Tutorial on methods for estimation of optical absorption and scattering properties of tissue.

Significance: The estimation of tissue optical properties using diffuse optics has found a range of applications in disease detection, therapy monitoring, and general health care. Biomarkers derived from the estimated optical absorption and scattering coefficients can reflect the underlying progression of many biological processes in tissues. Aim: Complex light-tissue interactions make it challenging to disentangle the absorption and scattering coefficients, so dedicated measurement systems are required. We aim to help readers understand the measurement principles and practical considerations needed when choosing between different estimation methods based on diffuse optics. Approach: The estimation methods can be categorized as: steady state, time domain, time frequency domain (FD), spatial domain, and spatial FD. The experimental measurements are coupled with models of light-tissue interactions, which enable inverse solutions for the absorption and scattering coefficients from the measured tissue reflectance and/or transmittance. Results: The estimation of tissue optical properties has been applied to characterize a variety of ex vivo and in vivo tissues, as well as tissue-mimicking phantoms. Choosing a specific estimation method for a certain application has to trade-off its advantages and limitations. Conclusion: Optical absorption and scattering property estimation is an increasingly important and accessible approach for medical diagnosis and health monitoring.

Absorption of 5G sub-6 GHz electromagnetic radiation from base station to male reproduction system.

BACKGROUND: The impact of electromagnetic radiation from communication on the male reproductive system has emerged as a significant concern in public health. A notable distinction of the 5G sub-6 GHz band, compared to traditional 2G, 3G, and 4G frequency bands, is the inclusion of higher frequency bands. This has raised public concerns regarding the potential effects of these higher frequencies on organisms, particularly their reproductive systems. While it is imperative to investigate the biological effects and potential risks associated with these new frequency bands in laboratory settings, comparing and evaluating differences between various frequency bands remain challenging due to the absence of standardized parameters such as exposure conditions and duration. In contrast, dose assessment offers a simpler and more reliable approach. MATERIALS AND METHODS: The dose assessment method was employed in this study to investigate the risks associated with sub-6 GHz electromagnetic radiation from 5G base stations on the male reproductive system. A classical human body model (Duke) was utilized, and an electromagnetic simulation environment was established based on the actual polarization direction of the exposed base stations and various body postures. This research explored the effects of field direction, posture, public population, and frequency on the specific absorption rate of the reproductive system. RESULTS AND CONCLUSIONS: While maintaining the same level of exposure, a higher frequency results in a reduced dosage on reproductive system. Further analysis reveals that, considering the public exposure threshold, the employment of higher frequency bands in 5G sub-6 GHz does not present a greater dosage on reproductive system compared to lower frequency bands. Consequently, with regard to dosage, there is no need for excessive concern among the general public regarding the impact of electromagnetic radiation emitted by 5G base stations operating below 6 GHz on male reproductive health.

Polynomial chaos expansion of SAR and temperature increase variability in 3 T MRI due to stochastic input data.

Objective.Numerical simulations are largely adopted to estimate dosimetric quantities, e.g. specific absorption rate (SAR) and temperature increase, in tissues to assess the patient exposure to the radiofrequency (RF) field generated during magnetic resonance imaging (MRI). Simulations rely on reference anatomical human models and tabulated data of electromagnetic and thermal properties of biological tissues. However, concerns may arise about the applicability of the computed results to any phenotype, introducing a significant degree of freedom in the simulation input data. In addition, simulation input data can be affected by uncertainty in relative positioning of the anatomical model with respect to the RF coil. The objective of this work is the to estimate the variability of SAR and temperature increase at 3 T head MRI due to different sources of variability in input data, with the final aim to associate a global uncertainty to the dosimetric outcomes.Approach.A stochastic approach based on arbitrary Polynomial Chaos Expansion is used to evaluate the effects of several input variability's (anatomy, tissue properties, body position) on dosimetric outputs, referring to head imaging with a 3 T MRI scanner.Main results.It is found that head anatomy is the prevailing source of variability for the considered dosimetric quantities, rather than the variability due to tissue properties and head positioning. From knowledge of the variability of the dosimetric quantities, an uncertainty can be attributed to the results obtained using a generic anatomical head model when SAR and temperature increase values are compared with safety exposure limits.Significance.This work associates a global uncertainty to SAR and temperature increase predictions, to be considered when comparing the numerically evaluated dosimetric quantities with reference exposure limits. The adopted methodology can be extended to other exposure scenarios for MRI safety purposes.

