Q. Show technical aspects of the postero-anterior film?
1) Identification: Patient identification and side marker must be present.
2) Centering: The thoracic spinous process should be equidistant from the medial ends of both clavicles. Rotation to the left or right may produce incorrect assessment of cardiac size, as well as undue prominence of normal structures.
3) Penetration: The vertebral bodies and disc spaces must be just visible through the cardiac shadow. These may not be defined in an underpenetrated film. Pulmonary vascularity or lung pathology may then be exaggerated. Overpenetration may lead to poor visualization of pulmonary vascularity and soft opacities in the lung parenchyma.
4) Inspiratory Effort: If the inspiratory effort is adequate, the 6th rib anteriorly or 8th rib posteriorly must cross the dome of diaphragm. The cardiac size cannot be assessed if the inspiratory effort is inadequate, and pulmonary vasculature may appear unduly prominent.
5) Field of View: The entire lung, from the apex to the depth of costophrenic angle must be included in the film.