Bronchiectasis and airspace enlargement surrounding the lung nodule in dual-energy CT pulmonary angiography: comparison between iodine map and monochromatic image

Abstract

The purpose of the study is to investigate the degree and performance in the differential diagnosis of bronchiectasis/airspace enlargement in an iodine map obtainable from CT pulmonary angiography compared with monochromatic images. This retrospective study included 62 patients with a lung nodule who underwent CT pulmonary angiography. The iodine map and monochromatic image (70 keV) were reconstructed. Three readers evaluated the degree of bronchiectasis/airspace enlargement with a 4-point scale. A reference standard was established in 39 patients, and the performance of bronchiectasis/airspace enlargement in the differential diagnosis was evaluated in them. The degree of bronchiectasis/airspace enlargement in the iodine map (median score = 1/2/1 for reader 1/2/3) was significantly more prominent than that in the monochromatic image (median score = 0/1/0 for reader 1/2/3) (p < 0.001 for all readers). Using bronchiectasis/airspace enlargement, primary lung carcinoma and malignant lymphoma could be differentiated from other diseases, excluding lung infarct, with an area under the receiver operating characteristic curve (AUC) (reader 1/2/3) of 0.718/0.867/0.803 in the combinations of iodine map plus monochromatic image and 0.496/0.828/0.450 in the monochromatic image (p ≤ 0.047 for two readers). Lung metastasis from colorectal carcinoma could be differentiated from other diseases with an AUC of 0.851/0.976/0.838 in the combinations of iodine map plus monochromatic image, which was significantly superior to the monochromatic image (0.378/0.780/0.459) (p ≤ 0.012 for all readers). Bronchiectasis/airspace enlargement was more prominently observed in the iodine map than in the monochromatic image. This image finding in the iodine map provided added value in the differential diagnosis of malignant lung nodules compared with monochromatic images alone.

Keywords: Bronchiectasis; Lung cancer; Lung nodule; Multidetector computed tomography.

Fig. 1

Flowchart of the patient inclusion process

Fig. 2

Iodine map and monochromatic image of a 74-year-old male patient with a primary lung squamous cell carcinoma (white arrows). Readers 1/2/3 rated the degree of bronchiectasis/airspace enlargement (arrowheads) surrounding the nodule as 2 (prominent)/2/2 and 0 (the same degree)/2/0 for the iodine map (a) and monochromatic image (b), respectively

Fig. 3

Iodine map and monochromatic image of a 65-year-old male patient with a primary lung adenocarcinoma (white arrows). Readers 1, 2, and 3 rated the degree of bronchiectasis/airspace enlargement (arrowheads) surrounding the nodule as 2 (prominent), 2, and 2 and 0 (the same degree), 1 (slightly greater), and 0 for the iodine map (a) and monochromatic image (b), respectively

Fig. 4

Box and whisker plots for the averaged bronchiectasis/airspace enlargement scores vs. diseases in the iodine map (a) and monochromatic image (b)

Fig. 5

Receiver operating characteristic curves in differentiating primary lung carcinoma and malignant lymphoma from other diseases excluding lung infarct by readers 1 (a), 2 (b), and 3 (c). Dotted and solid lines indicate curves for the combined model (iodine map plus monochromatic image) and monochromatic image, respectively

Fig. 6

Receiver operating characteristic curves in differentiating lung metastasis from colorectal carcinoma from other diseases by readers 1 (a), 2 (b), and 3 (c). Dotted and solid lines indicate curves for the combined model (iodine map plus monochromatic image) and monochromatic image, respectively