Description of Event or Problem · 1
A MEDICAL PHYSICIST AT THE USER FACILITY CALLED NOMOS CUSTOMER SERVICE CONCERNING A RADIATION THERAPY PLAN HE WAS DEVELOPING USING THE CORVUS SYSTEM. THE CUSTOMER HAD JUST CREATED A TREATMENT PLAN IN CORVUS 5.0 FOR HIS ELEKTA LINEAR ACCELERATOR AND NOMOS MIMIC MULTI-LEAF COLLIMATOR (MLC). THE CUSTOMER STATED THAT DURING PRE-TREATMENT QA, HE NOTICED TAHT THE DOSE DISTRIBUTION APPEARED TO BE QUITE DIFFERENT THAN WHAT WAS EXPECTED. IT WAS NOTED THAT THE CUSTOMER HAD AN OLDER ELEKTA ACCELERATOR USING IEC 601 COORDINATES, RATHER THAN THE CURRENT IEC 1217 CONVENTION, WHICH USES DIFFERENT X AND Y DIAPHRAGM ORIENTATIONS. NOMOS CORPORATION EVALUATED THE CORVUS SOFTWARE AND FOUND THAT THE SOFTWARE DID NOT SUPPORT THE ELEKTA X-Y JAW ORIENTATION BASED ON THE OLDER IEC 601 CONVENTION WHEN THE NOMOS MIMIC MLC IS USED. AS A RESULT, THE TREATMENT PLAN REPORT WILL SHOW THE DIAPHRAGM POSITION SETTINGS FOR THE X AND Y JAWS TO BE REVERSED, BUT ONLY FOR PLANS CREATED FOR THE NOMOS MIMIC. THIS ERROR WOULD BE VERY OBVIOUS DURING THE VISUAL INSPECTION OF THE FIELD SHAPE PERFORMED BEFORE TREATMENT BEGINS. FAILING THAT, ANY NORMAL PATIENT QA INVOLVING COMPARISON TO MEASUREMENT IS LIKELY TO DETECT THIS CONDITION. IF, IN THE UNLIKELY EVENT THAT THIS ERROR CONTINUED TO BE UNDETECTED THROUGH BOTH OF THESE STANDARD PRE-TREATMENT QA STEPS, THE RESULTING TREATMENT COULD DELIVER UNINTENDED RADIATION WHICH COULD REACH THE PATIENT. IT MUST BE NOTED THAT THIS ERROR CAN ONLY OCCUR FOR CORVUS PLANS GENERATED FOR ELEKTA LINEAR ACCELERATORS USING THE MIMIC MLC, AND THE ELEKTA ACCELERATOR MUST USE THE OLDER IEC 601 DIAPHRAGM COORDINATE LABELING SYSTEM. VERY FEW CORVUS/MIMIC CUSTOMERS HAVE SUCH ACCELERATORS. FURTHERMORE, THIS ERROR SHOULD BE READILY DETECTABLE DURING NORMAL PRE-TREATMENT QA. NOMOS CORPORATION PREPARED AND DISTRIBUTED A CUSTOMER NOTIFICATION, IN THE FORM OF A TECHNICAL BULLETIN, DESCRIBING THE POTENTIAL PROBLEM TO ALL CORVUS CUSTOMERS. THE NOTIFICATION WAS NOT LIMITED TO JUST ELEKTA SITES POTENTIALLY AFFECTED BY THE ERROR, CONSIDERING THE POSSIBILITY THAT NON-ELEKTA SITES MAY SOMEDAY CREATE PLANS FOR AFFECTED ELEKTA ACCELERATORS AT OTHER SITES, OR MAY ACQUIRE AN ELEKTA ACCELERATOR WITHOUT THEIR KNOWLEDGE. THE TECHNICAL BULLETIN ADVISED CUSTOMERS TO BE PARTICULARLY VIGILANT FOR THIS ISSUE DURING NORMAL PRE-TREATMENT QA, AND ADVISE ALL STAFF MEMBERS ACCORDINGLY. THE TECHNICAL BULLETIN ADVISED THAT THE ISSUE WILL BE RESOLVED IN THE NEXT CORVUS PATCH RELEASE FOR CORVUS 5.0 AND CORVUS 5.0M. THE TECHNICAL BULLETIN ALSO ASKED REMAINING CORVUS 4.0 CUSTOMERS TO CONTACT NOMOS TO HAVE A MANUAL FIX PERFORMED ON THEIR SYSTEMS. NOMOS IS PREPARING A PATCH RELEASE FOR ALL CORVUS CUSTOMERS TO INSTALL ON THEIR SYSTEMS, AND WILL SEND THIS PATCH IN THE VERY NEAR FUTURE. CUSTOMERS WILL BE ASKED TO INSTALL THE PATCH AND NOTIFY NOMOS WHEN THEY HAVE DONE SO SUCCESSFULLY. CORVUS 4.0 CUSTOMERS' SYSTEMS THAT ARE FIXED MANUALLY WILL ALSO BE TRACKED. THIS WILL ELIMINATE THE POTENTIAL PROBLEM.