Search

Among different FAPIs (fibroblast activation protein inhibitors) developed for PET imaging, 68Ga-FAPI-04 has demonstrated the most impressive properties with low nanomolar affinity to FAP, near-complete internalization of radioactivity bound to FAP, and rapid blood clearance. The application of 68Ga-FAPI-04 has been extended to 28 different kinds of clinical cancer detection. The manual synthesis of 68Ga-FAPI-04 is like other 68Ga-labeling peptides, such as PSMA-11 and DOTATATE. However, because the radiochemical conversion (RCC) is about 90%, it is required to conduct a purification and isolation process to meet the required standard for clinical application. The purpose of this work is to characterize the increase of isolation efficiency (IE) by increasing the volume of eluting liquid applied to C18 columns and sterile filters. We designed an experiment and measured the residual activity distribution on both C18 columns and sterile filters for different eluting volumes. We characterized the change of activity residuals and isolation efficiencies with different eluting volumes in the process of purification and isolation. As a result, it was found that there were more activity leftovers on sterile filters than on C18 columns. By increasing the eluting volume from 6 mL to 12 mL, we measured the average IE being improved from 62.4% to 87.4%, which is greatly beneficial to clinical applications. In addition, the fluctuation of IE which might come from the different radiolabeling operators or materials used in the experiment, was also obviously decreased from 11.3% to 4.5%. This method has been proven to be efficient in the production of 68Ga-FAPI-04.

68Ga-radiolabeled small molecules that specifically target prostate specific membrane antigen (PSMA) has been extensively investigated, and some of those tracers have been used in diagnosis of prostate cancer with 68Ga-positron emission tomography (68Ga-PET). Nevertheless, current 68Ga-labeled radiotracers show fair detection rates to metastasized prostate cancer lesions, especially to those with lower level of prostate specific antigen (PSA), which often occur in biochemical recurrence of prostate cancer. The goal of this study was to design and synthesize a new PSMA-targeted radiotracer 68Ga-SC691 with high affinity to prostate cancer cells and excellent pharmacokinetics. To this end, structural optimum was made on the bifunctional group, target motif, and linker while high affinity targeting scaffold was remained. In order to explore its potential in clinical, a comparative study was further performed in vitro and in vivo between 68Ga-SC691 and 68Ga-PSMA-11, the clinically approved tracer for PSMA-positive prostate cancer. SC691 was radiolabeled to provide 68Ga-SC691 in 99% radiolabeling yield under mild conditions. High uptake and internalization ratio into LNCaP cells were observed in in vitro studies. In vivo studies showed that 68Ga-SC691 had a favorable biodistribution property and can specifically accumulate on PSMA-positive LNCaP xenografts visualized by micro-PET/CT. This radiotracer showed excellent PET imaging quality and comparable uptake at LNCaP xenografts if not higher than 68Ga-PSMA-11.

The push for ever more powerful and shorter laser pulse sources demands optical coatings that can handle large bandwidths while operating near the threshold of permanent damage. We review some of the current challenges in the understanding of film behavior under load and opportunities that arise from tailored coating stacks for nonlinear optical harmonic generation.

We present a novel technique to characterize coating imperfections that limit the performance under pulsed laser irradiation. We also discuss the use of 1D photonic crystals based on dielectric metal oxides as nonlinear optical frequency converters.

A well-known method for the determination of the threshold fluence for laser-induced damage (LIDT) and ablation with single laser pulses is the measurement of the ablated crater area as a function of incident fluence and extrapolation to zero crater area. In this paper, we introduce a general incubation model for a large class of materials, for example dielectric materials and metals, and we compare it to experimental data. We conclude that multi-pulse LIDT measurements can also be based on crater size measurements similar to 1-on-1 damage tests if the incubation does not involve coupling between spatial and temporal processes.

Damage mechanisms in thin films are reviewed from femtosecond pulse to CW laser illumination. Special emphasis is given to the role of native and laser induced defects, recent successes and the need for better diagnostic tools.

We present a consistent model supported by experimental data of damage of dielectric films by femtosecond to nanosecond pulses. Special emphasis is given to the role of defects and transient processes in the material. New imaging and diagnostic techniques are discussed to characterize the film performance.

We show that the concentration of oxygen defects trapped in Sc2O3 films by ion beam sputtering can be controlled by modifying deposition conditions. These defects play a role in the optical and structural properties of the thin film metal-oxides.

We have investigated the role of native point defects in the laser damage behavior of amorphous thin films of Sc 2 O 3 deposited by ion beam sputtering. Through systematic characterization and detailed modeling we show that native defects influence the 1-on-1 laser induced damage threshold fluence of the Sc 2 O 3 . This effect, as shown by the model and confirmed by experiments, is pulse duration dependent.

