Training Emergency Responders to Use a Colorimetric Dosimeter

Training Emergency Responders to Use a Colorimetric Dosimeter Arthur Desrosiers Sc.D. CHP Dade Moeller & Associates David Lewis Ph.D. International Specialty Products

RADView PD Detector • Visual reading dosimeter • Wallet card size • 14 month expiration • 3-7 days incident use • Penetrating radiation • ~0-500 rem by densitometer or scanner • 2-100 rem visual – 95% response within 0.1 s • Photons 50 keV – 10 MeV; β >150 keV • Dose thresholds set at protective action guides (PAGs) of EPA, DHS, CRCPD, etc. • Dade Moeller is design consultant to RADeCO

Radiochromic Film: 20 yrs Experience

RAD-SURE Irradiation Indicators

GAFCHROMIC Medical Dosimetry Films for Therapy

RADView PD Dosimeter Badge Radiochromic Film Reference Chart Protective Action Guidance

Temperature History Indicator “False Positive” film hidden under logo protected from UV Temperature History Indicator Film Non-reversible Change to Red at ~60C° Replace Badge if Red

Note: Linearity not required because PAGs used as reference thresholds

Note: Dark reaction determines expiration date at room temperature

Quantitative Evaluation • Based on ANSI N13.11 Category I Protocol • Irradiating Laboratory: University of Wisconsin Calibration Laboratory, 137Cs • Bias + std. dev. : 7.5%

Why Human Testing and Training • Visual dosimeters must be read by people • Goal – 70% correct assessment of PAG • Variations in eyesight and interpretation skill • Users cannot be calibrated – must adjust visual thresholds to compensate for human variances • Validate a training program for users • Measure bias and standard deviation of visual readings to calibrate reference chart thresholds • Participants read 20 badges with random doses in the range 2-100 rem and estimated dose in blind test • Data used to calculate |B| + SD for eye readings • ISP lab personnel not associated with project • Expand work by Gladys Klemic of DHS

True Dose vs. Eye Estimates A B C D E F G H I J K L M N O P Q R S T

Highest and Lowest Eye Bias

SD vs. Bias of Visual Readout VISUAL LAB

Frequency of Bias -20% 0%

Training and Testing Firefighters • Participants were told that the test supported research into how workers interpret the dose • “Testing the dosimeter, not the firefighter” • Firefighters scored on Protective Action Guide • A correct estimate or a conservative response in next higher category is “correct,” but two categories higher or any lower category is a “failure” • Example – badge with 6 rads actual dose read as “LT 5” or “GT 25” rem scored as “failure” • Firefighter did not estimate numerical dose, only dose category for PAG determination • PAGs are correlated with dose on the badge

Success Rates: Correct PAG • ~80% ISP participants • ~70% first fire company • ~80% for second fire company * Color shift & texture complicate reading

Adjusting the Reference Chart • Measurements of the human response curve were used to correct the visual reference chart • Account for negative bias of some users • Similar to setting a critical limit for lower limit of detection in lab measurements • Consistent with “projected dose” criterion of EPA and DHS guidance

Improved Training Program • Participants scored a set of three badges with known doses • Proctor then displayed true doses for feedback • Participants gained proficiency in scoring • Small groups of 6-8 with reference control badges

Subsequent Testing • 20 Dade Moeller office staff volunteers • Professional and hourly personnel • 21 badges tested in revised version and two variations: “Charley” and “Papa” • 420 total readouts • Variation “Papa” most accurate • Variation “Charley” highest safety

Result After Adjustments

Medical Dose Monitoring

Training Emergency Responders to Use a Colorimetric Dosimeter