What is a disadvantage of portal radiographs compared to simulator films?

Portal radiographs are used in radiation therapy to verify patient positioning and treatment delivery, while simulator films are created using a simulation device to plan treatment fields. One of the primary disadvantages of portal radiographs is that they tend to have poorer spatial resolution compared to simulator films. This reduced spatial resolution can limit the ability to accurately assess anatomical structures and their relationships in the images.

In clinical practice, spatial resolution refers to the capacity of an imaging modality to distinguish fine details, which is paramount when planning and verifying treatment fields. Simulator films are designed to provide detailed images that help delineate structures more clearly, allowing for precise treatment planning. In contrast, portal radiographs, although useful for verification, lack the fine detail required for accurate diagnosis and treatment planning, which can lead to challenges in ensuring accurate treatment delivery.

The other listed aspects, such as high contrast and easy usability, do not rightly reflect the comparison to simulator films or highlight their disadvantages effectively.