Imaging Regional Metabolic Changes in the Ischemic Rat Heart In Vivo Using Hyperpolarized [1-13C]Pyruvate

We evaluated the use of hyperpolarized ¹³C magnetic resonance imaging (MRI) in an open-chest rat model of myocardial infarction to image regional changes in myocardial metabolism. In total, 10 rats were examined before and after 30 minutes of occlusion of the left anterior descending coronary artery using hyperpolarized [1-¹³C]pyruvate. Cardiac metabolic images of [1-¹³C]pyruvate and its metabolites [1-¹³C]lactate, [1-¹³C]alanine, and [¹³C]bicarbonate were obtained before and after ischemia. Significant reduction in the [1-¹³C]alanine and [1-¹³C]lactate signals were observed in the ischemic region post ischemia. The severity of the ischemic insult was verified by increased blood levels of troponin I and by using late contrast-enhanced MRI that showed enhanced signal in the ischemic region. This study shows that hyperpolarized MRI can be used to image regional metabolic changes in the in vivo rat heart in an open-chest model of ischemia reperfusion. Hyperpolarized MRI enables new possibilities for evaluating changes in cardiac metabolism noninvasively and in real time, which potentially could be used for research to evaluate new treatments and metabolic interventions for myocardial ischemia and to apply knowledge to future application of the technique in humans.

Brain Metastases — Comparison of Gadodiamide Injection-Enhanced MR Imaging at Standard and High Dose, Contrast-Enhanced CT and Non-Contrast-Enhanced MR Imaging

The aim was to compare the abilities of contrast-enhanced CT, non-contrast-enhanced MR imaging and contrast-enhanced MR imaging using standard (0.1 mmol/kg b.w.) and high (0.3 mmol/kg b.w.) doses of Gadodiamide injection to detect brain metastases (i.e. blood-brain barrier damage). Sixteen patients with at least 2 metastases found by CT were evaluated by MR imaging using non-contrast-enhanced spin-echo, T1-weighted, T2-weighted sequences, and contrast-enhanced spin-echo T1-weighted sequences at 2 dose levels. Gadodiamide injection was first given at the dose of 0.1 mmol/kg b.w. After imaging, another 0.2 mmol/kg b.w. was given, yielding a cumulative dose of 0.3 mmol/kg b.w. No contrast media-related adverse events were recorded. The images were evaluated openly by one and blindly by 2 investigators and the number of metastases, size, delineation (open study) and diagnostic certainty (blind study) of each individual metastasis noted. High-dose MR imaging showed significantly more and smaller metastases than any other examination, and gave a higher diagnostic certainty. All high-dose images were superior to those with the standard dose MR imaging when compared blindly in pairs. We conclude that spin-echo MR imaging with a high dose of Gadodiamide injection is an efficient way to improve the detection of brain metastases, in particular of small ones.

Thoracic magnetic resonance venography using Gadofosveset in patients with venous pathology-A comparative study of image quality and inter-rater variability

Background High-quality non-invasive imaging of the deep venous system in the thorax is challenging, but nevertheless required for diagnosis of vascular pathology as well as for patient selection and preoperative planning for endovascular procedures. Purpose To compare the diagnostic quality of Gadofosveset-enhanced thoracic magnetic resonance venography, seven consecutive patients with suspected or known disease affecting the central thoracic veins were compared to seven consecutive magnetic resonance venography using conventional gadolinium-based contrast agents. Materials and methods Diagnostic capability, defined as the ability to assess vessel patency and pathologic conditions, for the major thoracic deep venous segments was assessed by two-independent readers. Both reviewers rated the overall subjective image quality on a four-graded scale, and inter-rater variability was analyzed using unweighted and weighted Cohen's kappa values. Results Diagnostic capability was generally considerably higher in the Gadofosveset group for all examined vessel segments. The overall images quality rating was significantly higher for the Gadofosveset group with a mean rating of 2.9 and 2.7 for the two-independent readers, compared to 1.2 and 1.0 for the control croup. Inter-rater variability showed less variability for the Gadofosveset group with a quadratic-weighted Cohen's Kappa value of 0.58 compared to 0.36 for the control group. Conclusion Our results show that Gadofosveset-enhanced magnetic resonance venography of the central thoracic veins is a reliable technique in clinical routine practice that results in diagnostic images, superior to conventional gadolinium-based contrast medium.

