Reconstruction for fan beam with an angular dependent displaced center of rotation

Carl R. Crawford, Grant T. Gullberg, Benjamin M.W. Tsui

Research output: Contribution to journalLetter

Abstract

A convolutional backprojection algorithm is derived for a fan beam geometry that has an angular dependent displacement in its center of rotation from the midline of the fan beam. In both x ray computed tomography and single photon emission computed tomography, misalignment can occur when the mechanical center of rotation is not colinear with midline of the fan beam. In some cases the shift in the center of rotation is constant for every angle, whereas, in other cases it varies with angular position. Standard reconstruction algorithms, which directly filter and backproject the fan beam data without rebinning into parallel beam geometry, have been derived for a geometry having its center of rotation at the midline of the fan beam. However, in the case of any misalignment of the center of rotation, if these conventional reconstruction algorithms are used to reconstruct the fan beam projections, structured artifacts and a loss of resolution will result. Simulations are performed that illustrate these artifacts and demonstrate how the new algorithm corrects for this misalignment. A method for estimating the parameters of the fan beam geometry, including the angular dependent shift in the center of rotation, is also described.

Original languageEnglish (US)
Pages (from-to)67-71
Number of pages5
JournalMedical physics
Volume15
Issue number1
DOIs
StatePublished - Jan 1988

Keywords

  • ALGORITHMS
  • ALIGNMENT
  • BIOMEDICAL RADIOGRAPHY
  • CAT SCANNING
  • COMPUTERIZED TOMOGRAPHY
  • CORRECTIONS
  • DIAGNOSTIC TECHNIQUES
  • PHOTON BEAMS
  • SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

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