Medical device manufacturer, Varian Medical Systems, has issued an urgent field safety notice concerning 4D Integrated Treatment Console (4DITC) v 8.6 or 8.8 in combination with treatment planning systems.
It has been identified that in certain configurations, the 4DITC can interpret a RapidArcTM or VMAT treatment field as 3D Conformal Arc Treatment Plan. If it happens, the field will be delivered with a constant dose rate and gantry speed for the entire duration of the delivery, which can lead to delivered dose being different from the planned dose.
According to Varian, this will only happen when the change in MU/deg between consecutive control points is small. In other words, it can only happen when the dose rate or gantry speed vary in a very smooth and progressive way for the entire RapidArc field. RapidArcTM treatment plans created with Eclipse 8.2 and higher or potentially VMAT treatment plans created with 3rd party treatment planning systems, when delivered on the 4DITC v8.6 and v8.8 can be incorrectly identified as 3D Conformal Arc Treatment Plan.
Varian is now notifying all affected customers and will update the 4DITC software to address issues related to proper recording of treatment information from Varian machines.
According to the local supplier, the affected devices have been distributed in Hong Kong. If you are in possession of the affected product, please contact your supplier for necessary actions.