Reproducibility of non-contrast enhanced multi breath-hold ultrashort echo time functional lung MRI.

PURPOSE: To evaluate the intraindividual reproducibility of functional lung imaging using non-contrast enhanced multi breath-hold 3D-UTE MRI. METHODS: Ten healthy volunteers underwent non-contrast enhanced 3D-UTE MRI at three time points for same-day and different-day measurements employing a stack-of-spirals trajectory at 3 T. At each time point, inspiratory and expiratory breathing states were acquired for tidal and deep breathing, each within a single breath-hold. For functional image analysis, fractional ventilation (FV) was calculated pixelwise after image registration from the MR signal change. To decouple FV from breathing depth, the individual lung volume was used for volume adjustment (rFV). Reproducibility evaluation was performed in eight lung segments. Statistical analyses included two way mixed intraclass correlation (ICC), sign-test, Friedman-test and modified Bland-Altman analyses. RESULTS: FV from tidal breathing showed an ICC of 0.81, a bias of 1.3% and an interval of confidence (CI) ranging from -67.1 to 69.6%. FV from deep breathing was higher reproducible with an ICC of 0.92 (bias, -0.2%; CI, -34.2 to 33.7%). Following volume adjustment, reproducibility of rFV for tidal breathing improved (ICC, 0,86; bias, 2.0%; CI, -34.3 to 38.3%), whereas it did not bear significant benefits for deep breathing (ICC, 0.89; bias, 2.8%; CI, -24.9 to 30.5%). Reproducibility was independent from the examination day. CONCLUSION: Non-contrast-enhanced multi breath-hold 3D-UTE MRI allows for highly reproducible ventilation imaging.

Noise-optimized virtual monoenergetic reconstructions of dual-energy CT angiographies improve assessability of the lower leg arterial segments in peripheral arterial occlusive disease.

INTRODUCTION: The aim of this study was to evaluate the influence of a noise optimized virtual monoenergetic reconstruction algorithm (VMI+) on the image quality and assessability of dual energy (DE) computed tomography angiography (CTA) of the lower extremity runoff. METHODS: A total of 118 lower extremity runoff CTA performed on a 3rd generation DE-CT scanner in 109 patients (54 females; 75.6 ± 9.5 years) were included in this retrospective study. Axial image stacks were reconstructed with a standard 120 kV setting and VMI+ of different keV levels. Objective image quality criteria (contrast attenuation, signal-to-noise [SNR] and contrast-to-noise ratio [CNR]) were measured. Two radiologists evaluated subjective image quality regarding intraluminal attenuation and image noise using a 5-point Likert scale. Diagnostic accuracy for significant stenosis (>75%) and vessel occlusion was assessed for 120 kV and 50 keV VMI+ images rated by two radiologists. In all patients, a digital subtraction angiography (DSA) rated by on board-certified radiologist served as the standard of reference. RESULTS: Intraluminal attenuation was highest in 40/50 keV VMI+ while SNR were similar to 120 kV images. In subjective assessment, intraluminal contrast of 50 keV images was deemed superior compared to 120 kV despite higher image noise. Sensitivity, specificity, and accuracy for detection of a vessel occlusion were similar in 50 keV VMI+ compared to 120 kV (70%/92%/84%; 70%/91%/83%; p < 0.001) but 13 of 118 (11%) lower leg runoffs were only assessable with 50 keV VMI+. CONCLUSION: VMI+ reconstructions improve assessability of DE-CTA by increased luminal attenuation with consistent image noise, also allowing the evaluation of lower leg arterial segments inassessable with standard reconstructions. IMPLICATIONS FOR PRACTICE: Providing higher intraluminal attenuation and similar image noise compared with conventional reconstructions, 50 keV VMI+ may be appropriate for routine evaluation of DE-CTA.

Glutamate as a spectroscopic marker of hippocampal structural plasticity is elevated in long-term euthymic bipolar patients on chronic lithium therapy and correlates inversely with diurnal cortisol.

