What type of radiograph is a pneumocystogram?

A pneumocystogram is specifically defined as a radiographic examination of the bladder that is performed after air has been introduced into the bladder. This technique helps to visualize the bladder's outline and internal structures more distinctly during the imaging process. The air provides a contrast to the surrounding tissues, making it easier to identify abnormalities within the bladder, such as lesions or tumors.

In contrast studies that involve liquid contrast agents (like the scenarios described in the other options), the purpose and methodology differ significantly. The focus of a pneumocystogram on air injection makes it unique compared to procedures involving positive contrast media or different imaging modalities. This is essential to understand, particularly when considering the distinct ways in which radiographic techniques are utilized to assess specific bodily structures.