* US 8,748,838 B2
The AccuRate* system is a Mirion patented solution that improves the performance of its current generation of gamma-sensitive whole body surface contamination monitors by correcting for the self shielding effect of an individual in the monitor. The AccuRate system enables the detection of lower levels of contamination, reduces false negatives and positives, and minimizes overall personnel monitoring effort. Its optimized analysis addresses the industry need to reduce cost, improve accuracy, and increase ALARA.
Argos-3/-5 Whole Body Contamination Monitors are used to assess surface contamination on the body of the workers. When a person is present in the portal during the monitoring cycle the gamma background can be significantly reduced because of the body's self-shielding effects.
Therefore, the gamma activity estimate is biased. Self-shielding effects can easily mask contamination levels of 5000 Bq in a 300 nGy/h (30 µR/h) background environment.
The AccuRate algorithm compensates self-shielding effects and the associated change in background count rate due to the presence of individuals inside the monitor. The algorithm enables the monitor to more accurately measure potential contamination levels.
Self-shielding varies greatly between individuals (anthropometric effect) and sites (background spectrum and spatial distribution). The site-to-site variations are taken into account through the calibration procedure which is done once, provided the background conditions are stable.
The advantage of the AccuRate system compared to the average correction method that can be deployed on current Argos-3/-5 monitors is its ability to correct for the self-shielding based on the actual measured anthropometrics of the subject being monitored. A large person would have an increased self-shield factor compared to the average person and thus could end up with a false negative (missed contamination). Conversely, a smaller person would have a reduced shielding effect compared to the average, increasing the probability of a false positive (false alarm).
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