Clinical Efficacy of Reduced-Dose Gadobutrol Versus Standard-Dose Gadoterate for Contrast-Enhanced MRI of the CNS: An International Multicenter Prospective Crossover Trial (LEADER-75).

BACKGROUND. Gadobutrol and gadoterate are widely used macrocyclic gadolinium-based contrast agents. Given gadobutrol's higher T1 relaxivity, a reduced gadobutrol dose should achieve essentially equivalent diagnostic efficacy as a standard dose of gadoterate. OBJECTIVE. The purpose of our study was to show efficacy of a 25% reduced dose of gadobutrol is noninferior to 100% standard dose of gadoterate for contrast-enhanced MRI of the CNS. METHODS. In this international prospective multicenter open-label crossover trial (LEADER-75 [Lower Administered Dose With Higher Relaxivity: Gadovist vs Dotarem]), adult patients with known or suspected CNS pathology underwent contrast-enhanced brain MRI with standard-dose gadoterate (0.1 mmol/kg); if an enhancing lesion was identified, a second MRI with reduced-dose gadobutrol (0.075 mmol/kg) was performed within 15 days of the first MRI. Three radiologists independently reviewed images to score three primary efficacy measures: subjective lesion enhancement, lesion border delineation, lesion internal morphology. A noninferiority analysis used readers' mean scores of the primary efficacy measures. Noninferiority of reduced-dose gadobutrol to standard-dose gadoterate for primary efficacy measures was defined as the difference in score between reduced-dose gadobutrol images and unenhanced images achieving at least 80% of the difference in score between standard-dose gadoterate images and unenhanced images. A post hoc analysis was performed to directly compare contrast-enhanced images for equivalence. Secondary efficacy variables included the number of lesions detected, reader confidence, diagnostic performance for malignancy, and reader preference in side-by-side comparison. RESULTS. The efficacy analysis included 141 patients (78 men, 63 women; mean age, 58.5 ± 13.5 [SD] years). Improvement of reduced-dose gadobutrol over unenhanced images was noninferior to improvement of standard-dose gadoterate over unenhanced images using a 20% noninferiority margin for all three primary efficacy measures using mean readings (p ≤ .025). In the post hoc analysis, the mean reading for the three primary efficacy measures differed by less than 1% between reduced-dose gadobutrol and standard-dose gadoterate, supporting equivalence of all measures using a narrow ± 5% margin (p ≤ .025). The total number of lesions detected by mean reading was 301 for reduced-dose gadobutrol versus 291 for standard-dose gadoterate. Mean reader confidence was 3.3 ± 0.6 for reduced-dose gadobutrol versus 3.3 ± 0.6 for standard-dose gadoterate. Sensitivity (58.7%), specificity (91.8%), and accuracy (70.2%) for malignancy from majority reading were identical for reduced-dose gadobutrol and standard-dose gadoterate. Reader preference was not different (95% CI, -0.10 to 0.11). CONCLUSION. A 25% reduced dose of gadobutrol is noninferior to standard-dose gadoterate for contrast-enhanced brain MRI. CLINICAL IMPACT. Use of reduced-dose gadobutrol should be considered for brain MRI, particularly in patients undergoing multiple contrast-enhanced examinations. TRIAL REGISTRATION. ClinicalTrials.gov NCT03602339; EU Clinical Trials Register EudraCT 2018-00690-78.

Tuning the p Ka of a pH Responsive Fluorophore and the Consequences for Calibration of Optical Sensors Based on a Single Fluorophore but Multiple Receptors.

