Screening human lung cancer with predictive models of serum magnetic resonance spectroscopy metabolomics.

The current high mortality of human lung cancer stems largely from the lack of feasible, early disease detection tools. An effective test with serum metabolomics predictive models able to suggest patients harboring disease could expedite triage patient to specialized imaging assessment. Here, using a training-validation-testing-cohort design, we establish our high-resolution magic angle spinning (HRMAS) magnetic resonance spectroscopy (MRS)-based metabolomics predictive models to indicate lung cancer presence and patient survival using serum samples collected prior to their disease diagnoses. Studied serum samples were collected from 79 patients before (within 5.0 y) and at lung cancer diagnosis. Disease predictive models were established by comparing serum metabolomic patterns between our training cohorts: patients with lung cancer at time of diagnosis, and matched healthy controls. These predictive models were then applied to evaluate serum samples of our validation and testing cohorts, all collected from patients before their lung cancer diagnosis. Our study found that the predictive model yielded values for prior-to-detection serum samples to be intermediate between values for patients at time of diagnosis and for healthy controls; these intermediate values significantly differed from both groups, with an F1 score = 0.628 for cancer prediction. Furthermore, values from metabolomics predictive model measured from prior-to-diagnosis sera could significantly predict 5-y survival for patients with localized disease.

Inorganic Phosphate-Induced Extracellular Vesicles from Vascular Smooth Muscle Cells Contain Elevated Levels of Hyaluronic Acid, Which Enhance Their Interaction with Very Small Superparamagnetic Iron Oxide Particles.

Patients with chronic kidney disease (CKD) have a high prevalence of hyperphosphatemia, where uremic toxins like inorganic phosphate (Pi) induce a cardiovascular remodeling. Related disorders like atherosclerosis bear the risk of increased morbidity and mortality. We previously found that Pi stimulates the synthesis and sulfation of the negatively charged glycosaminoglycans (GAGs) heparan sulfate and chondroitin sulfate in vascular smooth muscle cells (VSMC). Similar GAG alterations were detected in VSMC-derived exosome-like extracellular vesicles (EV). These EV showed a strong interaction with very small superparamagnetic iron oxide particles (VSOP), which are used as imaging probes for experimental magnetic resonance imaging (MRI). Hyaluronic acid (HA) represents another negatively charged GAG which is supposed to function as binding motif for VSOP as well. We investigated the effects of Pi on the amounts of HA in cells and EV and studied the HA-dependent interaction between VSOP with cells and EV. Rat VSMC were treated with elevated concentrations of Pi. CKD in rats was induced by adenine feeding. EV were isolated from culture supernatants and rat plasma. We investigated the role of HA in binding VSOP to cells and EV via cell-binding studies, proton relaxometry, and analysis of cellular signaling, genes, proteins, and HA contents. Due to elevated HA contents, VSMC and EV showed an increased interaction with VSOP after Pi stimulation. Amongst others, Pi induced hyaluronan synthase (HAS)2 expression and activation of the Wnt pathway in VSMC. An alternative upregulation of HA by iloprost and an siRNA-mediated knockdown of HAS2 confirmed the importance of HA in cells and EV for VSOP binding. The in vitro-derived data were validated by analyses of plasma-derived EV from uremic rats. In conclusion, the inorganic uremic toxin Pi induces HA synthesis in cells and EV, which leads to an increased interaction with VSOP. HA might therefore be a potential molecular target structure for improved detection of pathologic tissue changes secondary to CKD like atherosclerosis or cardiomyopathy using EV, VSOP and MRI.

Characterization of renal fibrosis in rats with chronic kidney disease by in vivo tomoelastography.

