Dynamic contrast-enhanced CT in suspected lung cancer: quantitative results

Abstract

Objectives: To examine whether dynamic contrastenhanced CT (DCE-CT) could be used to characterise and safely distinguish between malignant and benign lung tumours in patients with suspected lung cancer. Methods: Using a quantitative approach to DCE-CT, two separate sets of regions of interest (ROIs) in tissues were placed in each tumour: large ROIs over the entire tumour and small ROIs over the maximally perfused parts of the tumour. Using mathematical modelling techniques and dedicated perfusion software, this yielded a plethora of results. Results: First, because of their non-normal distribution, DCE-CT measurements must be analysed using log scale data transformation. Second, there were highly significant differences between large ROI and small ROI measurements (p,0.001). Thus, the ROI method used in a given study should always be specified in advance. Third, neither quantitative parameters (blood flow and blood volume) nor semi-quantitative parameters (peak enhancement) could be used to distinguish between malignant and benign tumours. This was irrespective of the method of quantification used for large ROIs (0.13,p,0.76) and small ROIs (0.084,p,0.31). Fourth, although there were no indications of systematic reproducibility bias, the 95% limits of agreement were so broad that the risk of disagreement between the measurements could affect the clinical use of the measurements. This lack of reproducibility should be addressed. Conclusion and advances in knowledge:A quantitative approach to DCE-CT is not a clinically usable method for characterising lung tumours.In the Western world, lung cancer remains the leading cause of cancer-related death in both males and females. The disease has a poor prognosis with an overall 5-year mortality rate of approximately 84% [1]. In patients with suspected lung cancer, the first imaging examination is that of a chest radiograph followed by a contrastenhanced CT of the thorax and upper abdomen. Depending on the local arrangements, this is followed by other examinations such as dynamic contrast-enhanced CT (DCE-CT).DCE-CT is a tool which, in theory, can quantify the perfusion of tissues by calculating the delivery of a contrast agent, and therefore blood, to these tissues [2][3][4]. This is expected to be clinically useful, and, accordingly, studies investigating the use of DCE-CT in oncology are increasingly reported in the literature [5][6][7].The fundamental principle of DCE-CT is based on the temporal changes in tissue density after an intravenous administration of iodinated contrast media. By obtaining, in quick succession, a series of images of a particular tissue of interest, it is possible to record the temporal changes in tissue attenuation occurring after intravenous injection of the contrast. The quantification of perfusion recorded by CT is performed using mathematical modelling techniques.In quantitative analysis, the operator places a region of interest (ROI) in the tumour, and a dedicated perfusion software is then used to calculate a numeric perfusion value for ...

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