نتایج جستجو برای: collimator angle

تعداد نتایج: 133117  

Journal: :Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics 2010
Alain Seret

This study was aimed at comparing the sensitivity and hot and cold contrasts obtained when imaging the PICKER thyroid phantom using gamma cameras fitted with either their ultra-high or high-resolution low-energy parallel hole collimator. Seventeen camera models from Elscint, General Electric, Siemens and Sopha Medical Vision were involved in the study for a total of 30 cameras and 52 camera hea...

Journal: :Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine 2005
A Kamali-Asl S Sarkar M Shahriari H Agha-Hosseini

Conventional single photon emission computed tomography (SPECT) collimators are not suitable for 511 keV imaging. In order to use a SPECT system for single positron emission tomography (SPET), we need to design high-efficiency collimators capable of absorbing 511 keV photons. Slit slat (SS) collimators have been proposed for this purpose even though the optimization of such collimators has not ...

2002
M. Squillante

An integrated imaging sensor system is being developed to enhance operations of robots and telerobotic systems used in nuclear industry . This system combines a gamma ray image of the distribution of radioactivity with a video image of the area, allowing a rapid and intuitive determination of the source location . The gamma ray imaging system is based upon a position sensitive photomultiplier t...

Journal: :Journal of Nuclear Medicine Technology 2021

The aim of this study was to analyze the interobserver agreement visual and quantitative assessment cardiac 123I-metaiodobenzylguanidine scintigraphy. Methods: Planar images were acquired using a low-energy collimator. heart-to-mediastinum (HM) ratio adjusted for use collimator, published formula. Interpretation undertaken both visually after addition HM ratios. Image findings...

Journal: :Medical physics 2010
Yang Lu Hengyong Yu Guohua Cao Jun Zhao Ge Wang Otto Zhou

PURPOSE In this article, the authors propose a multibeam field emission x-ray (MBFEX) system along with a half-scan fan-beam reconstruction algorithm. METHODS The proposed system consists of a linear CNT-based MBFEX source array, a single large area detector that is divided into same number of segments as the number of x-ray beams, a multihole collimator that aligns each beam with a correspon...

Journal: :Japanese Journal of Radiological Technology 1972

Introduction: Gamma cameras are proposed for online range verification and treatment monitoring in proton therapy.  An Analytical formula was derived and validated for sensitivity of a slit collimator based on the photon fluence concept. Methods: Fluence formulation was generalized for photons distribution function and solved for high-energy point sources. The...

Journal: :Medical physics 1999
J Y Cheung K N Yu R T Ho C P Yu

The Monte Carlo technique and GafChromic films were employed to verify the accuracy of the dose planning system (Leksell GammaPlan) used in Gamma Knife (type B) radiosurgery when plugged collimator helmets were used. The EGS4 Monte Carlo code was used to calculate the dose distribution along the x, y, and z axes when a single shot was delivered at the center point (unit center point: x = 100, y...

2014
Keiichi Nakagawa Akihiro Haga Akira Sakumi Hideomi Yamashita Hiroshi Igaki Takashi Shiraki Kuni Ohtomo Yoshio Iwai Kiyoshi Yoda

To the Editor, Volumetric modulated arc therapy (VMAT) serves as a means for stereotactic hypofractionated treatment of lung tumors [1]. The present authors proposed an efficient VMAT sequence by restricting leaf speeds of a multi-leaf collimator per gantry rotation angle to below 1 mm/degree, thereby reducing the dose delivery time down to 210 s for a D95 prescription dose of 50 Gy in four fra...

2003
I. Zagorodnov T. Weiland

Collimators are used to eliminate halo particles from the beam. To relax the wakefield effects a gradual transition from a large to a small aperture is used. However, the existing computer codes face severe problems for long tapered transitions. Two main sources of the problems are the grid dispersion and the staircase geometry approximation. Using recently developed time domain numerical appro...

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