Gadofosveset-enhanced magnetic resonance venography in patients with venous pathology of the lower limbs - Comparison of diagnostic image quality and inter-rater variability with gadobutrol venography and computed tomography venography

Purpose This study was performed to compare the diagnostic quality of Gadofosveset-enhanced magnetic resonance venography with Gadobutrol-enhanced magnetic resonance venography and computed tomography venography for the deep veins of the lower extremities in patients with iliocaval venous pathology. Materials and methods Diagnostic capability and image quality were assessed by two independent readers. Inter-reader variability was analyzed by unweighted and quadratic weighted Cohen's kappa values. Results The diagnostic capability was equal to or higher in the Gadofosveset group for all examined vessel segments compared with both control groups. The image quality score was significantly higher for the Gadofosveset group compared to both control groups. Inter-reader variability expressed by quadratic weighted Cohen's kappa value (k) showed less variability in the Gadofosveset group compared to the control groups. Conclusion Our results show that Gadofosveset-enhanced magnetic resonance venography is a reliable technique in clinical routine practice, with image quality superior to both Gadobutrol-enhanced magnetic resonance venography and computed tomography venography.

Left ventricular atrioventricular plane displacement is preserved with lifelong endurance training and is the main determinant of maximal cardiac output

Age-related decline in cardiac function can be prevented or postponed by lifelong endurance training. However, effects of normal ageing as well as of lifelong endurance exercise on longitudinal and radial contribution to stroke volume are unknown. The aim of this study was to determine resting longitudinal and radial pumping in elderly athletes, sedentary elderly and young sedentary subjects. Furthermore, we aimed to investigate determinants of maximal cardiac output in elderly. Eight elderly athletes (63 ± 4 years), seven elderly sedentary (66 ± 4 years) and ten young sedentary subjects (29 ± 4 years) underwent cardiac magnetic resonance imaging. All subjects underwent maximal exercise testing and for elderly subjects maximal cardiac output during cycling was determined using a dye dilution technique. Longitudinal and radial contribution to stroke volume did not differ between groups (longitudinal left ventricle (LV) 52-65%, P = 0.12, right ventricle (RV) 77-87%, P = 0.16, radial 7.9-8.6%, P = 1.0). Left ventricular atrioventricular plane displacement (LVAVPD) was higher in elderly athletes and young sedentary compared with elderly sedentary subjects (14 ± 3, 15 ± 2 and 11 ± 1 mm, respectively, P < 0.05). There was no difference between groups for RVAVPD (P = 0.2). LVAVPD was an independent predictor of maximal cardiac output (R(2) = 0.61, P < 0.01, β = 0.78). Longitudinal and radial contributions to stroke volume did not differ between groups. However, how longitudinal pumping was achieved differed; elderly athletes and young sedentary subjects showed similar AVPD whereas this was significantly lower in elderly sedentary subjects. Elderly sedentary subjects achieved longitudinal pumping through increased short-axis area of the ventricle. Large AVPD was a determinant of maximal cardiac output and exercise capacity.

Trichuris suis ova therapy in relapsing multiple sclerosis is safe but without signals of beneficial effect

Background:

An observational study has suggested that relapsing–remitting multiple sclerosis patients with helminth infections have lower disease activity and progression than uninfected multiple sclerosis patients.

Objective:

To evaluate the safety and efficacy on MRI activity of treatment with TSO in relapsing MS.

Methods:

The study was an open-label, magnetic resonance imaging assessor-blinded, baseline-to-treatment study including ten patients with relapsing forms of multiple sclerosis. Median (range) age was 41 (24–55) years, disease duration 9 (4–34) years, Expanded Disability Status Scale score 2.5 (1–5.0), and number of relapses within the last two years 3 (2–5). Four patients received no disease modifying therapy, while six patients received IFN-β. After an observational period of 8 weeks, patients received 2500 ova from the helminth Trichuris suis orally every second week for 12 weeks. Patients were followed with serial magnetic resonance imaging, neurological examinations, laboratory safety tests and expression of immunological biomarker genes.

