introduction wedge modifiers are commonly applied in external beam radiotherapy to change the dose distribution corresponding to the body contour and to obtain a uniform dose distribution within the target volume. since the radiation dose delivered to the target must be within ±5% of the prescribed dose, accurate dose calculation by a treatment planning system (tps) is important. the objective ...

background: the electron contamination may reduce or even diminish the skin sparing property of the megavoltage beam. the detailed characteristics of contaminant electrons are presented for different field sizes and cases. materials and methods: the monte carlo code, mcnpx, has been used to simulate 18 mv photon beam from a varian linac-2300 accelerator. all dose measurements were carried out u...

In treatment planning of brachytherapy, absorbed dose is calculated by superposing predetermined distributions of absorbed dose to water in water for the single source according to the irradiation pattern ͓i.e., placement of the source͑s͒ or dwelling position͑s͔͒. Single-source reference water data are derived from Monte Carlo ͑MC͒ simulations and/or experiments. For reasons of positional accuracy, exp...

State-of-the-art radiotherapy treatment planning systems provide reliable estimates of the therapeutic radiation but are known to underestimate or neglect the stray radiation exposures. Most commonly, stray radiation exposures are reconstructed using empirical formulas or lookup tables. The purpose of this study was to develop the basic physics of a model capable of calculating the total absorb...

For determining the absorbed dose of ionizing radiation is tissues, it is essential to have materials which behave like tissues. These kinds of materials are usually called phantom. Up to now many different compounds like water, rubber, Perspex etc have been used. Unfortunately, the practical use of each of them has had its own problems. Our suggested gelatin phantom is very similar to soft...

context appropriate management of neonates, tested positive for congenital hypothyroidism (ch), in particular, the initial dosage of levothyroxine and the time of initiation of treatment is a critical issue. the aim of this study was to assess all current evidence available on the subject to ascertain the optimal initial dose and optimal initiation time of treatment for children with ch. eviden...

OBJECTIVES Gallium-68 DOTA-DPhe1-Tyr3-Octreotide (68Ga-DOTATOC) has been applied by several European centers for the treatment of a variety of human malignancies. Nevertheless, definitive dosimetric data are yet unavailable. According to the Society of Nuclear Medicine and Molecular Imaging, researchers are investigating the safety and efficacy of this radiotracer to meet Food and Drug Administ...