The larynx: simplified radiological examination using heavy filtration and high voltage.

Abstract

Since the introduction of heavy filtration in conjunction with high peak kilovoltage (8, 25), it is possible to obtain a wealth of radiological information about the larynx and pharynx in the frontal projection by employing a stationary tube and short exposure times. The method can be used alone as a plain film study of the larynx in its various positions of function, or in combination with contrast medium studies and cineradiography to improve the information given by these specialized technics. We use a 1 mm brass filter and a peak kilovoltage in the order of 130 kVp. Material and Methods Proper assessment of the larynx requires examination of both the larynx and surrounding pharyngeal structures. This includes postero-anterior and lateral films of the neck with low peak kilovoltage and customary aluminum filtration for visualization of calcified and ossified cartilaginous structures and for assessment of fat tissue, particularly the pre-epiglottic space and submandibular soft tissues. Views obtained with the patient phonating provide information regarding the landmarks of the larynx because with heavy filtration the calcific and bony portions of the thyroid and cricoid cartilages are often almost completely obliterated. The following postero-anterior views of the larynx are then taken with heavy filtration and higher kilovoltage: a. During quiet respiration b. During expiratory phonation, phonating “e” c. During inspiratory phonation, phonating “e” d. During the true Valsalva maneuver e. During the modified Valsalva maneuver in which the patient is instructed to distend his neck as much as possible as well as puff out his cheeks. Lateral films are also obtained with heavy filtration during phonation and during the modified Valsalva maneuver. When slight asymmetries of the soft tissues are encountered, image-intensification fluoroscopy and cineradiography are needed to exclude the possibility that the asymmetries are due to minor degrees of rotation of the larynx not appreciable on plain films. In addition, barium studies are performed to outline the surrounding pharyngeal structures, in particular the piriform fossae and postcricoid region. These may be done with or without heavy filtration, but preferably with. For plain film studies the 1 mm brass filter is substituted for, or added to, the aluminum filter in the tube mounting. For cineradiographic studies a 1 mm brass plate is simply taped to the table top to superimpose upon the patient's larynx. Although this is not an ideal arrangement, it is adequate for the purpose and the under-couch tube is not readily accessible for placement of the filter in the tube-mounting itself.