Since Sørensen and Bjerrum defined the pH scale, we have relied on two methods for determining pH, the colorimetric or the electrochemical. For pH electrodes, calibration is easy as a linear response is observed in the interesting pH range from 1 to ∼12. For colorimetric sensors, the response follows the sigmoidal Bjerrum diagram of an acid-base equilibrium. Thus, calibration of colorimetric sensors is more complex. Here, seven pH responsive fluorescent dyes based on the same diazaoxatriangulenium (DAOTA) fluorophore linked to varying receptor groups were prepared. Photoinduced electron transfer (PeT) quenching from appended aniline or phenol receptors generated the pH response of the DAOTA dyes, and the position of the p Ka value of the dye was tuned using the Hammett relationship as a guideline. The fluorescence intensity of the dyes in a sol-gel matrix environment was measured as a function of pH in universal buffer, and it was found that the dyes behave as perfect pH responsive probes under these conditions. The response of optical pH sensors is nonlinear and was found to be limited to 2-3 pH units for a precision of 0.01 pH unit. As sensors with a broader sensitivity range can be achieved by mixing multiple dyes with different p Ka values, mixtures of dyes in solution were investigated, and a broad range pH sensor with a precision of 0.006 pH units over a range of 3.6 pH units was demonstrated. Further, approximating the sensor response as linear was considered, and a limiting precision for this approach was determined. As the responses of the pH responsive DAOTA dyes were found to be ideally sigmoidal and as the six dyes were shown to have p Ka values scattered over a range from ∼2 to ∼9, this allows for design of a broad range optical pH sensor in the pH range from 1 to 10. This hypothesis was tested using quaternary mixtures of the different DAOTA dyes, and these were found to behave as a direct sum of the individual components. Thus, while linear calibration is limited to a precision of 0.02 in a range of 2-3 pH units, calibration using ideal sigmoidal functions is possible in the range of 1-10 with a precision better than 0.01, and as good as 0.002 pH units.

Extended Triangulenium Ions: Syntheses and Characterization of Benzo-Bridged Dioxa- and Diazatriangulenium Dyes.

The very limited class of fluorophores, with a long fluorescence lifetime (>10 ns) and fluorescence beyond 550 nm, has been expanded with two benzo-fused triangulenium derivatives and two cationic [5]-helicene salts. The syntheses of the benzo-bridged dioxa- and diazatriangulenium derivatives (BDOTA+ and BDATA+, respectively) required two different synthetic approaches, which reflect the structural and physiochemical impact on the reactivity of [5]-helicenium precursors. Spectroscopic investigations show that the introduction of the benzo bridge into the triangulenium chromophore significantly redshifts the absorption and emission while maintaining fluorescence lifetimes above 10 ns. The combination of a high quantum yield, long fluorescence lifetime, and emission above 600 nm is possible only if the structural aspects of the triangulenium framework are perfectly harmonized to secure a low rate of nonradiative deactivation. The new benzo bridge may be a general motif to obtain red-shifted derivatives of other dye classes.

Biocompatible Microporous Organically Modified Silicate Material with Rapid Internal Diffusion of Protons.

A new four-component organically modified silicate (ORMOSIL) material was developed with optical pH sensors in mind. Through a sol-gel process, the porosity of an ORMOSIL framework was optimized to allow rapid diffusion of protons, ideal for fast response to pH in an optical sensor. The optically transparent material was produced by catalyzing the dual polymerization of 3-(glycidoxy)propyltrimethoxysilane (GPTMS) and propyltriethoxysilane (PrTES) with boron trifluoride diethyl etherate. The performance of the resulting material in fluorescence based optical pH sensors was evaluated by incorporation of active dye components in the inorganic polymer framework. It is demonstrated that the material has a short response time ( t90 < 30 s) and high stability in medium and during storage, and resulting sensor spots are biocompatible. It is concluded that this ORMOSIL material has excellent properties for optical pH sensors.

Gadobutrol in Renally Impaired Patients: Results of the GRIP Study.

