values were calculated after developing a correction map to compensate the artifactual T*₂ variations. The hepatic T*₂ value was determined over a region of interest. The intraoperator and interoperator reproducibility for T*₂ measurements at 3 T was good. A linear relationship was found between patients' R (1000/T*₂) values at 3 and 1.5 T. Segmental correction factors were significantly higher at 3 T. A conversion formula returning T*₂ values at 1.5 T from values at 3 T was proposed. A good diagnostic reliability for T*₂ assessment at 3 T was demonstrated. Lower limits of normal for 3 T T*₂ values were 23.3 ms, 21.1 ms, and 11.7 ms, for the global heart, mid‐ventricular septum, and liver, respectively. In conclusion, T*₂ quantification of iron burden in the mid‐ventricular septum, global heart, and no heavy–moderate livers resulted to be feasible, reproducible, and reliable at 3 T. Segmental heart T*₂ analysis at 3 T may be challenging due to significantly higher susceptibility artifacts. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

Interscanner reproducibility of cardiovascular magnetic resonance T2* measurements of tissue iron in thalassemia

PURPOSE: To assess interscanner reproducibility of tissue iron measurements in patients with thalassemia using gradient echo T2* measurements on two different MRI scanners. MATERIALS AND METHODS: Twenty-five patients with thalassemia major had liver and myocardial T2* assessment using a Picker Edge 1.5T Scanner and a Siemens Sonata 1.5T scanner, with similar gradient echo sequences. In a subset of 13 patients, two scans on the Siemens scanner were performed to assess interstudy reproducibility. RESULTS: There was a highly significant, linear correlation between T2* values obtained for both the heart (r = 0.95) and the liver (r = 0.99) between scanners. The mean difference, coefficient of variability, and 95% confidence intervals between scanners were 0.8 msec, 9.4% and -5.0 to 6.7 msec for the heart; and 0.9 msec, 7.9% and -2.0 to 3.9 msec for the liver. The interstudy mean difference and coefficient of variability on the Siemens scanner was 0.3 msec and 4.8% (r = 0.99) for the heart, and 0.04 msec and 1.9% (r = 0.99) for the liver. CONCLUSION: The T2* technique for measuring tissue iron is reproducible between the two manufacturers' scanners. This suggests that the widespread implementation of the technique is possible for clinical assessment of myocardial iron loading in thalassemia.     

Multicenter validation of the magnetic resonance t2* technique for segmental and global quantification of myocardial iron

Purpose

To assess the transferability of the magnetic resonance imaging (MRI) multislice multiecho T2* technique for global and segmental measurement of iron overload in thalassemia patients.

Materials and Methods

Multiecho T2* sequences were installed on six MRI scanners. Five healthy subjects (n = 30) were scanned at each site; five thalassemia major (TM) patients were scanned at the reference site and were rescanned locally (n = 25) within 1 month. T2* images were analyzed using previously validated software.

Results

T2* values of healthy subjects showed intersite homogeneity. On TM patients, for global heart T2* values the correlation coefficient was 0.97, coefficients of variation (CoV_s) ranged from 0.04–0.12, and intraclass coefficients (ICC_s) ranged from 0.94–0.99. The mean CoV and ICC for segmental T2* distribution were 0.198 and 88, respectively.

Conclusion

The multislice multiecho T2* technique is transferable among scanners with good reproducibility. J. Magn. Reson. Imaging 2009;30:62–68. © 2009 Wiley‐Liss, Inc.     