Detección y cuantificación de la captación de 223Ra en metástasis óseas en pacientes con carcinoma de próstata resistente a la castración con vistas a la determinación de la dosis absorbida en dichas metástasis / Detection and quantification of 223Ra uptake in bone metastases of patients with castration resistant prostate carcinoma, with the aim of determining the absorbed dose in the metastases

Objetivos. Obtener los parámetros necesarios, tanto de calibración como de adquisición, para poder estudiar la posibilidad de detectar y cuantificar la actividad captada en metástasis óseas en pacientes con carcinoma de próstata resistente a la castración tratados con 223Ra. Además, en los casos en los que sea posible cuantificar la actividad, estimar la dosis absorbida. Material y métodos. Se han realizado adquisiciones en la gammacámara de una placa Petri con 223Ra, que han sido complementadas con simulaciones Monte Carlo para estudiar el efecto de volumen parcial. Las fórmulas matemáticas para obtener los límites de detección y cuantificación de actividad de 223Ra fueron aplicadas a las imágenes planares de 2 pacientes 7días postadministración de 55kBq/kg de 223Ra. Para una localización previa de las lesiones se adquirieron barridos de cuerpo completo e imágenes SPECT/TC con 99mTc-HDP. Resultados. La ventana de adquisición óptima es de 82keV con un colimador de energías medias MEGP. De las lesiones presentes en los 2 pacientes, solo fueron cuantificables las lesiones que habían podido ser detectadas en las 2 proyecciones anterior y posterior. Estas lesiones eran las que captaban más actividad de 99mTc-HDP. Los valores estimados de dosis absorbidas estuvieron en un rango de 0,7 a 7,8Gy. Conclusiones. De entre las lesiones que se pueden detectar, en algunas no es posible cuantificar la actividad captada, ni por lo tanto determinar la dosis absorbida. Esto no implica que la dosis absorbida en esas lesiones pueda considerarse despreciable (AU)

Purposes. To obtain the necessary acquisition and calibration parameters in order to evaluate the possibility of detecting and quantifying 223Ra uptake in bone metastases of patients treated for castration resistant prostate carcinoma. Furthermore, in the cases in which the activity can be quantified, to determine the absorbed dose. Material and methods. Acquisitions from a Petri dish filled with 223Ra were performed in the gamma camera. Monte Carlo simulations were also performed to study the partial volume effect. Formulae to obtain the detection and quantification limits of 223Ra uptake were applied to planar images of two patients 7 days post-administration of 55kBq/kg of 223Ra. In order to locate the lesions in advance, whole-body scans and SPECT/CT images were acquired after injecting 99mTc-HDP. Results. The optimal energy window was found to be at 82keV with a medium-energy collimator MEGP. Of the lesions found in the patients, only those that had been detected in both the AP and PA projections could be quantified. These lesions were those which had shown a higher 99mTc-HDP uptake. The estimated values of absorbed doses ranged between 0.7Gy and 7.8Gy. Conclusions. Of the lesions that can be detected, it is not possible to quantify the activity uptake in some of them, which means that the absorbed dose cannot be determined either. This does not mean that the absorbed dose in these lesions can be regarded as negligible (AU)

Light curing in dentistry and clinical implications: a literature review

Abstract Contemporary dentistry literally cannot be performed without use of resin-based restorative materials. With the success of bonding resin materials to tooth structures, an even wider scope of clinical applications has arisen for these lines of products. Understanding of the basic events occurring in any dental polymerization mechanism, regardless of the mode of activating the process, will allow clinicians to both better appreciate the tremendous improvements that have been made over the years, and will also provide valuable information on differences among strategies manufacturers use to optimize product performance, as well as factors under the control of the clinician, whereby they can influence the long-term outcome of their restorative procedures.