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ABSTRACT: OBJECTIVE: To assess changes in diffusion properties in the fetal lung after cortisone administration with diffusion-weighted imaging (DWI) in fetal sheep. METHODS: DWI was performed on 11 pregnant sheep with singleton pregnancies on a 1.5-T MRI scanner. Four animals received cortisone injections before baseline imaging. Seven animals served as controls. Apparent diffusion coefficient (ADC) was measured on DWI in the fetal lungs by two independent readers. The Pearson test was used to correlate ADC and gestational age. A t-test was performed to compare differences in ADC values at the baseline and follow-up images within and between groups. Inter-rater reliability was calculated. RESULTS: In the cortisone group, ADC values increased about 10 % between the baseline and follow-up images (P = 0.039). Comparing the cortisone and control groups, ADC values of the baseline images did not differ; whereas in the follow-up imaging, ADC values were significantly higher in the cortisone group (P = 0.024). Lung ADC values did not correlate with gestational age (P = 0.970). Inter-rater reliability was high (0.970, P = 0.000). CONCLUSION: In this experimental model, MR-DWI can detect cortisone-induced changes in diffusion properties of the fetal lung. KEY POINTS : • Corticosteroids are frequently administered antenatally to prevent fetal lung immaturity at birth • DWI can detect changes in the fetal lung after corticosteroid administration • Changes can be detected as early as 5 days after treatment • Fetal MRI may offer a non-invasive method of monitoring lung maturation.
European Radiology 02/2013; · 3.22 Impact Factor
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ABSTRACT: Changes in water diffusion can be quantified by diffusion-weighted MR imaging. However, there are only few reports about changes in post mortem brain. The aim of this study was to investigate the temporal pattern of the apparent diffusion coefficient (ADC) in the brain after death, to compare the values to in vivo brain and to assess the value of ex vivo DWI as a forensic tool.
The study was approved by the local Ethics Committee, and informed consent was obtained from all relatives and the control subjects. Twenty-one corpses, died of natural cause, were examined (13 males, 8 females; age: 70.5±8.7 y, weight 74±18 kg). Diffusion-Weighted Imaging (DWI) was performed with b-values of 0 and 1000 s/mm(2) at 1.5 T. Scans were repeated in intervals of 1 h. ADC-maps were calculated in thalamus, cerebrum and cerebellum. The obtained values were statistically compared to healthy volunteers (n=3) and to literature data.
The ADC in the three regions decreased characteristically during the examination time. In the cerebrum there was a significant difference between ex vivo and in vivo ADC (p<0.001) as well as in the other regions (thalamus: p<0.001, cerebellum: p=0.045).
DWI of the postmortal brain can be added to the MRI methods for a post mortem imaging.
Forensic science international 03/2012; 220(1-3):180-3. · 2.10 Impact Factor
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ABSTRACT: To investigate MRI of the fetal heart by way of a novel triggering method with the use of an MR-compatible cardiotocography (CTG) in an animal model.
Fetal cardiac MRI was performed on four pregnant ewes on a 1.5 Tesla (T) MR system. A CTG was rendered MR compatible and its signal was used for the triggering of the fetal heart to perform cardiac cine MRI of the fetal heart with maternal free-breathing with cine steady-state free precession. The left ventricular volume and function were measured from the short-axis (view). The image quality of anatomical structures was assessed.
All cardiac valves and the foramen ovale could be visualized. Myocardial contraction was depicted in cine sequences. The average blood volume at the end systole was 1.7 mL (SD ± 0.12). The average volume at the end diastole was 4.6 mL (± 0.4); thus the average stroke volumes of the left ventricle were 2.87 mL (± 0.31) with ejection fractions of 60.53% (± 4.17).
The newly developed MR compatible CTG could be used as a tool for cardiac triggering method of the fetal heart. This novel device might help fetal cardiac MRI technology in the future.
Journal of Magnetic Resonance Imaging 01/2012; 35(5):1071-6. · 2.70 Impact Factor
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ABSTRACT: Patients with β-thalassemia major at risk of cardiac iron overload have to be identified to undergo myocardial iron measurements by magnetic resonance imaging (MRI), especially, in areas and centers with restricted access to MRI. Measurements of heart iron, liver iron, and pancreatic exocrine function were performed in 44 patients by MRI-R2* [the transverse relaxation rate R2* (= 1/T2*) characterizes the magnetic resonance decay from protons not being in phase with each other in contrast to R2 (= 1/T2)], biomagnetic liver susceptometry (LIC), and pancreatic serum amylase (PAM) and lipase (LIP), respectively. ROC analysis (area: 0.88) for detecting patients with cardiac R2* > 50 sec−1 (T2* < 20 msec) by LIP revealed a cut-off level of 19 U/L. In conclusion, patients at risk of elevated cardiac iron levels could be identified by the exocrine pancreatic lipase and amylase function parameters. Pediatr Blood Cancer 2011; 57: 674–676. © 2011 Wiley-Liss, Inc.