OBJECTIVE: The aim of this study was to assess the potential risk of gadobutrol-enhanced magnetic resonance imaging (MRI) in patients with moderate to severe renal impairment for the development of nephrogenic systemic fibrosis (NSF). MATERIALS AND METHODS: We performed a prospective, international, multicenter, open-label study in 55 centers. Patients with moderate to severe renal impairment scheduled for any gadobutrol-enhanced MRI were included. All patients received a single intravenous bolus injection of gadobutrol at a dose of 0.1 mmol/kg body weight. The primary target variable was the number of patients who develop NSF within a 2-year follow-up period. RESULTS: A total of 908 patients were enrolled, including 586 with moderate and 284 with severe renal impairment who are at highest risk for developing NSF. The mean time since renal disease diagnosis was 1.83 and 5.49 years in the moderate and severe renal impairment cohort, respectively. Overall, 184 patients (20.3%) underwent further contrast-enhanced MRI with other gadolinium-based contrast agents within the 2-year follow-up. No patient developed symptoms conclusive of NSF. CONCLUSIONS: No safety concerns with gadobutrol in patients with moderate to severe renal impairment were identified. There were no NSF cases.

Azadioxatriangulenium and Diazaoxatriangulenium: Quantum Yields and Fundamental Photophysical Properties.

Over the last decade, we have investigated and exploited the photophysical properties of triangulenium dyes. Azadioxatriangulenium (ADOTA) and diazaoxatriangulenium (DAOTA), in particular, have features that make them useful in various fluorescence-based technologies (e.g., bioimaging). Through our work with ADOTA and DAOTA, we became aware that the reported fluorescence quantum yields (ϕfl) for these dyes are lower than their actual values. We thus set out to further investigate the fundamental structure-property relationships in these unique conjugated cationic systems. The nonradiative processes in the systems were explored using transient absorption spectroscopy and time-resolved emission spectroscopy in combination with computational chemistry. The influence of molecular oxygen on the fluorescence properties was explored, and the singlet oxygen sensitization efficiencies of ADOTA and DAOTA were determined. We conclude that, for these dyes, the amount of nonradiative deactivation of the first excited singlet state (S1) of the azaoxa-triangulenium fluorophores is low, that the rate of such deactivation is slower than what is observed in common cationic dyes, that there are no observable radiative transitions occurring from the first excited triplet state (T1) of these dyes, and that the efficiency of sensitized singlet oxygen production is low (Ï•Δ ≤ 10%). These photophysical results provide a solid base upon which technological applications of these fluorescent dyes can be built.

Gadobutrol-Enhanced Magnetic Resonance Imaging of the Breast in the Preoperative Setting: Results of 2 Prospective International Multicenter Phase III Studies.

OBJECTIVES: The aim of this study was to evaluate the diagnostic efficacy of gadobutrol enhanced preoperative breast magnetic resonance imaging (MRI) in 2 prospective studies. MATERIALS AND METHODS: Approval of ethics committees and informed consent from patients were obtained. Both Gadobutrol-Enhanced MR Mammography (GEMMA) trials followed a standardized protocol using 1.5 T scanners. After unenhanced scans, patients received 0.1 mmol/kg of gadobutrol for the dynamic study. Six independent blinded readers, 3 for GEMMA1 and 3 for GEMMA2, assessed unenhanced images and, 2 or more weeks apart, contrast-enhanced plus unenhanced breast MRI images (CE-BMRI), using a standard 5-region scheme. Another 6 independent readers (3 for each study) evaluated mammograms alone. Sensitivity was calculated taking into account the identification of regions harboring malignancies (within-patient sensitivity), whereas specificity was based on cancer-free breasts. The first patient from each center was used for site qualification and blinded reader training and excluded from the efficacy analyses. Reference standard was pathology for regions harboring malignancy and a combination of negative pathology, mammography, and ultrasound for cancer-free regions. RESULTS: Of 906 breast cancer patients enrolled in 13 countries in the 2 studies, 865 received gadobutrol and 787 were evaluated for diagnostic performance (390 in GEMMA1 and 397 in GEMMA2). Within-patient sensitivity, that is, the detection rate of malignant disease extent per patient, ranged from 80% to 89% for CE-BMRI and was significantly superior to unenhanced breast MRI alone (37%-73%) and to mammography alone (68%-73%) for all readers in both trials. Specifity of the CE-BMRI ranged from 83% to 95%. CONCLUSION: In a very large multicenter preoperative setting, gadobutrol-enhanced breast MRI demonstrated high levels of sensitivity and specificity, consistent with published data on breast MRI.