Multislice multiecho T2* cardiovascular magnetic resonance for detection of the heterogeneous distribution of myocardial iron overload

PURPOSE: To assess the tissue iron concentration of the left ventricle (LV) using a multislice, multiecho T2* MR technique and a segmental analysis. MATERIALS AND METHODS: T2* multiecho MRI was performed in 53 thalassemia major patients. Three short-axis views of the LV were obtained and analyzed with custom-written software. The myocardium was automatically segmented into 12 segments. The T2* value on each segment as well as the global T2* value were calculated. Cine dynamic images were also obtained to evaluate biventricular function parameters by quantitative analysis. RESULTS: For the T2* global value, the coefficient of variation (CoV) for intra-/interobserver and interstudy reproducibility was 3.9% (r = 0.98), 5.5% (r = 0.98), and 4.7% (r = 0.99) respectively. Three groups were identified based on analysis of myocardial T2*: homogeneous (21%), heterogeneous (38%), and no myocardial iron overload (41%). The mean serum ferritin, liver iron concentration, and urinary iron excretion were significantly different among the groups. We did not find significant differences among groups in biventricular function. There was a correlation between the global T2* value and the T2* value in the mid-ventricular septum (r = 0.95, P < 0.0001). CONCLUSION: Multislice multiecho T2* MRI provides a noninvasive, fast, reproducible means of assessing myocardial iron distribution. The single measurement of mid-septal T2* correlated well with the global T2* value.     

Left ventricular diastolic function compared with T2* cardiovascular magnetic resonance for early detection of myocardial iron overload in thalassemia major

PURPOSE: To compare left ventricular (LV) diastolic function with myocardial iron levels in beta thalassemia major (TM) patients, using cardiovascular magnetic resonance (CMR). MATERIALS AND METHODS: We studied 67 regularly transfused patients with TM and 22 controls matched for age, gender, and body surface area. The early peak filling rate (EPFR) and atrial peak filling rate (APFR) were determined from high-temporal-resolution ventricular volume-time curves. Myocardial iron estimation was achieved using myocardial T2* measurements. RESULTS: Myocardial iron loading was found in 46 TM patients (69%), in whom the EPFR correlated poorly with T2* (r = -0.20, P = 0.19). The APFR (r = 0.49, P < 0.001) and EPFR/APFR ratio (r = -0.62, P < 0.001) correlated better with T2*. The sensitivity of the diastolic parameters for detecting myocardial iron loading ranged from 4% (EPFR and APFR) to 17% (EPFR/APFR ratio). CONCLUSION: Myocardial iron overload results in diastolic myocardial dysfunction, but low sensitivity limits the use of a single estimation for early detection of iron overload, for which T2* has a superior categorical limit of normality.     

Influence of myocardial fibrosis and blood oxygenation on heart T2* values in thalassemia patients

Purpose

To determine whether T2* measurements quantifying myocardial iron overload in thalassemia patients are influenced by myocardial fibrosis and blood oxygenation.

Materials and Methods

Multislice multiecho T2* was performed in 94 thalassemia patients in order to quantify myocardial iron overload. The left ventricle was automatically segmented into a 16‐segment standardized heart model, and the T2* value on each segment as well as the global T2* were calculated. Delayed enhanced cardiovascular magnetic resonance (DE‐CMR) images were obtained to detect myocardial fibrosis. The blood oxygenation was assessed by the noninvasive measurement of partial pressure of oxygen (pO2).

Results

Myocardial fibrosis was detected in 31 patients (33%). The global T2* value in patients with fibrosis was comparable with that of patients without fibrosis (P = 0.88) and T2* values in segments with fibrosis were comparable with those in segments without fibrosis (P = 0.83). The global T2* value was not correlated with the pO2 (Spearman's coefficient of correlation = 0.99).

Conclusion

Myocardial fibrosis and blood oxygenation did not significantly affect the T2* values. These data further support the use of heart T2* as equivalent of heart iron in the clinical arena. J. Magn. Reson. Imaging 2009;29:832–837. © 2009 Wiley‐Liss, Inc.     

A new approach towards improved visualization of myocardial edema using T2-weighted imaging: a cardiovascular magnetic resonance (CMR) study

Purpose:

To compare T2‐weighted cardiovascular magnetic resonance (CMR) imaging with AASPIR (asymmetric adiabatic spectral inversion recovery) and STIR (short T1 inversion recovery) for myocardial signal intensity, image quality, and fat suppression.

