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 language | English (US) |
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Pages (from-to) | 3904-3915 |
Number of pages | 12 |
Journal | Medical physics |
Volume | 34 |
Issue number | 10 |
DOIs | |
State | Published - 2007 |
Externally published | Yes |
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