Diazaoxatriangulenium: synthesis of reactive derivatives and conjugation to bovine serum albumin.

The azaoxa-triangulenium dyes are characterised by emission in the red and a long fluorescence lifetime (up to 25 ns). These properties have been widely explored for the azadioxatrianguelnium (ADOTA) dye. Here, the syntheses of reactive maleimide and NHS-ester forms of the diazaoxatriangulenium (DAOTA) system are reported. The DAOTA fluorophore was conjugated to bovine serum albumin (BSA) and investigated in comparison to the corresponding ADOTA-BSA conjugate. It was found that the fluorescence of DAOTA experienced a significantly higher degree of solvent quenching if compared to ADOTA as non-conjugated dyes in aqueous solution, while the fluorescence quenching observed upon conjugation to BSA was significantly reduced for DAOTA when compared to ADOTA. The differences in observed quenching for the conjugates can be explained by the different electronic structures of the dyes, which renders DAOTA significantly less prone to reductive photoinduced electron transfer (PET) quenching from e.g. tryptophan. We conclude that DAOTA, with emission in the red and inherent resistance to PET quenching, is an ideal platform for the development of long fluorescence lifetime probes for time-resolved imaging and fluorescence polarisation assay.

Safety and Efficacy of Gadobutrol for Contrast-enhanced Magnetic Resonance Imaging of the Central Nervous System: Results from a Multicenter, Double-blind, Randomized, Comparator Study.

PURPOSE: Contrast-enhanced magnetic resonance imaging (MRI) of the central nervous system (CNS) with gadolinium-based contrast agents (GBCAs) is standard of care for CNS imaging and diagnosis because of the visualization of lesions that cause blood-brain barrier breakdown. Gadobutrol is a macrocyclic GBCA with high concentration and high relaxivity. The objective of this study was to compare the safety and efficacy of gadobutrol 1.0 M vs unenhanced imaging and vs the approved macrocyclic agent gadoteridol 0.5 M at a dose of 0.1 mmol/kg bodyweight. MATERIALS AND METHODS: Prospective, multicenter, double-blind, crossover trial in patients who underwent unenhanced MRI followed by enhanced imaging with gadobutrol or gadoteridol. Three blinded readers assessed the magnetic resonance images. The primary efficacy variables included number of lesions detected, degree of lesion contrast-enhancement, lesion border delineation, and lesion internal morphology. RESULTS: Of the 402 treated patients, 390 patients received study drugs. Lesion contrast-enhancement, lesion border delineation, and lesion internal morphology were superior for combined unenhanced/gadobutrol-enhanced imaging vs unenhanced imaging (P < 0.0001 for all). Compared with gadoteridol, gadobutrol was non-inferior for all primary variables and superior for lesion contrast-enhancement, as well as sensitivity and accuracy for detection of malignant disease. The percentage of patients with at least one drug-related adverse event was similar for gadobutrol (10.0%) and gadoteridol (9.7%). CONCLUSION: Gadobutrol is an effective and well-tolerated macrocyclic contrast agent for MRI of the CNS. Gadobutrol demonstrates greater contrast-enhancement and improved sensitivity and accuracy for detection of malignant disease than gadoteridol, likely because of its higher relaxivity.

Azadioxatriangulenium: Synthesis and Photophysical Properties of Reactive Dyes for Bioconjugation.