Chronic kidney disease (CKD) is characterized by structural changes, such as tubular atrophy, renal fibrosis, and glomerulosclerosis, all of which affect the viscoelastic properties of biological tissues. However, detection of renal viscoelasticity changes because diagnostic markers by in vivo elastography lack histopathological validation through animal models. Therefore, we investigated in vivo multiparametric magnetic resonance imaging (mp-MRI), including multifrequency magnetic resonance elastography-based tomoelastography, in the kidneys of 10 rats with adenine-induced CKD and eight healthy controls. Kidney volume (in mm3 ), water diffusivity (apparent diffusion coefficient [ADC] in mm2 /s), shear wave speed (SWS; in m/s; related to stiffness), and wave penetration rate (PR; in m/s; related to inverse viscosity) were quantified by mp-MRI and correlated with histopathologically determined renal fibrosis (collagen area fraction [CAF]; in %). Kidney volume (40% ± 29%, p = 0.009), SWS (11% ± 12%, p = 0.016), and PR (20% ± 15%, p = 0.004) were significantly increased in CKD, which was accompanied by ADC (-24% ± 27%, p = 0.02). SWS, PR, and ADC were correlated with CAF with R = 0.63, 0.75, and -0.5 (all p < 0.05), respectively. In the CKD rats, histopathology showed tubule dilation due to adenine crystal deposition. Collectively, our results suggest that collagen accumulation during CKD progression transforms soft-compliant renal tissue into a more rigid-solid state with reduced water mobility. We hypothesized that tubule dilation-a specific feature of our model-might lead to higher intraluminal pressure, which could also contribute to elevated renal stiffness. Tomoelastography is a promising tool for noninvasively assessing disease progression, detecting biomechanical properties that are sensitive to different pathologic features of CKD.

Uremic Toxin-Induced Exosome-like Extracellular Vesicles Contain Enhanced Levels of Sulfated Glycosaminoglycans which Facilitate the Interaction with Very Small Superparamagnetic Iron Oxide Particles.

Uremic toxins exert pathophysiological effects on cells and tissues, such as the generation of a pro-calcifying subtype of exosome-like extracellular vesicles (EVs) in vascular cells. Little is known about the effects of the toxins on the surface structure of EVs. Thus, we studied the effects of uremic toxins on the abundance of sulfated glycosaminoglycans (GAGs) in EVs, and the implications for binding of ligands such as very small superparamagnetic iron oxide particles (VSOPs) which could be of relevance for radiological EV-imaging. Vascular cells were treated with the uremic toxins NaH2PO4 and a mixture of urea and indoxyl sulfate. Uremia in rats was induced by adenine feeding. EVs were isolated from culture supernatants and plasma of rats. By proton T1-relaxometry, magnetic particle spectroscopy, and analysis of genes, proteins, and GAG-contents, we analyzed the roles of GAGs in the ligand binding of EVs. By influencing GAG-associated genes in host cells, uremic toxins induced higher GAG contents in EVs, particularly of sulfated chondroitin sulfate and heparan sulfate chains. EVs with high GAG content interacted stronger with VSOPs compared to control ones. This was confirmed by experiments with GAG-depleted EVs from genetically modified CHO cells and with uremic rat-derived EVs. Mechanistically, uremic toxin-induced PI3K/AKT-signaling and expression of the sulfate transporter SLC26A2 in host cells contributed to high GAG contents in EVs. In conclusion, uremic conditions induce enhanced GAG contents in EVs, which entails a stronger interaction with VSOPs. VSOPs might be suitable for radiological imaging of EVs rich in GAGs.

Fibrin-targeting molecular MRI in inflammatory CNS disorders.

BACKGROUND: Fibrin deposition is a fundamental pathophysiological event in the inflammatory component of various CNS disorders, such as multiple sclerosis (MS) and Alzheimer's disease. Beyond its traditional role in coagulation, fibrin elicits immunoinflammatory changes with oxidative stress response and activation of CNS-resident/peripheral immune cells contributing to CNS injury. PURPOSE: To investigate if CNS fibrin deposition can be determined using molecular MRI, and to assess its capacity as a non-invasive imaging biomarker that corresponds to inflammatory response and barrier impairment. MATERIALS AND METHODS: Specificity and efficacy of a peptide-conjugated Gd-based molecular MRI probe (EP2104-R) to visualise and quantify CNS fibrin deposition were evaluated. Probe efficacy to specifically target CNS fibrin deposition in murine adoptive-transfer experimental autoimmune encephalomyelitis (EAE), a pre-clinical model for MS (n = 12), was assessed. Findings were validated using immunohistochemistry and laser ablation inductively coupled plasma mass spectrometry. Deposition of fibrin in neuroinflammatory conditions was investigated and its diagnostic capacity for disease staging and monitoring as well as quantification of immunoinflammatory response was determined. Results were compared using t-tests (two groups) or one-way ANOVA with multiple comparisons test. Linear regression was used to model the relationship between variables. RESULTS: For the first time (to our knowledge), CNS fibrin deposition was visualised and quantified in vivo using molecular imaging. Signal enhancement was apparent in EAE lesions even 12-h after administration of EP2104-R due to targeted binding (M ± SD, 1.07 ± 0.10 (baseline) vs. 0.73 ± 0.09 (EP2104-R), p = .008), which could be inhibited with an MRI-silent analogue (M ± SD, 0.60 ± 0.14 (EP2104-R) vs. 0.96 ± 0.13 (EP2104-La), p = .006). CNS fibrin deposition corresponded to immunoinflammatory activity (R2 = 0.85, p < .001) and disability (R2 = 0.81, p < .001) in a model for MS, which suggests a clinical role for staging and monitoring. Additionally, EP2104-R showed substantially higher SNR (M ± SD, 6.6 ± 1 (EP2104-R) vs. 2.7 ± 0.4 (gadobutrol), p = .004) than clinically used contrast media, which increases sensitivity for lesion detection. CONCLUSIONS: Molecular imaging of CNS fibrin deposition provides an imaging biomarker for inflammatory CNS pathology, which corresponds to pathophysiological ECM remodelling and disease activity, and yields high signal-to-noise ratio, which can improve diagnostic neuroimaging across several neurological diseases with variable degrees of barrier impairment.

