On the compensating filter in pulmonary hilar tomography

In recent years, it has been an important theme for the diagnosis of pulmonary hilar cancer to evaluate whether the lesion in hilar lymph nodes and the vicinity of the hilar bronchus exists or does not. It is shown that pulmonary hilar region is from main bronchus to segmental bronchus which is separating subsegmental bronchus. It is difficult to make the optimal density for all area of the pulmonary hilar region on a same film, because there is too much difference of density between medial region under the veil of thoracic vertebra, sternum, heart and great vessels, and lateral region in conventional tomography. Therefore, a compensating filter was constructed to equalize the uneven density of pulmonary hilar region on a X-ray film. As a result, trachea, main bronchus, upper local and segmental bronchus were observed simultaneously and serially on a same film by using this filter. In addition, we could study the condition in the inside and outside of bronchial wall in detail, and have many informations compared with conventional tomogram. Particularly, this is an useful method to determine the range of lesion in the pulmonary hilar cancer. (author)