While an excess of glucocorticoids is associated with hippocampal pathology in mood disorders, lithium exerts robust neuroprotective and neurotrophic effects. Here, 21 stably remitted bipolar I patients who had been on chronic lithium maintenance therapy, on average, for more than a decade, and 19 carefully matched healthy controls were studied using 3 T (1)H-magnetic resonance spectroscopy of left and right hippocampus. Salivary cortisol samples were obtained to assess activity of the hypothalamus-pituitary-adrenal system. Absolute concentrations of N-acetylaspartate (NAA), choline-containing compounds and total creatine were similar in euthymic bipolar patients and healthy controls. Hippocampal glutamate concentrations were significantly increased as an effect of patient status (patients>controls) and laterality (left hippocampus>right hippocampus). Hippocampal glutamate content (Glu) was strongly correlated with NAA. Across groups and within the patient group, diurnal saliva cortisol levels showed a significant inverse relationship with both Glu and NAA. Taken together, these results add to the concept of bipolar disorder as an illness involving disturbed hippocampal structural plasticity under the opposing influences of lithium and glucocorticoids.

The mass-independent fractionation of oxygen: a novel isotope effect and its possible cosmochemical implications.

Experimental evidence is presented which demonstrates a chemically produced, mass-independent isotopic fractionation of oxygen. The effect is thought to result from self-shielding by the major isotopic species (16)O(2), but other possible mechanisms such as molecular symmetry cannot be ruled out. In a three-isotope plot, the experimentally produced fractionation line is essentially equal in slope to the observed carbonaceous chondrite mixing line. The implications for the early history of the solar system are discussed.

Magnetic resonance imaging results can affect therapy decisions in hyperacute stroke care.

BACKGROUND: Despite some limitations, a perfusion/diffusion mismatch can provide a working estimate of the ischemic penumbra in hyperacute stroke and has successfully been used to triage patients. PURPOSE: To evaluate whether the addition of magnetic resonance imaging (MRI) to clinical and non-contrast computed tomography (CT) data alters diagnosis and choice of therapy. MATERIAL AND METHODS: We retrospectively analyzed clinical records, and CT and MRI data fully available in 97 of 117 patients. Upon clinical examination and CT, a diagnosis and treatment path was scored and compared to treatment path after addition of MRI data. The MRI protocol included T2-weighted images, diffusion-weighted images (DWI), and perfusion-weighted images (PWI), and MR angiography (MRA). RESULTS: MRI data were acquired in less than 15 min. In 20 of 97 patients (21%), the diagnosis changed after MRI. In 25 of 97 patients (26%), the presumptive treatment plan was changed after MRI evaluation. Thirteen patients had their treatment changed from thrombolytic to nonthrombolytic therapy. Three patients were changed from nonthrombolytic to intraarterial (IA) thrombolysis. In one patient, treatment was changed from intravenous (IV) to IA thrombolysis, and in five patients it was changed from IA to IV thrombolysis. In two patients, systemic heparin was added to antiplatelet therapy. CONCLUSION: The expansion of the acute stroke protocol to include MRI altered the therapy plan in 26% of our patients. The utility of MRI, shown here to improve patient stratification into best-treatment options, demonstrates the value of using MRI to optimize care in hyperacute stroke patients.

Bleeding complications after endovascular therapy of cerebral arteriovenous malformations.

