Sub-second Multi-Detector Spiral Computed Tomography for the Study of Structure-Function Relationships Within the Lung

Abstract

Gas exchange has been assessed over the years by numerous methods used to measure ventilation and perfusion, their functional determinants, and the outcome of the matching of the two. Pulmonary function tests have evolved that provide global measurements of airflow, lung volumes, and gas exchange, from which alterations in normal lung function and structure are inferred. Over the past 25 years, X-ray computed tomography (CT) has emerged as a method that can provide an integrated view of both structure and function on a regional basis, and with both temporal and spatial resolutions that continue to improve at a rapid pace. Techniques such as positron emission tomography (PET) and magnetic resonance imaging in conjunction with hyperpolarized gas (and more recently hyperpolarized 13C) offer unique information complimentary to X-ray CT. As they develop, they are expected to offer enhancements to the knowledge base of the normal human lung and early pathological changes leading to disease that ultimately are expressed globally through pulmonary function tests. Many groups are working on methods for cross modality data fusion. In this chapter, examples of the use of CT imaging technology to probe normal and abnormal pulmonary structure and function will be explored from the perspective of a single research laboratory (and its collaborators). Through this expose it is hoped that the reader will gain an appreciation that X-ray CT imaging and image analysis offers a unique and reasonably comprehensive approach to evaluating the structural and functional complexity of the respiratory system in a manner that raises the standards for non-invasiveness, sensitivity, and specificity. It is of particular importance for the reader to gain an understanding that the scanner itself is simply the portal to the new frontiers offered by imaging (regardless of which modality is being discussed). The protocols designed for use of the scanners, the methods used to extract data from the images, and finally the methods to convert the extracted data to varying levels of knowledge regarding the integrated function of the lung are the critical challenges. The analysis is only as good as the images and the images are only as good as the algorithms used for the image analysis.