European Radiology

, Volume 29, Issue 4, pp 1703–1713 | Cite as

The “solid” component within subsolid nodules: imaging definition, display, and correlation with invasiveness of lung adenocarcinoma, a comparison of CT histograms and subjective evaluation

  • WenTing Tu
  • ZhaoBin Li
  • Yun Wang
  • Qiong Li
  • Yi Xia
  • Yu Guan
  • Yi Xiao
  • Li FanEmail author
  • ShiYuan LiuEmail author



To validate three proposed definitions of the “solid” component of subsolid nodules, as compared to CT histograms and the use of different window settings, for discriminating the invasiveness of adenocarcinomas in a manner that facilitates routine clinical assessment.


We retrospectively analyzed 328 pathologically confirmed lung adenocarcinomas, manifesting as subsolid nodules. Three-dimensional CT histograms were generated by setting 11 CT attenuation intervals from − 400 to 50 HU, at 50 HU intervals, and the voxel percentage within each CT attenuation interval was generated automatically. Three definitions of the “solid” component were proposed, and 10 medium window settings were set to evaluate the “solid” component. The diagnostic performance of the three definitions for identifying invasive adenocarcinoma was compared with that of CT histogram analysis and subjective evaluation with medium window settings.


A parallel diagnosis using five intervals with the largest AUC (AUC ≥ 0.797) demonstrated good differential diagnostic performance, with 78% sensitivity and 73.7% specificity. Definition 2 (visibility in the mediastinum window) yielded higher accuracy (75.6%) than the other two definitions (p < 0.01). A medium window setting of − 50 WL/2 WW gave a larger AUC than the other nine medium window settings as well as definition 2, with 82.5% specificity and 88.5% PPV, which was higher than those of parallel diagnosis with CT histogram and definition 2.


Using − 50 WL/2 WW is the optimum approach for evaluating the “solid” component and discriminating invasiveness, superior to using 3D CT histograms and definition 2, and convenient in routine clinical assessment.

Key Points

• − 50 WL/2 WW gave a larger AUC than definition 2.

• The specificity of − 50 WL/2 WW was higher than CT histograms.

• − 50 WL/2 WW offers the best evaluation of the solid component.


Lung Adenocarcinoma Solitary pulmonary nodule Tomography, X-ray computed 



Atypical adenomatous hyperplasia


Adenocarcinoma in situ


Area under the curve


Computed tomography


Disease-free survival


Ground-glass nodules


Invasive adenocarcinoma


International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society


Lung window


Minimally invasive adenocarcinoma


Mediastinal window


Negative predictive value


Nonsolid nodules


Net reclassification improvement


Odds ratio


Part-solid nodules


Positive predictive value


Receiver operating characteristic



We would like to thank the assistance of the United Imaging Healthcare Co. Ltd. for the pulmonary nodule advanced analysis tool software development and technical support.


This study has received funding from the National Key R&D Program of China (grant number 2016YFE0103000, 2017YFC1308703), the National Natural Science Foundation of China (grant number 81871321, 81370035), and the Youth Fund of the National Natural Science Foundation of China (grant number 81501618, 81501470).

Compliance with ethical standards


The scientific guarantor of this publication is Prof. Li FAN.

Conflict of interest

The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.

Statistics and biometry

Prof. Jian Lu (Department of Statistics, Second Military Medical University) kindly provided statistical advice for this manuscript.

Informed consent

Written informed consent was waived by the Institutional Review Board.

Ethical approval

An Institutional Review Board approval was obtained.


• Retrospective

• Diagnostic or prognostic study

• Performed at one institution

Supplementary material

330_2018_5778_MOESM1_ESM.docx (112 kb)
ESM 1 (DOCX 112 kb)


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Copyright information

© European Society of Radiology 2018

Authors and Affiliations

  1. 1.Department of Radiology, Changzheng HospitalSecond Military Medical UniversityShanghaiChina
  2. 2.Department of Radiation OncologyShanghai Jiao Tong University Affiliated Sixth People’s HospitalShanghaiChina

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