BACKGROUND AND PURPOSE: Intracerebral hemorrhages after embolization of arteriovenous malformations (AVMs) are the most dreaded complications of this well-established therapy. Apart from the known risk factors, our center noticed a high incidence of complications during postinterventional monitoring in medical intensive care units (ICUs) and stroke units. MATERIALS AND METHODS: We report 125 consecutive interventions performed on 66 patients by using flow-dependent microcatheters and n-butyl cyanoacrylate as the embolic agent. Postinterventional intensive care monitoring was performed in an interdisciplinary operative ICU, a stroke unit, or a medical ICU. Patients were compared with regard to bleeding complications, AVM morphology, embolization result, postinterventional monitoring, and demographic factors. RESULTS: Intracerebral hemorrhages occurred in 7 patients. Significant differences in outcome were found between 66 patients monitored in the interdisciplinary operative ICU from medical ICU or stroke unit. This was also true when adjusted for age and extent of AVM reduction by using exact logistic regression. A partial AVM reduction of >60% was a considerable risk factor for hemorrhage (odds ratio [OR] = 18.8; 95% confidence interval [CI] [1.341, not available]. Age was also an essential risk factor. An age difference of 10 years leads to an OR of 2.545 (95% CI [1.56, 7.35]). DISCUSSION: A considerable AVM reduction in one session appears to increase the risk of hemorrhage technically. This suggests a distribution of the interventions in many partial steps.

Adverse hemodynamic effects of interrupting chest compressions for rescue breathing during cardiopulmonary resuscitation for ventricular fibrillation cardiac arrest.

BACKGROUND: Despite improving arterial oxygen saturation and pH, bystander cardiopulmonary resuscitation (CPR) with chest compressions plus rescue breathing (CC+RB) has not improved survival from ventricular fibrillation (VF) compared with chest compressions alone (CC) in numerous animal models and 2 clinical investigations. METHODS AND RESULTS: After 3 minutes of untreated VF, 14 swine (32+/-1 kg) were randomly assigned to receive CC+RB or CC for 12 minutes, followed by advanced cardiac life support. All 14 animals survived 24 hours, 13 with good neurological outcome. For the CC+RB group, the aortic relaxation pressures routinely decreased during the 2 rescue breaths. Therefore, the mean coronary perfusion pressure of the first 2 compressions in each compression cycle was lower than those of the final 2 compressions (14+/-1 versus 21+/-2 mm Hg, P<0.001). During each minute of CPR, the number of chest compressions was also lower in the CC+RB group (62+/-1 versus 92+/-1 compressions, P<0.001). Consequently, the integrated coronary perfusion pressure was lower with CC+RB during each minute of CPR (P<0.05 for the first 8 minutes). Moreover, at 2 to 5 minutes of CPR, the median left ventricular blood flow by fluorescent microsphere technique was 60 mL. 100 g(-1). min(-1) with CC+RB versus 96 mL. 100 g(-1). min(-1) with CC, P<0.05. Because the arterial oxygen saturation was higher with CC+RB, the left ventricular myocardial oxygen delivery did not differ. CONCLUSIONS: Interrupting chest compressions for rescue breathing can adversely affect hemodynamics during CPR for VF.

Critical off-target effects of the widely used Rac1 inhibitors NSC23766 and EHT1864 in mouse platelets.

BACKGROUND: Platelet aggregation at sites of vascular injury is essential for normal hemostasis, but may also cause pathologic vessel occlusion. Rho GTPases are molecular switches that regulate essential cellular processes, and they have pivotal functions in the cardiovascular system. Rac1 is an important regulator of platelet cytoskeletal reorganization, and contributes to platelet activation. Rac1 inhibitors are thought to be beneficial in a wide range of therapeutic settings, and have therefore been tested in vivo for a variety of disorders. Two small-molecule inhibitors, NSC23766 and EHT1864, have been characterized in different cell types, demonstrating high specificity for Rac1 and Rac, respectively. OBJECTIVES: To analyze the specificity of NSC23766 and EHT1864. METHODS: Platelet function was assessed in mouse wild-type and Rac1-deficient platelets by the use of flow cytometric analysis of cellular activation and aggregometry. Platelet spreading was analyzed with differential interference contrast microscopy, and activation of effector molecules was analyzed with biochemical approaches. RESULTS: NSC23766 and EHT1864 showed strong and distinct Rac1-independent effects at 100 µm in platelet function tests. Both inhibitors induced Rac1-specific inhibition of platelet spreading, but also markedly impaired agonist-induced activation of Rac1(-/-) platelets. Furthermore, glycoprotein Ib-mediated signaling was dramatically inhibited by NSC23766 in both wild-type and Rac1-deficient platelets. Importantly, these inhibitors directly affected the activation of the Rac1 effectors p21-activated kinase (PAK)1 and PAK2. CONCLUSIONS: Our results reveal critical off-target effects of NSC23766 and EHT1864 at 100 µm in mammalian cells, raising questions about their utility as specific Rac1/Rac inhibitors in biochemical studies at these concentrations and possibly as therapeutic agents.

