Measurement Uncertainties in Whole Body Counting and Radon Progeny

Abstract

Measurement uncertainty is an important quality index in gamma spectrometry related to the level of bias and precision involved in the measuring procedure. Quality control measurements during the commissioning of a 16-input whole body counter showed substantial deviations between the experimentally determined precision and the theoretical estimation, indicating either equipment malfunction or lack of reproducibility of the experimental setup. In this study, the role of the magnitude and variability of airborne background radiation present in the counting room and the human body in the deterioration of the precision of counters employing NaI(Tl) detectors was investigated. Correction methods and actions based on case-specific background features were developed and applied. The experimental observations were benchmarked using a mathematical model of the counter. The efficacy of the developed methods was tested by measurements, and updated precision values were obtained. Quasi-equilibrium between the gamma-emitters Bi and Pb in the counting room and the human body is a prerequisite for accurate direct low-level radioactivity measurements in the human body.

Limitations in the assessment of radon dose: the role of activity measurements in the human body

“…In addition, successive measurements in a group of volunteers during the cold period of the year, indicated TBBi levels during the second measurement carried out about 1 h after the first one were ~20% lower than in the first one, initiated no more than 20 min after the subjects' entrance to the room. These findings are attributed to the reduced in air activity in at the counting room [4,5]. Our the observed TBBi changes due to transient changes in the inhaled air quality are in accordance to the hypothesis that the volume and quality of the recently inhaled air is more important TBBi contributors than the "long-lived" radon inhaled at much earlier times and stored in the human body before its gradual decay to Bi.…”

“…Temperature regulation of the room is carried out by two airconditioning units augmented by a central heating system during the cold season of the year. Thus a 2.95% coefficient of variation of total body 40 K measurements in adult subjects of both sexes was obtained [3][4][5]).…”

“…In an attempt to keep airborne radioactivity at low and almost stable levels, the counting room that is located at the ground floor of the UIMPL building (there is no basement below), is constantly ventilated. More specifically, fresh air from the outdoor space is forced to enter in the counting room by two fans installed close to the openings of the shielding tunnel at 3 m height above the ground level [4]. Temperature regulation of the room is carried out by two airconditioning units augmented by a central heating system during the cold season of the year.…”

“…The first group reflects in large the quality of the inhaled air before entrance to the counting room, while the second the metabolic differences among individuals exposed to the more or less stable air quality at the WBC room (~40 Bq m -3 during the cold season of the year, i.e. about half of the geometric average in buildings at the city of Ioannina [4]).…”

Ανάλυση Της Συνολικής Και Τμηματικής Σύστασης Του Ανθρώπινου Σώματος Με Απορροφησιομετρία Δύο Ενεργειακών Ομάδων Ακτίνων Χ (DXA)

“…Λόγω της αναγκαίας χρήσης μετρητή υψηλής ευαισθησίας και υψηλού κόστους, η μέθοδος εφαρμόζεται κυρίως σε ακαδημαϊκά και ερευνητικά κέντρα όπου συνήθως επιτυγχάνεται επαναληπτικότητα μετρήσεων περίπου 2.5% -4.0% [72].…”