background: monte carlo (mc) modeling of a linear accelerator is a prerequisite for monte carlo dose calculations in external beam radiotherapy. in this study, a simple and efficient model was developed for elekta sl-25 linear accelerator using mcnp4c monte carlo code materials and methods: the head of elekta sl-25 linac was simulated for 6 and 18 mv photon beams using mcnp4c mc code. energy sp...

A simple semi-phenomenological model, which accurately predicts the dependence of thresholdcurrent for temperature of Resonant-phonon three well quantum cascade laser based on verticaltransitions is offered. We found that, the longitude optical phonon scattering of thermally excitedelectrons is the most important limiting factor for thermal performance of high frequency THz QCLs.In low frequenc...

We propose a region-based method for model-free object tracking. In our method the object information of temporal motion and spatial luminance are fully utilized. We first compute dominant motion of the tracked object. Using this result we warp the object template to generate a prediction template. Static segmentation is incorporated to modify this prediction, where the warping error of each wa...

Traditional GVF snake model has enlarged capture range and improved the convergence capability for boundary concavities, but it cannot efficiently solve the convergence problem for an image with deep boundary concavities and high noise. In this paper, by integrating the region force derived from the region information of interested object in an image into the force balance equation, a novel sna...

Robust segmentation of an iris image plays an important role in iris recognition. Most state-of-the-art iris segmentation algorithms focus on the processing of the ideal iris images that are captured in a controlled environment. In this paper, we process the unideal iris images that are acquired in an unconstrained situation and are affected severely by gaze deviation, eyelids and eyelashes occ...

Magnetic resonance imaging (MRI) is emerging as a powerful tool for the diagnosis of breast abnormalities. Dynamic analysis of the temporal pattern of contrast uptake has been applied in differential diagnosis of benign and malignant lesions to improve specificity. Selecting a region of interest (ROI) is an almost universal step in the process of examining the contrast uptake characteristics of...

This paper is concerned with linear transforms for arbitrarily shaped image segments. In contrast to other techniques described in the literature, the proposed transform is based upon a stochastic model of image co-variance within the considered region. Emerging from a separable stationary Markov model proposed for rectangular regions 7], we derive a non-stationary Markov model with natural bou...

In this paper, we introduce a new deformable model for image segmentation, by reformulating a region based active contours energy into a geodesic contour energy involving a Finsler metric. As a result, we solve the region based active contours energy minimization problem without resorting to level set functions, but using a robust Eikonal equation framework. By sampling a set of control points ...

Background: Monte Carlo (MC) modeling of a linear accelerator is a prerequisite for Monte Carlo dose calculations in external beam radiotherapy. In this study, a simple and efficient model was developed for Elekta SL-25 linear accelerator using MCNP4C Monte Carlo code Materials and methods: The head of Elekta SL-25 linac was simulated for 6 and 18 MV photon beams using MCNP4C MC code. Energ...