To develop a magnetic resonance (MR) "fingerprinting" technique for quantitative abdominal imaging.
This HIPAA-compliant study had institutional review board approval, and informed consent was ...obtained from all subjects. To achieve accurate quantification in the presence of marked B0 and B1 field inhomogeneities, the MR fingerprinting framework was extended by using a two-dimensional fast imaging with steady-state free precession, or FISP, acquisition and a Bloch-Siegert B1 mapping method. The accuracy of the proposed technique was validated by using agarose phantoms. Quantitative measurements were performed in eight asymptomatic subjects and in six patients with 20 focal liver lesions. A two-tailed Student t test was used to compare the T1 and T2 results in metastatic adenocarcinoma with those in surrounding liver parenchyma and healthy subjects.
Phantom experiments showed good agreement with standard methods in T1 and T2 after B1 correction. In vivo studies demonstrated that quantitative T1, T2, and B1 maps can be acquired within a breath hold of approximately 19 seconds. T1 and T2 measurements were compatible with those in the literature. Representative values included the following: liver, 745 msec ± 65 (standard deviation) and 31 msec ± 6; renal medulla, 1702 msec ± 205 and 60 msec ± 21; renal cortex, 1314 msec ± 77 and 47 msec ± 10; spleen, 1232 msec ± 92 and 60 msec ± 19; skeletal muscle, 1100 msec ± 59 and 44 msec ± 9; and fat, 253 msec ± 42 and 77 msec ± 16, respectively. T1 and T2 in metastatic adenocarcinoma were 1673 msec ± 331 and 43 msec ± 13, respectively, significantly different from surrounding liver parenchyma relaxation times of 840 msec ± 113 and 28 msec ± 3 (P < .0001 and P < .01) and those in hepatic parenchyma in healthy volunteers (745 msec ± 65 and 31 msec ± 6, P < .0001 and P = .021, respectively).
A rapid technique for quantitative abdominal imaging was developed that allows simultaneous quantification of multiple tissue properties within one 19-second breath hold, with measurements comparable to those in published literature.
Organic cavity polaritons are bosonic quasiparticles arising from the strong interaction between organic molecular excitons and photons within microcavities. The spectral dispersion of third‐harmonic ...generation near resonance with cavity polaritons is studied experimentally via angle‐resolved reflected third‐harmonic generation measurements with several pump wavelengths. Moreover, a three‐step nonlinear optical transfer matrix model is used to simulate the third‐harmonic generation using the sum‐over‐states dispersive nonlinear coefficients, which include polariton states. The angle‐dependent experiment and modeling agree, revealing the output of third‐harmonic generation is resonantly enhanced when third‐harmonic wavelengths are near upper polaritons. Lower‐polariton‐enhanced third‐harmonic generation is not experimentally observed due to inadequate coupling at the longer wavelength, which is also consistent with the nonlinear transfer matrix modeling. These results indicate that the sum‐over‐states nonlinear dispersion is descriptive of the nonlinear optical process so that the polariton states belong to a complete set of states for a perturbative determination of the nonlinear optical response. From these results, it might be expected that such a basis for perturbation theory would be widely applicable for nonlinear optical processes in the strong and ultrastrong limits. The results also indicate the possibility of wavelength agile nonlinear optical response by angle‐of‐incidence tuning.
The dispersion of third‐harmonic generation is studied near the upper‐polariton branch of an optical cavity containing an organic glass. Both the angle and wavelength dependence of the third‐harmonic generation are measured and compared with a nonlinear transfer matrix model indicating that the dispersion is described by the sum‐over‐states nonlinear susceptibility model having poles associated with the polariton branch.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Dark azido push−pull chromophores have the ability to be photoactivated to produce bright fluorescent labels suitable for single-molecule imaging. Upon illumination, the aryl azide functionality in ...the fluorogens participates in a photochemical conversion to an aryl amine, thus restoring charge-transfer absorption and fluorescence. Previously, we reported that one compound, DCDHF-V-P-azide, was photoactivatable. Here, we demonstrate that the azide-to-amine photoactivation process is generally applicable to a variety of push−pull chromophores, and we characterize the photophysical parameters including photoconversion quantum yield, photostability, and turn-on ratio. Azido push−pull fluorogens provide a new class of photoactivatable single-molecule probes for fluorescent labeling and super-resolution microscopy. Lastly, we demonstrate that photoactivated push−pull dyes can insert into bonds of nearby biomolecules, simultaneously forming a covalent bond and becoming fluorescent (fluorogenic photoaffinity labeling).
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IJS, KILJ, NUK, PNG, UL, UM
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