Purpose: To clarify the limitations of multidetector-row CT (MDCT) in detecting focal lung lesions of 5 mm or less in diameter by pathologic/high-resolution CT (HRCT) correlation.
Materials and methods: Twenty-two patients who underwent both preoperative HRCT of the entire lobe using MDCT (MD-HRCT) and lobectomy for primary (n = 21) or metastatic (n = 1) lung tumor were studied. The author attempted to locate any focal lung lesions other than the main tumor throughout the resected and sliced specimens and to identify the opacities corresponding to the macroscopic lesions on MD-HRCT before histopathologic evaluation. Then two observers without pathologic information attempted to detect the lesions on MD-HRCT.
Results: Ninety-one lesions of 5 mm or less in diameter were found in 15 patients. Histopathologically, 13 lesions were classified as bronchioloalveolar carcinoma (BAC), 38 as atypical adenomatous hyperplasia (AAH), 9 as reactive hyperplasia (RH), 19 as inflammatory lesion (INF), 8 as solid lesion (SL), and 4 as showing no organizing change. The author, who had knowledge of the gross pathologic examinations, identified the opacities at rates of 100%, 82%, 56%, 42%, and 88% for BAC, AAH, RH, INF, and SL, respectively. The rates of lesion detection in the absence of knowledge of the pathologic examinations were 85%, 58%, 22%, 32%, and 75% for BAC, AAH, RH, INF, and SL, respectively. The rates of identification and detection of lesions more than 3 mm in diameter were 90% and 57%, respectively, while those of lesions less than 2 mm in diameter were 71% and 35%, respectively.
Conclusions: MD-HRCT proved to be useful in detecting focal lung lesions of 5 mm or less in diameter; however, it is still difficult to detect lesions of less than 2 mm in diameter.