Uraemic extracellular vesicles augment osteogenic transdifferentiation of vascular smooth muscle cells via enhanced AKT signalling and PiT-1 expression.

Extracellular vesicles (EV) function as messengers between endothelial cells (EC) and vascular smooth muscle cells (VSMC). Since chronic kidney disease (CKD) increases the risk for vascular calcifications, we investigated whether EV derived from uraemic milieu-stimulated EC and derived from uraemic rats impact the osteogenic transdifferentiation/calcification of VSMC. For that purpose, human EC were treated with urea and indoxyl sulphate or left untreated. Experimental uraemia in rats was induced by adenine feeding. 'Uraemic' and control EV (EVUR ; EVCTRL ) were isolated from supernatants and plasma by using an exosome isolation reagent. Rat VSMC were treated with a pro-calcifying medium (CM) with or without EV supplementation. Gene expressions, miRNA contents and protein expressions were determined by qPCR and Western blots, respectively. Calcifications were determined by colorimetric assays. Delivery of miRNA inhibitors/mimics to EV and siRNA to VSMC was achieved via transfection. EVCTRL and EVUR differed in size and miRNA contents. Contrary to EVCTRL , EC- and plasma-derived EVUR significantly increased the pro-calcifying effects of CM, including altered gene expressions of osterix, runx2, osteocalcin and SM22α. Further, EVUR enhanced the protein expression of the phosphate transporter PiT-1 in VSMC and induced a phosphorylation of AKT and ERK. Knock down of PiT-1 and individual inhibition of AKT and ERK signalling in VSMC blocked the pro-calcifying effects of EVUR . Similar effects were achieved by inhibition of miR-221/-222 and mimicking of miR-143/-145 in EVUR . In conclusion, EVUR might represent an additional puzzle piece of the complex pathophysiology of vascular calcifications in CKD.

Temperatures in Pigs During 3 T MRI Temperatures, Heart Rates, and Breathing Rates of Pigs During RF Power Deposition in a 3 T (128 MHz) Body Coil.

Exposure to radiofrequency (RF) power deposition during magnetic resonance imaging (MRI) induces elevated body-tissue temperatures and may cause changes in heart and breathing rates, disturbing thermoregulation. Eleven temperature sensors were placed in muscle tissue and one sensor in the rectum (measured in 10 cm depth) of 20 free-breathing anesthetized pigs to verify temperature curves during RF exposure. Tissue temperatures and heart and breathing rates were measured before, during, and after RF exposure. Pigs were placed into a 60-cm diameter whole-body resonator of a 3 T MRI system. Nineteen anesthetized pigs were divided into four RF exposure groups: sham (0 W/kg), low-exposure (2.7 W/kg, mean exposure time 56 min), moderate-exposure (4.8 W/kg, mean exposure time 31 min), and high-exposure (4.4 W/kg, mean exposure time 61 min). One pig was exposed to a whole-body specific absorption rate (wbSAR) of 11.4 W/kg (extreme-exposure). Hotspot temperatures, measured by sensor 2, increased by mean 5.0 ± 0.9°C, min 3.9; max 6.3 (low), 7.0 ± 2.3°C, min 4.6; max 9.9 (moderate), and 9.2 ± 4.4°C, min 6.1, max 17.9 (high) compared with 0.3 ± 0.3°C in the sham-exposure group (min 0.1, max 0.6). Four time-temperature curves were identified: sinusoidal, parabolic, plateau, and linear. These curve shapes did not correlate with RF intensity, rectal temperature, breathing rate, or heart rate. In all pigs, rectal temperatures increased (2.1 ± 0.9°C) during and even after RF exposure, while hotspot temperatures decreased after exposure. When rectal temperature increased by 1°C, hotspot temperature increased up to 42.8°C within 37 min (low-exposure) or up to 43.8°C within 24 min (high-exposure). Global wbSAR did not correlate with maximum hotspot. Bioelectromagnetics. 2021;42:37-50. © 2020 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society.

