In single photon emission computed tomography (SPECT), pinhole and cone-beam collimators are used for small object imaging. It is accepted that a pinhole collimator should be used if the object is very small, and the cone-beam collimator should be used if the object is larger. This paper presents criteria to determine which collimation geometry is more advantageous in terms of spatial resolutio...

Although x-ray imaging is widely used in biomedical applications, biological soft tissues have small density changes, leading to low contrast resolution for attenuation-based x-ray imaging. Over the past years, x-ray small-angle scattering was studied as a new contrast mechanism to enhance subtle structural variation within the soft tissue. In this paper, we present a detection method to extrac...

A micrometer-scale “plasma lens” self-constructed by the prepulse and main pulse of Laguerre–Gaussian (LG) laser is realized to enhance collimation acceleration proton beams in a target normal sheath field mechanism. Hydrodynamic FLASH particle-in-cell simulations are carried out find that collimated source with beam divergence ∼2.7° generated LG laser, which smaller than case driven traditiona...

We present a simple and inexpensive design for a multichannel effusive oven nozzle which provides improved atomic beam collimation and thus extended oven lifetimes. Using this design, we demonstrate an atomic lithium source suitable for trapped-atom experiments. At a nozzle temperature of 525 °C, the collimated atomic beam flux directly after the nozzle is 1.2 × 10(14) atoms/s with a peak beam ...

We study self-collimation and beam splitting in low-refractive-index photonic crystals created within chalcogenide glass. We propose a beam splitter structure that allows direct experimental verification of photonic-crystal effects at optical wavelengths in a straightforward and definitive manner. The beam splitter provides angular separation of 90 using a highly compact spatial footprint, thus...

In digital radiography we are now able to electronically collimate images after acquisition. This may seem convenient in paediatric imaging, but we have to be aware that electronic collimation has two major downsides. Electronic collimation implicates that the original field size should have been smaller and the child has been exposed to unnecessary radiation. Also, by use of electronic collima...

OBJECTIVES The impact of two multileaf collimator (MLC) systems for linear accelerator-based intracranial stereotactic radiosurgery (SRS) was assessed. METHODS 68 lesions formed the basis of this study. 2.5 mm leaf width plans served as reference. Comparative plans, with identical planning parameters, were based on a 5 mm leaf width MLC system. Two collimation strategies, with collimation fix...

background: a set of hardware stereotactic radiosurgery is designed and constructed. the scope of this article is to describe how we have designed and developed stereotactic collimation assembly for a 9 mv neptun 10 pc linac. materials and methods: one collimator holder and six collimators were made, with their radiation field diameter between 12.5 mm to 25 mm at isocenter level. beam data, suc...

We demonstrate both experimentally and theoretically that a two-layer dielectric structure can provide collimation and enhanced transmission of a Gaussian beam passing through it. This is due to formation of surface localized states along the layered structure and the coupling of these states to outgoing propagating waves. A system of multiple cascading two-layers can sustain the beaming for la...