Pediatric Blood & Cancer 09/2011; 57(4):674 - 676. · 1.89 Impact Factor
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ABSTRACT: Patients with β-thalassemia major at risk of cardiac iron overload have to be identified to undergo myocardial iron measurements by magnetic resonance imaging (MRI), especially, in areas and centers with restricted access to MRI. Measurements of heart iron, liver iron, and pancreatic exocrine function were performed in 44 patients by MRI-R2* [the transverse relaxation rate R2* (= 1/T2*) characterizes the magnetic resonance decay from protons not being in phase with each other in contrast to R2 (= 1/T2)], biomagnetic liver susceptometry (LIC), and pancreatic serum amylase (PAM) and lipase (LIP), respectively. ROC analysis (area: 0.88) for detecting patients with cardiac R2* > 50 sec(-1) (T2* < 20 msec) by LIP revealed a cut-off level of 19 U/L. In conclusion, patients at risk of elevated cardiac iron levels could be identified by the exocrine pancreatic lipase and amylase function parameters.
Pediatric Blood & Cancer 06/2011; 57(4):674-6. · 1.89 Impact Factor
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ABSTRACT: To investigate the self-gating technique for MR imaging of the fetal heart in a sheep model.
MR images of 6 fetal sheep heart were obtained at 1.5 T. For self-gating MRI of the fetal heart a cine SSFP in short axis, two and four chamber view was used. Self-gated images were compared with real cardiac triggered MR images (pulse-wave triggering). MRI of the fetal heart was performed using both techniques simultaneously. Image quality was assessed and the left ventricular volume and function were measured and compared.
Compared with pulse-wave triggering, the self-gating technique produced slightly inferior images with artifacts. Especially the atrial septum could not be so clearly depicted. The contraction of the fetal heart was shown in cine sequences in both techniques. The average blood volumes could be measured with both techniques with no significant difference: at end-systole 3.1 ml (SD±0.2), at end-diastole 4.9 ml (±0.2), with ejection fractions at 38.6%, respectively 39%.
Both self-gating and pulse-wave triggered cardiac MRI of the fetal heart allowed the evaluation of anatomical structures and functional information. Images obtained by self-gating technique were slightly inferior than the pulse-wave triggered MRI.
European Radiology 01/2011; 21(1):142-9. · 3.22 Impact Factor
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ABSTRACT: The aim of this study was to perform fetal magnetic resonance angiography (MRA) in utero in a sheep model.
Images of the great vessels, the heart, and the tracheal tree were performed on four pregnant ewes with a 1.5-T scanner (Philips Medical Systems, Best, The Netherlands). MRA was achieved in utero using a nontriggered free-breathing three-dimensional balanced fast field echo (FFE) technique. All obtained MRA images were evaluated in consensus on a three-point scale by two radiologists with 9 and 4 years of experience in fetal MRI, respectively.
The fetal heart frequencies were between 130 and 160 bpm. The aorta from the aortic bulb to the bifurcation as well as some of the main aortic branches could be depicted. The pulmonary trunk and arteries, the superior and inferior caval veins, and the subsegmental branches of the trachea could also be visualized.
The nontriggered MRA of the fetal great vessels with images of the tracheal tree allowed an excellent evaluation of anatomical structures.
Japanese journal of radiology 12/2010; 28(10):720-6. · 0.65 Impact Factor
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ABSTRACT: To assess regional iron distribution by magnetic resonance imaging (MRI)-R(2)* within the heart of patients with β-thalassemia major (TM) and other iron overload diseases.
Breathhold electrocardiogram (ECG)-gated MRI (1.5 T) of the heart was used for the measurement of transverse relaxation rates R(2)* in 32 patients (11-79 years). In a mid-papillary short-axis slice divided into septal, anterior, lateral, and posterior quadrants, R(2)* was analyzed from region of interest (ROI)-based signal intensities from 12 echo times (TE = 1.3-26 msec). Typical boundary effects were evaluated in detail.
The segmentation of the cardiac wall resulted in highly significant correlations of R(2)* between septal and all other quadrants. In the patient group with R(2)* < 50 s(-1) (normal), all quadrants show higher normalized median rates (126%-174%) than the septum (P < 10(-4)), while this was relatively smaller in the group with septal R(2)* > 50 s(-1). Typical boundary effects on segmental R(2)* from blood, lung tissue, epicardial fat, and hepatic iron could not be easily separated from segmental iron distribution.
The measurement of MRI-R2* in the interventricular septum is the least affected method by boundary effects to detect patients with iron overload at risk of developing heart failure.