Metabolomic prostate cancer fields in HRMAS MRS-profiled histologically benign tissue vary with cancer status and distance from cancer.

In this article, we review the state of the field of high resolution magic angle spinning MRS (HRMAS MRS)-based cancer metabolomics since its beginning in 2004; discuss the concept of cancer metabolomic fields, where metabolomic profiles measured from histologically benign tissues reflect patient cancer status; and report our HRMAS MRS metabolomic results, which characterize metabolomic fields in prostatectomy-removed cancerous prostates. Three-dimensional mapping of cancer lesions throughout each prostate enabled multiple benign tissue samples per organ to be classified based on distance from and extent of the closest cancer lesion as well as the Gleason score (GS) of the entire prostate. Cross-validated partial least squares-discriminant analysis separations were achieved between cancer and benign tissue, and between cancer tissue from prostates with high (≥4 + 3) and low (≤3 + 4) GS. Metabolomic field effects enabled histologically benign tissue adjacent to cancer to distinguish the GS and extent of the cancer lesion itself. Benign samples close to either low GS cancer or extensive cancer lesions could be distinguished from those far from cancer. Furthermore, a successfully cross-validated multivariate model for three benign tissue groups with varying distances from cancer lesions within one prostate indicates the scale of prostate cancer metabolomic fields. While these findings could, at present, be potentially useful in the prostate cancer clinic for analysis of biopsy or surgical specimens to complement current diagnostics, the confirmation of metabolomic fields should encourage further examination of cancer fields and can also enhance understanding of the metabolomic characteristics of cancer in myriad organ systems. Our results together with the success of HRMAS MRS-based cancer metabolomics presented in our literature review demonstrate the potential of cancer metabolomics to provide supplementary information for cancer diagnosis, staging, and patient prognostication.

Dynamic contrast-enhanced MR imaging of the prostate: intraindividual comparison of gadoterate meglumine and gadobutrol.

OBJECTIVES: To intraindividually compare the signal-enhancing effect of 0.5 M gadoterate meglumine and 1.0 M gadobutrol in dynamic contrast-enhanced magnetic resonance (DCE-MR) imaging of the prostate. METHODS: Fifty patients who underwent two 3-T MR examinations of the prostate were included in this IRB-approved retrospective uncontrolled, unrandomized study. All received two scans (mean time interval, 20.5 months) including T1-weighted DCE-MR imaging, one with 0.5 M gadoterate meglumine and one with 1.0 M gadobutrol. Equimolar doses of gadolinium (0.1 mmol/kg body weight) were administered with identical injection speed (2 mL/s), resulting in differing gadolinium delivery rate. An identical region of interest (ROItz) within a BPH-node was identified on both scans. The area under the time-enhancement curve of each ROItz from 0 to 180 s post contrast arrival and pharmacokinetic parameters were calculated. Relative enhancement and signal-to-noise (SNR) and contrast-to-noise (CNR) ratios in the delayed phase at about 180 s were compared between both agents. RESULTS: There was a significantly larger area under the time-enhancement curve (5.53 vs 4.97 p = 0.0007) and higher relative enhancement of BPH nodules (2.23 vs 1.96 p < 0.0001) with gadobutrol compared with gadoterate meglumine. There were no significant differences in SNR (44.55 vs 37.63 p = 0.12), CNR (31.22 vs 26.39 p = 0.18), and pharmacokinetic parameters Ktrans (0.31 vs 0.32 p = 0.86), Ve (1.36 vs 0.98 p = 0.13), and Kep (0.34 vs 0.36 p = 0.12). CONCLUSIONS: At equimolar doses, increased gadolinium delivery over time using gadobutrol provides higher relative enhancement parameters in BPH nodules compared with gadoterate meglumine, but does not translate into improved SNR or CNR. KEY POINTS: • At equal injection rate and equimolar total dose, gadobutrol compared with gadoterate meglumine provides a significantly greater relative enhancement in DCE-MR imaging of BPH over the first 180 s. • There are no significant differences in SNRs, CNRs, and pharmacokinetic parameters between the two GBCAs.

