Brunella Favilli

Improved T2* assessment in liver iron overload by magnetic resonance imaging

In the clinical MRI practice, it is common to assess liver iron overload by T2* multi-echo gradient-echo images. However, there is no full consensus about the best image analysis approach for the T2* measurements. The currently used methods involve manual drawing of a region of interest (ROI) within MR images of the liver. Evaluation of a representative liver T2* value is done by fitting an appropriate model to the signal decay within the ROIs vs. the echo time. The resulting T2* value may depend on both ROI placement and choice of the signal decay model. The aim of this study was to understand how the choice of the analysis methodology may affect the accuracy of T2* measurements. A software model of the iron overloaded liver was inferred from MR images acquired from 40 thalassemia major patients. Different image analysis methods were compared exploiting the developed software model. Moreover, a method for global semiautomatic T2* measurement involving the whole liver was developed. The global method included automatic segmentation of parenchyma by an adaptive fuzzy-clustering algorithm able to compensate for signal inhomogeneities. Global liver T2* value was evaluated using a pixel-wise technique and an optimized signal decay model. The global approach was compared with the ROI-based approach used in the clinical practice. For the ROI-based approach, the intra-observer and inter-observer coefficients of variation (CoVs) were 3.7% and 5.6%, respectively. For the global analysis, the CoVs for intra-observers and inter-observers reproducibility were 0.85% and 2.87%, respectively. The variability shown by the ROI-based approach was acceptable for use in the clinical practice; however, the developed global method increased the accuracy in T2* assessment and significantly reduced the operator dependence and sampling errors. This global approach could be useful in the clinical arena for patients with borderline liver iron overload and/or requiring follow-up studies.

A Fast and Effective Method to Assess Myocardial Necrosis by Means of Contrast Magnetic Resonance Imaging

PURPOSE Contrast magnetic resonance (CMR) can identify myocardial necrosis after gadolinium administration as a hyperenhanced (HE) area. Yet there are no software tools that can effectively quantify such an area. The aim of this study is to develop a robust and effective algorithmic method for defining the extent of myocardial necrosis evidenced through CMR. METHOD Fifteen patients with previous myocardial infarction underwent nitrate Tetrofosmin G-SPECT and CMR. A software tool was developed, allowing semiautomatic detection of endocardial and epicardial borders and the automatic detection of HE regions. The accuracy of the proposed quantitative method of analysis has been tested with G-SPECT analysis that it is less than an ideal method for assessing myocardial viability, but at present is accepted and widely used in the clinical arena. RESULTS Segmental (SEHE) and global extension of HE were evaluated. HE was present in 161 of the 255 analyzed segments. Of the 161 HE segments, the mean SEHE was 36 +/- 30%. The operator independence (intraobserver: r = 0.97, p < 0.0001, interobserver: r = 0.95, p < 0.0001) was good and significant, with noticeable time savings with respect to manual analysis. There was strong and inverse correlation between SEHE and scintigraphic regional uptake reduction (r = -0.66, p < 0.0001), and also a positive correlation between SEHE and SPECT defect extension (r = 0.75, p < 0.0001). When assessing the global extent of necrosis, the correlation between the two techniques was strong (r = 0.79, p = 0.0004). CONCLUSIONS The proposed method of quantifying myocardial necrosis by CMR is highly reliable, reproducible, and operator-independent for quantifying.

Myocardial scarring by delayed enhancement cardiovascular magnetic resonance in thalassaemia major

Background: Cardiovascular magnetic resonance (CMR) by delayed enhancement (DE) enables visualisation of myocardial scarring, but no dedicated studies are available in thalassaemia major. Objective: To investigate the prevalence, extent, clinical and instrumental correlates of myocardial fibrosis or necrosis by DE CMR in patients with thalassaemia major. Patients: 115 Patients with thalassaemia major consecutively examined at an MRI laboratory. Methods: DE images were acquired to quantify myocardial scarring. Myocardial iron overload was determined by multislice multiecho T2*. Cine images were obtained to evaluate biventricular function. Results: DE areas were present in 28/115 patients (24%). The mean (SD) extent of DE was 3.9 (2.4)%. In 26 patients the location of fibrosis was not specific and patchy distribution was prevalent. Two patients showed transmural DE following coronary distribution. The DE group was significantly older than the no-DE group (31 (7.7) years vs 26 (7.7) years, p = 0.004). No significant relation with heart T2* values and biventricular function was found. A significant correlation was found between the presence of DE and changes in ECG (ECG abnormal in the DE group 22/28 patients and in the no-DE group 30/87 patients; χ2 = 14.9; p<0.001). Conclusions: In patients with thalassaemia the significant presence of myocardial fibrosis/necrosis seems to be a time-dependent process correlating with cardiovascular risk factors and cardiac complications. Levels of HCV antibodies are significantly higher in the serum of patients with thalassaemia with myocardial fibrosis/necrosis. ECG changes showed a good accuracy in predicting myocardial scarring.

Single region of interest versus multislice T2* MRI approach for the quantification of hepatic iron overload

To evaluate the effectiveness of the single ROI approach for the detection of hepatic iron burden in thalassemia major (TM) patients in respect to a whole liver measurement.