Avalanche ionization plays a crucial role in the photoionization of dielectric materials and as such is important for optical damage. Although it has been investigated closely during the last years, there is little experimental evidence of how the impact ionization parameter changes with electron density and/or incident pulse intensity. One reason is that in most dielectric materials there are several competing ionization and relaxation processes. Here we present an UV-pump IR-probe experiment that allowed us to isolate the avalanche ionization from other major ionization processes, especially multiphoton ionization, electron tunneling, and relaxation into traps and their re-excitation. We have measured the intensity dependence of a transmitted IR pulse, propagating through a thin sample of UV-grade sapphire (α-Al2O3), after seeding electrons in the conduction band with a UV pulse. We show that the assumption of an intensity independent impact ionization factor α cannot explain the results. Application of a simple avalanche ionization model within the flux-doubling approximation requires an intensity dependent coefficient a(I) to explain the data. We also determined the two photon absorption coefficient of sapphire at 266 nm (β(2) = (2.7 ± 0.1) • 10-11cm/W) as well as the "free" electron absorption cross section for 800 nm of conduction band electrons in sapphire (δ0 = (12.5 ± 0.2) •10-18 cm2).

The transient electron temperature in a weakly ionized femtosecond-laser-produced air plasma filament was determined from optical absorption and diffraction experiments. The electron temperature and plasma density decay on similar time scales of a few hundred picoseconds. Comparison with plasma theory reveals the importance of inelastic collisions that lead to energy transfer to vibrational degrees of freedom of air molecules during the plasma cooling.

The transient electron temperature in a fs laser air plasma (filament) was determined with ps resolution from pump-probe diffraction and absorption measurements. Plasma modeling shows good agreement with experiments if inelastic collisions are included.

In multi-pulse laser damage and ablation experiments, the laser-induced damage threshold (LIDT) usually changes with the number of pulses in the train, a phenomenon known as incubation. We introduce a general incubation model based on two physical mechanisms—pulse induced change of (i) absorption and (ii) critical energy that must be deposited to cause ablation. The model is applicable to a broad class of materials and we apply it to fit data for dielectrics and metals. It also explains observed changes of the LIDT as a function of the laser repetition rate. We discuss under which conditions the crater-size method to determine LIDTs can be applied in multi-pulse experiments.

A new surface plasmon resonance (SPR) sensor based on polarization interferometry and angle modulation is presented. Its feature is that it can provide the same sensitivity in a wide refractive index (RI) range. Moreover, the sensitivity ofthis SPR sensor is insensitive to the thickness of gold films over about 5 mu. Experimental results show that its resolution in an integration time of 0.5 second is 1.7 × 10-7 refractive index units (RIU). It demonstrates great potential to be commercialized and widely applied in biological research.

We show that the concentration of oxygen interstitials trapped in Sc2O3 films by ion beam sputtering from metal targets can be controlled by modifying deposition conditions. We have identified point defects in the form of oxygen interstitials that are present in Sc2O3 films, in significantly high concentrations, i.e., ∼10(18) cm(-3). These results show a correlation between the increase of oxygen interstitials and the increase in stress and optical absorption in the films. Sc2O3 films with the lowest stress and optical absorption loss at 1 μm wavelength were obtained when using a low oxygen partial pressure and low beam voltage.

Third harmonic generation by a weak femtosecond probe pulse intersecting a pump laser-induced plasma in air is investigated and a general model is developed to describe such signal, applicable to a wide range of focusing and plasma conditions. The effect of the surrounding air on the generated signal is discussed. The third-order nonlinear susceptibility of an air plasma with electron density N(e) is determined to be χ(p)((3)) = χ(a)((3)) + γ(p)N(e) with γ(p) = 2 ± 1 × 10(-49) m(5) V(-2) and χ(a)((3)) being the third-order susceptibility in air. Lateral scans of the probe through the plasma are used to determine electron density profiles and the effect of focusing and phase mismatch is discussed.

A surface plasmon resonance (SPR) sensing technique based on polarization interferometry and angle modulation is presented. Its sensitivity is not a direct function of variation of reflection intensity, nor of phase shift. Rather, it is a function of the complex reflection coefficient. A three times standard deviation detection limit of 5.1 x 10(-7) refractive index units in a 2 Hz bandwidth is obtained with our experimental setup. A theoretical analysis shows that this technique can provide a wide linear measurement range. Moreover, the sensitivity is insensitive to the thickness of gold films over approximately 5 nm. This SPR sensing technique is suitable for physical, chemical, and biological research.

Third harmonic generation by a femtosecond probe intersecting a laser-induced air plasma is measured and a general model developed to describe such signal. The electron density distribution and nonlinear coefficient of the plasma are determined.