Journal of Magnetic Resonance Imaging 11/2010; 32(5):1104-9. · 2.70 Impact Factor
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ABSTRACT: The purpose of this study was to assess the feasibility to determine fetal blood oxygen saturation (sO(2)) with T(2)-weighted MR sequences using a fetal sheep model. T(2) measurements were performed on a 1.5-T scanner using a T(2) preparation pulse in combination with a three-dimensional balanced steady-state free precession sequence repeated at different echo times. Eight sheep fetuses were examined during a control, hypoxic, and recovery phase to perform T(2)-weighted scans of the fetal blood in the heart. Signal intensities in the left and right ventricle were measured to calculate the MR blood sO(2). During each phase, fetal carotid artery sO(2) was directly measured and correlated with MR sO(2). A Bland-Altman plot was performed. Fetal carotid artery sO(2) was 69% sO(2) during control, 16% sO(2) during hypoxemia, and 67% sO(2) during recovery. Mean values of the MR sO(2) were 49% sO(2) and 40% sO(2) for control, 6% sO(2) and 3% sO(2) for hypoxemia, and 51% sO(2) and 43% sO(2) for recovery in left ventricle and right ventricle, respectively. Mean values of fetal carotid artery sO(2) and MR sO(2) were highly correlated (left ventricle: r = 0.87, right ventricle: r = 0.89). According to the Bland-Altman plot, MR sO(2) was lower compared to fetal carotid artery sO(2) (left ventricle: 15%, right ventricle: 20%). Based on our preliminary results, it seems to be possible to assess fetal sO(2) with MR oximetry.
Magnetic Resonance in Medicine 07/2010; 64(1):32-41. · 2.96 Impact Factor
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ABSTRACT: To investigate the feasibility of fetal blood oxygen level-dependent magnetic resonance (MR) imaging at 1.5 T and to compare DeltaR2* in the brains of fetal sheep during hypoxia at 3.0 T with that at 1.5 T.
All experimental protocols were reviewed and approved by the local authorities on animal protection. Between January 2006 and May 2006, fetal brain measurements were performed in eight pregnant ewes with 1.5-T and 3.0-T MR imaging units after fetal paralysis was achieved by administering pancuronium bromide. With both imaging units, a T2*-weighted single-shot gradient-echo echo-planar imaging sequence (echo time, 30 msec at 3.0 T and 50 msec at 1.5 T) was used to measure T2* signal changes (DeltaR2*) in the fetal brain in control conditions and during hypoxia (maternal oxygenation, 50%-70%). A carotid catheter was placed and maintained in the fetuses to enable measurement of the fetal arterial oxygen saturation (SaO(2)). DeltaR2* was correlated with fetal SaO(2), and linear regression analysis was performed. A paired t test was used to evaluate differences, with a significance level of P < .05.
At both field strengths, a signal intensity decrease on T2*-weighted images during hypoxia was detected. At 1.5 T, mean fetal SaO(2) was reduced from 65.4% +/- 9.2 (standard deviation) during control conditions to 17.7% +/- 6.2 during hypoxia. DeltaR2* and fetal SaO(2) correlated significantly (r = 0.98, P = .018). At 3.0 T, fetal SaO(2) was reduced from 62.4% +/- 7.5 during control conditions to 18% +/- 7.5 during hypoxia. DeltaR2* and fetal SaO(2) also correlated significantly (r = 0.95, P = .012). A linear fit resulted in a slope value of 0.084 +/- 0.003 for 1.5 T and 0.166 +/- 0.016 for 3.0 T. This means a doubled sensitivity of DeltaR2* for oxygen saturation variations at 3.0 T compared with 1.5 T.
MR imaging at 3.0 T is more sensitive than that at 1.5 T in the detection of DeltaR2* in the fetal brain during hypoxia. However, there was a signal decrease in the fetal brain in all 1.5-T experiments during hypoxia. Thus it is possible to measure fetal DeltaR2* at 1.5 T, which may be of more practical relevance for the evaluation of pregnant women.
