title: Optimal kvp selection for dual-energy imaging of the chest: evaluation by task-specific observer preference tests.
abstract: Human observer performance tests were conducted to identify optimal imaging techniques in dual-energy (DE) imaging of the chest with respect to a variety of visualization tasks for soft and bony tissue. Specifically, the effect of kVp selection in low- and high-energy projection pairs was investigated. DE images of an anthropomorphic chest phantom formed the basis for observer studies, decomposed from low-energy and high-energy projections in the range 60-90 kVp and 120-150 kVp, respectively, with total dose for the DE image equivalent to that of a single chest radiograph. Five expert radiologists participated in observer preference tests to evaluate differences in image quality among the DE images. For visualization of soft-tissue structures in the lung, the [60/130] kVp pair provided optimal image quality, whereas [60/140] kVp proved optimal for delineation of the descending aorta in the retrocardiac region. Such soft-tissue detectability tasks exhibited a strong dependence on the low-kVp selection (with 60 kVp providing maximum soft-tissue conspicuity) and a weaker dependence on the high-kVp selection (typically highest at 130-140 kVp). Qualitative examination of DE bone-only images suggests optimal bony visualization at a similar technique, viz., [60/140] kVp. Observer preference was largely consistent with quantitative analysis of contrast, noise, and contrast-to-noise ratio, with subtle differences likely related to the imaging task and spatial-frequency characteristics of the noise. Observer preference tests offered practical, semiquantitative identification of optimal, task-specific imaging techniques and will provide useful guidance toward clinical implementation of high-performance DE imaging systems.
authors.affiliation: Ontario Cancer Institute, Princess Margaret Hospital, Toronto, Ontario, Canada M5G 2M9.
authors.forename: D B
authors.initials: DB
authors.lastname: Williams
authors.forename: J H
authors.initials: JH
authors.lastname: Siewerdsen
authors.forename: D J
authors.initials: DJ
authors.lastname: Tward
authors.forename: N S
authors.initials: NS
authors.lastname: Paul
authors.forename: A C
authors.initials: AC
authors.lastname: Dhanantwari
authors.forename: N A
authors.initials: NA
authors.lastname: Shkumat
authors.forename: S
authors.initials: S
authors.lastname: Richard
authors.forename: J
authors.initials: J
authors.lastname: Yorkston
authors.forename: R
authors.initials: R
authors.lastname: Van Metter
mesh_terms: D001013:Aorta, Thoracic / Q000000981:diagnostic imaging / Q000473:pathology; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D015588:Observer Variation; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D015900:Radiography, Dual-Energy Scanned Projection / Q000295:instrumentation* / Q000379:methods*; D013902:Radiography, Thoracic / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D013909:Thorax / Q000473:pathology