Altered white and gray matter metabolism in CADASIL: a proton MR spectroscopy and 1H-MRSI study.

OBJECTIVE: Subcortical white matter hyperintensities (WMH) and small cystic lesions are the radiologic hallmark of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary angiopathy causing stroke in young adults. To further characterize the cerebral pathology in vivo we analyzed metabolite concentrations in normal and abnormal appearing brain tissue using single and multiple voxel proton MR spectroscopy (1H-MRS and 1H-MRSI). METHODS: Twenty patients with CADASIL and 21 age-matched controls were studied with 1H-MRSI at the level of the centrum semiovale; short echo time 1H-MRS was performed in six patients (WMH) and 10 controls. LCModel fits were used to estimate absolute and relative concentrations of N:-acetylaspartate (NAA), choline-containing compounds (Cho), total creatine (Cr) within WMH, normal appearing white matter (NAWM), and cortical gray matter (GM) as well as myo-inositol (mI) and lactate in WMH. RESULTS: 1H-MRSI-Patients with CADASIL showed significantly reduced NAA, Cho, Cr, and total metabolite content (Met(tot)) in WMH and NAWM. Normalization to Met(tot) revealed that NAA/Met(tot) was reduced in all regions, whereas Cho and Cr were relatively elevated in WMH. Short echo time 1H-MRS showed decreased NAA, Cr, Met(tot), and NAA/Met(tot) and elevated mI/Met(tot) and lactate in WMH. Metabolite changes were larger in severely affected subjects. Rankin scores correlated negatively with NAA/Met(tot) (all regions) and NAA/Cho (WMH), and positively with Cho/Met(tot) (WMH) and Cr/Met(tot) (NAWM). CONCLUSION: Marked metabolic abnormalities were observed in abnormal and normal appearing white matter in patients with CADASIL. The findings suggest axonal injury, enlarged extracellular spaces, myelin loss, and gliosis. The cortical abnormalities may reflect structural damage or functional neuronal impairment secondary to white matter pathology. NAA reductions were correlated with clinical disability emphasizing the clinicopathologic relevance of axonal injury in CADASIL.

Reduced NAA in the thalamus and altered membrane and glial metabolism in schizophrenic patients detected by 1H-MRS and tissue segmentation.

Functional and structural abnormalities in the thalamus as well as a generalized phospholipid membrane disorder have been implicated in the pathogenesis of schizophrenic psychosis. To determine whether thalamic neuronal abnormalities and altered membrane-associated metabolites can be detected in schizophrenic patients, we used in vivo proton magnetic resonance spectroscopy (1H-MRS) in 32 acutely-ill, medicated schizophrenic patients and 17 age-matched controls. Thalamic and white matter metabolite concentrations (myo-inositol (mI), choline-containing compounds (Cho), total creatine (Cr) and N-acetylaspartate (NAA)) were estimated and corrected for atrophy (CSF) and gray and white matter contributions (GM, WM) by use of image-based voxel segmentation. Thalamic NAA was significantly reduced in schizophrenic patients, whereas Cho and mI were significantly increased in the parietal white matter. White matter Cr was significantly elevated in patients and correlated positively with the brief psychiatric rating scores (BPRS). Regional metabolite levels were inversely associated with GM and WM content reaching significance for mI and Cr in the thalamus and Cho and NAA in the white matter. Reduced NAA in the left thalamus of schizophrenic patients confirms and extends previous spectroscopic data and agrees well with histologic and imaging findings of reduced neuronal density and volume. Elevated Cho in line with 31P-MRS studies suggests increased myelin degradation thus further supporting a generalized membrane disorder in schizophrenic patients. In addition, we demonstrate the need to correct metabolite concentrations for regional tissue composition in studies employing patients with altered brain morphology.

