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

Journal Article · Mon Oct 15 04:00:00 EDT 2007 · Medical Physics

DOI:https://doi.org/10.1118/1.2777278· OSTI ID:21032807

Shkumat, N A; Siewerdsen, J H; Dhanantwari, A C; Williams, D B; Richard, S; Paul, N S; Yorkston, J; Van Metter, R ^[1]

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1. Department of Medical Biophysics, University of Toronto, Toronto, Ontario, M5G 2M9 (Canada)

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 (Z{sub filter}=1-92), demonstrating the importance of differential filtration between low- and high-kVp projections and suggesting optimal high-kVp filters in the range Z{sub filter}=25-50. For example, added filtration of {approx}2.1 mm Cu, {approx}1.2 mm Zr, {approx}0.7 mm Mo, and {approx}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 [60/120] 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 {approx}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.

• OSTI ID: 21032807
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 10 Vol. 34; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BEAMS
CHEST
DIAGNOSIS
DOSIMETRY
FILTRATION
IMAGE PROCESSING
IMAGES
LUNGS
NEOPLASMS
OPTIMIZATION
PERIODIC SYSTEM
PHANTOMS
RADIATION DOSES
SYSTEMS ANALYSIS
THICKNESS
X RADIATION