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Optimization of image acquisition techniques for dual‐energy imaging of the chest
Author(s) -
Shkumat N. A.,
Siewerdsen J. H.,
Dhanantwari A. C.,
Williams D. B.,
Richard S.,
Paul N. S.,
Yorkston J.,
Van Metter R.
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2777278
Subject(s) - image quality , imaging phantom , iterative reconstruction , filtration (mathematics) , projection (relational algebra) , filter (signal processing) , materials science , biomedical engineering , nuclear medicine , mathematics , computer science , artificial intelligence , computer vision , algorithm , medicine , image (mathematics) , statistics
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 filter = 1 – 92 ) , demonstrating the importance of differential filtration between low‐ and high‐kVp projections and suggesting optimal high‐kVp filters in the rangeZ filter = 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 [ 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 ∼ 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.