background: a variable resolution x-ray (vrx) ct scanner provides a great increase in the spatial resolution. in vrx ct scanners, the spatial resolution of the system and its field of view (fov) can be changed according to the object size. one of the main factors that limit the spatial resolution of vrx ct scanner is the effect of the x-ray focal spot. materials and methods: a theoretical study...

introduction: variable resolution x-ray (vrx) ct is a new type of ct that can image objects at various spatial resolutions. in a vrx ct scanner, the spatial resolution increases at the cost of reduction in the field of view (fov). an important factor that limits the spatial resolution of the vrx ct is the effect of focal spot size. also, the optimum magnification is different at each incident a...

Background: A variable resolution X-ray (VRX) CT scanner provides a great increase in the spatial resolution. In VRX CT scanners, the spatial resolution of the system and its field of view (FOV) can be changed according to the object size. One of the main factors that limit the spatial resolution of VRX CT scanner is the effect of the X-ray focal spot. Materials and Methods: A theoreti...

Introduction: Variable resolution x-ray (VRX) CT is a new type of CT that can image objects at various spatial resolutions. In a VRX CT scanner, the spatial resolution increases at the cost of reduction in the field of view (FOV). An important factor that limits the spatial resolution of the VRX CT is the effect of focal spot size. Also, the optimum magnification is different at each incident a...

The purpose of this work is measurement of the system presampling MTF of a variable resolution x-ray (VRX) CT scanner. In this paper, we used the parameters of an actual VRX CT scanner for simulation and study of effect of different focal spot sizes on system presampling MTF by Monte Carlo method (GATE simulation software). Focal spot size of 0.6 mm limited the spatial resolution of the system ...

*Corresponding author: Dr. Ali Reza Kamali Asl, Radiation Medicine Department, Shahid Beheshti University, Tehran, Iran. Fax: +98 21 22431780 E-mail: [email protected] Background: A variable resolution X-ray (VRX) CT scanner provides a great increase in the spatial resolution. In VRX CT scanners, the spatial resolution of the system and its field of view (FOV) can be changed according to the...

Focal spot size is one of the crucial factors that affect the image quality of any x-ray imaging system. It is, therefore, important to measure the focal spot size accurately. In the past, pinhole and slit measurements of x-ray focal spots were obtained using direct exposure film. At present, digital detectors are replacing film in medical imaging so that, although focal spot measurements can b...

Butterfly wing color patterns often contain eyespots, which are developmentally determined at the late larval and early pupal stages by organizing activities of focal cells that can later form eyespot foci. In the pupal stage, the focal position of a future eyespot is often marked by a focal spot, one of the pupal cuticle spots, on the pupal surface. Here, we examined the possible relationships...

A modified Fresnel zone plate that can produce an approximate Gaussian focal spot is proposed for the focusing and imaging of soft x rays and extreme ultraviolet radiation. The selection conditions for the positions and the widths of the concentric open rings are analytically presented. The focal spot size can be much smaller than the width of the narrowest open ring, and the sidelobes and the ...