Background: In breast radiotherapy, enhanced dynamic wedge (EDW) and physical wedges are used to improve the homogeneity of the dose. Scattered photons are the major factor in the off-field organs' unwanted dose. In breast radiotherapy, the thyroid is a critical off-field organ at risk for scattered photons. This study was performed to compare the unwanted dose and the secondary fatal cancer risk to the thyroid in breast radiotherapy between EDW and physical wedge. Material and Methods: The 6-MV Varian 2100 C/D linac was used to irradiate the breast of a thorax phantom under two opposite tangential fields. The unwanted dose that reached the thyroid was estimated using Eclipse Treatment Planning System and Gafchromic film dosimetry. Corresponding fatal secondary cancer risks were also assessed according to the NCRP report 116 recommendations. Results: The measured dose for thyroid using a physical wedge and enhanced dynamic wedge were measured as 2. 1 and 0. 735 cGy, which are approximately 1% and 0. 37% of the prescribed dose to the breast (2 Gy), respectively. In the case of radiotherapy with the physical wedge, the lifetime risk of secondary fatal cancer attributed to the thyroid is 0. 0480 and 0. 0504 % using TPS and measured data, respectively. In the case of the dynamic wedge, the above values were reduced to 0. 0168 and 0. 0176 %, respectively. Conclusions: Using an enhanced dynamic wedge in breast radiotherapy reduced the thyroid dose by about 65% compared to the physical wedge technique. As a result, it was concluded that the application of EDW is safer than the physical wedge in breast radiotherapy.

Introduction: The objective of this study was the measurement and comparison of light output intensity at different points of lateral surfaces of conventional and novel designs of light-conducting interdental wedges.Materials & Methods: This study was conducted on five groups of five wedges. Group 1 (TW): the Sakti transparent wedge; Group 2 (TW1): the Sakti transparent wedge with one Reflective External Surface (RES); Group 3 (TW2): the Sakti transparent wedge with two Reflective External Surfaces (2RES); Group 4 (LW): the Luciwedge; and Group 5 (LW2): the Luciwedge with two Reflective External Surfaces (2RES). Light output intensity of a light-curing source and six points at the lateral surfaces of each wedge were measured through a diaphragm with a 1 mm diameter which had a selenium photoelectric cell connected to a moving coil galvanometer. Statistical analyses were done using the Kruskal-Wallis test, Hoteling’s Trace, Duncan test and Mann-Whitney U test.Results: There is a significant difference between light output intensity from different points of the groups. Light conduction efficacy of tested groups was significantly different and had decreased respectively TW2>LW>TW1>TW and LW2>LW).Conclusion: 1) Due to low light conduction efficacy in tested groups, we cannot obtain optimum polymerization and properties of proximal light-cured restorations through any of the light-conducting wedges or conventional light-curing units. 2) A new wedge mediated light-curing technique (the "Two-Step Wedge Application Technique") for a complete and homogenous polymerization in proximal composite resin restorations was introduced. 3) Adding External Reflective Surfaces (RES) on transparent wedges caused light conduction efficacy improvement and the 2RES design was superior to the others. 4) According to this study, a new type of light-conducting wedge with perfectly transparent material as the body of the wedge together with the 2RES design can be recommended.

Background: Physical wedges are still widely used as beam modifiers in external beam radiotherapy. However the presence of them in the beam trace may cause beam hardening which may not be considered in many treatment planning systems. The aim of this study is to investigate the beam hardening effect generated by physical wedges via different beam quality indexes as photon spectrum, half value layer, mean energy and tissue-phantom ratio.Materials and Methods: The effect of physical wedges on the photon beam quality of a 6‐18MV Varian 2100C/D accelerator was studied with the BEAMnrc Monte Carlo code. Good agreements were obtained between measured and calculated depth doses and beam profiles for open and wedged photon beams at both energies.Results: It was noticed that for 6 MV photon beams, physical wedges have more significant effects on beam quality than for 18 MV. Also it was obtained that at 18 MV photon beam as the wedge angle increased, the effect of wedge on beam quality becomes reversed and beam sotiening occurred.Conclusion: According to these results, it is recommended that beam hardening and softening of physical wedges should be considered in treatment planning systems in order to increase the accuracy in dose delivery.

In network code setting, a constant dimension subspace code is a set of k-dimensional subspaces of Fn q. If Fn q is a nondegenerate symplectic vector space with bilinear form f, an Isotropic subspace U of Fn q is a subspace for which U  U? . We introduce Isotropic subspace codes simply as a set of Isotropic subspaces and show how the property of being Isotropic is used in decoding process, then we demonstrate the structure of an Isotropic spread code. In network code setting, a constant dimension subspace code is a set of k-dimensional subspaces of Fn q. If Fn q is a nondegenerate symplectic vector space with bilinear form f, an Isotropic subspace U of Fn q is a subspace for which U  U? . We introduce Isotropic subspace codes simply as a set of Isotropic subspaces and show how the property of being Isotropic is used in decoding process, then we demonstrate the structure of an Isotropic spread code.

Background: The presence of a wedge filter in the beam trajectory can modify the beam quality and cause some changes in the dosimetry parameters which are usually difficult to be measured directly and accurately. Material and Methods: In this study the MCNP-4C Monte Carlo code was used to simulate the 9 MV photon beam generated by a linear accelerator. Upon getting a good agreement between the Monte Carlo simulated and measured dose distribution in open fields, the model was used to simulate the physical wedges. The steel wedges with angles from 15°-60° were modeled and the primary and the secondary photon beams were calculated. The beam profiles and wedges factors were calculated for each wedge. The output factors were determined for 45 wedge. The calculated data were compared with the measured values of the same parameters. Results: The results showed that the use of wedges reduced the fluencies of the primary and scattered photons and also increased the average energy of the primary and the scattered photons. The agreement between the calculated and the measured data was better than 2% for all wedges. The results also showed that as the wedge angle increased, the electron contamination of photon beam decreased. Conclusion: The presence of a wedge in a 9 MV photon beam alters the primary and the scattered components generated by a linear accelerator. The simulated linac machine and its associated data can be used to predict the dose distribution in other complex fields.

The general relatively Isotropic mean Landsberg metrics contain the general relatively Isotropic Landsberg metrics. A class of Finsler metrics is given, in which the mentioned two concepts are equivalent. In this paper, an interpretation of general relatively Isotropic mean Landsberg metrics is found by using C-conformal transformations. Some necessary conditions for a general relatively Isotropic mean Landsberg metric, as well as generalized Landsberg metric to be a Riemannian metric are also found.

In this paper we study Isotropic Lagrangian submanifolds, in complex space forms M~n (4C). It is shown that they are either totally geodesic or minimal in the complex projective space Cpn, if n³3 when n=2 they are either totally geodesic or minimal in. We also give a classification of semi-parallel Lagrangian H-umbilical submanifolds.

This paper presents a general formulation for an Isotropic wedge reinforced by an orthotropic coating involving multiple arbitrarily oriented defects under out of plane deformation. The exact closed form solution of the problem weakened by a screw dislocation in the Isotropic wedge is obtained by making use of finite Fourier cosine transform. Also, the closed-form solutions of the out of plane stress and displacement fields are obtained. After that, by making use of a distributed dislocation approach, a set of singular integral equations of the domain involving smooth cavities and cracks subjected to out of plane external loading are achieved. The cracks and cavities are considered to be only in the Isotropic wedge. The presented integral equations have Cauchy singularity and must be evaluated numerically. Multiple numerical examples will be presented to show the applicability and efficiency of the presented solution. The geometric and point load singularities of the stress components are obtained and compared with the available data in the literature.