introduction: the selection of suitable beam angles and weights in external-beam radiotherapy is at present generally based upon the experience of the planner. therefore, automated selection of beam angles and weights in forward-planned radiotherapy will be beneficial. material and methods: in this work, an efficient method is presented within the matlab environment to investigate how to improv...

The gamma tool was developed to quantitatively compare dose distributions, either measured or calculated. Before computing gamma, the dose and distance scales of the two distributions, referred to as evaluated and reference, are renormalized by dose and distance criteria, respectively. The renormalization allows the dose distribution comparison to be conducted simultaneously along dose and dist...

The gamma index is a tool that compares a dose distribution with a reference distribution by combining dose-difference and distance-to-agreement criteria. It has been widely used for ten years despite its high computational cost. This cost is due to both a search process for each reference point and the necessity to remove overestimations caused by the discrete nature of dose grids. The method ...

Background: in radiation treatment of moving targets located in thorax region of patient body, the delivered dose does not match with the planned treatment, resulting in some over and under dosage in the tumor volume, as a function of motion magnitude and frequency. Several efforts have been done to investigate the target motion effects on dose distribution in the target and surrounding normal ...

In this paper, I develop a duopoly location model of differentiated products in which consumers’ product preferences vary positively with product prices. The level of preference price-dependence (“PPD”) is allowed to vary across consumers. I find that equilibrium prices increase with the PPD level of the marginal, or “just indifferent,” consumer, but are not influenced by the PPD levels of othe...

The gamma dose comparison tool has been used by numerous investigators to quantitatively compare multidimensional dose distributions. The gamma tool requires the specification of dose and distance-to-agreement (DTA) criteria for acceptable variations between the dose distributions. The tool then provides a comparison that simultaneously evaluates the dose difference and distance to agreement of...

Introduction: The functionality and quality of any treatment planning system (TPS) strongly depends on the type of Algorithm which is used by it. Obviously, the role of dose distribution algorithms in calculation of prescribed dose inside the tumor in modern radiotherapy techniques has more important than past to achieve the best clinical outcomes, especially in tumors which ar...

Aims: It was aimed to investigate postoperative conformal radiotherapy planning that provides the best target volume and the least dose for critical organs in cancers of stomach. Methods: This study was conducted on the CT simulation images of thirty patients diagnosed with gastric cancer. Target volumes and the organs at risk were contoured. AP-PA reciprocal parallel field conventional plan an...

Introduction: Metal prostheses in patients affect the radiotherapy dose distribution. Metal prostheses with high density and atomic number cause major changes in scattering and attenuation of radiation. The present study aims to assess the impact of metal knee prosthesis with various dimensions and materials on radiotherapy dose distribution. Material and Methods: In this research, the Varian L...