The focus rtp system is sending incorrect data to elekta/philips linear accelerators under certain conditions that could result in a pt overdose. No patients have been incorrectly treated as a result of this malfunction.

A customer reported that, when sending a plan from the cms focus radiation treatment planning (rtp) system via rtp link to an elekta linear accelerator (linac) through an impac access record and verifty (r&v) system, the plan has an added wedged monitor unit (mu) value when none should have existed in the original plan in focus. The problem was obvious when looking at the information on the r&v system since the wedged mu value was other than zero. However, the cms complaint investigation committee felt that it would be possible that a user might not notice this problem and deliver treatment using the un-planned wedged mu, thus over-radiating the pt. No pt treatment was reported as having occurred. Investigation showed that there was a particular series of steps that must be taken to experience this situation. 1. The user had to calculate a plan which contained a motorized wedge (only used by elekta). 2. The plan then had the wedge removed and dose recalculated. 3. The plan was then stored as a permanent plan. 4. This permanent plan was recalled and send via rtp link to an elekta linac through an r&v system. The source of the problem was entirely within the focus rtp system. The r&v system and linac were both working as expected. When the permanent plan was recalled and sent via rtp link to an elekta linac through an r&v system, the wedged mu from step 1 above was exported to the r&v system even though it had been removed in step 2. Focus was not clearing out the register containing the wedged mu value when the plan was modified to remove the wedge. This would result in an overdose to the pt if delivered as is. Corrective action: all users that had the rtp link feature activated in their focus rtp system software were sent a customer advisory informing them of the problem. Users were asked to advise cms if they had the problem system set-up (focus rtp system transmitting via rtp link to an elekta linac with electronic wedge through an r&v system). Those sites with the problem set-up will be provided a software patch (referred to at cms as a production deviation authorization or pda) to resolve the problem in the current (release 2. 7. 0) software. The problem will be resolved permanently in focus release 3. 0. 0 which will be available in july, 2001.