This paper presents analytical fan-beam and cone-beam reconstruction algorithms that compensate for uniform attenuation in single photon emission computed tomography. First, a fan-beam algorithm is developed by obtaining a relationship between the two-dimensional (2D) Fourier transform of parallel-beam projections and fan-beam projections. Using this relationship, 2D Fourier transforms of equiv...

• Review the existing literature on diver visibility. • Carry out experimental determinations of the sighting range of a black disk using DaviesColley’s method together with spectral absorption and attenuation measurements in a wide range of natural optical environments. • Determine the proper wavelength or wavelength combination for the limiting beam attenuation for the horizontal black target...

Introduction: Cone-beam CT (CBCT) is an imaging system which offers three-dimensional (3D), multiplanar images and has many advantages over computed tomography (CT) including shorter acquisition times for the resolution desired in dentistry, lower radiation dose to the patient, reasonable price and higher spatial resolution but CBCT scanners are unable to display actual Hounsf...

We read with interest the recent paper by Shiga et al. published in the European Journal of Nuclear Medicine [1]. The authors report some interesting results concerning the effect of triple-energy window-based scatter correction on brain perfusion SPET using statistical para-metric mapping (SPM) analysis. The research performed is worthwhile and contributes significantly to our understanding of...

In this paper, Novikov's inversion formula of the attenuated two-dimensional (2D) Radon transform is applied to the reconstruction of attenuated fan-beam projections acquired with equal detector spacing and of attenuated cone-beam projections acquired with a flat planar detector and circular trajectory. The derivation of the fan-beam algorithm is obtained by transformation from parallel-beam co...

Knowledge of the monochromaticity of an x-ray source is increasingly important in fundamental experiments and critical applications. The bandwidth of an x-ray beam, selected from a synchrotron radiation spectrum for example, ultimately defines the limiting resolution of the synchrotron source. The development of x-ray technology through the use of characteristic line sources of fixed line shape...

This study is concerned with the use of the concrete samples produced by tincal concentrator waste as a gamma radiation shield. The values of mass attenuation coefficients for concrete samples measured at 59.54 (Am-241) and 80.99 (Ba-133) keV photon energies. Gamma rays were counted by a NaI(Tl) detector coupled to multi channel analyzer (MCA) using narrow beam transmission arrangement. Theoret...

In the past decades, analytical (non-iterative) methods have been extensively investigated and developed for the reconstruction of three-dimensional (3D) single-photon emission computed tomography (SPECT). However, it becomes possible only recently when the exact analytic non-uniform attenuation reconstruction algorithm was derived. Based on the explicit inversion formula for the attenuated Rad...

Background: In Radiation Therapy, the sparing of normal tissues can be performed using either multi-leaf collimators or Cerrobend blocks. The current work focuses on the physical characteristics of Cerrobend blocks including attenuation coefficient, effective penumbra width and isodose curves undulation in penumbral regions. Materials and Methods: All measurements were performed using ...