Azadioxatriangulenium (ADOTA) is a fluorescent triangulenium dye with a long fluorescence lifetime, highly polarized transitions and emission in the red part of the visible spectrum. These properties make the chromophore suited for application in fluorescence polarization/anisotropy assay. To be useful for these applications, reactive forms of the dyes must be available in significant quantities. Here, the synthesis and photophysical properties of amine-reactive NHS esters and a thiol-reactive maleimide derivate of ADOTA are reported. The synthesis involves two steps of nucleophilic bridge forming reactions starting from tris(2,6-dimethoxyphenyl) methylium tetrafluoroborate, which can readily be made on 100 gram scale. In the third and final step the reactive NHS or maleimide groups are formed. The beneficial photophysical properties of the ADOTA chromophore are maintained in these derivatives, and we conclude that these systems are ideal to study protein motion and protein-protein interactions for systems of up towards 1000 kDa.

Phase 3 efficacy and safety trial of gadobutrol, a 1.0 molar macrocyclic MR imaging contrast agent, in patients referred for contrast-enhanced MR imaging of the central nervous system.

PURPOSE: Gadobutrol is a 1.0 M macrocyclic magnetic resonance imaging (MRI) contrast agent. A study was performed to evaluate the efficacy and safety of gadobutrol-enhanced versus unenhanced imaging for central nervous system (CNS) lesion visualization and detection. MATERIALS AND METHODS: An international, multicenter, open-label, Phase III clinical trial. Patients underwent unenhanced and gadobutrol 1.0 M-enhanced (0.1 mmol/kg BW) MR imaging using a standardized protocol. Unenhanced and combined unenhanced/gadobutrol-enhanced images were scored by three independent, blinded readers for degree of lesion enhancement, border delineation, internal morphology, and total number of lesions detected (primary efficacy variables). Exact match of the MR diagnoses with the final clinical diagnosis, detection of malignant CNS lesions, and confidence in diagnosis were secondary efficacy variables. RESULTS: Of 343 enrolled patients, 321 were evaluated for efficacy. All primary efficacy endpoints were met: superiority was demonstrated for gadobutrol-enhanced versus unenhanced MR images (P < 0.0001 in all cases) for lesion enhancement, border delineation, and internal morphology. Noninferiority was met for mean number of lesions detected. There were improvements in the sensitivity of malignant lesion detection, without a loss in specificity, exact-match diagnostic accuracy, and reader confidence. Treatment-related adverse events were reported in 4.1% (n = 14); all were nonserious. CONCLUSION: Gadobutrol 1.0M is an effective and well-tolerated contrast agent for CNS MRI.

Azadioxatriangulenium: exploring the effect of a 20 ns fluorescence lifetime in fluorescence anisotropy measurements.

Azaoxatriangulenium (ADOTA) has been shown to be highly emissive despite a moderate molar absorption coefficient of the primary electronic transition. As a result, the fluorescence lifetime is ~20 ns, longer than all commonly used red fluorescent organic probes. The electronic transitions in ADOTA are highly polarised (r 0 = 0.38), which in combination with the long fluorescence lifetime extents the size-range of biomolecular weights that can be detected in fluorescence polarisation-based experiments. Here, the rotational dynamics of bovine serum albumin (BSA) are monitored with three different ADOTA derivatives, differing only in constitution of the reactive linker. A detailed study of the degree of labelling, the steady-state anisotropy, and the time-resolved anisotropy of the three different ADOTA-BSA conjugates are reported. The fluorescence quantum yields (ϕ fl) of the free dyes in PBS solution are determined to be ~55%, which is reduced to ~20% in the ADOTA-BSA conjugates. Despite the reduction in ϕ fl, a ~20 ns intensity averaged lifetime is maintained, allowing for the rotational dynamics of BSA to be monitored for up to 100 ns. Thus, ADOTA can be used in fluorescence polarisation assays to fill the gap between commonly used organic dyes and the long luminescence lifetime transition metal complexes. This allows for efficient steady-state fluorescence polarisation assays for detecting binding of analytes with molecular weights of up to 100 kDa.

