Optimum Photon Energy in Ordinary Radiography of the Larynx

The soft tissue of the larynx is defined radiographically by its contrast against the adjacent air. The cervical spine is always superimposed upon the larynx in a frontal roentgenogram of the region. This film contains closely spaced density variations due to the different radiation absorption within the spongy bone and variations at wider intervals, i.e. due to spinous processes. The laryngeal structures may be distinguished from the latter by slightly altering the projection. The fundamental problem in frontal radiographic examination of the larynx is however the 'disturbance' in the film caused by the trabeculae of the spongy bone. The difference in contrast between soft tissue and air and soft tissue and bone may be varied in radiologic examinations by changes in the energy spectrum of the roentgen photons. The linear attenuation at low energies is greater in bone than in soft tissue whereas at higher energies the difference is much less. A high voltage technique with a tube potential of 150 kV or more has therefore been re-