Port Film
A verification radiograph taken through the treatment beam to confirm field placement and patient positioning.
Full Definition
Port films, also called portal images, are radiographic images acquired using the treatment beam itself to verify the accuracy of field placement and patient positioning. These images show the radiation field outline superimposed on patient anatomy, allowing verification that the intended target is properly covered and critical structures are adequately spared. While largely replaced by electronic portal imaging devices (EPIDs) in modern practice, the term remains in use for any verification imaging that confirms treatment field placement and setup accuracy.
Usage
Usage note: Term persists despite transition to digital portal imaging; context usually clarifies whether film or digital.
In Context
- "The port film revealed a 3mm shift in patient positioning that required correction." — Treatment verification note
- "Weekly port films will be obtained to monitor setup reproducibility throughout the course." — Treatment protocol