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Patient Dose Estimates After Lactated Ringer's Related Breakthrough of a Rubidium-82 Generator

N Busse1*, B Lofton2, J Stickel3, (1) Denver Health, Denver, CO, (2) Colorado Assn in Medical Phys (CAMP), Colorado Springs, CO, (3) Colorado Assn in Medical Phys (CAMP), Golden, CO

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Retrospective patient dose and risk estimates were calculated for 8 Rb-82 cardiac rest/stress patients imaged over 3 days with PET/CT. Lactated Ringers’ (LR) solution was mistakenly used for infusion instead of 0.9% Sodium Chloride, causing elevated levels of Sr-82 and Sr-85 to be administered.

Methods: Limited data was available for analysis including Wash, Strontium, and Calibration vials from three days of quality control (QC) activities and generator printouts for the QC vials and patients. Breakthrough per milliliter and per mCi of Rb-82 was calculated using decay corrected QC vials from each day. Dose conversion factors from the package insert were used to calculate effective dose. Excess relative risk of cancer (ERRC) incidence was calculated using a coefficient of 4.5% per sievert.

Results: Ten days after the incident, the highest measured patient dose rate at 1m was 0.2 mR/hr. Sr-82 breakthrough over three days ranged from 4.7 to 17.6 µCi/ml and 6.5 to 23.0 µCi/mCi. Sr-85 breakthrough ranged from 3.4 to 13.0 µCi/ml and 4.7 to 17.0 µCi/mCi. Total contaminant activities ranged from 370 to 1761 µCi Sr-82 and 242 to 1172 µCi Sr-85. Effective doses ranged from 101 to 439 mSv, corresponding to an ERRC of 0.6 to 2.4%.

Conclusion: While Rb-82 generator manufacturers have repeatedly warned users of the risk LR solution, this work is thought to be the first published patient dose estimate for that scenario. The long half-lives of Sr-82 and Sr-85 and biological behavior lead to substantial doses from µCi activity levels. These results also indicate the importance of daily QC testing as mandated by the manufacturer. In this case, QC vials were being eluted properly but incorrectly analyzed.

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Keywords

Not Applicable / None Entered.

Taxonomy

IM- PET : Radiation dosimetry & risk

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