Elsevier

Clinical Radiology

Volume 64, Issue 2, February 2009, Pages 127-132
Clinical Radiology

Usefulness of concurrent reading using thin-section and thick-section CT images in subcentimetre solitary pulmonary nodules

https://doi.org/10.1016/j.crad.2008.09.003Get rights and content

Aim

To evaluate the differences in the characterization and recommendation for follow-up of subcentimetre solitary pulmonary nodules (SSPNs) between 5 and 1 mm section CT, and to compare the assessments generated by four radiologists

Materials and methods

Five hundred and twenty-nine patients who had SSPNs on chest CT reconstructed using both 5 and 1 mm sections were enrolled. Two image subsets of 5 and 1 mm CT images of each nodule were interpreted independently by four radiologists. Nodule size, consistency (solid, partly solid, non-solid), the presence of calcification, and recommendations for follow-up were evaluated. If a non-calcified solid nodule was confirmed using CT, recommendation for follow-up was based on Fleischner Society guidelines. Data assessed by each radiologist were compared, and interobserver agreements were determined using the intraclass correlation coefficients and kappa value.

Results

Using 1 mm CT images, the nodule sizes were significantly larger than on 5 mm CT images (paired t-test, p < 0.01). The presence of calcification and nodule consistency were significantly different between 5 and 1 mm CT images (McNemar test for the presence of calcification, p < 0.01; Wilcoxon signed test for nodule consistency, p < 0.01). On 1 mm CT images there was significantly higher agreement regarding nodule consistency than on 5 mm CT (kappa = 0.78 and 0.67, respectively).

Conclusions

Concurrent use of thin-section and thick-section CT can provide more accurate nodule assessment and higher interobserver agreement in SSPN.

Introduction

With widespread clinical use of computed tomography (CT), subcentimetre solitary pulmonary nodules (SSPN) have became a common finding during CT examinations.1, 2, 3 The majority of these lesions are benign,4 even in patients at high-risk of developing lung cancer or metastatic disease; therefore, histological proof may not be necessary in every case. Unnecessary follow-up CT examinations can be reduced if radiological features more accurately predict benignity with satisfactory certainty.

The thin-section CT obtained through the nodule has been shown to provide more accurate information regarding nodule size, consistency, edge characteristics, and the presence of calcification, cavitation, or fat.5 However, reading the whole volume data obtained with thin-section chest CT requires long interpretation times. If CT is obtained using submillimetre collimation, both thin- and thick-section CT images could be reconstructed from the same raw data without additional radiation exposure.6 With the concurrent use of thick- and thin-section CT, the nodule can be detected using thick-section CT, and then can be characterized using thin-section CT by reviewing the selective images that cover the nodule.

Therefore, the purpose of the present study was to evaluate the differences in the characterization and recommendation for follow-up of SSPNs between 5 and 1 mm section CT examinations, and to compare the assessments generated by four different radiologists, in order to evaluate the usefulness of concurrent reading with 5 and 1 mm section CT in SSPNs.

Section snippets

Materials and methods

This study was approved by the Institutional Review Board and patients' informed consent was waived in this retrospective study. Between January 2006 and January 2007, a consecutive review of the CT findings was retrospectively performed and patients who met the following CT criteria were included: 5 and 1 mm sections concurrently obtained; a single pulmonary nodule detected; and a lesion that had a maximum diameter ≤10 mm. The decision for nodule presence was established by consensus reading

Comparison between CT Interpretations of the 5 and 1 mm sections

In terms of nodule size, the diameter of nodules measured on 5 mm section CT were usually smaller than that on 1 mm section for all reviewers (Table 1). Smaller nodules tended to show higher variation in calculated diameter compared with larger nodules. The difference in the diameters between 5 and 1 mm section CT was statistically significant (p < 0.001). On 1 mm section CT, 28–48 more calcifications (5–9% of the nodules) were detected within the nodules than on 5 mm section CT. There were

Discussion

The results of the present study clearly showed significant differences in the characterization and recommendation for follow-up of SSPN between 5 and 1 mm section CT. The reduced section thickness improved the accuracy of the measurement of nodule size and increased the detection rate of calcification.9, 10 More accurate detection of benign calcified nodules could help to reduce unnecessary follow-up, especially in patients with low cancer risk. This is why only patients with SSPN at initial CT

Acknowledgement

This study was supported by Seoul R&BD program (10888).

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