DCE-MR imaging of orbital lesions: diagnostic performance of the tumor flow residence time τ calculated by a multi-compartmental pharmacokinetic tumor model based on individual factors.

BACKGROUND: Differentiating benign from malignant orbital lesions by imaging and clinical presentation can be challenging. PURPOSE: To differentiate benign from malignant orbital masses using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) based on tumor flow residence time τ calculated with the aid of a pharmacokinetic tumor model. MATERIAL AND METHODS: Sixty patients with orbital masses were investigated by 3-T MRI including dynamic sequences. The signal intensity-time curve after i.v. contrast medium administration within lesions was approximated by Gd-concentration profiles on the basis of model calculations where the tumor is embedded in a whole-body kinetic model. One output of the model was tumor flow residence time τ, defined as the ratio of the tumor volume and the tumor blood flow rate. Receiver operating characteristic (ROC) curves were used to analyze the diagnostic performance of τ. The results were compared with those of Ktrans, kep, ve, iAUC, and ADC. RESULTS: Thirty-one benign and 29 malignant orbital masses were identified (reference standard: histopathology, clinical characteristics). Mean τ was significantly longer for benign masses (94 ± 48 s) than for malignant masses (21 ± 19 s, P < 0.001). ROC analysis revealed the highest area under the curve (AUC = 0.94) for τ in orbital masses compared to standard methods. CONCLUSION: Tumor flow residence times τ of benign and malignant orbital masses are valuable in the diagnostic work-up of orbital tumors. Measures of diagnostic accuracy were superior for τ compared to ADC, Ktrans, ve, and iAUC.

Very small superparamagnetic iron oxide nanoparticles: Long-term fate and metabolic processing in atherosclerotic mice.

We investigated the biotransformation of very small superparamagnetic iron oxide nanoparticles (VSOP) in atherosclerotic LDLR-/- mice. Transmission electron microscopy revealed an uptake of VSOP not only by macrophages but also by endothelial cells in liver, spleen, and atherosclerotic lesions and their accumulation in the lysosomal compartment. Using magnetic particle spectroscopy (MPS), we show that the majority of VSOP's superparamagnetic iron was degraded within 28 days. MPS spectrum shape indicated changes in the magnetic properties of VSOP during the biodegradation process. Experiments with primary murine bone marrow derived macrophages, primary murine liver sinusoidal endothelial cells, and primary human aortic endothelial cells demonstrated that loading with VSOP induced a differential response of cellular iron homeostasis mechanisms with increased levels of ferritin and iron transport proteins in macrophages and increased levels of ferritin in endothelial cells.

Synthesis of europium-doped VSOP, customized enhancer solution and improved microscopy fluorescence methodology for unambiguous histological detection.

BACKGROUND: Intrinsic iron in biological tissues frequently precludes unambiguous the identification of iron oxide nanoparticles when iron-based detection methods are used. Here we report the full methodology for synthesizing very small iron oxide nanoparticles (VSOP) doped with europium (Eu) in their iron oxide core (Eu-VSOP) and their unambiguous qualitative and quantitative detection by fluorescence. METHODS AND RESULTS: The resulting Eu-VSOP contained 0.7 to 2.7% Eu relative to iron, which was sufficient for fluorescent detection while not altering other important particle parameters such as size, surface charge, or relaxivity. A customized enhancer solution with high buffer capacity and nearly neutral pH was developed to provide an antenna system that allowed fluorescent detection of Eu-VSOP in cells and histologic tissue slices as well as in solutions even under acidic conditions as frequently obtained from dissolved organic material. This enhancer solution allowed detection of Eu-VSOP using a standard fluorescence spectrophotometer and a fluorescence microscope equipped with a custom filter set with an excitation wavelength (λex) of 338 nm and an emission wavelength (λem) of 616 nm. CONCLUSION: The fluorescent detection of Eu-doped very small iron oxide nanoparticles (Eu-VSOP) provides a straightforward tool to unambiguously characterize VSOP biodistribution and toxicology at tissue, and cellular levels, providing a sensitive analytical tool to detect Eu-doped IONP in dissolved organ tissue and biological fluids with fluorescence instruments.

