Lung cancer screening with submillisievert chest CT: Potential pitfalls of pulmonary findings in different readers with various experience levels.

PURPOSE: To assess the interreader variability of submillisievert CT for lung cancer screening in radiologists with various experience levels. METHOD: Six radiologists with different degrees of clinical experience in radiology (range, 1-15 years), rated 100 submillisievert CT chest studies as either negative screening finding (no nodules, benign nodules, nodules <5 mm), indeterminate finding (nodules 5-10 mm), positive finding (nodules >10 mm). Each radiologist interpreted scans randomly ordered and reading time was recorded. Interobserver agreement was assessed with ak statistic. Reasons for differences in nodule classification were analysed on a case-by-case basis. Reading time was correlated with reader experience using Pearson correlation (r). RESULTS: The overall interobserver agreement between all readers was moderate (k = 0.454; p < 0.001). In 57 patients, all radiologists agreed on the differentiation of negative and indeterminate/positive finding. In 64 cases disagreement between readers led to different nodule classification. In 8 cases some readers rated the nodule as benign, whereas others scored the case as positive. Overall, disagreement in nodule classification was mostly due to failure in identification of target lesion (n = 40), different lesion measurement (n = 44) or different classification (n = 26). Mean overall reading time per scan was of 2 min 2 s (range: 7s-7 min 45 s) and correlated with reader-experience (r = -0.824). CONCLUSIONS: Our study showed substantial interobserver variability for the detection and classification of pulmonary nodules in submillisievert CT. This highlights the importance for careful standardisation of screening programs with the objective of harmonizing efforts of involved radiologists across different institutions by defining and assuring quality standards.

Quantification of coronary artery stenosis with high-resolution CT in comparison with histopathology in an ex vivo study.

PURPOSE: To investigate the ex vivo performance of high-resolution computed tomography (CT) for quantitative assessment of percentage diameter stenosis in coronary arteries compared to histopathology. MATERIALS AND METHODS: High-resolution CT was performed in 26 human heart specimens after the injection of iodinated contrast media into the coronary arteries. Coronary artery plaques were visually identified on CT images and the grade of stenosis for each plaque was measured with electronic calipers. All coronary plaques were characterized by histopathology according to the Stary classification, and the percentage of stenosis was measured. RESULTS: CT depicted 84% (274/326) of all coronary plaques identified by histology. Missed plaques by CT were of Stary type I (n=31), type II (n=16), and type III (n=5). The stenosis degree significantly correlated between CT and histology (r=0.81, p<0.001). CT systematically overestimated the stenosis of calcified plaques (mean difference - 11.0 ± 9.5%, p<0.01) and systematically underestimated the stenosis of non-calcified plaques (mean difference -6.8 ± 10.4%, p<0.05), while there was no significant difference for mixed-type plaques (mean difference -0.4 ± 11.7%, p=0.85). There was a significant underestimation of stenosis degree as measured by CT for Stary II plaques (mean difference -14 ± 9%, p<0.01) and a significant overestimation for Stary VII plaques (mean difference 9 ± 10%, p<0.05), but there was no significant difference in stenosis degree between both modalities for other plaque types. CONCLUSIONS: High-resolution CT reliably depicts advanced stage coronary plaques with an overall good correlation of stenosis degree compared to histology, however, the degree of stenosis is systematically overestimated in calcified and underestimated in non-calcified plaques.

A systematic approach for analysis, interpretation, and reporting of coronary CTA studies.

Over the past years, the number of coronary computed tomography angiography (CTA) studies performed worldwide has been steadily increasing. Performing a coronary CTA study with appropriate protocols tailored to the individual patient and clinical question is mandatory to obtain an image quality that is diagnostic for the study purpose. This process can be considered the primary mainstay of each coronary CTA study. The secondary mainstay is represented by the correct analysis and interpretation of the acquired data, as well as reporting of the pertinent imaging findings to the referring physician. The latter process requires knowledge of the advantages and disadvantages of various post-processing methods. In addition, a standardized approach can be helpful to avoid false-positive and false-negative findings regarding the presence or absence of coronary artery disease. By implementing various radiation dose reduction techniques, care needs to be taken to keep the radiation dose of coronary CTA as low as reasonably achievable while maintaining the diagnostic capacity of the examination. This review describes a practical approach to the analysis and interpretation of coronary CTA data, including the standardized reporting of the relevant imaging findings to the referring physicians.