Background— In this study, we developed and validated a new approach for in vivo visualization of inflammatory processes by magnetic resonance imaging using biochemically inert nanoemulsions of perfluorocarbons (PFCs). Methods and Results— Local inflammation was provoked in 2 separate murine models of acute cardiac and cerebral ischemia, followed by intravenous injection of PFCs. Simultaneous acquisition of morphologically matching proton ( ¹ H) and fluorine ( ¹⁹ F) images enabled an exact anatomic localization of PFCs after application. Repetitive ¹ H/ ¹⁹ F magnetic resonance imaging at 9.4 T revealed a time-dependent infiltration of injected PFCs into the border zone of infarcted areas in both injury models, and histology demonstrated a colocalization of PFCs with cells of the monocyte/macrophage system. We regularly found the accumulation of PFCs in lymph nodes. Using rhodamine-labeled PFCs, we identified circulating monocytes/macrophages as the main cell fraction taking up injected nanoparticles. Conclusions— PFCs can serve as a “positive” contrast agent for the detection of inflammation by magnetic resonance imaging, permitting a spatial resolution close to the anatomic ¹ H image and an excellent degree of specificity resulting from the lack of any ¹⁹ F background. Because PFCs are nontoxic, this approach may have a broad application in the imaging and diagnosis of numerous inflammatory disease states.

Although the primary function of myoglobin (Mb) has been considered to be cellular O ₂ storage and supply, recent studies have shown that Mb in addition can act as NO oxidase. Here we report that Mb also significantly contributes to the attenuation of oxidative stress in cardiac muscle. In support of this hypothesis, we found that in isolated perfused hearts of Mb‐deficient (myo ^‒/‒ ) mice oxidative challenge by intracoronary infused H ₂ O ₂ (1‐300 µM) or superoxide formed by 2,3‐dimethoxy‐1,4‐naphtoquinone (0.1‐30 µM), respectively, depressed cardiac contractility to a greater extent than in wild‐type (WT) hearts, e.g., up to [H ₂ O ₂ ] = 10 µM there was a significant left ventricular developed pressure (LVDP) decrease in myo ^‒/‒ hearts only (90.4±4.2 vs. 98.1±0.7% of control, n =6, P <0.05). Likewise in an ischemia/reperfusion protocol, myo ^‒/‒ hearts showed a delayed recovery of postischemic function as compared with WT controls (e.g., LVDP was 35.6±7.5 vs. 22.4±5.3 mmHg, respectively, after 10 min of reperfusion, P <0.05, n =8), which correlated well with an enhanced release of reactive oxygen species in myo ^‒/‒ hearts as measured by online lucigenin‐enhanced chemiluminescence [e.g. 465±87 relative light units (RLU) in myo ^‒/‒ vs. 287±73 RLU in WT after 2.5 min of reperfusion, P <0.05, n =8]. ³¹ P NMR spectroscopy revealed concomitantly a more pronounced phosphocreatine overshoot during reperfusion in the knockout but only minute alterations in ATP and pH _i . Our data show that lack of Mb leads to increased vulnerability of cardiac function to oxidative challenge either pharmacologically induced or endogenously generated. We propose that Mb is a key element influencing redox pathways in cardiac muscle to functionally and metabolically protect the heart from oxidative damage.

Background— Emulsified perfluorocarbons (PFCs) are preferentially phagocytized by monocytes/macrophages and are readily detected by ¹⁹ F MRI. This study tests the hypothesis that ¹⁹ F MRI can be used to quantitate pulmonary inflammation by tracking of infiltrating PFC-loaded monocytes. Methods and Results— Pneumonia was induced in mice by intratracheal instillation of lipopolysaccharides (LPS) followed by intravenous injection of PFCs. Whereas regular ¹ H MRI provided no evidence of lung injury 24 hours after LPS, the concurrent ¹⁹ F images clearly show PFC accumulation in both pulmonary lobes. Imaging at 48 hours after LPS revealed signals in ¹ H images at the same location as the 24-hour ¹⁹ F signals. Thus, progressive pneumonia was first predicted by ¹⁹ F MRI early after PFC administration. Without LPS, at no time were ¹⁹ F signals observed within the lung. Histology and fluorescence-activated cell sorting (FACS) combined with ¹⁹ F MRI confirmed the presence of infiltrating PFC-loaded monocytes/macrophages after LPS challenge. Additional experiments with graded doses of LPS demonstrated that ¹⁹ F signal intensity strongly correlated with both LPS dose and pathological markers of lung inflammation. In separate studies, dexamethasone and CGS21680 (adenosine 2A receptor agonist) were used to demonstrate the ability of ¹⁹ F MRI to monitor anti-inflammatory therapies. Conclusions— PFCs serve as a contrast agent for the prognostic and quantitative assessment of pulmonary inflammation by in vivo ¹⁹ F MRI, which is characterized by a high degree of specificity due to the lack of any ¹⁹ F background. Because PFCs are biochemically inert, this approach may also be suitable for human applications.