Results:

Treatment with Trichuris suis orally was well-tolerated apart from some gastrointestinal symptoms. Magnetic resonance imaging revealed 6 new or enlarged T2 lesions in the run-in period, 7 lesions in the early period and 21 lesions in the late treatment period. Two patients suffered a relapse before treatment and two during treatment. Eight patients developed eosinophilia. The expression of cytokines and transcription factors did not change.

Conclusions:

In a small group of relapsing multiple sclerosis patients, Trichuris suis oral therapy was well tolerated but without beneficial effect.

Monitoring mammary tumor progression and effect of tamoxifen treatment in MMTV-PymT using MRI and magnetic resonance spectroscopy with hyperpolarized [1-13C]pyruvate

PURPOSE

To use dynamic magnetic resonance spectroscopy (MRS) of hyperpolarized (13)C-pyruvate to follow the progress over time in vivo of breast cancer metabolism in the MMTV-PymT model, and to follow the response to the anti-estrogen drug tamoxifen.

METHODS

Tumor growth was monitored by anatomical MRI by measuring tumor volumes. Dynamic MRS of hyperpolarized (13)C was used to measure an "apparent" pyruvate-to-lactate rate constant (kp) of lactate dehydrogenase (LDH) in vivo. Further, ex vivo pathology and in vitro LDH initial reaction velocity were evaluated.

RESULTS

Tamoxifen significantly halted the tumor growth measured as tumor volume by MRI. In the untreated animals, kp correlated with tumor growth. The kP was somewhat but not significantly lower in the treated group. Studies in vitro confirmed the effects of tamoxifen on tumor growth, and here the LDH reaction velocity was reduced significantly in the treated group.

CONCLUSION

These hyperpolarized (13)C MRS findings indicate that tumor metabolic changes affects kP. The measured kp did not relate to treatment response to the same extent as did tumor growth, histological evaluation, and in vitro determination of LDH activity.

Enhancing the [13C]bicarbonate signal in cardiac hyperpolarized [1-13C]pyruvate MRS studies by infusion of glucose, insulin and potassium

A change in myocardial metabolism is a known effect of several diseases. MRS with hyperpolarized (13)C-labelled pyruvate is a technique capable of detecting changes in myocardial pyruvate metabolism, and has proven to be useful for the evaluation of myocardial ischaemia in vivo. However, during fasting, the myocardial glucose oxidation is low and the fatty acid oxidation (β-oxidation) is high, which complicates the interpretation of pyruvate metabolism with the technique. The aim of this study was to investigate whether the infusion of glucose, insulin and potassium (GIK) could increase the myocardial glucose oxidation in the citric acid cycle, reflected as an increase in the [(13)C]bicarbonate signal in cardiac hyperpolarized [1-(13)C]pyruvate MRS measurements in fasted rats. Two groups of rats were infused with two different doses of GIK and investigated by MRS after injection of hyperpolarized [1-(13)C]pyruvate. No [(13)C]bicarbonate signal could be detected in the fasted state. However, a significant increase in the [(13)C]bicarbonate signal was observed by the infusion of a high dose of GIK. This study demonstrates that a high [(13)C]bicarbonate signal can be achieved by GIK infusion in fasted rats. The increased [(13)C]bicarbonate signal indicates an increased flux of pyruvate through the pyruvate dehydrogenase enzyme complex and an increase in myocardial glucose oxidation through the citric acid cycle.

Source localization of rhythmic ictal EEG activity: a study of diagnostic accuracy following STARD criteria

PURPOSE

Although precise identification of the seizure-onset zone is an essential element of presurgical evaluation, source localization of ictal electroencephalography (EEG) signals has received little attention. The aim of our study was to estimate the accuracy of source localization of rhythmic ictal EEG activity using a distributed source model.

METHODS

Source localization of rhythmic ictal scalp EEG activity was performed in 42 consecutive cases fulfilling inclusion criteria. The study was designed according to recommendations for studies on diagnostic accuracy (STARD). The initial ictal EEG signals were selected using a standardized method, based on frequency analysis and voltage distribution of the ictal activity. A distributed source model-local autoregressive average (LAURA)-was used for the source localization. Sensitivity, specificity, and measurement of agreement (kappa) were determined based on the reference standard-the consensus conclusion of the multidisciplinary epilepsy surgery team. Predictive values were calculated from the surgical outcome of the operated patients. To estimate the clinical value of the ictal source analysis, we compared the likelihood ratios of concordant and discordant results. Source localization was performed blinded to the clinical data, and before the surgical decision.

