Ultrashort echo time MRI of the lung in children and adolescents: comparison with non-enhanced computed tomography and standard post-contrast T1w MRI sequences.

OBJECTIVES: To compare the diagnostic value of ultrashort echo time (UTE) magnetic resonance imaging (MRI) for the lung versus the gold standard computed tomography (CT) and two T1-weighted MRI sequences in children. METHODS: Twenty-three patients with proven oncologic disease (14 male, 9 female; mean age 9.0 + / - 5.4 years) received 35 low-dose CT and MRI examinations of the lung. The MRI protocol (1.5-T) included the following post-contrast sequences: two-dimensional (2D) incoherent gradient echo (GRE; acquisition with breath-hold), 3D volume interpolated GRE (breath-hold), and 3D high-resolution radial UTE sequences (performed during free-breathing). Images were evaluated by considering image quality as well as distinct diagnosis of pulmonary nodules and parenchymal areal opacities with consideration of sizes and characterisations. RESULTS: The UTE technique showed significantly higher overall image quality, better sharpness, and fewer artefacts than both other sequences. On CT, 110 pulmonary nodules with a mean diameter of 4.9 + / - 2.9 mm were detected. UTE imaging resulted in a significantly higher detection rate compared to both other sequences (p < 0.01): 76.4% (84 of 110 nodules) for UTE versus 60.9% (67 of 110) for incoherent GRE and 62.7% (69 of 110) for volume interpolated GRE sequences. The detection of parenchymal areal opacities by the UTE technique was also significantly higher with a rate of 93.3% (42 of 45 opacities) versus 77.8% (35 of 45) for 2D GRE and 80.0% (36 of 45) for 3D GRE sequences (p < 0.05). CONCLUSION: The UTE technique for lung MRI is favourable in children with generally high diagnostic performance compared to standard T1-weighted sequences as well as CT. Key Points • Due to the possible acquisition during free-breathing of the patients, the UTE MRI sequence for the lung is favourable in children. • The UTE technique reaches higher overall image quality, better sharpness, and lower artefacts, but not higher contrast compared to standard post-contrast T1-weighted sequences. • In comparison to the gold standard chest CT, the detection rate of small pulmonary nodules small nodules ≤ 4 mm and subtle parenchymal areal opacities is higher with the UTE imaging than standard T1-weighted sequences.

MRI as an alternative to serum ferritin for diagnosis of iron overload in children in the context of immune response after stem cell transplantation.

Multiple blood cell transfusions may cause iron overload or even liver fibrosis, requiring early diagnosis and intervention. SF is the standard for estimating iron levels in the body, but it also increases with inflammation. We hypothesized that T2 * magnetic resonance (MR) relaxometry is a more accurate alternative for follow-up in pediatric patients before and after allogenic SCT. Twenty-three children (mean age 10.2 years, 10 female, 13 male) were evaluated prospectively before SCT as well as at least 1 year after SCT with T2 * relaxometry on a 1.5 T MR-scanner to estimate liver iron concentrations from the T2 * values ("MR-Fe"). The results were compared with SF, while also considering CRP, and correlated with the number of transfusions. Overall, 24.3 transfusions were administered in average, mainly within 100 days of SCT (mean 10.5 units). Both MR-Fe and SF increased after SCT and decreased in the absence of new transfusions 1 year later without chelate therapy. This suggests regeneration of LP and iron loss, although the original states were not reached. Additionally, simultaneous peaks of CRP and SF were observed directly after SCT. MR-Fe did neither reveal these peaks nor was it associated with CRP (P = .39). We postulate that these early CRP and SF peaks after SCT are probably related to inflammatory reactions and not to iron overload. Thus, SF is not reliable for iron overload diagnosis after SCT in every condition. Beside this interaction, SF and MR-Fe revealed similar accuracy. MRI, however, has practical and economical disadvantages in routine estimation of iron.

Quantitative Susceptibility Mapping Indicates a Disturbed Brain Iron Homeostasis in Neuromyelitis Optica - A Pilot Study.

