introduction evaluation of the delivered dose of externally wedged photon beams by external diode dosimeters during the treatment process requires the estimation of exit surface dose correction factors in various wedge angles and field sizes. materials and methods a system of absorbed dose evaluation, using p-type diode dosimeters placed on the exit surface of a phantom, was characterized for e...

Sinus-node function was characterized in 13 patients during cardiac catheterization by the introduction of progressively premature atrial depolarizations. Curves relating the extent of sinus-node depression following these premature depolarizations and their degree of prematurity were constructed. The maximum extent of sinus-node depression following premature depolarizations and A-V-nodal and ...

INTRODUCTION It is well recognized that, apart from natural background, medical exposures are at present by far the largest source of exposure to ionizing radiation of the population and that several radiation protection measures should be taken by each country to prevent unnecessary or unproductive medical radiation exposure. The main tools generally to achieve this aim are justification of pr...

Entrance and exit doses are commonly measured in in vivo dosimetry for comparison with expected values, usually generated by the treatment planning system (TPS), to verify accuracy of treatment delivery. This report aims to evaluate the accuracy of six TPS algorithms in computing entrance and exit doses for a 6 MV beam. The algorithms tested were: pencil beam convolution (Eclipse PBC), analytic...

The impact of spectral filtration in digital ('cine') acquisition was investigated using a flat panel cardiac interventional X-ray imaging system. A 0.1-mm copper (Cu) and 1.0-mm aluminium (Al) filter added to the standard acquisition mode created the filtered mode for comparison. Image sequences of 35 patients were acquired, a double-blind subjective image quality assessment was completed and ...

Nesting cavities are often a limited resource that multiple species use. There is an ongoing discussion on whether invasive cavity nesting birds restrict the availability of this key limited resource. While the answer to this question has important conservation implications, little experimental work has been done to examine it. Here, we aimed to experimentally test whether alien cavity nesting ...

Introduction: Phantom studies facilitate the implementation of radiation dose surveillance as a function of radiographic technical parameters for minimizing patient radiation dose. The evidence of such investigations can then be used to evaluate technical parameters used in the radiographic procedures to reduce radiation dose without compromising the image quality. Material and Methods: This ex...

Stingless bees (Meliponini) construct their own species-specific nest entrance. The size of this entrance is under conflicting selective pressures. Smaller entrances are easier to defend; however, a larger entrance accommodates heavier forager traffic. Using a comparative approach with 26 species of stingless bees, we show that species with greater foraging traffic have significantly larger ent...