Original researchSingle source dual energy CT: What is the optimal monochromatic energy level for the analysis of the lung parenchyma?

- Lung parenchyma aspect varies with the monochromatic energy level in spectral CT.
- Optimal diagnostic and image quality is obtained at 50-55 keV.
- Mediastinum and parenchyma could be read on the same monochromatic energy level.

ObjectiveTo determine the optimal monochromatic energy level for lung parenchyma analysis in spectral CT.MethodsAll 50 examinations (58% men, 64.8 ± 16yo) from an IRB-approved prospective study on single-source dual energy chest CT were retrospectively included and analyzed.Monochromatic images in lung window reconstructed every 5 keV from 40 to 140 keV were independently assessed by two chest radiologists. Based on the overall image quality and the depiction/conspicuity of parenchymal lesions, each reader had to designate for every patient the keV level providing the best diagnostic and image quality.Results72% of the examinations exhibited parenchymal lesions.Reader 1 picked the 55 keV monochromatic reconstruction in 52% of cases, 50 in 30% and 60 in 18%. Reader 2 chose 50 keV in 52% cases, 55 in 40%, 60 in 6% and 40 in 2%. The 50 and 55 keV levels were chosen by at least one reader in 64% and 76% of all patients, respectively.Merging 50 and 55 keV into one category results in an optimal setting selected by reader 1 in 82% of patients and by reader 2 in 92%, with a 74% concomitant agreement.ConclusionThe best image quality for lung parenchyma in spectral CT is obtained with the 50-55 keV monochromatic reconstructions.

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