Felix G. Meinel MD, Presenter: Nothing to Disclose

U. Joseph Schoepf MD, Abstract Co-Author: Research Grant, Bracco Group Research Grant, Bayer AG Research Grant, General Electric Company Research Grant, Siemens AG

Xin Sui MD, Abstract Co-Author: Nothing to Disclose

Wei Song MD, Abstract Co-Author: Nothing to Disclose

Huadan Xue MD, Abstract Co-Author: Nothing to Disclose

Zheng Yu Jin MD, Abstract Co-Author: Nothing to Disclose

Bernhard Schmidt PhD, Abstract Co-Author: Employee, Siemens AG

Thomas G. Flohr PhD, Abstract Co-Author: Employee, Siemens AG

Rui Wang, Abstract Co-Author: Nothing to Disclose

To determine whether ultra-low radiation dose (ULD) chest CT allows for quantification of lung density and emphysema detection in lung cancer screening participants and to assess the influence of iterative reconstruction (IR) in this indication.

Fifty-two patients were prospectively enrolled in this study and scanned twice using a low-dose (LD) CT protocol (reference parameters 120 kV, 50 eff. mAs) and an ULD CT protocol (reference parameters 80 kV, 4-5 eff. mAs). Images were reconstructed using filtered back projection (FBP) for LD CT datasets and using FBP and IR for ULD CT datasets. Radiation dose was recorded. Image noise, total lung volume, mean lung density, 15th percentile of lung density and emphysema index were measured in each reconstructed image series. The measurements were compared using one-way analysis of variance (ANOVA) for repeated measures. Measurement bias was assessed using Bland-Altman analysis. We additionally calculated the test characteristics of ULD CT to detect patients with more-than-minimal emphysema, which we defined as an emphysema index ≥3 %.

The effective doses of LD and ULD CT were 2.1 ± 0.5 and 0.13 ± 0.04 mSv, respectively. Compared to LD CT, the emphysema index was overestimated by 7 % on ULD CT reconstructed with FBP, and by 2 % using IR. The 15th percentile of lung density was underestimated by 21 HU on ULD CT using FBP, and by 6 HU using IR. No relevant bias was observed for total lung volume and mean lung density measurements using the ULD CT protocol with FBP or IR. Four patients (8 %) had more-than-subtle emphysema with an emphysema index ≥ 3 %. The emphysema index measured at ULD CT with FBP / IR had 100 % / 100 % sensitivity and 92 % / 96 % specificity in identifying the patients with more-than-subtle emphysema using an emphysema index cutoff of >12.1% for FBP and >6.7% for IR. 

ULD chest CT performed for lung cancer screening allows for quantification of lung density and emphysema detection. By reducing image noise, IR improves the accuracy of ULD CT in this setting.

Ultra-low dose chest CT for lung cancer screening retains the potential for quantification of lung density and emphysema detection while reducing radiation dose by >90% compared to low dose CT.

Meinel, F, Schoepf, U, Sui, X, Song, W, Xue, H, Jin, Z, Schmidt, B, Flohr, T, Wang, R, Ultra-low Radiation Dose Chest CT for Lung Cancer Screening: Accuracy for Lung Densitometry and Emphysema Detection.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14018090.html