Dysregulation of brain iron homeostasis is a hallmark of many neurodegenerative diseases and can be associated with oxidative stress. The objective of this study was to investigate brain iron in patients with Neuromyelitis Optica (NMO) using quantitative susceptibility mapping (QSM), a quantitative iron-sensitive MRI technique. 12 clinically confirmed NMO patients (6 female and 6 male; age 35.4y±14.2y) and 12 age- and sex-matched healthy controls (7 female and 5 male; age 33.9±11.3y) underwent MRI of the brain at 3 Tesla. Quantitative maps of the effective transverse relaxation rate (R2*) and magnetic susceptibility were calculated and a blinded ROI-based group comparison analysis was performed. Normality of the data and differences between patients and controls were tested by Kolmogorov-Smirnov and t-test, respectively. Correlation with age was studied using Spearman's rank correlation and an ANCOVA-like analysis. Magnetic susceptibility values were decreased in the red nucleus (p<0.01; d>0.95; between -15 and -22 ppb depending on reference region) with a trend toward increasing differences with age. R2* revealed significantly decreased relaxation in the optic radiations of five of the 12 patients (p<0.0001; -3.136±0.567 s(-1)). Decreased relaxation in the optic radiation is indicative for demyelination, which is in line with previous findings. Decreased magnetic susceptibility in the red nucleus is indicative for a lower brain iron concentration, a chemical redistribution of iron into less magnetic forms, or both. Further investigations are necessary to elucidate the pathological cause or consequence of this finding.

Antipsychotic drug effects on left prefrontal phospholipid metabolism: a follow-up 31P-2D-CSI study of haloperidol and risperidone in acutely ill chronic schizophrenia patients.

INTRODUCTION: ³¹Phosphorous magnetic resonance spectroscopy (2D chemical shift imaging, CSI) allows multiregional study of membrane phospholipids and high-energy phosphates in vivo. Increased membrane lipid turnover and impaired energy supply have repeatedly been shown in first-episode schizophrenia patients, and might be a target of drug actions other than dopamine receptors. Here, we explored differential metabolic effects of a typical vs. an atypical antipsychotic on brain phospholipids. METHODS: We applied 2D-CSI MR spectroscopy in 17 recurrent-episode schizophrenia patients off antipsychotics at baseline and at follow-up after 6 weeks, during which 7 patients were treated with haloperidol (10-16 mg/d) and 10 with risperidone (4-6 mg/d). Psychopathology changes were assessed using PANSS, BPRS and CGI scores. RESULTS: Follow-up analysis using repeated measure ANOVA revealed different effects of both antipsychotic agents: while risperidone generally increased metabolite levels, haloperidol showed a tendency to decrease them. This diverging effect was significant for ATP levels in the left lateral frontal cortex. Furthermore, risperidone increased ATP in the left dorsolateral prefrontal cortex, left anterior temporal cortex and left insular cortex, basal ganglia, and anterior cerebellum, along with left frontal and prefrontal increase of PCr, PDE and PME in these brain regions. CONCLUSION: Risperidone seems to stimulate neuronal and synaptic phospholipid remodeling in left frontal and prefrontal regions, and to a lesser extent also in temporal and insular cortices. We discuss these effects with respect to clinical effects on negative and cognitive symptoms, as well as interaction of phospholipid metabolism with glutamatergic neurotransmission.

Compatibility of temporary pacemaker myocardial pacing leads with magnetic resonance imaging: an ex vivo tissue study.

The presence of temporary myocardial pacing leads is considered a safety contraindication for magnetic resonance imaging (MRI). The aim of this ex vivo tissue study was to measure the heating effects at the tip of the leads using proton magnetic resonance spectroscopy ((1)HMRS) thermometry. The tissue effects were verified by histological analyses. Pig hearts with implanted temporary pacemaker myocardial pacing leads were examined by whole-body MRI at 1.5 Tesla. The tests were performed either by a sequence with high specific absorption rate (SAR) or by standard clinical sequences with lower SAR. Temperature changes were detected via (1)HMRS thermometry, by monitoring the frequency difference between water protons and the reference signals of N-methyl protons of creatine/phosphocreatine (Cr/PCr) and trimethylamine (TMA). Histology was performed using several staining techniques. Standard low-SAR and high-SAR sequences did not cause significant temperature increases in the myocardial tissue surrounding the implanted leads. There were no histopathological signs of thermal damage around the tips of the leads in any of the hearts or in a control implanted heart not subjected to MRI. The present data suggest that temporary pacemaker myocardial pacing leads may be compatible with MR scanning at 1.5 Tesla. However, further in vivo studies and carefully monitored patient studies are needed before final safety recommendations can be made.

