Simulation Of Radiation Propagation Research Articles

Theoretical and experimental modeling of interstitial laser hyperthermia with surface cooling device using Nd3+-doped nanoparticles.

To improve methods of laser hyperthermia for the treatment of bulk malignant neoplasms, an urgent task is the development of techniques and devices that automatically control heating at a given tissue depth and ensure its uniformity. The article proposes the concept of a system for performing hyperthermia with real-time spectroscopic temperature control and surface cooling, which allows to record spectra of diffusely scattered radiation and fluorescent signal from various depths of biological tissues by the means of the variation of the angle and distance between the fiber source of laser radiation and the receiving fiber. Theoretical and experimental modeling of the spatial distribution of diffusely scattered radiation and temperature inside the tissue with a fiber optic device providing surface cooling of the irradiated tissue, and recording spectral information from a given depth in real time, is presented. Simulation of radiation propagation in biological tissues, depending on the distance between the source and the receiver and the angle of their tilt, was carried out using the Monte Carlo method. Modeling of the temperature distribution inside the tissues was carried out by means of a numerical solution of the heat conduction equation. Experimental modeling was carried out on phantoms of biological tissues simulating their scattering properties as well as accumulation of the investigated nanoparticles doped with Nd3+ ions. It was shown that inorganic nanoparticles doped with rare-earth Nd3+ ions can be used as temperature labels for feedback to the therapeutic laser. According to the results of the theoretical simulation, optimal configurations of the relative arrangement of the fibers were chosen, as well as the optimum surface cooling temperatures for the given power densities. The heating of the phantom of the neoplasm containing the investigated nanoparticles doped with Nd3+ ions by laser radiation with an 805-nm wavelength and power density of 1W/cm2 up to 42°C at a depth of 1cm while maintaining the surface temperature within the limits of the norm was demonstrated.

3D global estimation and augmented reality visualization of intra-operative X-ray dose.

The growing use of image-guided minimally-invasive surgical procedures is confronting clinicians and surgical staff with new radiation exposure risks from X-ray imaging devices. The accurate estimation of intra-operative radiation exposure can increase staff awareness of radiation exposure risks and enable the implementation of well-adapted safety measures. The current surgical practice of wearing a single dosimeter at chest level to measure radiation exposure does not provide a sufficiently accurate estimation of radiation absorption throughout the body. In this paper, we propose an approach that combines data from wireless dosimeters with the simulation of radiation propagation in order to provide a global radiation risk map in the area near the X-ray device. We use a multi-camera RGBD system to obtain a 3D point cloud reconstruction of the room. The positions of the table, C-arm and clinician are then used 1) to simulate the propagation of radiation in a real-world setup and 2) to overlay the resulting 3D risk-map onto the scene in an augmented reality manner. By using real-time wireless dosimeters in our system, we can both calibrate the simulation and validate its accuracy at specific locations in real-time. We demonstrate our system in an operating room equipped with a robotised X-ray imaging device and validate the radiation simulation on several X-ray acquisition setups.

Numerical simulation of a water spray—Radiation attenuation related to spray dynamics

Radiation attenuation by a water spray is predicted on the basis of a detailed simulation. First of all, a two-way coupling treatment of the spray dynamics is achieved through an Eulerian–Lagrangian modeling. Droplet distribution combined with water vapor and carbon dioxide volume fractions are then used to compute the radiative properties of the medium. A simulation of radiation propagation is performed, aimed at the computation of the spectral transmittance through the spray. A Monte Carlo technique is used to describe radiation absorption and scattering phenomena for a real droplet polydispersion and an equivalent monodispersion. Numerical results of spray attenuation are compared to experimental data obtained on a laboratory spray with low flow rate. Satisfying accuracy can be obtained for the numerical prediction if a realistic size distribution is used for the pulverization. The mean Sauter diameter and the volumetric fraction of droplets are found to vary with the position in the spray. Tentative predictions with a monodispersion therefore fail in predicting the attenuation ability of the spray at various vertical positions below the injection point.