Despite their advantageous chemical properties for nuclear imaging, radioactive sodium-22 (²²Na) tracers have been excluded for biomedical applications because of their extremely long lifetime. In the current study, we proposed, for the first time, the use of ²²Na radiotracers for pre-clinical applications by efficiently loading with silica nanoparticles (SiNPs) and thus offering a new life for this radiotracer. Crown-ether-conjugated SiNPs (300 nm; -0.18±0.1 mV) were successfully loaded with ²²Na with a loading efficacy of 98.1%±1.4%. Noninvasive positron emission tomography imaging revealed a transient accumulation of ²²Na-loaded SiNPs in the liver and to a lower extent in the spleen, kidneys, and lung. However, the signal gradually decreased in a time-dependent manner to become not detectable starting from 2 weeks postinjection. These observations were confirmed ex vivo by quantifying ²²Na radioactivity using γ-counter and silicon content using inductively coupled plasma-mass spectrometry in the blood and the different organs of interest. Quantification of Si content in the urine and feces revealed that SiNPs accumulated in the organs were cleared from the body within a period of 2 weeks and completely in 1 month. Biocompatibility evaluations performed during the 1-month follow-up study to assess the possibility of synthesized nanocarriers to induce oxidative stress or DNA damage confirmed their safety for pre-clinical applications. ²²Na-loaded nanocarriers can thus provide an innovative diagnostic agent allowing ultra-sensitive positron emission tomography imaging. On the other hand, with its long lifetime, onsite generators or cyclotrons will not be required as ²²Na can be easily stored in the nuclear medicine department and be used on-demand.

In this work, we investigate the potential of exploiting TiO₂ thin films as sensing layers on silicon micro-electromechanical systems for the detection of gamma radiations. All samples are exposed to gamma rays produced by ⁶⁰Co, with different doses ranging from 0 kGy to 40 kGy. Properties of silicon coated with a 200-nm-thick layer of TiO₂ grown at 200 °C by atomic layer deposition are studied before and after its gamma irradiation using x-ray diffraction (XRD), scanning electron microscopy, and spectroscopic ellipsometry. Atomic force microscopy (AFM) is carried out on functionalized microcantilevers to measure the resonance frequency shift (Δf ₀) resulting from irradiation of the TiO₂ thin film. XRD results show a change in the films from a mixture of rutile and anatase phases to an anatase phase upon irradiation. Spectroscopic ellipsometry results show a change with a fixed pattern in the film thickness, roughness, void, and optical constants with different irradiation doses. This pattern appears as Δf ₀ in AFM, where the response of sensors to doses between 0 kGy and 20 kGy was linear. The values of Δf ₀ are convenient to control parameters for the proposed dosimeter, which is characterized by the reproducibility and sensitivity of measurements. The maximum detectable linear effect of the proposed dosimeter was found at a dose of 20 kGy. This makes a 200-nm thin layer of TiO₂ coated on a microcantilever surface, a possible candidate for dosimetry for the range lower than 20 kGy applications, such as in personal dosimeters.

This study generally relates to nuclear sensors and specifically to detecting nuclear and electromagnetic radiation using an ultrasensitive quartz tuning fork (QTF) sensor. We aim to detect low doses of gamma radiation with fast response time using QTF. Three different types of QTFs (uncoated and gold coated) were used in this study in order to investigate their sensitivity to gamma radiations. Our results show that a thick gold coating on QTF can enhance the quality factor and increase the resonance frequency from 32.7 to 32.9 kHz as compared to uncoated QTF. The results also show that increasing the surface area of the gold coating on the QTF can significantly enhance the sensitivity of the QTF to radiation. We investigated the properties of gold-coated and uncoated QTFs before and after irradiation by scanning electron microscopy. We further investigated the optical properties of SiO₂ wafers (quartz) by spectroscopic ellipsometry (SE). The SE studies revealed that even a small change in the microstructure of the material caused by gamma radiation would have an impact on mechanical properties of QTF, resulting in a shift in resonance frequency. Overall, the results of the experiments demonstrated the feasibility of using QTF sensors as an easy to use, low-cost, and sensitive radiation detector.

A polymer-coated microelectromechanical system (MEMS) sensor was used in this study to detect electromagnetic nuclear radiation (gamma radiation) with high sensitivity. The resonance frequencies shift (RFS) resulting from the effect of gamma irradiation on the MEMS sensors coated with two polymeric thin films (polyacrylic acid [PAA] and polystyrene [PS]) were measured. The mechanical and optical properties of the coated polymer layers on Si wafers were evaluated before and after irradiation using atomic force microscopy (AFM) and ultraviolet–visible spectrophotometry. Further, surface roughness and reflectivity of the PS polymer thin film were found to be linear as a function of the gamma irradiation time. However, there was no noticeable change in the RFS, surface roughness, or reflectivity of the PAA polymer thin film. These results were confirmed using spectroscopic ellipsometry measurements which showed that the surface roughness increased linearly as a function of the gamma irradiation time. Based on these findings, the interaction between gamma radiation and PS polymer revealed that the MEMS coated with PS produced a linear response that could be used to develop radiation sensors for low gamma doses. Although many techniques exist for detecting nuclear radiation, the sensor proposed has ultrasensitivity, high measurement accuracy, and low cost. Graphical Abstract

Gamma rays have been extensively investigated for breast imaging using collimators; however, the coded-aperture technique needs to be investigated more. In this paper, we propose an experimental study and Geant4 simulations of MURA mask breast imaging. First, we compare the experimental data against the simulation results carried out using Geant4 (version 10.4) and accreditation phantom. Second, we virtually extend our work by changing the tumor-to-background (TBR) and lesion location parameters. We used ${}^{99m}Tc$ as a radioactive source. Good agreement has been seen for the benchmark stage, especially in terms of tumor localization. Moreover, the calculated full width at half maximum (FWHM) and contrast for decoded images (having average values of 8 and 3.5 for TBR between 2 and 10) permitted us to conclude that we can accurately localize small lesions up to lower TBR values by following the decoding procedure of deducing the image of a “blank phantom” (phantom with TBR = 1) every time within a matlab-based program. Hence, this work can be considered a continuously added value to previous investigations for scintimammography imaging.