Inflammation-induced brain endothelial activation leads to uptake of electrostatically stabilized iron oxide nanoparticles via sulfated glycosaminoglycans.

Based on our previous data on the presence of very small superparamagnetic iron oxide nanoparticles (VSOP) on brain endothelial structures during experimental autoimmune encephalomyelitis (EAE), we investigated the mechanisms of VSOP binding on inflamed brain endothelial cells in vivo and in vitro. After intravenous application, VSOP were detected in brain endothelial cells of EAE animals at peak disease and prior to clinical onset. In vitro, inflammatory stimuli increased VSOP uptake by brain endothelial bEnd.3 cells, which we confirmed in primary endothelial cells and in bEnd.3 cells cultured under shear stress. Transmission electron microscopy and blocking experiments revealed that during inflammation VSOP were endocytosed by bEnd.3. Modified sulfated glycosaminoglycans (GAG) on inflamed brain endothelial cells were the primary binding site for VSOP, as GAG degradation and inhibition of GAG sulfation reduced VSOP uptake. Thus, VSOP-based MRI is sensitive to visualize early neuroinflammatory processes such as GAG modifications on brain endothelial cells.

Paclitaxel-Coated Balloons: Investigation of Drug Transfer in Healthy and Atherosclerotic Arteries - First Experimental Results in Rabbits at Low Inflation Pressure.

PURPOSE: Beyond antiproliferative properties, paclitaxel exhibits anti-inflammatory activity, which might be beneficial in the local treatment of nonocclusive coronary artery disease. Paclitaxel release and tissue concentrations after paclitaxel-coated balloon treatment using different pressures have not been investigated so far. The aim of the study was to investigate in an atherosclerotic rabbit model whether drug transfer from paclitaxel-coated balloons into the vessel wall is affected by the presence of atherosclerotic lesions and to which extent it depends on the inflation pressure used. METHODS: Paclitaxel-coated balloons (3.5 µg/mm(2) paclitaxel) were inflated with pressures of 1, 2, or 6 atm (60s) in healthy (n = 39) and atherosclerotic (n = 22) arteries of New Zealand White Rabbits. Paclitaxel content in arterial walls (10 min after interventions) and paclitaxel remaining on balloons after treatment were analyzed using high-performance liquid chromatography. RESULTS: Median paclitaxel tissue concentrations were 829.3 µg/g (IQR 636.5-1487 µg/g) in healthy and 375.7 µg/g (IQR 169.8-771.6 µg/g) in atherosclerotic arteries (p = 0.0002). The paclitaxel tissue concentration was dependent on inflation pressure (1 atm vs. 2 atm vs. 6 atm) in atherosclerotic arteries (p = 0.0106) but not in healthy arteries (p ≥ 0.05). CONCLUSIONS: Atherosclerotic lesions impede the transfer of paclitaxel into arterial walls. Higher inflation pressures resulted in an increased paclitaxel transfer in atherosclerotic but not in healthy arteries. However, it is assumed that the tissue concentrations achieved with an inflation pressure of 2 atm are potentially effective in this model.

Intraindividual, randomized comparison of the macrocyclic contrast agents gadobutrol and gadoterate meglumine in breast magnetic resonance imaging.

