Daily ISO Phantom

Accurate radiation dose delivery requires daily checks of the alignment between the true radiation isocenter and the isocenters of the imaging, localization and targeting systems. The CIRS Daily ISO Phantom provides a cost-effective, quick, and accurate means for testing isocenter coincidence.

Using the Daily ISO Phantom, LINAC lasers and light field can be “tuned” to the true radiation isocenter using the engraved markings on the phantom’s exterior. The light field and radiation field alignment can be checked using built-in radiographic markers. More importantly, the isocenters of both the OBI and the EPID can be checked for true spatial alignment and coincidence with that of the treatment beam.

The Daily ISO Phantom contains a unique center point fiducial and an offset target. The offset target is used to ensure the table offset coordinates generated by kV/MV matching are accurate by locating the target, moving the table the determined amounts and verifying that the offset target has been positioned at the isocenter. The center fiducial and offset target measure 6.35 mm in diameter and are made of ceramic. The exterior is machined with concentric circle targets to allow user to objectively assess all setup errors, including rotations, and to easily align the phantom to the true radiation isocenter. The Daily ISO Phantom is manufactured with machining tolerance of ± 0.02 mm. Target positioning accuracy is ± 0.1 mm.

There are two platform supports available for use with the Daily ISO Phantom. The 6DOF ISO Base is designed to register with couch indexing bars and provide known phantom translations and rotations to check corrections made by 6DOF couches. The ISO Base is used to position and level the Daily ISO Phantom on 3DOF (conventional) treatment couches. Both platforms provide leveling legs and embedded markers for kV/MV pixel size computation using ISO Analyze™ software.