Fronto-cingulate effective connectivity in obsessive compulsive disorder: a study with fMRI and dynamic causal modeling.

Evidence suggests that obsessive compulsive disorder (OCD) is associated with an overactive error control system. A key role in error detection and control has been ascribed to the fronto-cingulate system. However, the exact functional interplay between the single components of this network in OCD is largely unknown. Therefore, the present study combined a univariate data analysis and effective connectivity analysis using dynamic causal modeling (DCM) to examine error control in 21 patients with OCD and 21 matched healthy controls. All subjects performed an adapted version of the Stroop color-word task while undergoing fMRI scans. Enhanced activation in the fronto-cingulate system could be detected in OCD patients during the incongruent task condition. Additionally, task-related modulation of effective connectivity from the dorsal ACC to left DLPFC was significantly stronger in OCD patients. These findings are consistent with an overactive error control system in OCD subserving suppression of prepotent responses during decision-making.

Improved elimination of phase effects from background field inhomogeneities for susceptibility weighted imaging at high magnetic field strengths.

To enhance susceptibility-related contrast of magnetic resonance images, the phase of susceptibility weighted data needs to be corrected for background inhomogeneities and phase wraps caused by them. Current methods either use homodyne filtering or a combination of phase unwrapping and high pass filtering. The drawback of homodyne filtering is incomplete elimination of phase wraps in areas with steep phase topography produced by background inhomogeneities of the static magnetic field. The disadvantage of phase unwrapping is that it requires subsequent high pass filtering, which introduces artifacts in areas with very steep transitions, such as areas near interfaces between parenchyma and bone or air. A method is proposed that reduces the artifacts associated with high pass filtering without sacrificing the advantages of phase unwrapping. This technique is demonstrated with phantom data at 1.5 T and with human data at 1.5, 3 and 7 T.

Detection of multiple intracranial hemorrhages in a child with acute lymphocytic leukemia (ALL) by susceptibility weighted imaging (SWI).

Susceptibility weighted imaging (SWI) combines magnitude and phase information from a high-resolution, fully velocity compensated, three-dimensional (3D) gradient echo sequence. We report on the use of this MRI technique in a young patient with acute lymphocytic leukemia (ALL) and demonstrate a higher detection rate of hemorrhagic lesion in comparison with other T2*-weighted sequences.

Radio-frequency ablation of VX2 rabbit tumors: assessment of completeness of treatment by using contrast-enhanced harmonic power Doppler US.

PURPOSE: To assess contrast material-enhanced harmonic power Doppler and fundamental color Doppler ultrasonography (US) in the detection of residual viable tumor tissue after radio-frequency (RF) ablation in tumors embedded in fat. MATERIALS AND METHODS: Twenty-eight VX2 tumors were implanted into the retroperitoneum of 14 rabbits. Tumors were examined with contrast-enhanced fundamental color Doppler US and harmonic power Doppler US before and 10 minutes after RF ablation. Saline-enhanced RF ablation (30 mL/h) was performed over 10 minutes with 28-W RF power. Follow-up included repeat US examinations. Necropsies and histopathologic assessment were performed after detection of residual untreated tumor at US or 3 weeks after ablation. RESULTS: VX2 tumors reached a mean size of 21 mm +/- 9 (SD) (size range, 6-43 mm) 25 days after implantation. All tumors larger than 31 mm showed signs of central necrosis at US. Before ablation, intense vascularity was detected in all tumors with both contrast-enhanced US modes. Histopathologic assessment at the end of the follow-up period revealed local relapses due to incomplete ablation in 14 (50%) of 28 cases. Detection of residual tumor was missed in all cases with contrast-enhanced color Doppler US. Contrast-enhanced harmonic power Doppler US depicted residual flow in 12 of the 14 cases (sensitivity, 86%) in which local relapses occurred. There was a significant (P <.005, McNemar test) improvement in detection of residual tumor when the harmonic power Doppler mode was used. CONCLUSION: Contrast-enhanced harmonic power Doppler US has greater sensitivity than contrast-enhanced color Doppler US for detecting residual VX2 tumor following ablation. Therefore, contrast-enhanced harmonic power Doppler US may be a useful additional method for the detection of residual tumors after RF ablation.