Background—: Noninvasive detection of deep venous thrombi and subsequent pulmonary thromboembolism is a serious medical challenge, since both incidences are difficult to identify by conventional ultrasound techniques. Methods and Results—: Here, we report a novel technique for the sensitive and specific identification of developing thrombi using background-free ¹⁹ F magnetic resonance imaging, together with α2-antiplasmin peptide (α2 ^AP )–targeted perfluorocarbon nanoemulsions (PFCs) as contrast agent, which is cross-linked to fibrin by active factor XIII. Ligand functionality was ensured by mild coupling conditions using the sterol-based postinsertion technique. Developing thrombi with a diameter 60 minutes after thrombus induction no longer resulted in detectable ¹⁹ F magnetic resonance imaging signals. Corresponding results were obtained in ex vivo generated human clots. Thus, α2 ^AP -PFCs can visualize freshly developed thrombi that might still be susceptible to pharmacological intervention. Conclusions—: Our results demonstrate that ¹ H/ ¹⁹ F magnetic resonance imaging, together with α2 ^AP -PFCs, is a sensitive, noninvasive technique for the diagnosis of acute deep venous thrombi and pulmonary thromboemboli. Furthermore, ligand coupling by the sterol-based postinsertion technique represents a unique platform for the specific targeting of PFCs for in vivo ¹⁹ F magnetic resonance imaging.

T2 mapping indicates to be a sensitive method for detection of tissue oedema hidden beyond the detection limits of T2-weighted Cardiovascular Magnetic Resonance (CMR). However, due to variability of baseline T2 values in volunteers, reference values need to be defined. Therefore, the aim of the study was to investigate the effects of age and sex on quantitative T2 mapping with a turbo gradient-spin-echo (GRASE) sequence at 1.5 T. For that reason, we studied sensitivity issues as well as technical and biological effects on GRASE-derived myocardial T2 maps. Furthermore, intra- and interobserver variability were calculated using data from a large volunteer group. GRASE-derived multiecho images were analysed using dedicated software. After sequence optimization, validation and sensitivity measurements were performed in muscle phantoms ex vivo and in vivo. The optimized parameters were used to analyse CMR images of 74 volunteers of mixed sex and a wide range of age with typical prevalence of hypertension and diabetes. Myocardial T2 values were analysed globally and according to the 17 segment model. Strain-encoded (SENC) imaging was additionally performed to investigate possible effects of myocardial strain on global or segmental T2 values. Ex vivo studies in muscle phantoms showed, that GRASE-derived T2 values were comparable to those acquired by a standard multiecho spinecho sequence but faster by a factor of 6. Besides that, T2 values reflected tissue water content. The in vivo measurements in volunteers revealed intra- and interobserver correlations with R2=0.91 and R2=0.94 as well as a coefficients of variation of 2.4% and 2.2%, respectively. While global T2 time significantly decreased towards the heart basis, female volunteers had significant higher T2 time irrespective of myocardial region. We found no correlation of segmental T2 values with maximal systolic, diastolic strain or heart rate. Interestingly, volunteers´ age was significantly correlated to T2 time while that was not the case for other coincident cardiovascular risk factors. GRASE-derived T2 maps are highly reproducible. However, female sex and aging with typical prevalence of hypertension and diabetes were accompanied by increased myocardial T2 values. Thus, sex and age must be considered as influence factors when using GRASE in a diagnostic manner.

Prediction of the transition from stable to acute coronary syndromes driven by vascular inflammation, thrombosis with subsequent microembolization, and vessel occlusion leading to irreversible myocardial damage is still an unsolved problem. Here, we introduce a multi-targeted and multi-color nanotracer platform technology that simultaneously visualizes evolving danger patterns in the development of progressive coronary inflammation and atherothrombosis prior to spontaneous myocardial infarction in mice. Individual ligand-equipped perfluorocarbon nanoemulsions are used as targeting agents and are differentiated by their specific spectral signatures via implementation of multi chemical shift selective¹⁹F MRI. Thereby, we are able to identify areas at high risk of and predictive for consecutive development of myocardial infarction, at a time when no conventional parameter indicates any imminent danger. The principle of this multi-targeted approach can easily be adapted to monitor also a variety of other disease entities and constitutes a technology with disease-predictive potential.