HaloTag, a Platform Technology for Protein Analysis.

Understanding protein function and interaction is central to the elucidation of biological processes. Systematic analysis of protein interactions have shown that the eukaryotic proteome is highly interconnected and that biological function frequently depends on the orchestrated action of many proteins. Perturbation of these functions or interactions can lead to various disease states and pharmacologic intervention can result in corrective therapies. The fact that proteins rarely act in isolation, but rather comprise complex machines that stably and/or transiently interact with many different partners at different times, demands the need for robust tools that allow comprehensive global analyses of these events. Here we describe a powerful protein fusion technology, the HaloTag platform, and how it enables the study of many facets of protein biology by offering a broad choice of applications. We review the development of the key aspects of the technology and it's performance in both in vitro and in vivo applications. In particular, we focus on HaloTag's multifunctional utility in protein imaging, protein isolation and display, and in the study of protein complexes and interactions. We demonstrate it's potential to help elucidate important facets of proteomic biology across complex biological systems at the biochemical, cell-based and whole animal level.

Exploration of the π-electronic structure of singlet, triplet, and quintet states of fulvenes and fulvalenes using the electron localization function.

The singlet ground states and lowest triplet states of penta- and heptafulvene, their benzannulated derivatives, as well as the lowest quintet states of pentaheptafulvalenes, either the parent compound or compounds in which the two rings are intercepted by either an alkynyl or a phenyl segment, were investigated at the (U)OLYP/6-311G(d,p) density functional theory level. The influence of (anti)aromaticity was analyzed by the structure-based aromaticity index HOMA, the harmonic oscillator model of aromaticity. The extent of (anti)aromatic character was also evaluated in terms of the π-electron (de)localization as measured by the π component of the electron localization function (ELF(π)). The natural atomic orbital (NAO) occupancies were calculated in order to evaluate the degree of π-electron shift caused by the opposing electron-counting rules for aromaticity in the electronic ground state (S(0); Hückel's rule) and the first ππ* excited triplet state (T(1); Baird's rule). Pentaheptafulvalene (5) shows a shift of 0.5 π electrons from the 5-ring to the 7-ring when going from the S(0) state to the lowest quintet state (Qu(1)). The pentaheptafulvalene 5 and [5.6.7]quinarene 7 were also investigated in their 90° twisted conformations. From our study it is apparent that excitation localization in fulvalenes, but not in fulvenes, to a substantial degree is determined by aromaticity localization to triplet biradical 4n π-electron cycles. Isolated benzene rings in these compounds tend to remain as closed-shell 6π-electron cycles.

Far-UV photochemical bond cleavage of n-amyl nitrite: bypassing a repulsive surface.

We have investigated the deep-UV photoinduced, homolytic bond cleavage of amyl nitrite to form NO and pentoxy radicals. One-color multiphoton ionization with ultrashort laser pulses through the S(2) state resonance gives rise to photoelectron spectra that reflect ionization from the S(1) state. Time-resolved pump-probe photoionization measurements show that upon excitation at 207 nm, the generation of NO in the v = 2 state is delayed, with a rise time of 283 (16) fs. The time-resolved mass spectrum shows the NO to be expelled with a kinetic energy of 1.0 eV, which is consistent with dissociation on the S(1) state potential energy surface. Combined, these observations show that the first step of the dissociation reaction involves an internal conversion from the S(2) to the S(1) state, which is followed by the ejection of the NO radical on the predissociative S(1) state potential energy surface.

Influence of excited state aromaticity in the lowest excited singlet states of fulvene derivatives.