Materials and Methods:

Forty consecutive patients (47 ± 16 years old) referred by cardiologists for CMR‐based myocardial tissue characterization were scanned with both STIR and AASPIR T2‐weighted imaging approaches. Signal intensity of left ventricular myocardium was normalized to a region of interest generating a signal‐to‐noise ratio (SNR). In six patients with regional edema on STIR the contrast‐to‐noise ratio (CNR) was assessed. Two independent observers used a scoring system to evaluate image quality and artifact suppression. Six healthy volunteers (three males, 32 ± 7 years) were recruited to compare fat suppression between AASPIR and STIR.

Results:

SNR of AASPIR was greater than STIR for basal (128 ± 44 vs. 83 ± 40, P < 0.001), mid‐ (144 ± 65 vs. 96 ± 39, P < 0.01), and apical (145 ± 59 vs. 105 ± 35, P < 0.05) myocardium. Improved image quality and greater suppression of artifacts was demonstrated with AASPIR. In patients with regional edema, CNR increased by 49% with AASPIR, while SNR of pericardial fat did not differ (44 ± 39 vs. 33 ± 30, P > 0.05).

Conclusion:

Our findings support the implementation of an AASPIR‐based approach for T2‐weighted imaging due to improved pericardial fat suppression, image quality, and artifact suppression with greater CNR and SNR. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Fast T2 mapping of the patellar articular cartilage with gradient and spin-echo magnetic resonance imaging at 1.5 T: validation and initial clinical experience in patients with osteoarthritis

Objective To evaluate the T2 mapping of patellar articular cartilage in patients with osteoarthritis using gradient and spin-echo (GRASE) magnetic resonance (MR) imaging. Materials and methods After the imaging of a phantom consisting of two sealed 50-ml test objects with different concentrations (30% and 90% weight/volume) of copper sulphate, the T2 mapping of patellar articular cartilage was performed in 35 patients (21 male and 14 female; mean age ± SD 42 ± 17 years) with moderate degree of patellar osteoarthritis. Turbo-spin-echo (TSE) (TR milliseconds/minimum–maximum TE milliseconds 3,000/15–120; total acquisition time 5 min 52 s) and GRASE (TR milliseconds/minimum–maximum TE milliseconds 3,000/15–120; total acquisition time 1 min 51 s) were employed. In each patient patellar cartilage was segmented at nine locations (three superior, three central, and three inferior) by manually defined regions of interest. T2 relaxation times were calculated using a linear fit applied to the logarithm of signal intensity decay. Results In the phantom the T2 values measured by GRASE were similar to those measured by MR spectroscopy (test object 1: 48.1 ms vs 51 ms; test object 2: 66.8 ms vs 71 ms; P > 0.05, Wilcoxon test). In patients GRASE and TSE-derived T2 values demonstrated good agreement (mean difference ± SD, 1.81 ± 3.63 ms). The within-patient coefficient of variation was 22% for TSE and 23% for GRASE. Conclusion Fast T2 mapping of the patellar articular cartilage can be performed with GRASE within a third of the time of that of standard sequences. This study was performed thanks to the support of a private grant, “Arduino Ratti”, provided through the Italian Society of Medical Radiology.     

T_2~*值在慢性肝病肝纤维化定量评价中的作用初探

目的探讨T_2*值在定量评估慢性肝病肝纤维化分级中的价值。方法回顾性分析2012年12月—2015年12月收治的慢性肝病肝纤维化病人66例,根据肝纤维化分期将病人(男42例、女24例,中位年龄40岁)分为5组,S0组(24例)、S1组(20例)、S2组(11例)、S3组(6例)、S4组(5例)。所有病人均行常规MRI扫描及屏气多回波T_2*加权成像,测得T_2*值。对5组影像的T_2*值进行分析,相关性分析采用Spearman秩相关分析,多组间比较采用Kruskal-Wallis H检验,进一步两两比较采用Mann-Whitney U检验。应用ROC曲线评估T_2*值预测肝纤维化程度的能力。结果不同分期的肝纤维化病人间T_2*值比较差异有统计学意义(H=28.954,P0.001);进一步组间比较,除S3与S4组间比较T_2*值差异无统计学意义(P0.05),其余各组两两比较均有统计学意义(P0.05)。慢性肝病肝纤维化程度与T_2*值呈负相关(rs=-0.665,P0.001);T_2*值在定量评估有无肝纤维化(≥S1)和中重度肝纤维化(≥S2和≥S3)的ROC曲线下面积(AUC)分别为0.988、0.814、0.812,约登指数分别为96.8%、69.3%、54.2%,敏感度分别为100%、79%、91.7%,特异度分别为96.8%、90.3%、57.1%。结论T_2*值对于量化评估慢性肝病肝纤维化分级有一定的临床价值。     

