Important Safety Alerts

Medical device manufacturer, Varian Medical Systems, has issued a medical device safety alert concerning Eclipse Treatment Planning Systems [Versions 8.9 and 10.0].

According to the manufacturer, an anomaly that has been identified with the Eclipse Treatment Planning System where an outdated assigned Hounsfield Unit [HU] value can be used for dose calculation when the clock on the Eclipse Client Workstation is not synchronized with the Database/System Server.

When the Eclipse client workstation clock is running behind the clock on the Database/System server, it is possible that a change to the assigned HU value for a structure does not invalidate the density image stored in the cache, and for the subsequent dose and Monitor Unit [MU] calculation to be based on the outdated HU assignment. The resultant MUs may be higher or lower than expected, dependent on the specific HU assignments. Treatment of the patient using these values can therefore lead to under- or over-dose.

For this situation to arise, the Eclipse Workstation client clock must show an earlier time than that on the Database/System Server clock (for example, Client time shows 09:05:17, Server time shows 09:13:47). The following activities must take place on that Client workstation for the discrepancy to occur:

1. An HU value must be assigned to one or more structures.
2. The plan must be saved. This places a timestamp (S) on the DCF cache files, where S is the current server time.
3. The dose is then calculated.
4. The dose is cleared (for example by resetting the calculation area).
5. Then either a new HU value is assigned to a structure, or an existing HU value is modified.
6. Before the current client time reaches the time the server showed at S, the plan must be recalculated. The calculation will then be based on the outdated HU value that existed at time S.

An independent verification of the MUs will highlight the discrepancy.

The manufacturer advises all users to ensure that the workstation clock is synchronized with the Database/System server clock.

According to the manufacturer, the affected products were distributed in Hong Kong.

If you are in possession of the affected product, please contact your supplier for necessary actions.

Posted on 31 August 2012