Authors: Marco Das, MD, Georg Mühlenbruch, MD, Andreas H. Mahnken, MD, Rolf W. Günther, MD, Joachim Ernst Wildberger, MD, all from the Department of Diagnostic Radiology, RWTH Aachen University, Aachen, Germany

The detection of pulmonary nodules is one of the most common exams in chest multidetector-row CT (MDCT). Small pulmonary nodules can easily be overlooked and lead to false negative results, which could have severe consequences for the patient. Improved visualization using maximum intensity projection (MIP) and computer-aided detection (CAD) are beneficial for significant improvement of radiologist’s detection rate for small pulmonary nodules. However, the diagnostic challenge of how to characterize nodules remains. Criteria like shape, density or enhancement are often used, but size and size change are the most effective way for characterization. New guidelines from the Fleischner Society¹ address this problem, for the first time providing radiologists with practical follow up suggestions for small pulmonary nodules. This guideline is based on recent lung cancer screening trials, and suggests follow-up for pulmonary nodules depending on nodule size and patient risk classification. Thus, objective and reliable nodule detection and follow-up measurements have become more and more important as manual measurements yield high intra- and interreader variability.

History

This case presents a 64 year old female with colorectal cancer, who underwent chest MDCT for detection of pulmonary metastasis.

Diagnosis

The initial read was negative for pulmonary nodules, but the use of syngo Lung CAD indicated the presence of two very small nodules (both with a nodule diameter about 2 mm). Short term follow-up was performed to detect potential growth of these two nodules, and assess the degree of metastatic disease.

Comments

Using the automatic follow-up mode in syngo LungCARE, previously marked nodules were automatically aligned with the corresponding nodule (counterpart) in the follow-up examination. Volumetry results were directly compared and growth rate estimated. Additionally CAD was run on the follow up examination, enhancing diagnostic confidence. In our experience, syngo Lung CAD is a clinically valuable tool, helping physicians to be sure that all potential lesions are identified. The automatic follow-up feature of syngo LungCARE CT helps to eliminate errors in assessing the growth progression, or regression, of lesions, thereby enhancing our diagnostic confidence for chest exams.

Fig. 1: A small pulmonary nodule (diameter 2.1 mm) in the apical segment of the upper lobe on the left lung was found by the CAD software and marked after verification by the Radiologist. Using the automated follow up function [Fig. 1A], the corresponding counterpart in the follow up examination is automatically marked [Fig. 1B].

Fig. 2: syngo Lung CAD software was used for the detection of additional pulmonary nodules on the follow up examination. Findings of the software (circled in red) indicating the need for verification by the radiologist. Finally reported nodules are marked in green.

1 MacMahon H, Austin JH, Gamsu G, Herold CJ, Jett JR, Naidich DP, Patz EF Jr, Swensen SJ; Fleischner Society. Guidelines for management of small pulmonary nodules detected on CT scans: a statement from the Fleischner Society. Radiology 2005; 237: 395–400.