Abnormalities in T2-weighted cardiovascular magnetic resonance images of hypertrophic cardiomyopathy: regional distribution and relation to late gadolinium enhancement and severity of hypertrophy

PURPOSE: To explore if focal T2 abnormalities accompany late gadolinium enhancement (LGE) lesions in hypertrophic cardiomyopathy (HCM). MATERIALS AND METHODS: All studies were performed under the guidelines of the local ethics committee, which approved the study, and a written informed consent was obtained from each subject. We studied 27 patients (24 males, 51 +/- 18 years) with HCM and evidence for myocardial injury as defined by LGE. The following sequences were performed: steady-state free precession (SSFP) (ventricular volumes, mass, and function), T2-weighted triple inversion-recovery spin-echo and inversion-recovery gradient-echo 10 minutes after intravenous (IV) gadolinium-DTPA (late enhancement). RESULTS: Focal high T2 signal intensity (SI) frequently matching areas of LGE was observed in nine patients (33%). The presence of these abnormalities correlated with more severe left ventricular hypertrophy (1.5 +/- 0.6 vs. 1.0 +/- 0.4 g/cm; P < 0.05). CONCLUSION: In this observational study, we identified focal T2 abnormalities in a subgroup of HCM patients. T2 abnormalities are associated with severe left ventricular hypertrophy. This may provide new insights into the mechanisms of focal irreversible injury in HCM and help in managing these patients.     

Quantification of the magnetic resonance signal response to dynamic (C)O2‐enhanced imaging in the brain at 3 T: R*2 BOLD vs. balanced SSFP

Purpose:

To compare two magnetic resonance (MR) contrast mechanisms, R*₂ BOLD and balanced SSFP, for the dynamic monitoring of the cerebral response to (C)O₂ respiratory challenges.

Materials and Methods:

Carbogen and CO₂‐enriched air were delivered to 9 healthy volunteers and 1 glioblastoma patient. The cerebral response was recorded by two‐dimensional (2D) dynamic multi‐gradient‐echo and passband‐balanced steady‐state free precession (bSSFP) sequences, and local changes of R*₂ and signal intensity were investigated. Detection sensitivity was analyzed by statistical tests. An exponential signal model was fitted to the global response function delivered by each sequence, enabling quantitative comparison of the amplitude and temporal behavior.

Results:

The bSSFP signal changes during carbogen and CO₂/air inhalation were lower compared with R*₂ BOLD (ca. 5% as opposed to 8–13%). The blood‐oxygen‐level‐dependent (BOLD) response amplitude enabled differentiation between carbogen and CO₂/air by a factor of 1.4–1.6, in contrast to bSSFP, where differentiation was not possible. Furthermore, motion robustness and detection sensitivity were higher for R*₂ BOLD.

Conclusion:

Both contrast mechanisms are well suited to dynamic (C)O₂‐enhanced MR imaging, although the R*₂ BOLD mechanism was demonstrated to be superior in several respects for the chosen application. This study suggests that the R*₂ BOLD and bSSFP‐response characteristics are related to different physiologic mechanisms. J. Magn. Reson. Imaging 2010;31:1300–1310. © 2010 Wiley‐Liss, Inc.     

Evaluation of small (<or=2 cm) dysplastic nodules and well-differentiated hepatocellular carcinomas with ferucarbotran-enhanced MRI in a 1.0-T MRI unit: utility of T2*-weighted gradient echo sequences with an intermediate-echo time

PURPOSE: To evaluate the detectability and signal intensities of small (相似文献