Portal dosimetry (PD) was performed for 181 fields from 14 IMRT plans of various clinical sites at gantry zero and source-to-detector distance (SDD) of 100 cm. PD was realized using aSi1000 electronic portal imaging device (EPID) and portal dose prediction (PDP) algorithm implemented in Eclipse treatment planning system (TPS). Agreement of PDP predicted and EPID measured photon fluence/dose dis...

We investigated the effects of photon fluence rate on internode elongation in fully de-etiolated plants growing under sunlight. Our goal was to find out whether perception by the stetns of fluence rate changes related to canopy density tnay be involved in the modulation of internode growth in canopies formed by plants of sitnilar stature (e.g. crop stands). Using Datuta ferox L. and Sinapis alb...

BACKGROUND The study summarised in this report aimed to investigate the interplay between fluence complexity, dose calculation algorithms, dose calculation spatial resolution and delivery characteristics (monitor units, effective field width and dose delivery against dose prediction agreement) was investigated. A sample set of complex planning cases was selected and tested using a commercial tr...

The presented virtual energy fluence (VEF) model of the patient-independent part of the medical linear accelerator heads, consists of two Gaussian-shaped photon sources and one uniform electron source. The planar photon sources are located close to the bremsstrahlung target (primary source) and to the flattening filter (secondary source), respectively. The electron contamination source is locat...

We propose a physical model of gamma-ray burst spectral evolution in which impulsively accelerated nonthermal leptons cool by saturated Compton upscattering of soft photons. This model naturally explains the recently discovered exponential decay of the spectral break energy with photon fluence, the hard-to-soft spectral evolution patterns, and other spectral and temporal properties of gamma-ray...

Results of a phenomenological model to estimate the GRB detection rate by the Fermi Gamma ray Space Telescope are reported. This estimate is based on the BATSE 4B GRB fluence distribution, the mean ratio of fluences measured at 100 MeV – 5 GeV with EGRET and at 20 keV – 2 MeV with BATSE, and the mean EGRET GRB spectrum for the 5 EGRET spark-chamber GRBs. For a 10% fluence ratio and a number spe...

Computed tomography (CT) is a widely used medical imaging modality. By rotating an x-ray tube and an x-ray detector around the patient, a CT scanner is able to measure the x-ray transmission from all directions and form an image of the patient’s interior. CT scanners in clinical use today all use energy-integrating detectors, which measure the total incident energy for each measurement interval...

The main target of this study is the GRB light curve during the decay phase of long, bright pulses. As shown by Ryde & Svensson (2000; hereafter RS00) approximately half of these decays can be described by a power law ∝ 1/(time). This happens for cases when the hardness-fluence correlation (HFC) is an exponential function, Epk(Φ) ∝ e −Φ/Φ0 , and the hardness-intensity correlation (HIC) is a pow...

PURPOSE To ensure the quality assurance of small field, dynamic radiotherapy, we present and validate a radiation tracking system based on long scintillating fibers that allows for the real-time measurement of the position and energetic fluence of a small incident radiation field. METHOD We aligned 60 parallel scintillating fibers on a thin grooved acrylic slab with a 100-cm source-to-fibers ...

The International Commission on Radiation Units and Measurements Report 62 (ICRU 1999) introduced the concept of expanding the clinical target volume (CTV) to form the planning target volume by a two-step process. The first step is adding a clinically definable internal margin, which produces an internal target volume that accounts for the size, shape and position of the CTV in relation to anat...