KEY FINDINGS

Reference standard was available for 33 patients. The ictal source localization had a sensitivity of 70% and a specificity of 76%. The mean measurement of agreement (kappa) was 0.61, corresponding to substantial agreement (95% confidence interval (CI) 0.38-0.84). Twenty patients underwent resective surgery. The positive predictive value (PPV) for seizure freedom was 92% and the negative predictive value (NPV) was 43%. The likelihood ratio was nine times higher for the concordant results, as compared with the discordant ones.

SIGNIFICANCE

Source localization of rhythmic ictal activity using a distributed source model (LAURA) for the ictal EEG signals selected with a standardized method is feasible in clinical practice and has a good diagnostic accuracy. Our findings encourage clinical neurophysiologists assessing ictal EEGs to include this method in their armamentarium.

Chronic cerebrospinal venous insufficiency and venous stenoses in multiple sclerosis

OBJECTIVES

The traditional view that multiple sclerosis (MS) is an autoimmune disease has recently been challenged by the claim that MS is caused by chronic cerebrospinal venous insufficiency (CCSVI). Although several studies have questioned this vascular theory, the CCSVI controversy is still ongoing. Our aim was to assess the prevalence of CCSVI in Danish MS patients using sonography and compare these findings with MRI measures of venous flow and morphology.

METHODS

We investigated cervical and cerebral veins in 24 patients with relapsing-remitting MS (RRMS) and 15 healthy controls, using extracranial high-resolution ultrasound colour Doppler (US-CD) and transcranial colour Doppler sonography (TCDS), as well as magnetic resonance imaging (MRI) and phase-contrast MR blood flow measurements (PC-MR) of the cervical veins.

RESULTS

US-CD could not identify the left internal jugular vein (IJV) in one MS patient, other ultrasound examinations were normal in patients with MS. There was no difference in mean cross-sectional area of the IJV in MS patients compared with controls. Only one patient with MS and two healthy controls fulfilled one CCSVI criterion, and none fulfilled more than one CCSVI criterion. MR venography showed insignificant IJV stenosis (1-49%) in two patients with MS, whereas 50-69% IJV stenosis was detected in two healthy controls. There was no difference in PC-MR measurements of mean IJV blood flow between patients with MS and controls.

CONCLUSION

Our results do not corroborate the presence of vascular pathology in RRMS and we found no evidence supporting the CCSVI hypothesis.

Plasma NT-proBNP and white matter hyperintensities in type 2 diabetic patients

Abstract

Elevated plasma N-terminal (NT)-proBNP from the heart as well as white matter hyperintensities (WMH) in the brain predict cardiovascular (CV) mortality in the general population. The cause of poor prognosis associated with elevated P-NT-proBNP is not known but WMH precede strokes in high risk populations. We assessed the association between P-NT-proBNP and WMH or brain atrophy measured with magnetic resonance imaging (MRI) in type 2 diabetic patients, and age-matched controls.

Methods and results

We measured P-NT-proBNP(ng/l) in 20 diabetic patients without prior stroke but with(n = 10) or without(n = 10) asymptomatic coronary artery disease(CAD) in order to include patients with a wide-ranging CV risk profile. All patients and 26 controls had a 3D MRI and brain volumes(ml) with WMH and brain parenchymal fraction(BPF), an indicator of brain atrophy, were determined.

P-NT-proBNP was associated with WMH in linear regression analysis adjusted for CV risk factors(r = 0.94, p = 0.001) and with BPF in univariate analysis(r = 0.57, p = 0.009). Patients divided into groups of increased P-NT-proBNP levels were paralleled with increased WMH volumes(geometric mean[SD];(2.86[5.11] ml and 0.76[2.49] ml compared to patients with low P-NT-proBNP 0.20[2.28] ml, p = 0.003)) and also when adjusted for age, sex and presence of CAD(p = 0.017). The association was strengthened by CV risk factors and we did not find a common heart or brain specific driver of both P-NT-proBNP and WMH. Patients and particular patients with CAD had higher WMH, however no longer after adjustment for age and sex.

Conclusion

P-NT-proBNP was associated with WMH in type 2 diabetic patients, suggesting a linkage between heart and brain disease.