We have modified the existing convolution method of the Monte Carlo simulation for finite photon beams with both translational and rotational invariance. The modified convolution method was applied to simulate the optical fluence distribution in tissue in dark-field confocal photoacoustic microscopy. We studied the influence of the size of the dark field and the illumination incident angle on t...

Background: The aim of this work was to establish how well gel dosimeters performed, as substitutes for brain tissue compared with standard phantom materials such as water, polymethyl-methacrylate (or PMMA), A150 plastic and TE- liquid phantom material for dosimetry of neutron beams in boron neutron capture therapy. Materials and Methods: Thermal neutron fluence, photon dose and epithermal neu...

In field experiments photoinhibition of photosynthesis'in the intertidal brown alga Fucus serratus was investigated by means of both fluorescence and oxygen measurements. Samples were taken from thalli floating just below the water surface. Dunng falling tides the ratio variable fluorescence/maxlrnum fluorescence (FJF,) decreased with increasing photon fluence rates. As during rising tides only...

The shielding calculations for high energy (>10 MV) linear accelerators must include the photoneutron production within the head of the accelerator. Procedures have been described to calculate the treatment room door shielding based on the neutron source strength (Q value) for a specific accelerator and energy combination. Unfortunately, there is currently little data in the literature stating ...

Background: Monte Carlo method (MC) has played an important role in design and optimization of medical linacs head and beam modeling. The purpose of this study was to compare photon beam features of two commercial linacs, Varian 21EX and Elekta SL-25 using MCNP4C MC code. Materials and Methods: The 6MV photon beams of Varian 21EX and Elekta Sl-25 linacs were simulated based on manufacturers pro...

Knowledge of the local optical fluence in biological tissue is of fundamental importance for biomedical optical techniques to achieve quantification. We report a method to noninvasively measure the local optical fluence in optically inhomogeneous scattering media. The concept is based on two aspects: the local tagging of light using ultrasonic modulation and the photon path reversibility princi...

One limitation to the widespread implementation of Monte Carlo (MC) patient dose-calculation algorithms for radiotherapy is the lack of a general and accurate source model of the accelerator radiation source. Our aim in this work is to investigate the sensitivity of the photon-beam subsource distributions in a MC source model (with target, primary collimator, and flattening filter photon subsou...

A bright high harmonic source is presented delivering up to 10 photons per second around a central photon energy of 120 eV. Fully phase matched harmonics are generated in an elongated capillary reaching a cut-off energy of 160 eV. The high HHG photon fluence opens new perspectives towards seeding free electron lasers at shorter wavelengths than the state of the art. Characterization of the phas...

background: the aim of this work was to establish how well gel dosimeters performed, as substitutes for brain tissue compared with standard phantom materials such as water, polymethyl-methacrylate (or pmma), a150 plastic and te- liquid phantom material for dosimetry of neutron beams in boron neutron capture therapy. materials and methods: thermal neutron fluence, photon dose and epithermal neut...

We report on the results of optical follow-up observations of the counterpart of GRB 970508, starting 7 hours after the event. Multi-color U, B, V, R c and I c band observations were obtained during the first three consecutive nights. The counterpart was monitored regularly in R c until ∼ 4 months after the burst. The light curve after the maximum follows a decline that can be fitted with a pow...