Imaging description

Window and level settings can significantly affect the appearance of CT images. Therefore, over time, relatively standard window and level settings have been established for evaluation of the lungs, soft tissues, and bones. However, there are occasions when alteration of the window and level settings may be helpful in diagnosis of disease.

Alteration of window and level settings may be helpful in detecting pulmonary emboli [1]. When the contrast bolus is very dense, small emboli may be obscured on a standard soft tissue (mediastinal) window and level setting (Figure 82.1). By narrowing the window and level settings, the embolus can be more easily detected (Figure 82.1). Narrow CT window widths can also be useful in detecting subtle emphysema [2, 3]. However, care must be taken in evaluating other structures in the chest since narrow CT window widths – especially when combined with low level settings – can simulate the appearance of infiltrative lung disease or bronchial wall thickening [2, 3].