Comparison of metric analysis of spinal structures, exemplarily of the ligamentum flavum, obtained with CT and MRI.

PURPOSE: Comparison of metric analysis of spinal structures, exemplarily of the ligamentum flavum, obtained with computed tomography (CT) (soft tissue window and bone window) and magnetic resonance imaging (MRI) (T1 and T2 weighted images). MATERIAL AND METHODS: Forty-six lumbar ligamenta flava of 46 patients (25 women and 21 men) were examined at a Somatom Plus 4 (Siemens, Erlangen, FRG) and at a 1.5 T clinical scanner (Magnetom Vision, Siemens, Erlangen, FRG). Two independent neuroradiologists measured the thickness of the ligamenta flava in mm. Statistics included Pearson's correlation coefficient and the intra-class correlation coefficient. RESULTS: Mean values did not differ significantly. The correlation coefficients varied between 0.69 and 0.98. The best correlation occurred comparing the same techniques in different windowing and weighting (CT: r = 0.98; MRI: r = 0.95). Correlating different techniques the combination of CT bone window and T1 weighted images presented the best result (r = 0.75). CONCLUSIONS: Because of the excellent correlation between the examined techniques CT as well as MRI can equally be used to measure distances of spinal structures.

[Changes of the fat/water ratio in the erector trunci muscle in patients with lumbar disc herniation: a comparative study with 1H-MRS]. / Veränderungen des Fett/Wasser-Quotienten im Musculus erector trunci bei Patienten mit lumbalem Bandscheibenvorfall: eine vergleichende.

PURPOSE: To evaluate whether metabolic changes of the erector trunci muscle in patients with lumbar disc herniation can be detected with proton magnetic resonance spectroscopy ( (1)H-MRS). MATERIALS AND METHODS: In 10 patients with lumbar disc herniation and 16 healthy volunteers, proton spectra were obtained from the erector trunci muscle and analyzed for fat-water ratio. The axial images were evaluated for the degree of atrophy of the erector trunci muscle. The muscular tissue was histopathologically examined in 2 patients. RESULTS: The examination was well tolerated by all patients and volunteers and all acquired spectra could be analyzed. Patients with lumbar disc herniation have a significantly increased fat-water ratio of 0.19 compared to 0.09 in the control group, with a p-value of 0.003. This result correlates well with the bioptical findings of increased intracellular lipid deposits and lipomatous transformation of the muscle parenchyma. CONCLUSION: (1)H-MRS is a useful method to detect metabolic changes in lumbar back musculature and, as a non-invasive technique, might play a role in monitoring exercise in lumbar disc herniation. It can be expected that muscle regeneration will be shown as precisely as muscle degeneration. This hypothesis, however, remains to be proven.

Capacity of the bovine intestinal mucus and its components to support growth of Escherichia coli O157:H7.

