Description of Event or Problem · 1
HDR GAMMAMED AFTER-LOADER EQUIPMENT, SOURCE POSITIONING OUT OF TOLERANCE. ON THE 1ST OF THE MONTH, THE FOLLOWING NOTICE WAS SENT TO THE VARIAN PRIMARY SERVICE ENGINEER: "THE LAST TWO DAYS OF HDR POSITIONING INDICATE AN OFFSET IN DISTAL DIRECTION OF JUST UNDER 1 MM. THAT SEEMS TO INDICATE A SHIFT FROM THE TEST DONE DURING THE SOURCE EXCHANGE LAST MONTH ON THE 22ND. OUR PHYSICIST IS OUT UNTIL THE 6TH, BUT WE HAVE TWO HDR PROCEDURES SCHEDULED THE (B)(6) OF THIS MONTH. THE POSITIONING SHOULD (IN CASE FURTHER SLIPPAGE OCCURS) BE RECALIBRATED BEFORE THE PROCEDURES ON THE (B)(6). PLEASE LET ME KNOW YOUR THOUGHTS." PRIMARY SERVICE ENGINEER'S RESPONSE, LATER THAT DAY BY PHONE WAS THAT THE SLIPPAGE WAS A NORMAL SETTLING-IN EFFECT AFTER SOURCE EXCHANGE AND AN ADJUSTMENT WAS NOT NECESSARY (BY HOSPITAL'S CERTIFIED RADIOLOGICAL PHYSICIST #1). ON THE 7TH, VARIAN HDR ENGINEER (NOT PRIMARY ENGINEER) JUST COMPLETED A POSITION ACCURACY ADJUSTMENT. HERE ARE THE BEFORE AND AFTER IMAGES. THE LINE (FROM RADIATION BACKSCATTER FROM TUNGSTEN LINE IN THE QC PHANTOM) SHOULD GO THROUGH THE CENTER OF THE RADIATION POSITION DISK. THE DEVIATION IN THE TOP IMAGE IS ABOUT 1 - 1.2 MM (AN OLDER FILM WAS USED SO CLARITY SUFFERS). THE LOWER IMAGE IS AFTER ADJUSTMENT TODAY. HOPEFULLY, WE'LL BE TROUBLE-FREE FROM HERE ON. NOTE THAT THIS QC TEST IS CONDUCTED EACH HDR TREATMENT DAY BEFORE AN HDR CT SIMS IN ORDER TO ASSURE APPROPRIATE DOSE DELIVERY. IF OUTSIDE HOSPITAL/VARIAN TOLERANCE (1MM), THE PHYSICIST CONSULTS WITH THE PHYSICIAN BEFORE PROCEEDING. (BY HOSPITAL'S CERTIFIED RADIOLOGICAL PHYSICIST #2). ON THE 15TH: THE EXPLANATION OF THE SLIPPAGE TO 1.2 MM BY THE SECOND VARIAN SERVICE ENGINEER WHO MADE THE ADJUSTMENT, IS INCONSISTENT WITH THE EXPLANATION BY THE FIRST ENGINEER. NAMELY, THE SLIPPAGE IS CAUSED BY A FLAT SPOT (KNOWN DEFECT) ON THE SHAFT THAT CAN INTRODUCE THE OFFSET AND REQUIRES CORRECTION. (BY HOSPITAL'S CERTIFIED RADIOLOGICAL PHYSICIST #1).