Description of Event or Problem · 1
THIS INCIDENT IS REPORTED LATE AS THE INITIAL EVALUATION WAS THAT IT WAS A MINOR ISSUE, NOT REQUIRING REPORTING. HOWEVER, FINAL REVIEW OF THE INCIDENT REPORT CONCLUDED THAT THERE MAY BE NON-REMOTE RISK OF HARM IF THE USE ERROR WERE TO RECUR AND IT WAS DECIDED TO FILE A REPORT. A CBCT SCAN WAS IMPORTED FOR DOSE RE-EVALUATION OF AN EXISTING PLAN. TO COMPENSATE FOR THE LIMITED FIELD-OF-VIEW, A REGION-OF-INTEREST (ROI) "EXTERNAL-FIELD-OF-VIEW" WITH A DENSITY OVERRIDE WAS CREATED ON THE CBCT. THIS ROI WAS EQUAL TO THE EXTERNAL ROI OF THE CBCT MINUS THE "FIELD-OF-VIEW" ROI AND HAD A DENSITY OVERRIDE OF 1G/CM³. USING THE CBCT, A RE-EVALUATION OF THE DOSE WAS DONE IN PLAN EVALUATION. BASED ON THIS, IT WAS DECIDED TO CREATE A NEW TREATMENT PLAN FOR THE PATIENT USING A NEW PLANNING CT. THE NEW PLANNING CT WAS IMPORTED, AND A NEW PLAN WAS CREATED. IN RAYSTATION, THE STRUCTURE-SET IS SHARED BETWEEN ALL IMAGE SETS FOR A PATIENT CASE. THE "EXTERNAL-FIELD-OF-VIEW" THEREFOR EXISTED ALSO ON THE NEW PLANNING CT. SINCE NO "FIELD-OF-VIEW" ROI WAS PRESENT ON THE NEW CT, THE "EXTERNAL-FIELD-OF-VIEW" ROI WAS EQUAL TO THE "EXTERNAL" ROI WITH A DENSITY OVERRIDE OF 1G/CM³, SO DOSE CALCULATION WAS PERFORMED USING A HOMOGENEOUS DENSITY INSTEAD OF ACCOUNTING FOR THE REDUCED DENSITY IN THE LUNGS. THE PLAN WAS OPTIMIZED ON THE NEW CT WITH THE UNINTENDED DENSITY OVERRIDE. THE UNINTENDED DENSITY OVERRIDE WAS NOT DETECTED DURING PLAN EVALUATION OR APPROVAL, AND THE PATIENT WAS TREATED USING THIS TREATMENT PLAN. THE ERROR WAS DETECTED AFTER ONE FRACTION. THE EFFECT OF THE DENSITY OVERRIDE ON THE PLAN ONLY RESULTED IN A MINOR INCREASE IN DOSE ON THE ORGANS AT RISK AND A 7% INCREASE OF MAX DOSE INSIDE THE GTV. NO HARM TO THE PATIENT IS EXPECTED. THE INCIDENT WAS REPORTED BY THE CLINIC AS A USE ERROR. RAYSTATION FUNCTIONS AS INTENDED. THE CLINIC HAS RECEIVED ASSISTANCE IN MODIFYING THE PLAN REPORT TO BETTER HIGHLIGHT DENSITY OVERRIDES. USABILITY IMPROVEMENTS WILL BE CONSIDERED FOR FUTURE PRODUCT VERSIONS.