Multislice multiecho T2* cardiac magnetic resonance for the detection of heterogeneous myocardial iron distribution in thalassaemia patients

The present study investigated myocardial T2* heterogeneity in thalassaemia major (TM) patients by cardiac magnetic resonance (CMR), to determine whether is related to inhomogeneous iron overload distribution. A total of 230 TM patients consecutively referred to our laboratory were studied retrospectively. Three short‐axis views (basal, medium and apical) of the left ventricle (LV) were obtained by multislice multiecho T2* CMR. T2* segmental distribution was mapped on a 16‐segment LV model. The level of heterogeneity of the T2* segmental distribution, evaluated by the coefficient of variation (CoV), was compared with that of a surrogate data set, to determine whether the inhomogeneous segmental distribution of T2* could be generated by susceptibility artefacts. Susceptibility artefacts offer an explanation for the T2* heterogeneity observed in patients without iron overload. In subjects with global T2* below the lower limit of the normal, T2* heterogeneity increased abruptly which could not be explained by artefactual effects. Some segmental T2* values were below and others above the limit of normal threshold (20 ms) in 104 (45%) TM patients. Among these patients, 74% showed a normal T2* global value. In conclusion, a true heterogeneity in the iron overload distribution may be present in TM patients. Heterogeneity seemingly appears in the borderline myocardial iron and stabilizes at moderate to severe iron burden. Copyright

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

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

Evaluation of left ventricular diastolic function with a dedicated cadmium-zinc-telluride cardiac camera: comparison with Doppler echocardiography

AIMS To evaluate the relationships between measures of left ventricular (LV) filling dynamics at cadmium-zinc-telluride (CZT) imaging and indexes of LV diastolic function at transthoracic echocardiography. METHODS AND RESULTS Two hundred and forty-seven patients underwent myocardial perfusion imaging at rest and after stress with a low-dose CZT protocol and a baseline transthoracic echocardiography study. All patients were submitted to invasive or computed coronary angiography. The peak filling rate (PFR) and the time to PFR (TPFR) were derived from gated CZT images as measures of LV filling dynamics. LV diastolic function was also evaluated at echocardiography and the presence of significantly increased LV filling pressures determined. Increased LV filling pressures at transthoracic echocardiography were evident in 103 (42%) patients. Interestingly, independently from the presence of coronary artery disease, there was a strict correlation between the presence and severity of LV diastolic dysfunction at echocardiography and CZT-derived measures of filling dynamics, i.e., PFR (P = 0.001) and TPFR (P = 0.001). At receiving operating characteristic analysis, a composite index of reduced PFR (≤2.11 end-diastolic volume s(-1)) and increased TPFR (>234 ms) showed a sensitivity of 84% and a specificity of 67% in unmasking the presence of elevated LV filling pressures at echocardiography. CONCLUSIONS CZT-derived measures of LV filling dynamics correlate with echocardiographic parameters of diastolic function and may identify the presence of increased LV filling pressures.

Left Ventricular Volumes, Mass and Function Normalized to the Body Surface Area, Age and Gender From CMR in a Large Cohort of Well-Treated Thalassemia Major Patients without Myocardial Iron Overload

Cardiovascular Magnetic Resonance (CMR) allows an accurate and reproducible quantification of left ventricular (LV) parameters. In Thalassemia major (TM) patients have been reported different “normal” LV values due to chronic anemia and eventually pre-existing iron burdens. Moreover, in this population it is unknown the influence of sex and age on LV parameters and no ranges of normal have been reported using MASS® software. The aim of this study was to establish the ranges for normal LV volumes, mass and ejection fraction normalized to the influence of body surface area(BSA), age and sex from CMR in a large cohort of well-treated TM patients without myocardial iron overload.

Myocardial perfusion by first pass contrast magnetic resonance: a robust method for quantitative regional assessment of perfusion reserve index

Assessing myocardial perfusion is a key issue in the diagnosis and subsequent treatment of patients with coronary artery disease (CAD).1,2 A single magnetic resonance (MR) examination can assess perfusion by monitoring the upslope of the signal change in dependence on the first pass of gadolinium derivatives. We propose a method of evaluating the regional distribution of the perfusion reserve index (PRI), defined as the ratio between stress and resting upslopes. The PRI regional distribution was assessed in patients with and without CAD and a PRI cut off was identified. Thirty two patients (mean (SD) age 65 (10) years, 20 men) underwent MR imaging and quantitative coronary angiography to assess the presence of coronary artery stenoses. The protocol was approved by the institutional ethics committees and informed consent was obtained from all patients. MR images were acquired with a GE Signa 1.5 T scanner during gadolinium-diethylenetriaminepentaacetic acid (DTPA) infusion (Omniscan, Nycomed Imaging, Roskilde, Denmark) into a cubital vein (0.1 mmol/kg, 5 ml/s) followed by 10 ml of saline flush. A cardiac array coil was used, with fast gradient echo with an echo train readout sequence. For each examination, three 256 × 256 short axis slices (basal, middle, and distal) were acquired in the diastolic phase during an RR interval with a slice thickness of 8 mm. The acquisition was repeated along 60 RR intervals. All the patients were asked to hold their …

Right Ventricular Volumes and Function normalized to body surface area, age and sex in a large cohort of well-treated Thalassemia Major without myocardial iron overload

Cardiovascular Magnetic Resonance CMR has provided the opportunity to quantify right ventricular (RV) parameters with excellent reproducibility and accuracy. The role of the RV is gaining ground in thalassemia major (TM) patients and this population could experience different “normal” RV values due to chronic anemia and eventually pre-existing iron burdens. In literature, there are no data on the ranges for “normal” RV volumes and ejection fraction (EF) in TM patients. The aim of this study was to establish the ranges for normal RV volumes, mass and ejection fraction normalized to the influence of body surface area (BSA), age and sex from CMR in a large cohort of well-treated TM patients without myocardial iron overload.