- Journal Details
- First Published
- 30 Dec 2008
- Publication timeframe
- 4 times per year
- Open Access
Page range: 1 - 10
The increasing use of mobile phones has raised concerns regarding the potential health effects of exposure to the radiofrequency electromagnetic fields. An increasing amount research related to mobile phone use has focussed on the possible effects of mobile phone exposure on human brain activity and function. In particular, the use of sleep research has become a more widely used technique for assessing the possible effects of mobile phones on human health and wellbeing especially in the investigation of potential changes in sleep architecture resulting from mobile phone use. Acute exposure to a mobile phone prior to sleep significantly enhances electroencephalogram spectral power in the sleep spindle frequency range. This mobile phone-induced enhancement in spectral power is largely transitory and does not linger throughout the night. Furthermore, a reduction in rapid eye movement sleep latency following mobile phone exposure was also found, although interestingly, neither this change in rapid eye movement sleep latency or the enhancement in spectral power following mobile phone exposure, led to changes in the overall quality of sleep. In conclusion, a short exposure to the radiofrequency electromagnetic fields emitted by a mobile phone handset immediately prior to sleep is sufficient to induce changes in brain activity in the initial part of sleep. The consequences or functional significance of this effect are currently unknown and it would be premature to draw conclusions about possible health consequences.
- mobile phones
- health effects
- brain activity and function
- sleep architecture
- Open Access
Position of effective electron source for shielded electron beams from a therapeutic linear accelerator
Page range: 11 - 21
The effective electron source positions for the standard electron cones and for the shielded field sizes with cerrobend inserts were measured based on Inverse Square Law (ISL) and the Inverse Slope (IS) method for various electron energies.
The charge measurements were carried out using a 0.6 cc ion chamber (PTW, Type 30001) connected to a PTW Unidos E digital electrometer in a polystyrene phantom for electron beam energies of 6-18 MeV. The resultant charge for 100 MU setting was measured at nominal source to surface distances (SSDs) of 100-120 cm for cone and cerrobend defined field sizes.
The effective SSD (SSDeff) was found to be different for the same field size defined by electron applicator and the cerrobend shield placed in 25×25 cm standard cone. Strong dependency of SSDeff with field size and electron beam energy was noticed.
The results from the ISL and IS method are consistent, hence either of the two methods can be used to determine the effective source position. Whenever treatment is to be given with shielded electron portal, the SSDeff for that field needs to be determined. Same SSDeff as that of the standard cone can be used for minimum shielded electron portals.
- electron beam
- effective electron source
- inverse square law
- inverse slope
- Open Access
Treatment planning system and dose delivery accuracy in extracranial stereotactic radiotherapy using Elekta body frame
Page range: 23 - 34
The purpose of this study was to measure the photon beam transmission through the Elekta Stereotactic Body Frame (ESBF) and treatment couch, to determine the dose calculations accuracy of the MasterPlan Treatment Planning System (TPS) using Pencil Beam (PBA) and Collapsed Cone (CCA) algorithms during the use of Elekta Stereotactic Body Frame (ESBF), and to demonstrate a simple calculation method to put this transmission into account during the treatment planning dose calculations.
The dose was measured at the center of an in-house custom-built inhomogeneous PMMA thorax phantom with and without ‘the frame + treatment couch’. The phantom was CT-imaged inside the ESBF and planned with multiple 3D-CRT fields using PBA and CCA for photon beams of energies 6 MV and 10 MV. There were two treatment plans for dose calculations. In the first plan, the ‘frame + couch’ were included in the body contour and, therefore, included in the TPS dose calculations. In the second plan, the ‘frame + couch’ were not included in the body contour and, therefore, not included in the calculations. Transmission of the ‘frame + couch’ was determined by the ratio of the dose measurements with the ‘frame + couch’ to the measurements without them. To validate the accuracy of the calculation model, plans with and without the ‘frame + couch’ surrounding the phantoms were compared with their corresponding measurements.
The transmission of the ‘frame + couch’ varies from 90.23-97.54% depending on the energy, field size, the angle of the beams and whether the beams also intercept them. The validation accuracy of the Pencil Beam (PBA) and Collapsed Cone (CCA) algorithms were within 5.33% and 4.04% respectively for the individual measurements for all gantry angles under this study. The results showed that both PBA and CCA algorithms can calculate the dose to the target within 4.25% and 1.95% of the average measured value.
The attenuation caused by the ESBF and couch must be accounted into the planning process. For MasterPlan, the ‘frame + couch’ should be contoured and included in all calculations. This can be done easily and accurately.
- body frame
- plan verification
- beam attenuation
- Open Access
Page range: 35 - 42
Radiation Protection Measurements Laboratory (RPLM) of the Institute of Atomic Energy POLATOM determines radionuclides in human urine to estimate the effective dose. Being an accredited laboratory, RPLM participated in interlaboratory comparisons in order to assure the quality of services concerning monitoring of internal contamination. The purpose of the study was to examine the effect of interlaboratory comparisons on the accuracy of the provided measurements. The results regarding tritium (3H) and strontium (90Sr) determination, obtained within the radiotoxicological intercomparison exercises, organized by PROCORAD, in 2005-2010, were analyzed and the methods used by the laboratory were verified and improved.
- effective dose
- Open Access
Page range: 43 - 53
Altered flow conditions, such as separation and recirculationg zones, low and oscillatory shear stress, play an important role in the development of arterial disease. Endothelial denudation by the blood flow is the first step in atherosclerosis. The description of blood flow in vivo is complicated due to the viscoelasticity of vessel walls. However, conventional researches of the effect of the blood vessel viscoelasticity on the blood pressure wave propagation using non-linear one-dimensional models do not take into account the viscoelasticity, despite it being importance in the analysis of pulse wave propagation in arteries.
The purpose of this paper is to study the impact of the arterial pulse wave on the viscoelastic blood flow and initial factors of atherosclerosis.
In 12 healthy men (25-39 years of age) peak velocity, mean velocity, mean flow and net flow in the aorta have been investigated by MR angiography.
Initial velocity was registered after 43msec of the ECG-R wave, and it differed from zero at all sites of the aorta, although net flow was equal to zero. Womersley's number from the ascending to the thoracic aorta decreased from 12.5 ± 1.5 to 7.3 ± 1.2; flow modified from inertio-elastic to viscous. Pulse pressure wave move on artery walls fifteen or more times more rapidly than the blood flow. In the aortic arch in protodiastole blood flow separated into the opposite directed streams resulting in wave superposition with the high net flow. At the isthmus area separated waves interferences and reflects to anterograde direction.
Pulse oscillation increases strain rate to the contiguous vessel wall flow layers. At the sites with the flow wave negative interference vessel pulse oscillation attenuates and at the boundary reflection flow wave can shift the vessel wall.
- arterial pulse
- blood flow
- wave propagation
- blood viscoelasticity
- endothelial denudation
- magnetic resonance imaging