OBJECTIVES: To compare intraindividually two macrocyclic contrast agents - gadobutrol and gadoterate meglumine (Gd-DOTA) - for dynamic and quantitative assessment of relative enhancement (RE) in benign and malignant breast lesions. METHODS: This was an ethically approved, prospective, single-centre, randomized, crossover study in 52 women with suspected breast lesions referred for magnetic resonance imaging (MRI). Each patient underwent one examination with gadobutrol and one with Gd-DOTA (0.1 mmol/kg BW) on a 1.5 T system 1 - 7 days apart. Dynamic, T1-weighted, 3D gradient echo sequences were acquired under identical conditions. Quantitative evaluation with at least three regions of interest (ROI) per lesion was performed. Primary endpoint was RE during the initial postcontrast phase after the first and second dynamic acquisition, and peak RE. All lesions were histologically proven; differences between the examinations were evaluated. RESULTS: Forty-five patients with a total of 11 benign and 34 malignant lesions were assessed. Mean RE was significantly higher for gadobutrol than Gd-DOTA (p < 0.0001). Gadobutrol showed significantly less washout (64.4 %) than Gd-DOTA (75.4 %) in malignant lesions (p = 0.048) CONCLUSIONS: Gadobutrol has higher RE values compared with Gd-DOTA, whereas Gd-DOTA shows more marked washout in malignant lesions. This might improve the detection of breast lesions and influence the specificity of breast MRI-imaging.

Assessment of inflammation with a very small iron-oxide particle in a murine model of reperfused myocardial infarction.

PURPOSE: To investigate a very small iron-oxide particle (VSOP) in a mouse model of acute ischemia-reperfusion to access the mechanism of such particles in areas of myocardial inflammation. MATERIALS AND METHODS: Animals were injected with VSOP at several time points, in a mouse model of acute myocardial infarction (MI), before and after MI. MRI was used to localize areas of VSOP enhancement, evaluate VSOP areas extension, and determine the related T2* values. Histology, electron microscopy, macrophage counting, and Evan's Blue staining were also performed. RESULTS: We found that areas of VSOP uptake decreased from 1 to 8 days post-MI while the related T2* values increased. T2* and VSOP areas, defined from MRI data, correlated well between 1 and 3 days post-MI but not at 7 days after injection. Histological analysis and electron microscopy showed colocalization of macrophages with areas of VSOP staining. However, there was no correlation between number of macrophages and the extension of the VSOP areas achieved by MR. We found that only areas of increased permeability (assessed by Evan's Blue staining) showed colocalization of macrophages and VSOP uptake. CONCLUSION: This study demonstrates that VSOP allows the assessment of myocardial inflammation associated with increased permeability during infarct healing in a mouse model of ischemia-reperfusion.

Repeated Injection of Very Small Superparamagnetic Iron Oxide Particles (VSOPs) in Murine Atherosclerosis: A Safety Study.

Citrate-coated electrostatically stabilized very small superparamagnetic iron oxide particles (VSOPs) have been successfully tested as magnetic resonance angiography (MRA) contrast agents and are promising tools for molecular imaging of atherosclerosis. Their repeated use in the background of pre-existing hyperlipidemia and atherosclerosis has not yet been studied. This study aimed to investigate the effect of multiple intravenous injections of VSOPs in atherosclerotic mice. Taurine-formulated VSOPs (VSOP-T) were repeatedly intravenously injected at 100 µmol Fe/kg in apolipoprotein E-deficient (ApoE KO) mice with diet-induced atherosclerosis. Angiographic imaging was carried out by in vivo MRI. Magnetic particle spectrometry was used to detect tissue VSOP content, and tissue iron content was quantified photometrically. Pathological changes in organs, atherosclerotic plaque development, and expression of hepatic iron-related proteins were evaluated. VSOP-T enabled the angiographic imaging of heart and blood vessels with a blood half-life of one hour. Repeated intravenous injection led to VSOP deposition and iron accumulation in the liver and spleen without affecting liver and spleen pathology, expression of hepatic iron metabolism proteins, serum lipids, or atherosclerotic lesion formation. Repeated injections of VSOP-T doses sufficient for MRA analyses had no significant effects on plaque burden, steatohepatitis, and iron homeostasis in atherosclerotic mice. These findings underscore the safety of VSOP-T and support its further development as a contrast agent and molecular imaging tool.

Imaging of magnetic microfield distortions allows sensitive single-cell detection.