Colonization of the gastrointestinal tract of cattle by Shiga toxin-producing Escherichia coli increases the risk of contamination of food products at slaughter. Our study aimed to shed more light on the mechanisms used by E. coli O157:H7 to thrive and compete with other bacteria in the gastrointestinal tract of cattle. We evaluated, in vitro, bovine intestinal mucus and its constituents in terms of their capacity to support growth of E. coli O157:H7 in presence or absence of fecal inoculum, with and without various enzymes. Growth of E. coli O157:H7 and total anaerobic bacteria were proportionate to the amount of mucus added as substrate. Growth of E. coli O157:H7 was similar for small and large intestinal mucus as substrate, and was partially inhibited with addition of fecal inoculum to cultures, presumably due to competition from other organisms. Whole mucus stimulated growth to the greatest degree compared with other compounds evaluated, but the pathogen was capable of utilizing all substrates to some extent. Addition of enzymes to cultures failed to impact growth of E. coli O157:H7 except for neuraminidase, which resulted in greater growth of E. coli O157 when combined with sialic acid as substrate. In conclusion, E. coli O157 has capacity to utilize small or large intestinal mucus, and growth is greatest with whole mucus compared with individual mucus components. There are two possible explanations for these findings (i) multiple substrates are needed to optimize growth, or alternatively, (ii) a component of mucus not evaluated in this experiment is a key ingredient for optimal growth of E. coli O157:H7.

Adult presentation of PHACES syndrome.

A significant percentage of children with hemangiomas may have PHACES syndrome which refers to the association of posterior fossa malformations, facial hemangiomas, arterial cerebrovascular abnormalities, cardiovascular anomalies, eye abnormalities and ventral defects like sternal clefting or supraumbilical raphe. A variety of factors have led to under diagnosis of PHACES syndrome in the past including lack of awareness and limited imaging modalities. Also, patients with PHACES syndrome with arterial cerebrovascular abnormalities can present with acute ischemic stroke. However, these patients usually present before one year of age. We describe a 29-year-old woman with no history of cerebrovascular disease who initially presented with symptoms of a stroke and was subsequently diagnosed to have PHACES syndrome exhibiting an array of multiple unusual imaging findings. We also discuss the current literature and recommendations about PHACES syndrome.

Idiopathic lingual artery aneurysm: CT findings and endovascular therapy. A case report.

SUMMARY: We describe a 65-year-old woman with an asymptomatic idiopathic lingual artery aneurysm which is suspected to be congenital. We review the literature on external carotid artery branch aneurysms, diagnostic evaluation and discuss treatment options for the various types and the specific chosen in the case presented.

Assessment of 3D-TOF-MRA at 3.0 Tesla in the characterization of the angioarchitecture of cerebral arteriovenous malformations: a preliminary study.

BACKGROUND: The characterization of brain arteriovenous malformation (AVM) angioarchitecture remains rewarding in planning and predicting therapy. The increased signal-to-noise ratio at higher field strength has been found advantageous in vascular brain pathologies. PURPOSE: To evaluate whether 3.0T time-of-flight (TOF) magnetic resonance angiography (MRA) is superior to 1.5T TOF-MRA for the characterization of cerebral AVMs. MATERIAL AND METHODS: Fifteen patients with AVM underwent TOF-MRA at 3.0T and 1.5T and catheter angiography (DSA), which was used as the gold standard. Blinded readers scored image quality on a four-point scale, nidus size, and number of feeding arteries and draining veins. RESULTS: Image quality of TOF-MRA at 3.0T was superior to 1.5T but still inferior to DSA. Evaluation of nidus size was equally good at 3.0T and 1.5T for all AVMs. In small AVMs, however, there was a tendency of size overestimation at 3.0T. MRA at 3.0T had increased detection rates for feeding arteries (+21%) and superficial (+13%) and deep draining veins (+33%) over 1.5T MRA. CONCLUSION: 3.0T TOF-MRA offers superior characterization of AVM angioarchitecture compared with 1.5T TOF-MRA. The image quality of MRA at both 3.0 and 1.5T is still far from equal to DSA, which remains the gold standard for characterization of AVM.

[Pitfalls and special features of modern imaging diagnostics of the upper cervical spine]. / Fallgruben und Besonderheiten der modernen bildgebenden Diagnostik der oberen Halswirbelsäule.

Recent technical developments led to a change in the significance of the different imaging modalities in the whole spectrum of neuroradiology and thus also in the field of imaging of the cervical spine. The main part in diagnostic imaging of the upper cervical spine is taken by high-resolution multislice CT and MRI. Conventional X-rays serve as an initial screening technique if required.