[Evaluation of low dose chest expiratory high resolution computed tomography for diagnosis of air trapping].

In our hospital, expiratory high resolution computed tomography (HRCT) is being performed in patients with chronic obstructive pulmonary disease (COPD). Because expiratory HRCT is used in combination with inspiratory HRCT, it can provide less exposure according to diagnostic purposes. In the present study, we tried low-dose expiratory HRCT in terms of visual assessment and analysis software of phantom experiments. As a result, visual assessment in the dose reduction rate was about 50% to 75% against conventional exposure doses. Thoracic examinations are common in organs with high tissue weighting factors, and the present study shows a very effective means for medical exposure reduction.