Optimization of image acquisition techniques for dual-energy imaging of the chest

N. A. Shkumat, J. H. Siewerdsen, A. C. Dhanantwari, D. B. Williams, S. Richard, N. S. Paul, J. Yorkston, R. Van Metter

Research output: Contribution to journalArticlepeer-review

Abstract

Experimental and theoretical studies were conducted to determine optimal acquisition techniques for a prototype dual-energy (DE) chest imaging system. Technique factors investigated included the selection of added x-ray filtration, kVp pair, and the allocation of dose between low- and high-energy projections, with total dose equal to or less than that of a conventional chest radiograph. Optima were computed to maximize lung nodule detectability as characterized by the signal-difference-to-noise ratio (SDNR) in DE chest images. Optimal beam filtration was determined by cascaded systems analysis of DE image SDNR for filter selections across the periodic table (Zfilter =1-92), demonstrating the importance of differential filtration between low- and high-kVp projections and suggesting optimal high-kVp filters in the range Zfilter =25-50. For example, added filtration of ∼2.1 mm Cu, ∼1.2 mm Zr, ∼0.7 mm Mo, and ∼0.6 mm Ag to the high-kVp beam provided optimal (and nearly equivalent) soft-tissue SDNR. Optimal kVp pair and dose allocation were investigated using a chest phantom presenting simulated lung nodules and ribs for thin, average, and thick body habitus. Low- and high-energy techniques ranged from 60-90 kVp and 120-150 kVp, respectively, with peak soft-tissue SDNR achieved at [60120] kVp for all patient thicknesses and all levels of imaging dose. A strong dependence on the kVp of the low-energy projection was observed. Optimal allocation of dose between low- and high-energy projections was such that ∼30% of the total dose was delivered by the low-kVp projection, exhibiting a fairly weak dependence on kVp pair and dose. The results have guided the implementation of a prototype DE imaging system for imaging trials in early-stage lung nodule detection and diagnosis.

Original languageEnglish (US)
Pages (from-to)3904-3915
Number of pages12
JournalMedical physics
Volume34
Issue number10
DOIs
StatePublished - 2007

Keywords

  • Cardiac gating
  • Dual-energy imaging
  • Flat-panel detector
  • Image acquisition technique
  • Image quality
  • Imaging dose
  • Imaging performance
  • Lung cancer
  • Optimization
  • Thoracic imaging

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

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