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