Читать книгу Respiratory Medicine - Stephen J. Bourke - Страница 115

Computed tomography scanning uses a technique of multiple projection with reconstruction of the image from X‐ray detectors by a computer so that structures can be displayed in cross‐section. A number of different techniques can be used depending on the area of interest. CT scanning is particularly useful in providing a detailed cross‐sectional image of mediastinal disease, which is often difficult to assess on plain chest X‐ray. Fig. 4.10 shows the principal mediastinal structures with horizontal lines indicating the levels of the CT sections illustrated diagrammatically in Fig. 4.11. CT scanning is a key investigation in the staging of lung cancer (see Chapter 12) and detecting and determining the extent of bronchiectasis (see Chapter 8).

High‐resolution CT scans are much more sensitive than plain X‐ray in assessing the lung parenchyma and can provide a detailed image of emphysema (see Chapter 11) and interstitial lung disease. A ‘ground glass’ appearance on a high‐resolution CT scan of a patient with interstitial lung disease is relatively non‐specific whereas a ‘reticular honeycomb pattern’ indicates advanced fibrosis. CT scanners have the capacity to perform very rapid spiral images and this imaging technique combined with injection of radiocontrast material into a peripheral vein yields the CT pulmonary angiogram (CTPA) which can be used to identify emboli in central pulmonary arteries in thromboembolic disease (see Chapter 15).