Cell tracking with magnetic resonance imaging (MRI) is mostly performed using superparamagnetic iron oxide (SPIO) nanoparticle-labeled cells. However, negative contrast in T2*-weighted imaging is inherently problematic as a homogeneous background signal is required to visualize the negative signal. In a magnetic field, SPIO-labeled cells develop their own magnetization, distorting the main field. We show here a method to visualize these distortions and use them to identify single cells with increased sensitivity and certainty compared to T2* images. We labeled HeLa cells with SPIOs, suspended labeled cells in agarose to make phantoms, and performed high-resolution gradient-echo MRI. Phase images were processed to enhance the visibility of single cells. To quantify SPIO content, we generated a map of frequency differences. MRI of cell phantoms showed that single cells could be detected at concentrations ranging from 200 to 10,000 cells mL(-1). Postprocessing of the magnetic resonance phase images reveals characteristic microfield distortions, increasing dramatically the sensitivity of cell recognition, compared to unprocessed T2* images. Calculating frequency shifts and comparing microfield distortions to simulations permit estimation of the nanoparticle load of single cells. We expect the ability to detect and quantify the iron load of single cells to prove useful in studies of cell trafficking, especially in rare cell populations.

Rapid binding of electrostatically stabilized iron oxide nanoparticles to THP-1 monocytic cells via interaction with glycosaminoglycans.

Magnetic resonance imaging (MRI) with contrast agents that target specific inflammatory components of atherosclerotic lesions has the potential to emerge as promising diagnostic modality for detecting unstable plaques. Since a high content of macrophages and alterations of the extracellular matrix are hallmarks of plaque instability, these structures represent attractive targets for new imaging modalities. In this study, we compared in vitro uptake and binding of electrostatically stabilized citrate-coated very small superparamagnetic iron oxide particles (VSOP) to THP-1 cells with sterically stabilized carboxydextran-coated Resovist(®). Uptake of VSOP in both THP-1 monocytic cells and THP-derived macrophages (THP-MΦ) was more efficient compared to Resovist(®) without inducing cytotoxicity or modifying normal cellular functions (no changes in levels of reactive oxygen species, caspase-3 activity, proliferation, cytokine production). Importantly, VSOP bound with high affinity to the cell surface and to apoptotic membrane vesicles. Inhibition of glycosaminoglycan (GAG) synthesis by glucose deprivation in THP-MΦ was associated with a significant reduction of VSOP attachment suggesting that the strong interaction of VSOP with the membranes of cells and apoptotic vesicles occurs via binding to negatively charged GAGs. These in vitro experiments show that VSOP-enhanced MRI may represent a new imaging approach for visualizing high-risk plaques on the basis of targeting pathologically increased GAGs or apoptotic membrane vesicles in atherosclerotic lesions. VSOP should be investigated further in appropriate in vivo experiments to characterize accumulation in unstable plaque.

Macrocyclic contrast agents for magnetic resonance imaging of chronic myocardial infarction: intraindividual comparison of gadobutrol and gadoterate meglumine.

OBJECTIVES: To compare 0.15 mmol/kg gadobutrol for late gadolinium enhancement (LGE) imaging of chronic myocardial infarction with a relaxivity-adjusted dose of gadoterate meglumine (Gd-DOTA). METHODS: Seventeen patients with suspected chronic myocardial infarction underwent LGE imaging at 1.5 T, acquiring an inversion-recovery-prepared gradient echo sequence 15 min after contrast agent administration. Each patient underwent LGE imaging twice, once after administration of 0.15 mmol/kg gadobutrol (r1 = 5.2 l mmol(-1) s(-1)) and after 0.22 mmol/kg Gd-DOTA (r1 = 3.6 l mmol(-1) s(-1)). Two readers independently determined infarct size and contrast-to-noise ratios of infarcted myocardium to remote myocardium (CNR(remote)) and to the left ventricular lumen (CNR(lumen)). RESULTS: LGE was present in 14 patients. Infarct sizes determined after administration of gadobutrol [23.4 ml; 95 % CI (14.4; 32.5)] and Gd-DOTA [22.1 ml; 95 % CI (13.0; 31.1)] were not statistically different (P = 0.22). The CNR(remote) of LGE in infarcted myocardium on gadobutrol- and Gd-DOTA-enhanced images was 44.1 [95 % CI (31.0; 57.1)] and 45.2 [95 % CI (32.2; 58.3)], respectively (P = 0.73). CNR(lumen) was significantly higher on gadobutrol-enhanced LGE images [12.7; 95 % CI (2.5; 23.0) versus 6.8; 95 % CI (-3.5; 17.0); P = 0.02]. CONCLUSION: At relaxivity-adjusted doses, gadobutrol and Gd-DOTA yielded similar infarct sizes with superior contrast between infarcted myocardium and left ventricular lumen on gadobutrol-enhanced images.