Feldkamp-based cone-beam reconstruction for gantry-tilted helical multislice CT

Ilmar Hein, Katsuyuki Taguchi, Michael D. Silver, Masahiro Kazama, Issei Mori

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Depending on the clinical application, it is frequently necessary to tilt the gantry of an x-ray CT system with respect to the patient and couch. For single-slice fan-beam systems, tilting the gantry introduces no errors or artifacts. Most current systems, however, are helical multislice systems with up to 16 slices. The multislice helical reconstruction algorithms used to create CT images must be modified to account for tilting of the gantry. If they are not, the quality of reconstructed images will be poor with the presence of significant artifacts, such as smearing and double-imaging of anatomical structures. Current CT systems employ three primary types of reconstruction algorithms: helical fan-beam approximation, advanced single-slice rebinning, and Feldkamp-based algorithms. This paper presents a generalized helical cone-beam Feldkamp-based algorithm that is valid for both tilted and nontilted orientations of the gantry. Unlike some of the other algorithms, generalization of the Feldkamp algorithm to include gantry tilt is simple and straightforward with no significant increase in computational complexity. The effect of gantry tilt for helical Feldkamp reconstruction is to introduce a lateral shift in the isocenter of the reconstructed slice of interest, which is a function of the tilt, couch speed, and view angle. The lateral shift is easily calculated and incorporated into the helical Feldkamp backprojection algorithm. A tilt-generalized helical Feldkamp algorithm has been developed and incorporated into AquilionTM 16-slice CT (Toshiba, Japan) scanners. This paper describes modifications necessary for the tilt generalization and its verification.

Original languageEnglish (US)
Pages (from-to)3233-3242
Number of pages10
JournalMedical physics
Issue number12
StatePublished - Dec 2003
Externally publishedYes


  • CT
  • Computed tomography
  • Cone beam
  • Feldkamp
  • Helical
  • Multislice
  • Tilted gantry
  • X-ray

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging


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