Medical device manufacturer, RaySearch Laboratories AB, has issued a medical device safety alert concerning its RayStation 4.5, RayStation 4.7, RayStation 5, RayStation 6 and RayStation 7 [Build Number: 4.5.0.19, 4.5.1.14, 4.5.2.7, 4.7.0.15, 4.7.1.10, 4.7.2.5, 4.7.3.13, 4.7.4.4, 4.7.5.4, 5.0.0.37, 5.0.1.11, 5.0.2.35, 6.0.0.24, 6.1.0.26, 6.2.0.7, 7.0.0.19]
According to the manufacturer, robust optimization for plans using beam set + background dose is not supported in RayStation 4.5, RayStation 4.7, RayStation 5, RayStation 6 and RayStation 7. It is not possible to define an optimization function as robust if the function relates to beam set + background dose when using these RayStation versions. However, the following cases allow robust functions to be added, which are displayed as if they relate to beam set + background dose:
For these cases, the robust functions are displayed as if they relate to beam set + background dose. However, only the current beam set is taken into account during optimization and background dose will not be considered for the perturbed scenarios. Background dose is only accounted for in the nominal scenario.
This may lead to that a too high dose is allowed in the optimization, since the dose level in the objective function is based on beam set + background dose, but only the beam set dose is considered for that objective function in the perturbed scenarios. The resulting plan is typically less robust than intended. The magnitude of the error depends on the background dose level.
For target objectives, the error will most likely push the optimization to a too high target dose that is easy to detect. For an OAR (Organ At Risk) objective, too high dose may be allowed, and the problem may not always be detectable in the nominal dose. However, detectability is always high when using the Compute Perturbed Dose function in the Plan Evaluation module to evaluate the perturbed scenarios, as recommended in the RayStation Instructions for Use: "Evaluate the dose after robust optimization. After a robust optimization has been performed, the user is strongly advised to evaluate the dose using the perturbed dose tool in the Plan Evaluation module to verify that the dose is robust as intended".
The issue relates to an error that is triggered only for certain conditions in some well-defined use cases. There is an acceptable workaround that can be easily understood by users and adhered to in order to avoid harm. The issue will therefore be corrected by means of updated labeling. A FSN will be distributed to all affected customers. For future installations of the affected versions, the description of the error and the workaround shall be included in the product installation as an additional release note.
The long term solution is resolved in RayStation 8A, (subject to market clearance in some markets). If customers wish to continue using versions of RayStation affected by this notice, all users must maintain awareness of this notice. Alternatively, customers can choose to upgrade to the new version once it becomes available for clinical use.
Currently, the affected users are advised to take the following actions:
According to the local supplier, the affected product is distributed in Hong Kong.
If you are in possession of the affected products, please contact your supplier for necessary actions.
Posted on 28 Sep 2018