We present a unified treatment of the phase space of a spatially flat homogeneous and isotropic universe dominated by a phantom field. Results on the dynamics and the late time attractors (Big Rip, de Sitter, etc.) are derived without specifying the form of the phantom potential, using only general assumptions on its shape. Many results found in the literature are quickly recovered and predicti...

Optical tomography is being developed at UCL as a tool for understanding the mechanisms of haemorrhagic and hypoxic-ischaemic brain injury and assessing the effectiveness of novel neural rescue therapies in the newborn infant. Our 32-channel time-resolved optical imaging system measures photon flight times between multiple pairs of points on the surface of the head, and images sensitive to loca...

background: to enhance the dose to tumor, the use of high atomic number elements has been proposed. objective: the aim of this study is to investigate the effect of gold nanoparticle distribution on dose enhancement in tumor when the tumor is irradiated by typical monoenergetic x-ray beams by considering homogeneous and inhomogeneous distributions of gold nanoparticles (gnps) in the tumor. meth...

Introduction Polymer gel dosimeters offer a practical solution to 3D dose verification for conventional radiotherapy as well as intensity-modulated and stereotactic radiotherapy. In this study, EGSnrc calculated and PAGAT polymer gel dosimeter measured dose profiles from single shot irradiation with 18 mm collimator of Gamma Knife in homogeneous and inhomogeneous phantoms were compared with eac...

Accuracy and limitation of energy-window based scatter correction techniques have been evaluated for myocardial 201Tl SPECT by means of Monte Carlo simulation. In particular, projection view-dependency of energy distribution of the scattered photons was evaluated. Two geometrical configurations were simulated: namely a homogeneous cylindrical radioactivity located asymmetrically in a homogeneou...

*Corresponding author: Dr. Tayyeb Allahverdi Pourfallah, Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran. Fax: +98 21 88973653 E-mail: [email protected] Background: Polymer gel dosimetry is still the only dosimetry method for direct measuring of threedimensional dose distributions. MRI Polymer gel dosimeters are tissue equi...

OBJECTIVE: To compare data regarding dosimetry and photons fluence in different breast phantoms, discussing constancy tests and dosimetry applied to mammography. MATERIALS AND METHODS: Different homogeneous breast phantoms and one anthropomorphic voxel phantom were developed for collection of data regarding total absorbed dose in the phantom, absorbed dose in the glandular tissue material-equiv...

introduction relative dose computation is a necessary step in radiation treatment planning. therefore, finding an approach that is both fast and accurate seems to be necessary. the purpose of this work was to investigate the feasibility of natural cubic spline to reconstruct dose maps for linear accelerator radiation treatment fields in comparison with those of the simulation. materials and met...

Background: The purpose of this study is to fabricate inexpensive in-house low cost homogeneous and heterogeneous human equivalent thorax phantom and assess the dose accuracy of the Treatment Planning Systems (TPS) calculated values for different lung treatment dosimetery. It is compared with Thermoluminescent Dosimeter (TLD) measurement. Materials and Methods: Homogeneous and heterogeneous tho...

The purpose of this study is to evaluate the accuracy of the electron Monte Carlo (eMC) dose calculation algorithm included in a commercial treatment planning system and compare its performance against an electron pencil beam algorithm. Several tests were performed to explore the system's behavior in simple geometries and in configurations encountered in clinical practice. The first series of t...