The absorption spectra and excited state dipole moments of four differently substituted fulvenes have been investigated both experimentally and computationally. The results reveal that the excited state dipole moment of fulvenes reverses in the first excited singlet state when compared to the ground state. The oppositely polarized electron density distributions, which dominate the ground state and the first excited singlet state of fulvenes, respectively, reflect the reversed π-electron counting rules for aromaticity in the two states (4n + 2 vs. 4n, respectively). The results show that substituents indeed influence the polarity of fulvenes in the two states, however, cooperative interactions between the substituents and the fulvene moiety are most pronounced in the ground state.

Safety of gadobutrol, a new generation of contrast agents: experience from clinical trials and postmarketing surveillance.

OBJECTIVE: To assess the clinical safety and tolerability of the macrocyclic contrast agent gadobutrol (Gadovist/Gadavist) overall and in specific patient populations based on clinical trials and postmarketing experience. MATERIALS AND METHODS: In total, 5545 patients enrolled in 34 prospective clinical studies were evaluated in an integrated analysis of safety. Of all enrolled patients, 4549 received gadobutrol at a dose of ≤ 0.09 mmol/kg body weight to a maximum of 0.51 mmol/kg body weight, with most patients (53.5%) receiving the recommended dose of >0.09 to 0.11 mmol/kg body weight. Data include comparisons with other extracellular contrast agents and subgroup analyses in pediatric patients, and patients with allergic disposition, renal impairment, hepatic impairment, or cardiovascular disease. Furthermore, worldwide postmarketing safety surveillance results, including nephrogenic systemic fibrosis reports, based on more than 5.7 million estimated applications are described. RESULTS: One or more adverse events (AEs) assessed as related to the administration of gadobutrol were reported by 182 (4.0%) of the 4549 patients who participated in clinical trials. This is comparable to the incidence observed with the comparator contrast agents (74/1844 patients, 4.0%). The most common AEs, independent of drug relationship, were headache, nausea, feeling hot, and dysgeusia. The favorable safety profile of gadobutrol was also demonstrated in the following specific subpopulations in whom similar incidence rates were seen: pediatric patients aged 2 to 17 years (8/138 patients, 5.8%), patients with severe or moderate renal impairment (9/366 patients, 2.5%), patients with severe or moderate hepatic impairment (9/214 patients, 4.2%), and patients with cardiovascular disorders (42/1506 patients, 2.8%). Having been established in controlled clinical trials, this safety profile was also confirmed by postmarketing surveillance data. With more than 5.7 million estimated administrations of gadobutrol, a total of 1175 (0.02%) suspected adverse drug reactions have been reported. The most serious adverse reactions seen in postmarketing surveillance included rare reports of cardiac arrest, respiratory arrest, anaphylactoid shock, and nephrogenic systemic fibrosis. Incidence and type of AEs from postmarketing surveillance were consistent with the established safety profile. CONCLUSION: The comprehensive analysis of safety data obtained from 34 clinical studies demonstrates that gadobutrol has an excellent safety profile and a positive benefit risk profile when used in patients in need of contrast-enhanced magnetic resonance imaging. Gadobutrol was well tolerated by adults, by children, by patients with impaired liver or kidney function, and by patients with cardiovascular disease. The favorable safety profile is confirmed by the available postmarketing surveillance data and is compared with that of other gadolinium-based contrast agents.

Probing the lifetimes of internally excited amyl nitrite cations.

The photoelectron spectrum shows that multiphoton ionization of amyl nitrite, C(5)H(11)ONO, using ultrafast laser pulses deposits up to 3.7 eV of energy into internal degrees of freedom. As a result, the molecules fragment to produce various daughter ions of masses 87, 71, 60, 57, 41, 30, 29, and 27. Absorption of an additional photon with 3 eV of energy by the ions yields transients with picosecond decay times, revealing the time scale of the decomposition dynamics of the initially prepared parent ion. Each mass peak has a distinct time constant, in the range of 1.2 to 7.9 ps, emphasizing the dependence of the fragmentation mechanism on the ion internal energy.