Radiology 06/2009; 252(2):394-400. · 5.73 Impact Factor
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ABSTRACT: The aim of this study was to perform fetal cardiac magnetic resonance imaging (MRI) with triggering of the fetal heart beat in utero in a sheep model. All experimental protocols were reviewed and the usage of ewes and fetuses was approved by the local animal protection authorities. Images of the hearts of six pregnant ewes were obtained by using a 1.5-T MR system (Philips Medical Systems, Best, Netherlands). The fetuses were chronically instrumented with a carotid catheter to measure the fetal heart frequency for the cardiac triggering. Pulse wave triggered, breath-hold cine-MRI with steady-state free precession (SSFP) was achieved in short axis, two-, four- and three-chamber views. The left ventricular volume and thus the function were measured from the short axis. The fetal heart frequencies ranged between 130 and 160 bpm. The mitral, tricuspid, aortic, and pulmonary valves could be clearly observed. The foramen ovale could be visualized. Myocardial contraction was shown in cine sequences. The average blood volume at the end systole was 3.4 + or - 0.2 ml (+ or - SD). The average volume at end diastole was 5.2 + or - 0.2 ml; thus the stroke volumes of the left ventricle in the systole were between 1.7 and 1.9 ml with ejection fractions of 38.6% and 39%, respectively. The pulse wave triggered cardiac MRI of the fetal heart allowed evaluation of anatomical structures and functional information. This feasibility study demonstrates the applicability of MRI for future evaluation of fetuses with complex congenital heart defects, once a noninvasive method has been developed to perform fetal cardiac triggering.
European Radiology 06/2009; 19(10):2383-90. · 3.22 Impact Factor
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ABSTRACT: To retrospectively evaluate the impact of diffusion-weighted imaging (DWI) on the detection of prostate cancer in comparison with sextant biopsy.
Fifty patients with clinical suspicion of prostate cancer underwent a combined endorectal-body-phased array magnetic resonance imaging examination at a 1.5 T magnetic resonance imaging (Siemens, Erlangen, Germany). The DWI was performed using b values of 50, 400, 800 s/mm. The prostate was divided into sextants, including the apex, the middle aspect, and the base for the left and right sides, separately. Regions of interest were placed in the peripheral zone of each sextant to evaluate the apparent diffusion coefficient (ADC) values. The results of the DWI were compared side by side with the findings of the histological examination of endorectal sonographically guided sextant biopsy. The sensitivity and specificity of ADC for the identification of the tumor tissue were computed for variable discrimination thresholds to evaluate its receiver operating characteristic. An association between ADC and Gleason score was tested for both the whole study group and on an individual basis using the nonparametric Spearman ρ test and the Pearson correlation, respectively.
Histopathology identified tumor tissue in 21 (42%) of the 50 patients. The ADC value was 1.65 ± 0.32 mm/s 10 in normal tissue and 0.96 ± 0.24 mm/s 10 in tumor tissue (mean ± 1 SD). The area under the receiver operating characteristic curve was 0.966. Using the discrimination threshold 1.21 mm/s 10, for example, the ADC value provided a sensitivity of 0.92 and a specificity of 0.93. There was a highly significant negative correlation between the ADC value and the Gleason score in the tumor-positive tissue probes (n = 62, ρ = -0.405, P = 0.001) in the whole study group. On the individual patient basis, the Pearson correlation revealed a mean coefficient of r = -0.89 (SD ± 0.12) with a P < 0.001.
Diffusion-weighted imaging of the prostate can be used to differentiate benign from malignant tissue in the peripheral zone. In the present study, ADC values were significantly lower in prostate cancer than in benign tissue.
Journal of computer assisted tomography 35(2):223-8. · 1.38 Impact Factor
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ABSTRACT: Image quality of chest and abdominal computed tomographic (CT) scans was evaluated at different doses to assess the lowest value of x-ray dose at which the image quality was not being affected.
Using multislice CT (MSCT), 29 patients who submitted to follow-up examinations were examined using a combined MSCT protocol of the chest and the abdomen on 4-raw MSCT (Siemens, Erlangen, Germany). For each examination, approximately 120 mL of contrast agent (Bracco-Altana, Konstanz, Germany) was applied intravenously. The raw data were transferred to an external personal computer equipped with an image reconstruction software (CardioRecon 6; Siemens, Forchheim, Germany) to simulate 5 different dose levels. To simulate them correctly, a milliampere second-dependent noise was added to every image, so that the changes in a current-time product could be imitated. The images were compared in consensus by 2 radiologists who were not informed about the technical scanning parameters, that is, dose parameters, and were graded in 4 different subcategories on a 1-to-5-point scale. For statistical analysis, the Friedman test was used. Additional evaluations for lesions smaller than 1.0 cm were performed and analyzed separately.
For image noise, there was a significant change between 40 and 60 mA s. For lesion detection, there was no significant change. The contour of the small objects did not differ between 90, 60, and 40 mA s. However, a dose reduction to 30 mA s had a significant effect. The contrast did not differ between 90, 60, 40, and even down to 30 mA s. Only a maximal dose reduction to 20 mA s had a significant effect on the contrast. The level of noise was most sensitive to the current. Whereas a dose reduction to 60 mA s did not yet have a significant effect, there was a significant increase of noise at 40 mA s.
The MSCT can be applied with a lower dose than that usually selected in examinations at present to follow-up and stage the oncological patients adequately.
Journal of computer assisted tomography 34(2):302-8. · 1.38 Impact Factor
