AGREEMENT STATE REPORT - POTENTIAL MEDICAL EVENT DUE TO LEAKING I-125 SEEDS
The following was received via e-mail:
"On 6/28/12 Saint Joseph Hospital personnel were surveying a packing materials used to ship I-125 seeds, for a procedure conducted earlier that day, when they noted elevated readings. Further surveys revealed that the elevated readings were not coming from the packing material associated with the 6/28/12 procedure but from packing material that was used to ship I-125 seeds for a previous procedure, which was in the area of the survey. Surveys of the packing material revealed no loose contamination on the exterior or interior of the box but elevated readings of 2500-350000 cpm and .2 mrem/hr. Receipt and post procedure surveys of the procedure associated with contaminated box did not reveal any abnormal readings. The Saint Joseph RSO assumes the material is I-125 but they do not have the capability to verify this. No loose seeds were found in any of the packing material. The I-125 seeds were accompanied by the manufacturers leak test report which indicated no contamination.
"The patient, whose procedure was associated with the contaminated packing material, will be evaluated on Monday 7/2/12 to determine if there was any uptake in his urine or thyroid of I-125 as a result of leaking seeds."
CA Report Number: 062912
A Medical Event may indicate potential problems in a medical facility's use of radioactive materials. It does not necessarily result in harm to the patient.
* * * UPDATE ON 7/2/12 AT 1806 EDT FROM EUGENE FORRER TO DONG PARK VIA EMAIL * * *
"This is a follow up of an incident, as information only, on Friday, June 29, 2012. Radiologic Health Branch reference would be 5010 #062912. The notification was about contaminated packaging that had contained Best Medical I-125 seeds. A thyroid count was performed on the patient who had the seeds implanted in May. The thyroid count verified that there had been an uptake of iodine by the thyroid. Below is the write up and preliminary dose estimate from the licensee regarding.
"Based upon this morning's patient measurements, instrument-manufacturer supplied efficiency data, and reference data for dose conversion, we estimate the patient involved received a thyroid uptake of 0.1 mCi of I-125 and a dose to the thyroid of 300 cGy.
"1) Conversion of counts per minute (cpm) to activity
Two[Pi] counting efficiency for I-125 (per manufacturer) is 133.5%
fraction of 2[Pi] solid angle subtended by a 2 inch diameter detector at a distance of 30 cm from the thyroid is 10.13 squared cm / 5654.9 squared cm = 0.00179
overall efficiency = 1.335 x 0.00179 = 0.00239
(190493 - 30) net cpm / 0.00239 x 4.505x10-10 mCi/dpm = 0.0359 mCi present thyroid burden.
Back-correcting 60 days to time of implantation (conservatively assuming that all uptake occurred at that time) with 42-day effective half-life, initial uptake given by 0.0359 / 0.3715 = 0.0967 approximately 0.1 mCi
"2) Taking the value quoted by Chen et.al. (attached) from NUREG/CR-6345, we assume the dose to thyroid is 780 cGy per mCi of I-125 administered, and this value assumes 25% uptake into the thyroid. Our calculated estimated thyroid burden of 0.1 mCi then gives an estimated absorbed dose of 0.0967 mCi x 780 cGy/mCi / 0.25 (since we measured actual thyroid burden v. amount administered) = 302 cGy approximately 300 cGy (rad) to thyroid.
"3) Whole body committed effective dose equivalent (CEDE) from a 300 rad dose to the thyroid (using a thyroid weighting factor of 0.04) would be 12 rem."
Notified R4DO (Allen) and FSME (Einberg). |